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Climate change is rapidly transforming the coastal margins of Greenland. At the same time, there is increasing recognition that marine‐terminating glaciers provide unique and critical habitats to ice‐associated top predators. We investigated the connection between a top predator occupying glacial fjord systems in Northwest Greenland and the properties of Atlantic‐origin water and marine‐terminating glaciers through a multiyear interdisciplinary project. Using passive acoustic monitoring, we quantified the summer presence and autumn departure of narwhals (Monodon monoceros) at glacier fronts in Melville Bay and modeled what glacier fjord physical attributes are associated with narwhal occurrence. We found that narwhals are present at glacier fronts after Greenland Ice Sheet peak summer runoff and they remain there during the period when the water column is becoming colder and fresher. Narwhals occupied glacier fronts when ocean temperatures ranged from −0.6 to 0.8°C and salinities between 33.2 and 34.0 psu at around 200 m depth and they departed on their southbound migration between October and November. Narwhals' departure was approximately 4 weeks later in 2019 than in 2018, after an extreme 2019 summer heatwave event that also delayed sea ice formation by 2 months. Our study provides further support for the niche conservative narwhal's preference for cold ocean temperatures. These results may inform projections about how future changes will impact narwhal subpopulations, especially those occupying Greenland glacial fjords. [ABSTRACT FROM AUTHOR]

In recent decades, the Greenland ice sheet has been losing mass through glacier retreat and ice flow acceleration. This mass loss is linked with variations in submarine melt, yet existing ocean models are either coarse global simulations focused on decadal‐scale variability or fine‐scale simulations for process‐based investigations. Here, we unite these scales with a framework to downscale from a global state estimate (15 km) into a regional model (3 km) that resolves circulation on the continental shelf. We further downscale into a fjord‐scale model (500 m) that resolves circulation inside fjords and quantifies melt. We demonstrate this approach in Scoresby Sund, East Greenland, and find that interannual variations in submarine melt at Daugaard‐Jensen glacier induced by ocean temperature variability are consistent with the decadal changes in glacier ice dynamics. This study provides a framework by which coarse‐resolution models can be refined to quantify glacier submarine melt for future ice sheet projections. Plain Language Summary: Over the past several decades, the Greenland ice sheet has been losing ice and contributing to sea‐level rise. About half of this ice loss is induced by melt that occurs where glaciers meet the ocean. Using coarse‐scale ocean models that simulate circulation around the globe, previous studies have noted a strong link between ocean temperature and enhanced glacier ice loss. However, due to the small scale of Greenland's fjords, coarse models are unable to directly quantify circulation in these fjords and melt on submerged glaciers. In this study, we develop a new framework to "zoom in" on a fjord, using high‐resolution models driven by larger coarse‐resolution models. In this approach, we simulate melt on one of Greenland's biggest glaciers and find that periods of higher melt coincide with more ice loss as observed from satellites. Since this framework is adaptable to other regions, it could also be used to simulate melt on other glaciers and support estimates of future sea‐level rise. Key Points: Subsurface temperature variability is simulated in a narrow fjord network using regional models downscaled from a global state estimateModeled increases in ocean melt at Daugaard‐Jensen glacier coincide with the onset of acceleration in 2005 and retreat and thinning in 2011Model variations in shelf‐to‐fjord ocean properties match with observations, providing a basis to estimate ocean forcing in ice projections [ABSTRACT FROM AUTHOR]

The Ice, Cloud, and Land Elevation Satellite‐2 (ICESat‐2) mission has collected surface elevation measurements for over 5 years. ICESat‐2 carries an instrument that emits laser light at 532 nm, and ice and snow absorb weakly at this wavelength. Previous modeling studies found that melting snow could induce significant bias to altimetry signals, but there is no formal assessment on ICESat‐2 acquisitions during the melting season. We performed two case studies over the Greenland Ice Sheet to quantify bias in ICESat‐2 signals over snow: one to validate Airborne Topographic Mapper (ATM) data against Next Generation Airborne Visible/Infrared Imaging Spectrometer (AVIRIS‐NG) grain sizes, and a second to estimate ICESat‐2 bias relative to ATM. We used snow optical grain sizes derived from ATM and AVIRIS‐NG to attribute altimetry bias to snowpack properties. For the first case study, the mean and standard deviation of optical grain sizes were 340 ± 65 µm (AVIRIS‐NG) and 670 ± 420 µm (ATM). A mean altimetry bias of 4.81 ± 1.76 cm was found for ATM, with larger biases linked to increases in grain size. In the second case study, we found a mean grain size of 910 ± 381 µm and biases of 6.42 ± 1.77 cm (ICESat‐2) and 9.82 ± 0.97 cm (ATM). The grain sizes and densities needed to recreate biases with a model are uncommon in nature, so we propose that additional surface attributes must be considered to characterize ICESat‐2 bias over snow. The altimetry biases are within the accuracy requirements of the ICESat‐2 mission, but we cannot rule out more significant errors over coarse‐grained snow. Plain Language Summary: The Ice, Cloud, and Land Elevation Satellite‐2 (ICESat‐2) mission has been used to measure changes in land ice, vegetation cover, and sea ice, and there is growing interest to use ICESat‐2 for snow science. ICESat‐2 uses a green laser to estimate the elevation of the Earth's surface, and recent work has shown that snow can introduce errors in green laser measurements such as ICESat‐2. In this study, we used ICESat‐2 and airborne data to (a) identify errors in the ICESat‐2 data and (b) link the errors to snow properties over the Greenland Ice Sheet. We found that ICESat‐2 errors are linked to two snow properties: the size of individual snow grains and the density of the snow. Two retrieval methods were used to estimate snow grain size, though the methods show significant differences when large snow grains are observed. Snow grain size and density are insufficient to fully explain ICESat‐2 biases, so we propose that other factors also play a role. The ICESat‐2 errors are within the accuracy requirements of ICESat‐2, but more significant errors may be possible during the Northern Hemisphere melting season. Key Points: Very large snow grains and densities are needed to explain centimeter‐level differences between ICESat‐2 and airborne lidarBiases from snow grain size and other factors may be influenced by different height measurement methods between ICESat‐2 and airborne lidarSnow grain size retrievals strongly differ between airborne lidar and AVIRIS‐NG over regions with coarse‐grained snow [ABSTRACT FROM AUTHOR]

Sea ice edges play an essential role in the Earth's climate and weather systems through active atmosphere‐ice‐ocean interactions. However, our understanding of the observed positions of sea ice edges remains limited. The present study investigated, on seasonal and longer timescales from 1979 to 2023, the variability in sea ice edge positions in the Barents and Greenland Seas. We objectively derived the positions of sea ice edges based on satellite‐derived sea ice concentration gridded on a 25‐km resolution. In the Barents Sea, warm, narrow currents flow eastward along the northern and southern rims of the Central Bank. Until the mid‐2000s, sea ice edges fluctuated between these currents interannually during December–June, depending on the surface wind direction. However, after the mid‐2000s, the sea ice edges were mostly positioned near the northern current or farther to the north. Furthermore, sea ice edges during October–March were identified frequently near the warm current flowing along the continental slope in the northern Barents Sea after the mid‐2000s. In the Greenland Sea, sea ice edges were typically positioned near the East Greenland Current (EGC) throughout the year until 2006. However, sea ice edges in summer were located far to the west of the EGC after 2006. These observations suggest that the geographical relationship between sea ice edges and ocean currents has changed due to global warming. Plain Language Summary: Sea ice edges in the Arctic play an important role in the Earth's climate system. They can strengthen atmospheric cyclones and vertical motion in the atmosphere and the ocean in the Arctic by inducing intense heat and moisture releases from the ocean to the atmosphere. Furthermore, they could exert distinct impacts on global‐scale atmosphere and ocean circulations. Therefore, a deeper understanding of the geographical positions of sea ice edges is essential for elucidating the climate system. This study investigated the sea ice edge positions in the Barents and Greenland Seas using satellite observations from 1979 to 2023. Sea ice edges rapidly advance southward during winter. Until the mid‐2000s, sea ice edges were frequently identified along warm ocean currents in the Barents and Greenland Seas because warm currents obstruct further sea ice edge advances. However, sea ice edges have shifted far to the north of warm ocean currents after the mid‐2000s in association with the recent shrinking in sea ice extent due to global warming. The change in sea ice edge positions might have affected the atmosphere and ocean circulations globally, which should be addressed in future studies. Key Points: In the central Barents Sea, sea ice edge positions fluctuated in winter until the mid‐2000s but have lately fixed along a warm currentSince the mid‐2000s, sea ice edges have been frequently identified along the continental slope in the northern Barents Sea in winterUntil 2006, sea ice edges in the Greenland Sea were located at the East Greenland Current, but they shifted far west after 2006 in summer [ABSTRACT FROM AUTHOR]

Accelerated melting of the Greenland Ice Sheet is considered a tipping element in the freshwater balance of the subpolar North Atlantic (SPNA). The East Greenland Current (EGC) and Coastal Current (EGCC) are the major conduits for transporting Arctic‐sourced and Greenland glacial freshwater. Understanding freshwater changes in the EGC system and drivers thereof is crucial for connecting tipping elements in the SPNA. Using the eddy‐rich model VIKING20X (1/20°) and Copernicus GLORYS12 (1/12°), we find that from 1993 to 2019 freshwater remains close to the shelf with interannual extremes in freshwater content (FWC) attributable to the imprint of Greenland melt only in years 2010 and 2012. Runoff increased significantly from 1995 to 2005 and Arctic freshwater export after 2005. Overall, regional wind patterns, sea ice melt and increasingly glacial ice and snow meltwater runoff along with the Arctic‐sourced Polar Water set interannual FWC variations in the EGC system. We emphasize that these freshwater sources have different seasonal timing. South of 65°N sea ice melts year round and retreats to north of 65°N, where melt in summer prevails. Greenland runoff peaks in June–August with only some locations of year round discharge. Alongshore winds intensify in fall and winter where reduced onshore Ekman transport allows for freshwater to spread laterally in the EGC. We show that sea ice melt, runoff and wind can cause interannual variations of comparable magnitude. All of which makes attributing ocean freshening events to Greenland meltwater inflow at current magnitudes a major challenge. Plain Language Summary: The intensity of Greenland ice sheet melt has greatly accelerated over the past decades bringing more freshwater to the surrounding ocean. The additional freshwater has the potential to reach areas where deep waters are formed, which are an important part of the global ocean circulation. A lid of cool and low salinity water would weaken deep water formation and circulation affecting global heat redistribution. In this study we use a high‐resolution model to investigate the effect of Greenland melt, sea ice export, and alongshore winds on freshwater content in the East Greenland Current and its coastal twin from Fram Strait to Cape Farewell. Two fresh extremes in 2010 and 2012 are attributable to local Greenland runoff maxima. We find that it takes 4–8 months for freshwater to propagate all along Greenland's east coast, with freshwater anomalies originating from the Arctic Ocean and additional input from sea ice melt along the journey often masking the Greenland runoff signal. Our results emphasize the need for ocean models and observations to resolve and record meltwater runoff, fjord and shelf processes, and boundary current dynamics to detect and attribute local freshening events. Key Points: During 1993–2019, the East Greenland Coastal Current is freshest in 2010 and 2012 notably matching years of exceptional Greenland runoffFreshwater anomalies from sea‐ice melt and Arctic export advected along east Greenland are of similar magnitudes as those linked to runoffSimulation of fresh coastal waters requires improved surface boundary conditions and/or models capable of representing mesoscale dynamics [ABSTRACT FROM AUTHOR]

Sea ice modulates the energy exchange between the atmosphere and the ocean through its kinematics. Marginal ice zone (MIZ) dynamics are complex and are not well resolved in routine observations. Here, we investigate sea ice dynamics in the Greenland Sea MIZ using in situ and remote sensing Lagrangian drift datasets. These datasets provide a unique view into ice dynamics spanning spatial scales. We find evidence of tidal currents strongly affecting sub‐daily ice motion. Velocity anomalies show abrupt transitions aligned with gradients in seafloor topography, indicating changes in ocean currents. Remote‐sensed ice floe trajectories derived from moderate resolution satellite imagery provide a view of small‐scale variability across the Greenland continental shelf. Ice floe trajectories reveal a west‐east increasing velocity gradient imposed by the East Greenland Current, with maximum velocities aligned along the continental shelf edge. These results highlight the importance of small scale ocean variability for ice dynamics in the MIZ. Plain Language Summary: Sea ice in the Arctic Ocean plays an important role in climate due to its influence on ocean circulation and air‐sea energy exchange. Ice motion results from competing and interacting effects of winds, ocean currents, and internal ice stresses. This study uses two novel observational datasets to analyze ice motion in the Greenland Sea and Fram Strait marginal ice zones. We find abrupt changes in the primary causes of ice motion associated with seafloor topography. In shallow seas, strong tidal currents affect ice drift, resulting in repeated opening and closing of the ice. Near the shelf edge, boundary currents increase ice drift speeds, causing ice pack shear. Sea ice models that ignore small‐scale ocean currents will underestimate ice deformation. Key Points: Ice dynamics measured with two new Lagrangian datasets show strong bathymetry dependent differences over short spatial scalesWind variability is insufficient to describe drift variability in regions with abrupt changes in bathymetry and large gradients in currentsDrifting buoy observations show a spatially heterogeneous imprint of tidal currents on ice dynamics [ABSTRACT FROM AUTHOR]

Understanding the future fate of the Greenland Ice Sheet (GIS) in the context of anthropogenic CO2 emissions is crucial to predict sea level rise. With the fully coupled Earth system model of intermediate complexity CLIMBER‐X, we study the stability of the GIS and its transient response to CO2 emissions over the next 10 Kyr. Bifurcation points exist at global temperature anomalies of 0.6 and 1.6 K relative to pre‐industrial. For system states in the vicinity of the equilibrium ice volumes corresponding to these temperature anomalies, mass loss rate and sensitivity of mass loss to cumulative CO2 emission peak. These critical ice volumes are crossed for cumulative emissions of 1,000 and 2,500 GtC, which would cause long‐term sea level rise by 1.8 and 6.9 m respectively. In summary, we find tipping of the GIS within the range of the temperature limits of the Paris agreement. Plain Language Summary: With ongoing carbon dioxide emissions from the burning of fossil fuels, the atmosphere heats up, which has dramatic consequences for the ice sheets on Earth. In this study, we focus on the Greenland ice sheet (GIS), which holds so much ice that a complete melting would cause the global sea level to rise by 7 m. However, future mass loss of the GIS is challenging to predict because it is a non‐linear function of temperature and occurs over long timescales. For this reason, we use CLIMBER‐X, which is a coupled model of the whole Earth system. We find that the GIS features two critical volume thresholds, whose crossing would imply extensive further mass loss so that it would be difficult for the ice to grow back, even in thousands of years. Near these critical ice volumes, the mass loss rates are particularly high, and differences in the total carbon dioxide emission have a large impact. In summary, if cumulative emissions larger than 1,000 Gt carbon are released into the atmosphere, the GIS will shrink below a critical threshold and mass loss will inevitably continue until a substantial part of the ice sheet has melted. Key Points: Bifurcation points exist at global mean temperature anomalies of 0.6 and 1.6 K relative to pre‐industrialMass loss rate and sensitivity to cumulative CO2 emission peak near the equilibrium ice volumes belonging to these temperature anomaliesSubstantial long‐term mass loss of the Greenland ice sheet for cumulative emissions larger than 1,000 Gt carbon [ABSTRACT FROM AUTHOR]

Summertime Greenland blocking (GB) can drive melting of the Greenland ice sheet, which has global implications. A strongly increasing trend in GB in the early twenty‐first century was observed but is missing in climate model simulations. Here, we analyze the temporal evolution of GB in nearly 500 members from the CMIP6 archive. The recent period of increased GB is not present in the members considered. The maximum 10‐year trend in GB in the reanalysis, associated with the recent increase, lies almost outside the distributions of trends for any 10‐year period in the climate models. GB is shown to be partly driven by the sea surface temperatures and/or sea ice concentrations, as well as by anthropogenic aerosols. Further work is required to understand why climate models cannot represent a period of increased GB, and appear to underestimate its decadal variability, and what implications this may have. Plain Language Summary: An increasing trend in summertime atmospheric blocking over Greenland was observed during the early twenty‐first century. However, this trend is not reproduced in climate models. This may have important implication for climate change projections, as summertime Greenland blocking drives the melting of its ice sheet which is a major contributing factor to global sea level rise. Here, recent trends in Greenland blocking are assessed in nearly 500 ensemble members from a large archive of state‐of‐the‐art climate models. We find that a recent increasing trend like that observed is absent in all of the ensemble members, and a trend of such magnitude is very unlikely to be simulated in them, which suggests a deficiency in the climate model simulation of Greenland blocking. The model simulations do however suggest that Greenland blocking is partly forced by sea surface temperatures/sea ice concentrations and/or anthropogenic aerosols, but the response of the models to these forcings may be too weak. These results provide new understanding on drivers of Greenland blocking in climate models and offer avenues for model development designed to improve simulations of Greenland climate. Key Points: The observed rapid increase in summertime Greenland blocking during the first decade of the twenty‐first century has not continuedA period of increased summer Greenland blocking of similar magnitude to observed is rarely reproduced in a large ensemble of climate modelsDecadal variability in Greenland blocking in climate models is partly driven by SST/sea ice and/or anthropogenic aerosols [ABSTRACT FROM AUTHOR]

At mid‐latitudes, a narrow band of near‐surface wind convergence (NSWC) overlies the western boundary currents in long‐term climatology as a response to steep sea surface temperature gradients. The underlying dynamics shaping mean convergence in the mid‐latitude region have been investigated in detail. In polar regions, surface temperature gradients are intense along the sea ice edges. However, literature concerning NSWC near sea ice edges is limited. This study investigates time‐mean NSWC along sea ice edges and its shaping processes, focusing on the Greenland Sea, based on atmospheric reanalysis. In cold‐season climatology, positive NSWC overlies the sea ice edge, resulting in a localized upward motion reaching the free atmosphere. The mean NSWC was insensitive to sea ice thickness and surface roughness in the regional model. This study suggests that, in addition to local atmospheric boundary processes, extreme NSWC events play a vital role in shaping the mean distribution. Although these features are similar to those along the Gulf Stream, atmospheric fronts appear to play a relatively minor role in the Greenland Sea. Instead, the frequent cyclone generation near the sea ice edge and the anticyclonic circulation over Greenland in conjunction with the transient synoptic circulation seem essential. In the warm season, positive NSWC was virtually missing in the Greenland Sea, unlike in the Gulf Stream region, reflecting the shallow virtual temperature response to the surface thermal forcing. This study contributes to understanding the mechanisms by which sea ice variability affects large‐scale atmospheric circulation in remote regions. Plain Language Summary: Previous studies have argued that sea ice variability in Arctic regions could affect large‐scale atmospheric circulation in remote regions. However, the underlying mechanisms remain unclear. A deeper understanding of the impact of sea ice on the local atmosphere will aid in revealing these mechanisms. The present study investigates small‐scale (less than 1,000 km) atmospheric features close to sea‐ice edges, where surface temperature gradients are intense and can exert distinct impacts on the atmosphere. In the winter, the sea‐ice edge distinctly modulates the near‐surface wind, leading to an narrow band of intense upward wind. This upward wind reaches the middle of the atmosphere, suggesting that these features could relate to the effect of sea ice variability on large‐scale atmospheric circulation in remote regions. The physical processes modulating the mean near‐surface winds near the sea‐ice edge are found to be similar to those along the warm currents at the western edge of the basins (such as the Gulf Stream). However, atmospheric fronts appear to play a less important role. Instead, the frequent cyclone generation near the sea‐ice edge and the combination of the clockwise near‐surface wind around Greenland and near‐surface wind blowing from the ocean to sea‐ice regions appear essential. Key Points: A distinct band of mean near‐surface wind convergence overlies the sea ice edge in the Greenland Sea during winterThe mean near‐surface wind convergence along the sea ice edge is insensitive to ice thickness and surface roughness in a numerical modelThe anticyclonic circulation over Greenland and transient synoptic circulation are essential for shaping the time‐mean wind convergence [ABSTRACT FROM AUTHOR]

Satellite radar interferometry data reveals that the grounding line of Petermann Glacier, Greenland migrates by several kilometers during the tidal cycle, bringing pressurized, subsurface, warm ocean waters in regular contact with a large sector of grounded ice. We use the Massachusetts Institute of Technology general circulation model in two dimensions to calculate the ice melt rates as a function of grounding zone (GZ) length and ocean Thermal Forcing (TF). Ice melt rates are found to be higher in the GZ cavity than anywhere else in the ice shelf cavity. The melt rates increase sub‐linearly with the length of the GZ and ocean TF. The model results agree well with remote sensing estimates of ice melt. High basal ice melt rates in tidally flushed grounding zones imply that marine‐terminating glaciers are more sensitive to ocean TF than anticipated, which will increase their projected contribution to sea level rise. Plain Language Summary: The traditional view of ice melting in contact with ocean waters is that melt rates drop to zero at the grounding line, which is a semi‐fixed boundary at the junction between grounded ice and the ocean. In reality, the grounding line migrates by kilometers during the tidal cycle, more than 10 times beyond the range expected from hydrostatic equilibrium, which brings warm, saline water in rapid contact with broad sectors of grounded ice. We use an ocean model to calculate the melt rates caused by seawater intrusions. We find that the melt rates in the GZ are higher than anywhere else in the ice shelf cavity and increase as the GZ becomes wider and the ocean gets warmer. Ice melt in kilometer‐size grounding zones will reduce the basal resistance to flow and will increase the sensitivity of the glacier flow to ocean warming, hence projections of sea level rise from the glacier will go up. Key Points: First modeling of ice melt rates from seawater intrusions in the kilometer‐size grounding zone (GZ) of Petermann Glacier using an ocean modelModeled melt rates are highest in the GZ and increase linearly with GZ width and ocean thermal forcingHigh melt rates in kilometer‐size grounding zones imply a higher sensitivity of glaciers to ocean warming than anticipated [ABSTRACT FROM AUTHOR]

This study presents a comprehensive climatology of coastal fog from four synoptic weather stations operated by the Danish Meteorological Institute along the entire East Greenland coast between 1958 and 2016. Elements investigated include fog frequency, daily timing, temperature, wind, visibility and radiosonde profiles during fog. The spatiotemporal patterns in fog from the low‐ to high‐Arctic locations were related to varying regional seasonal temperatures, surface and upper‐air wind and sea ice conditions, and to correlations with the North Atlantic Oscillation (NAO) and the Greenland Blocking Index (GBI). Results indicate that ˜70–80% of East Greenland fog occurs in summer (MJJA), and yearly fog onset is near‐coincident with the start of sea ice break‐up. This warm‐season fog has the typical characteristics of advection fog, as shown in the radiosonde profiles and the association with a gentle sea breeze. More than 95% of warm‐season fog is warmer than −10°C, and peaks close to 0°C and, therefore, consists of liquid or supercooled water droplets. In the cold season, mixed‐phase fog prevails in the high‐Arctic locations, accounting for ˜70% of observations. Ice fog (T < −30°C) occurs in only 2% of observations and is limited to Northeast Greenland during the cold season. The cold‐season composite radiosonde fog profiles in the high‐Arctic locations are characterized by deep (˜1000 m) and strong (˜6°C) surface‐based temperature inversions. Visibility during most fog conditions is lowest during the warm season (<500 m) and highest during the cold season (<800 m). In Northeast Greenland, visibility during warm‐season fog has decreased by ˜50 m·dec−1 between 1981 and 2016. In Southeast Greenland, fog visibility is high during low GBI and a positive phase of NAO, but no other correlations with climate indices were found. [ABSTRACT FROM AUTHOR]

The Greenland ice sheet has become a significant contributor to global sea level rise over the last 40–50 years. Approximately half of Greenland's mass loss since 1992 was due to increased ice discharge from marine‐terminating outlet glaciers. Here, we present high temporal resolution (∼monthly) time series of ice frontal positions for 24 marine‐terminating outlet glaciers along Greenland's east coast between 2013 and 2020. The glaciers are located north and south of 69°N, which has previously been identified as a potential divide in glacier response to climate forcing. Frontal positions are compared to ice velocity, atmospheric and oceanic data, allowing investigation of change at both seasonal and interannual timescales. Our results reveal 19 of 24 study glaciers underwent net retreat. We find marked differences in interannual patterns of frontal position between glaciers located north and south of 69°N. South of 69°N, glaciers underwent multiyear retreat initiated in 2016, which we attribute to over‐winter calving, resulting from warmer ocean waters and repeated ice‐mélange break‐up. North of 69°N glaciers show either limited or gradual changes in frontal positions and retreat patterns are characterized by more year‐on‐year variability between glaciers. Although similar atmospheric conditions occur across both regions, glaciers north of 69°N experience minimal change in ocean conditions, and are strongly influenced by glacier‐specific factors. Our results show that 69°N continues to represent a boundary between different glacier responses and climate forcing, which is likely to persist under current conditions. Plain Language Summary: The Greenland ice sheet has contributed substantially to global sea level rise over the last 40–50 years. Half of Greenland's mass loss since 1992 is attributed to increased ice discharge from glaciers reaching the ocean. Here we present time series of ice frontal positions for 24 ocean‐terminating outlet glaciers along Greenland's east coast between 2013 and 2020. The glaciers are located north and south of 69°N, which has been identified as a potential watershed in glacier behavior. We compared ice front positions to ice velocity and environmental factors, allowing investigation of change at different scales. Our results show 19 of 24 study glaciers underwent overall retreat. We observe different year‐to‐year patterns of change in frontal position between glaciers located north and south of 69°N. Year‐on‐year retreat for glaciers south of 69°N began in 2016, coinciding with reduced sea ice and warmer ocean conditions. Glaciers north of 69°N showed more limited change and greater variability between glaciers. Air temperature warming was similar between the two regions, but ocean warming was greater south of 69°N. Overall, these results show 69°N continues to be a boundary in east Greenland glacier behavior, likely due to differing environmental forcing. Key Points: Contrasting glacier dynamics north and south of 69°N along Greenland's east coast persists under a warming climateSouth of 69°N glaciers underwent multiyear retreat due to overwinter calving, attributed to warmer ocean waters and ice‐mélange break‐upNorth of 69°N glaciers showed limited retreat with the pattern and magnitude of change strongly influenced by glacier‐specific factors [ABSTRACT FROM AUTHOR]

The rate of land ice loss due to iceberg calving is a key source of variability among model projections of the 21st century sea level rise. It is especially challenging to account for mass loss due to iceberg calving in Greenland, where ice drains to the ocean through hundreds of outlet glaciers, many smaller than typical model grid scale. Here, we apply a numerically efficient network flowline model (SERMeQ) forced by surface mass balance to simulate an upper bound on decadal calving retreat of 155 grounded outlet glaciers of the Greenland Ice Sheet—resolving five times as many outlets as was previously possible. We show that the upper bound holds for 91% of glaciers examined and that simulated changes in terminus position correlate with observed changes. SERMeQ can provide a physically consistent constraint on forward projections of the dynamic mass loss from the Greenland Ice Sheet associated with different climate projections. Key Points: We test an upper‐bound model of calving retreat of 155 ocean‐terminating outlet glaciers that drain the Greenland Ice SheetOur physics‐based method produces terminus positions that correlate with observed positions for 103 glaciers without model tuningOur model bounds retreat rates on 91% of glaciers tested, providing a constraint for future sea level projections [ABSTRACT FROM AUTHOR]

Meltwater inputs to moulins regulate Greenland Ice Sheet sliding speeds by controlling water pressure in the most connected regions of the subglacial drainage system. While moulin storage capacities are a critical control on subglacial water pressure, few observations exist to constrain storage. Using direct observations inside moulins, we show that moulin cross‐sectional areas can be at least 500 m2, far greater than is observed at the surface or assumed in models. Moulin water level measurements and numerical modeling reveal that diurnal variability in moulin water pressure is highly attenuated in moulins with large storage volumes (∼3% ice pressure), relative to moulins with smaller storage volumes (∼25% ice pressure). Because large variability in moulin water pressure is linked to processes that ultimately reduce ice sliding speeds, ice sliding speeds in areas drained by large moulins may be more sensitive to long‐term increases in meltwater than areas drained by small moulins. Plain Language Summary: Each summer season on the Greenland Ice Sheet, meltwater forms stream networks on the ice surface that deliver water to moulins, which are holes in the ice that carry the water to the base of the ice sheet. When water backs up into moulins, and the water pressure beneath the ice increases, glacier sliding accelerates, leading to more rapid loss of ice into the ocean. We directly explored two moulins that contained immense storage volumes that are much larger than previously assumed to exist. Our observations of water levels inside moulins, and a model of water flow through the ice, indicate that storage of water within these large moulins during daily meltwater pulses has a big impact on how much the water pressure beneath the ice changes. Our work suggests that moulin sizes influence the interactions between summer melt and sliding of the Greenland Ice Sheet. Consequently, we need a more complete understanding of how moulin volumes vary in order to better predict how future increases in melt will impact the rate of ice loss from Greenland and to constrain its future contribution to sea level rise. Key Points: Moulin volumes on the Greenland Ice Sheet are much larger than previously thoughtAmplitudes of diurnal variation in moulin water level are negatively correlated with moulin volumeIce sliding speeds in areas drained by large moulins may be more sensitive to long‐term melt increases [ABSTRACT FROM AUTHOR]

Meltwater runoff from the Greenland Ice Sheet (GrIS) significantly contributes to sea level rise and is the dominant driver of enhanced mass loss. While most melt occurs during summer, little is known about its seasonal and/or interannual retention within the GrIS. Here, we document evidence of runoff during winter, ~4 months after summer melt. Ground‐penetrating radar and borehole surveys in the proglacial Isortoq River reveal slowly flowing water beneath >0.5 m of river ice. Geochemical analysis of this water indicates previous contact with the ice sheet bed. Comparable surveys in proglacial rivers draining four neighboring catchments found no winter drainage, despite a brief surface melt event ~10 days prior. We attribute the observed runoff to residual meltwater storage and release enabled by a >600 m deep trough beneath Isunguata Sermia, but not neighboring glaciers. We conclude that the GrIS bed can stay wet and drain small amounts of meltwater year‐round. Plain Language Summary: Meltwater runoff from the Greenland Ice Sheet substantially contributes to global sea level rise. Summer melting of the ice sheet surface produces most of this runoff, which flows over and into the ice sheet before emerging at its edge. Current climate and ice sheet models assume rapid evacuation of this meltwater to the ocean with a shutdown of ice sheet drainage in winter. Using ground‐penetrating radar and borehole measurements through seasonal ice cover in rivers draining the ice sheet, we find modest winter meltwater export in the Isortoq River, which drains a large area of the southwestern Greenland Ice Sheet. This signifies active subglacial hydrological processes year‐round. Key Points: Winter liquid water drainage is discovered in a frozen proglacial river draining Greenland's Isunguata Sermia outlet glacierNo winter drainage is found in proglacial rivers draining neighboring Russell, Leverett, Ørkendalen, and Isorlersuup outlet glaciersSeasonal and/or interannual meltwater retention and a deep, spatially pervasive subglacial trough may enable winter export from Isunguata Sermia [ABSTRACT FROM AUTHOR]

The Greenland Ice Sheet (GrIS) mass balance is examined with an Earth system/ice sheet model that interactively couples the GrIS to the broader Earth system. The simulation runs from 1850 to 2100, with historical and SSP5‐8.5 forcing. By the mid‐21st century, the cumulative GrIS contribution to global mean sea level rise (SLR) is 23 mm. During the second half of the 21st century, the surface mass balance becomes negative in all drainage basins, with an additional SLR contribution of 86 mm. The annual mean GrIS mass loss in the last two decades is 2.7‐mm sea level equivalent (SLE) year−1. The increased SLR contribution from the surface mass balance (3.1 mm SLE year−1) is partly offset by reduced ice discharge from thinning and retreat of outlet glaciers. The southern GrIS drainage basins contribute 73% of the mass loss in mid‐century but 55% by 2100, as surface runoff increases in the northern basins. Plain Language Summary: The Greenland Ice Sheet (GrIS) gains mass at the surface from snowfall, and it loses mass from melting and runoff and from glacier calving at the ocean front. When these processes are in balance, the ice sheet does not contribute to global sea level change. Recent observations have shown that the ice sheet is losing mass and raising global mean sea level. This study uses a global Earth system model that calculates ice flow of the GrIS, as well as processes in the atmosphere, ocean, land, and sea ice. For a modern reference, the model is forced with atmospheric greenhouse gas concentrations for the period 1850–2014. Next, the model is forced for the rest of the 21st century following the SSP5‐8.5 scenario to study how the GrIS and the Earth system respond to a worst‐case scenario. By 2050, the GrIS loses mass that is equal to 23 mm of global mean sea level rise. During the second half of the 21st century, all regions of the GrIS lose mass because of increased surface melting and runoff, with the dry north playing a greater role. By 2100, the projected GrIS contribution to sea level rise is 109‐mm sea level equivalent. Key Points: CESM2.1‐CISM2.1 simulates a 5.4 K global mean temperature increase and strong NAMOC weakening by 2100 in SSP5‐8.5 w.r.t. preindustrialThe Greenland Ice Sheet contributes 23 mm to global mean sea level rise by 2050 and 109 mm by 2100The role of the northern basins becomes more important as surface runoff strongly increases during the second half of the 21st century [ABSTRACT FROM AUTHOR]

Variability in oceanic conditions directly impacts ice loss from marine outlet glaciers in Greenland, influencing the ice sheet mass balance. Oceanic conditions are available from Atmosphere‐Ocean Global Climate Model (AOGCM) output, but these models require extensive computational resources and lack the fine resolution needed to simulate ocean dynamics on the Greenland continental shelf and close to glacier marine termini. Here, we develop a statistical approach to generate ocean forcing for ice sheet model simulations, which incorporates natural spatiotemporal variability and anthropogenic changes. Starting from raw AOGCM ocean heat content, we apply: (a) a bias‐correction using ocean reanalysis, (b) an extrapolation accounting for on‐shelf ocean dynamics, and (c) stochastic time series models to generate realizations of natural variability. The bias‐correction reduces model errors by ∼25% when compared to independent in‐situ measurements. The bias‐corrected time series are subsequently extrapolated to fjord mouth locations using relations constrained from available high‐resolution regional ocean model results. The stochastic time series models reproduce the spatial correlation, characteristic timescales, and the amplitude of natural variability of bias‐corrected AOGCMs, but at negligible computational expense. We demonstrate the efficiency of this method by generating >6,000 time series of ocean forcing for >200 Greenland marine‐terminating glacier locations until 2100. As our method is computationally efficient and adaptable to any ocean model output and reanalysis product, it provides flexibility in exploring sensitivity to ocean conditions in Greenland ice sheet model simulations. We provide the output and workflow in an open‐source repository, and discuss advantages and future developments for our method. Plain Language Summary: Model simulations of the Greenland ice sheet (GrIS) require knowledge of ocean conditions. The evolution of ocean conditions has a strong impact on ice sheet model predictions, as there are more than 200 glaciers in Greenland flowing directly into the ocean. However, modeling oceanic forcing is difficult. The state‐of‐the‐art approach is to use output from Atmosphere‐Ocean Global Climate Models (AOGCMs). But these models cannot accurately capture the ocean dynamics on the Greenland shelf, and they can show strong biases compared to observations. Furthermore, AOGCMs are computationally expensive, meaning that it is impossible to thoroughly characterize the uncertainty associated with the chaotic nature of climate. Here, we propose a procedure to bias‐correct and extrapolate oceanic output from AOGCMs. Our method exploits observational datasets, as well as available high‐resolution ocean model results. Using statistical models, we reproduce patterns of spatiotemporal ocean variability at low computational expense, and represent internal climate variability and global warming trends. The goal is to provide a scalable procedure to generate ocean forcing for long‐term GrIS model predictions. Key Points: We develop a statistical method to generate ocean forcing boundary conditions for Greenland ice sheet model simulationsThe method bias‐corrects and extrapolates global climate model output using reanalysis products and high‐resolution model resultsStochastic time series models reproduce the spatiotemporal variability of ocean conditions at negligible computational expense [ABSTRACT FROM AUTHOR]

The combined impact of Greenland sea ice, Eurasian snow, and the El Niño–Southern Oscillation (ENSO) on the out‐of‐phase relationship between the Indian summer monsoon (ISM) and Korean summer monsoon (KSM) were investigated through numerical experiments. The results revealed that Indian and Korean summer rainfalls showed nonlinear responses to ENSO and Greenland sea ice forcing when the events co‐occurred. Above‐normal Greenland sea ice and a concurrent La Niña showed a distinct in‐phase relationship with ISM and out‐of‐phase relationship with KSM. Below‐normal and above‐normal Greenland sea ice during boreal autumn surrounded the Greenland region with anomalous low pressure and high pressure, respectively. These were associated with a barotropic +west/−east or –west/+east dipole pattern, respectively, over Eurasia during the subsequent winter and spring seasons. Furthermore, these patterns led to positive and negative snow depth anomalies, respectively, over western Eurasia and the opposite snow tendency over eastern Eurasia during the subsequent spring. This variability in Eurasian snow patterns may play a crucial role in ISM and KSM. The co‐occurrence of ENSO variability also generates high‐ and low‐pressure anomaly patterns over the Indian Ocean that may be related to unfavourable or favourable ISM, respectively, while influencing the negative or positive phases of a Pacific Japan (PJ)‐like teleconnection pattern that may be related to unfavourable or favourable KSM, respectively. Therefore, coexisting ENSO forcing may play a dominant role in ISM and KSM, but Greenland sea ice forcing and Eurasian snow variation intensify the out‐of‐phase relationship between ISM and KSM. [ABSTRACT FROM AUTHOR]

The two dominant patterns of the winter (December–February) intraseasonal surface air temperature (SAT) over central Asia is derived by empirical orthogonal function analysis, with the first (mode 1) featuring a regional monopole and the second (mode 2) featuring a northwest–southeast‐orientated dipole. Mode 1 is characterized with warmer (colder) Arctic and colder (warmer) Eurasia along with an anomalous high (low) over the Ural Mountains, while mode 2 is characterized with northwest–southeast dipole over Eurasia along with wave train‐like atmospheric circulation anomalies from the western Atlantic to Asia. Whether the two intraseasonal modes are modulated by lower‐boundary forcing is then investigated, and the results suggest that mode 1 is significantly modulated by sea ice concentration over the Greenland Sea, but by central‐Pacific ENSO for mode 2. Finally, the underlying mechanisms are diagnosed, and the results suggest that the diabatic heating related with decreased sea ice in Greenland Sea induce a positive height anomaly over Urals which favours the formation of Ural blocking and therefore tends to intensify the occurrence of mode 1. Also, central‐Pacific El Niño excites the Pacific–North American teleconnection, which alters North Atlantic subtropical jet extension, favours intensified energy conversion to intraseasonal wave train and subsequently intensifies the occurrence of mode 2. This study highlights the joint role of Arctic sea ice and the SST in the tropical central Pacific. [ABSTRACT FROM AUTHOR]

Greenland halibut (Reinhardtius hippoglossoides) sustain one of the most lucrative fisheries in the eastern Canadian Arctic and Labrador Sea. This species also plays an important role in food web connectivity and benthic–pelagic coupling. Despite the relatively rich knowledge of this species, R. hippoglossoides ecology in these specific areas remains poorly understood. The main aim of this study was to characterize the diet of this deepwater fish in the Labrador Sea and Davis and Hudson Straits and characterize the predator–prey relationship with northern shrimp (Pandalus borealis), another commercially important species in the region. Stomach contents analyses were conducted on 1199 fish captured from 2018 to 2020. Small specimens (<20 cm) fed on invertebrates, whereas larger individuals (>60 cm) fed primarily on fish, indicative of size‐related changes in diet composition. The relative abundance of Pandalus shrimp species in the environment was reflected in the diet. Location appeared to be the most influential variable on feeding patterns. Distinct oceanographic conditions among areas, resulting in differences in prey availability, could explain these results. Arctic cod (Boreogadus saida) and redfish (Sebastes sp.) were selected in locations where fish prey were the most abundant. These results shed light on the opportunistic nature of R. hippoglossoides and its preference for fish at large size. With the rapidly changing oceanographic conditions of Arctic waters, a distributional change in the biomass of shrimp is expected. Results suggest that an increase in abundance of predatory groundfish species in the system (e.g., Sebastes sp.) could lead to acute predation on shrimp and competition with R. hippoglossoides. By revealing key trophic links within the demersal ecosystem, this work provides valuable information on the development of ecosystem approaches to fisheries management for the region. [ABSTRACT FROM AUTHOR]

High‐resolution records from past interglacial climates help constrain future responses to global warming, yet are rare. Here, we produce seasonally resolved climate records from subarctic‐Canada using micron‐scale measurements of oxygen isotopes (δ18O) in speleothems with apparent annual growth bands from three interglacial periods—Marine Isotope Stages (MIS) 11, 9, and 5e. We find 3‰ lower δ18O values during MIS 11 than MIS 5e, despite MIS 11 likely being warmer. We explore controls on high‐latitude speleothem δ18O and suggest low MIS 11 δ18O values reflect greater contribution of cold‐season precipitation to dripwater from longer annual ground thaw durations. Other potential influences include changes in precipitation source and/or increased fraction of cold‐season precipitation from diminished sea ice in MIS 11. Our study highlights the potential for high‐latitude speleothems to yield detailed isotopic records of Northern Hemisphere interglacial climates beyond the reach of Greenland ice cores and offers a framework for interpreting them. Plain Language Summary: Few climate records pre‐dating the last ice age exist from high‐latitude North America, which inhibits our understanding of how regions with permafrost responded to past warming and how they might change in the future. Here, we help fill this data gap by using six speleothems (cave mineral deposits) from a cave in the Northwest Territories, Canada to produce climate records that span thousands of years during former warm periods of Earth's history. We find that speleothems that grew during an exceptionally warm super‐interglacial period 400,000 years ago have 3‰ lower oxygen isotope (δ18O) values compared to those that grew during a likely cooler interglacial 125,000 years ago. We explore potential explanations for the difference in δ18O across interglacials, and suggest that lower δ18O values during warmer periods reflect greater infiltration of cool‐season precipitation with longer annual ground thaw durations. This study highlights the importance of high‐latitude speleothems to provide detailed climate records beyond the range available from Greenland ice cores. Key Points: Long high‐latitude terrestrial climate records are rare in the Northern HemisphereHigh‐latitude speleothems can provide ultra‐high‐resolution climate records beyond the reach of Greenland ice coresMean oxygen isotopes of Arctic and subarctic speleothems likely are controlled by annual ground thaw durations [ABSTRACT FROM AUTHOR]

Greenland's marine‐terminating glaciers connect the ice sheet to the ocean and provide a critical boundary where heat, freshwater, and nutrient exchanges take place. Buoyant freshwater runoff from inland ice sheet melt is discharged at the base of marine‐terminating glaciers, forming vigorous upwelling plumes. It is understood that subglacial plumes modify waters near glacier fronts and increase submarine glacier melt by entraining warm ambient waters at depth. However, ocean observations along Greenland's coastal margins remain biased toward summer months which limits accurate estimation of ocean forcing on glacier retreat and acceleration. Here, we fill a key observational gap in northwest Greenland by describing seasonal hydrographic variation at glacier fronts in Melville Bay using in situ observations from moorings deployed year‐round, CTDs, and profiling floats. We evaluated local and remote forcing using remote sensing and reanalysis data products alongside a high‐resolution ocean model. Analysis of the year‐round hydrographic data revealed consistent above‐sill seasonality in temperature and salinity. The warmest, saltiest waters occurred in spring (April–May) and primed glaciers for enhanced submarine melt in summer when meltwater plumes entrain deep waters. Waters were coldest and freshest in early winter (November–December) after summer melt from sea ice, glacier ice, and icebergs provided cold freshwater along the shelf. Ocean variability was greatest in the summer and fall, coincident with increased freshwater runoff and large wind events before winter sea ice formation. Results increase our mechanistic understanding of Greenland ice‐ocean interactions and enable improvements in ocean model parameterization. Plain Language Summary: Many of Greenland's glaciers terminate in the ocean and form an important boundary between coastal waters and the ice sheet. During summer months, meltwater from the ice sheet flows out below glaciers that terminate in the ocean. The less‐dense meltwater rises to the surface as a plume, increasing near‐glacier ocean mixing and submarine glacier melt. Understanding processes at the glacier‐ocean interface, including how plumes modify nearshore waters, requires sustained observations near glacier termini. However, ocean measurements are largely taken during the summer and do not necessarily represent the total variability observed in the system. Here, we fill an important knowledge gap by presenting year‐round measurements of temperature and salinity near glacier fronts in Northwest Greenland. We found the warmest, saltiest waters in the spring and coldest, freshest waters in early winter at all sites. Warm waters in the spring prime deep glaciers for submarine melt during summer. Increased winds in the fall initiated vertical mixing in nearshore waters before winter sea ice created a surface barrier, stabilizing the water column. Results advance our understanding of the ocean's role in the acceleration and retreat of Greenland's glaciers, which is important for estimating large‐scale ocean circulation and Greenland's ice sheet mass loss. Key Points: Moored hydrographic observations at glacier fronts in NW Greenland revealed consistent above‐sill seasonality in temperature and salinityOcean temperatures reached a maximum in spring, priming deep glaciers for submarine melt during summerRemote forcing supplied the renewal of warm, salty water in the spring and local forcing controlled increased variability in the summer/fall [ABSTRACT FROM AUTHOR]

Projections of sea‐level rise from ice‐sheet shrinkage in a warming world have large uncertainties, linked to limited knowledge of changes at the ocean‐ice sheet interface. This interface most typically is modeled as a grounding line, across which still‐connected ice flows into the ocean to float as an ice shelf, or where icebergs calve from a cliff before the ice begins to float. But, extensive and rapidly increasing evidence shows that this is really a grounding zone, and that processes in this grounding zone omitted from many models could exert major controls on sea‐level rise. Plain Language Summary: Marine‐terminating glaciers flow into the ocean across extensive grounding zones. These kilometers‐long and glacier‐wide zones represent the last broad region of glacier contact with the rock and sediments below before the ice enters the ocean as a floating ice shelf or calved icebergs. Loss of this basal drag along with enhanced basal melting caused by tidally driven seawater intrusion leads to faster outflow and rapid thinning of the overlying ice. As a result of the local thinning, grounding zones retreat inland and sea level rises with more loss of previously grounded ice. Most ice‐sheet models used in sea‐level projections do not include grounding‐zone processes, but rather stop their ice‐ocean interactions at a grounding line. They are thereby omitting important dynamic feedbacks and underestimating future sea‐level contributions from the marine‐based sectors of the Greenland and Antarctic ice sheets. Key Points: Tidally modulated seawater intrusion leads to loss of ice‐bed contact as well as significant (maximal) basal melting within grounding zonesThe future dynamics of marine outlet glaciers are ultimately controlled by coupled processes operating within and through grounding zonesDespite the importance of grounding zones to ice‐sheet dynamics, most ice‐sheet models used in sea‐level projections do not include them [ABSTRACT FROM AUTHOR]

Using two case studies, we analyze the effects of explicitly resolving polar lows in a global climate model (ICON‐Sapphire) with a high resolution of 2.5 km on the upper ocean and sea ice. We aim to understand the mechanism of how polar lows form in a global coupled model and how they interact with the upper ocean and sea ice. When polar lows form at the sea ice edge, they induce marine cold air outbreaks that lead to large heat loss from the ocean. This heat loss contributes to dense water formation in the Iceland and Greenland Seas, which replenishes the climatically important Denmark Strait Overflow Water (DSOW). The high wind speeds of polar lows open leads and polynyas in the sea ice cover, such as the Sirius Water Polynya in northeastern Greenland. Heat loss in polynyas is compensated for by the formation of new ice, and the rejected brine densifies the water on the Greenland shelf. In the Labrador Sea, polar lows intensify cold air outbreaks from the sea ice and rapidly deepen the ocean mixed layer. Resolving polar lows and kinematic features in the sea ice improves the realism of climate models, in particular the surface heat loss and the dense water formation in (sub)polar oceans. Plain Language Summary: We show for the first time that resolving polar lows (strong storms over polar oceans) in a global climate model, which has a high resolution of 2.5 km, leads to strong heat loss from the ocean near the sea ice edge and from leads and polynyas, which are open water areas in an otherwise closed ice cover. Heat loss and salt rejection during ice formation contributes to dense water formation along the sea ice margin and in polynyas above the Greenland shelf. Resolving polar lows and kinematic features in the sea ice improves the realism of climate models, in particular the surface heat loss and the dense water formation in (sub)polar oceans. Key Points: First explicit simulation of polar lows in a globally coupled climate simulation with kilometer‐scale (2.5 km) resolution in all componentsPolar lows lead to considerable heat loss from the ocean near the sea ice edge and from leads and polynyas in the sea ice coverPolar lows are important for water mass transformation in the western Iceland and Greenland Seas, in the Labrador Sea, and within polynyas [ABSTRACT FROM AUTHOR]

Two major oceanographic changes have recently propagated through several trophic levels in coastal areas of Southeast Greenland (SEG). Firstly, the amount of drift‐ice exported from the Fram Strait and transported with the East Greenland Current (EGC) has decreased significantly over the past two decades, and a main tipping element (summer sea ice) has virtually disappeared since 2003 leading to a regime shift in oceanographic and ecological conditions in the region. The following 20‐year period with low or no coastal sea ice is unique in the 200‐year history of ice observations in the region, and the regime shift is also obvious in the volume of ice export through the Fram Strait after 2013. In the same period, the temperature of the EGC south of 73.5 N has increased significantly (>2°C) since 1980. Secondly, the warm Irminger Current, which advects warm, saline Atlantic Water into the region, has become warmer since 1990. The lack of pack ice in summer together with a warming ocean generated cascading effects on the ecosystem in SEG that are manifested in a changed fish fauna with an influx of boreal species in the south and the subarctic capelin further north. At higher trophic levels there has been an increase in the abundance of several boreal cetaceans (humpback, fin, killer, and pilot whales and dolphins) that are either new to this area or occur in historically large numbers. It is estimated that the new cetacean species in SEG are responsible for an annual predation level of 700,000 tons of fish. In addition, predation on krill species is estimated at >1,500,000 tons mainly consumed by fin whales. Simultaneously, there has been a reduction in the abundance and catches of narwhals and walruses in SEG and it is suggested that these species have been impacted by the habitat changes. [ABSTRACT FROM AUTHOR]

During the Last Interglacial, approximately 129 to 116 ka (thousand years ago), the Arctic summer climate was warmer than the present, and the Greenland Ice Sheet retreated to a smaller extent than its current state. Previous model‐derived and geological reconstruction estimates of the sea‐level contribution of the Greenland Ice Sheet during the Last Interglacial vary widely. Here, we conduct a transient climate simulation from 127 to 119 ka using the Community Earth System Model (CESM2), which includes a dynamic ice sheet component (the Community Ice Sheet Model, CISM2) that is interactively coupled to the atmosphere, land, ocean, and sea ice components. Vegetation distribution is updated every 500 years based on biomes simulated using a monthly climatology to force the BIOME4 equilibrium vegetation model. Results show a substantial retreat of the Greenland Ice Sheet, reaching a minimum extent at 121.9 ka, equivalent to a 3.0 m rise in sea level relative to the present day, followed by gradual regrowth. In contrast, a companion simulation employing static vegetation based on pre‐industrial conditions shows a much smaller ice‐sheet retreat, highlighting the importance of the changes in high‐latitude vegetation distribution for amplifying the ice‐sheet response. Plain Language Summary: Arctic summer climates during the Last Interglacial period (approximately 129‐116 thousand years ago) were warmer than the present, and part of the Greenland Ice Sheet likely melted, contributing substantially to global sea‐level rise. Estimates of how much the ice sheet melted range widely. We use a coupled climate model that represents different parts of the Earth system (atmosphere, ocean, sea ice, land) with an evolving Greenland Ice Sheet model to simulate the period from 127‐119 thousand years ago. Our results show that the Greenland Ice Sheet reached its minimum size 121.9 thousand years ago, losing an equivalent of 3.0 m of sea level compared to the present day. We also show that changes in Arctic vegetation distribution during the Last Interglacial have a strong influence on the climate, and therefore how much the Greenland Ice Sheet retreats. Key Points: A simulation from 127 to 119 ka with CESM2‐CISM2 reveals retreat and incipient regrowth of the Greenland Ice Sheet for the Last InterglacialThe Greenland Ice Sheet reaches a minimum extent at 121.9 ka with a contribution of 3.0 m sea‐level equivalent relative to present daySimulated forest and tundra expansion in Canada and Greenland leads to greater warming and ice loss than with a pre‐industrial land cover [ABSTRACT FROM AUTHOR]

Substantial marine, terrestrial, and atmospheric changes have occurred over the Greenland region during the last century. Several studies have documented record‐levels of Greenland Ice Sheet (GrIS) summer melt extent during the 2000s and 2010s, but relatively little work has been carried out to assess regional climatic changes in other seasons. Here, we focus on the less studied cold‐season (i.e., autumn and winter) climate, tracing the long‐term (1873–2013) variability of Greenland's air temperatures through analyses of coastal observations and model‐derived outlet glacier series and their linkages with North Atlantic sea ice, sea surface temperature (SST), and atmospheric circulation indices. Through a statistical framework, large amounts of west and south Greenland temperature variance (up to r2 ~ 50%) can be explained by the seasonally‐contemporaneous combination of the Greenland Blocking Index (GBI) and the North Atlantic Oscillation (NAO; hereafter the combination of GBI and NAO is termed GBI). Lagged and concomitant regional sea‐ice concentration (SIC) and the Atlantic Multidecadal Oscillation (AMO) seasonal indices account for small amounts of residual air temperature variance (r2 < ~10%) relative to the GBI. The correlations between GBI and cold‐season temperatures are predominantly positive and statistically‐significant through time, while regional SIC conditions emerge as a significant covariate from the mid‐20th century through the conclusion of the study period. The inclusion of the cold‐season Pacific Decadal Oscillation (PDO) in multivariate analyses bolsters the air temperature variance explained by the North Atlantic regional predictors, suggesting the remote, background climate state is important to long‐term Greenland temperature variability. These findings imply that large‐scale tropospheric circulation has a strong control on surface temperature over Greenland through dynamic and thermodynamic impacts and stress the importance of understanding the evolving two‐way linkages between the North Atlantic marine and atmospheric environment in order to more accurately predict Greenland seasonal climate variability and change through the 21st century. [ABSTRACT FROM AUTHOR]

Global mean sea level has been rising at a rate of 3.25 ± 0.4 mm yr−1 over 1993–2018. Yet several regions are increasing at a much faster rate, such as the Beaufort Gyre in the Arctic Ocean at a rate of 9.3 ± 7.0 mm yr−1 over 2003–2014. At interannual to decadal time scales, the Beaufort Gyre sea level is controlled by salinity changes due to sea ice melt and wind‐driven lateral Ekman convergence–divergence of freshwater. This study uses recent Greenland discharge and river runoff estimates to isolate and quantify the sea level response to freshwater fluxes variability over the period 1980–2018. It relies on sensitivity experiments based on a global ocean model including sea‐ice and icebergs. These sensitivity experiments only differ by the freshwater fluxes temporal variability of Greenland and global rivers which are either seasonal climatologies or fully time varying, revealing the individual and combined impact of these freshwater sources fluctuations. Fully varying Greenland discharge and river runoff produce an opposite impact on sea level trends over 2005–2018 in the Beaufort Gyre region, the former driving an increase, while the latter, a decrease. Their combined impact leads to a fairly weak sea level trend. The sea level response is primarily driven by salinity variations in the upper 300 m, which are mainly caused by salinity advection involving complex compensations between passive, active, and nonlinear advection. This study shows that including the temporal variability of freshwater fluxes in forced global ocean models results in a better representation of regional sea level change. Plain Language Summary: Sea level is rising globally but not at the same rate everywhere. In the Arctic Ocean, the Beaufort Gyre sea level has been increasing at a fast rate of 9.3 ± 7.0 mm yr−1 over 2003–2014. At long time scales, the Beaufort Gyre sea level change is controlled by salinity, which depends mainly on continental freshwater runoff—particularly high in this region—and sea ice melt. This study uses recent estimates of Greenland discharge and river runoff in a global ocean model. The aim is to isolate and quantify the sea level response of the Beaufort Gyre to freshwater fluxes variability. We compare numerical simulations where Greenland discharge and river runoff are fully varying or set to a repeated seasonal cycle to reveal the individual and combined impacts of the variability of these freshwater sources on regional sea level. Both Greenland discharge and global river runoff impact remotely the Beaufort Gyre sea level. They induce salinity variations in the upper 300 m of the gyre through salinity advection. This study highlights the importance of the variability of continental freshwater fluxes in models in order to better represent regional sea level variability. Key Points: Greenland discharge and river runoff variability contribute to sea level rise and fall in the Beaufort GyreThe positive impact of Greenland is greater than the negative impact of rivers in the 0–78‐m range, and vice versa in the 78–300‐m rangeSea level change in the sensitivity experiments is mostly halosteric with salinity changes mainly controlled by advection [ABSTRACT FROM AUTHOR]

Increased oceanic heat transport plays a key role in the accelerated mass loss of Greenland's marine‐terminating glaciers. The melt rate of major glaciers in Northeast Greenland (NEG) is controlled by ocean variability, in particular warm Atlantic Intermediate Water (AIW), on the continental shelf. A high‐resolution configuration of the ocean sea‐ice model FESOM2.1 is assessed at local and regional scales, and used to investigate the drivers of AIW temperature variability on the NEG continental shelf. The seasonal to decadal variability of AIW is characterized, featuring both pronounced interannual fluctuations and a long‐term warming trend. A major source of AIW is Atlantic Water (AW) originating from the West Spitsbergen Current that recirculates in Fram Strait. AW anomalies are advected westwards and partly control the AIW temperatures on the continental shelf. Increased AIW temperatures are also connected to pronounced northern and central branches of recirculating AW in Fram Strait, and enhanced AW temperatures more regionally. The strengthening of the pathways brings more warmer AIW onto the northern part of the NEG continental shelf. There, it circulates anti‐cyclonically and results in shelf‐wide warming. Regional atmospheric forcing is connected to the changes in the AW circulation. The strengthening of the northern AW branches is likely caused by anticyclonic wind anomalies over the Barents Sea that drive an enhanced northward AW transport in Fram Strait. Thus, controlled by a combination of both upstream and regionally forced circulation conditions, the changes in local AIW temperatures may also affect the oceanic heat transport reaching the Central Arctic Ocean. Plain Language Summary: The Greenland Ice Sheet has been melting at faster rates in the last two decades, likely due to rising ocean temperatures. Warm water found below the glaciers in Northeast Greenland controls the submarine melting. Changes in the temperature of the water are connected to ocean currents on the continental shelf of Northeast Greenland and in Fram Strait. The warm water found under the glaciers originates from the West Spitsbergen Current (WSC), over several hundred kilometers away, which carries warm water northwards within the Arctic Ocean. Part of the current turns westwards and transports the warm water toward Greenland. The changes in the strength of the westward flow are connected with particular wind patterns in the Barents Sea, as the wind forcing impacts the northward transport of the warm water in the WSC. This means that more warm water flows across the continental shelf edge at higher latitudes so there is more warm water circulating on the continental shelf itself. The circulation guides this warm water through a deep channel toward the glaciers. Therefore, the variability of the water temperature below the glaciers in Northeast Greenland is controlled by both regional winds and changes in the upstream ocean currents. Key Points: Warm temperature anomalies in the West Spitsbergen Current partly control Atlantic Water temperatures on the Northeast Greenland continental shelfPronounced northern recirculation branches transport more Atlantic Water across Fram Strait to the northern shelf where it circulatesAnomalous anticyclonic winds over the Barents Sea drive the enhanced recirculation of more northern Atlantic Water pathways [ABSTRACT FROM AUTHOR]

Heat transport via ocean currents can affect the melting of marine‐terminating glaciers in Greenland. Studying past changes of marine‐terminating glaciers allows assessing the regional sensitivity of the Greenland Ice Sheet to ocean temperature changes in the context of a warming ocean. Here, we present a high‐resolution multiproxy marine sediment core study from Skjoldungen Fjord, close to the marine‐terminating Thrym Glacier. Grain‐size data are obtained to reconstruct the calving activity of Thrym Glacier; sortable silt is used as a proxy for fjord water circulation, and sea surface temperatures (SSTs) are reconstructed from alkenone paleothermometry (Uk'37). Measurements of 210Pb, 137Cs, and 14C indicate that the core covers the past 220 years (1796–2013 CE). Comparisons with modeled SST data (Hadley Centre Sea Ice and SST) and instrumental temperatures (International Council for the Exploration of the Sea) suggest that the SST proxy record reflects temperature variability of the surface waters over the shelf and that alkenones are advected into the fjord. Additionally, average temperatures and the amplitude of fluctuations are influenced by alkenones advected from upstream the Irminger Current. We find that the SST record compares well with other alkenone‐based reconstructions from SE‐Greenland and thus features regional shelf water variability. The calving activity as well as the terminus position of Thrym Glacier did not seem to respond to the SST variability. Limited ice‐ocean interactions owing to the specific setting of the glacier would explain this. Instead, the fjord circulation may have been influenced by enhanced meltwater production as well as to larger scale changes in the Atlantic Meridional Overturning Circulation. Key Points: Alkenone‐based sea surface temperature reconstructions reveal common SE‐Greenland shelf variability during the 20th centuryIncreasing ocean temperature did not result in a retreat of Thrym GlacierSortable silt parameters indicate that fjord water column flow is influenced by increased meltwater release and/or shelf water circulation [ABSTRACT FROM AUTHOR]

Greenland's glacial fjords modulate the exchange between the ice sheet and ocean. Subglacial‐discharge‐driven plumes adjacent to glaciers may exert an important influence on fjord water properties, submarine glacier melting and the export of glacially‐modified waters to the shelf. Here we use a numerical plume model in conjunction with observations from proximal to 14 glaciers in northwest Greenland to assess the impact of these plumes on near‐glacier water properties. We find that in late summer, waters emanating from glacial plumes often make up >50% of the fjord water composition at intermediate depths. These plume waters are comprised largely of upwelled Atlantic Water, warming the near‐glacier water profile and likely increasing submarine melting. Our findings demonstrate the key role played by plumes in driving water modification in Greenland's fjords, and the potential for simple models to capture these impacts across a range of settings. Plain Language Summary: Fjords form an important point of contact between the Greenland Ice Sheet and surrounding ocean. Warm ocean waters in these fjords melt the submerged sections of marine‐terminating glaciers, whilst freshwater draining from the ice sheet modifies coastal water properties, impacting ocean circulation. In this study, we use observations of fjord temperature and salinity in combination with numerical modeling to evaluate the mechanisms through which glaciers modify fjord circulation and water properties. Across 14 glaciers in northwest Greenland, we find that the input of glacial meltwater drives the upwelling of warm, deep Atlantic‐origin waters, which mix with the cooler Arctic‐origin waters typically found above ∼250 m depth. These glacially modified waters thus cause a substantial warming of fjord waters relative to those off the coast, a feedback that will amplify the oceanic melting of these glaciers. Key Points: We assess the impact of subglacial‐discharge plumes on water properties proximal to 14 tidewater glaciers in northwest GreenlandIn late summer, waters emanating from glacial plumes often make up >50% of the fjord water composition at intermediate depthsThese plume waters are comprised largely of upwelled Atlantic Water, warming the near‐glacier water profile and likely increasing submarine melting [ABSTRACT FROM AUTHOR]

Mass loss of the Greenland Ice Sheet (GrIS) plays a major role in the global sea level rise. The west coast of the GrIS has contributed 1,000 Gt of the 4,488 Gt GrIS mass loss between 2002 and 2021, making it a hotspot for GrIS mass loss. Surface melting is driven by changes in the radiative budget at the surface, which are modulated by clouds. Previous works have shown the impact of North Atlantic transport for influencing cloudiness over the GrIS. Here we used space‐based lidar cloud profile observations to show that a polar low circulation promotes the presence of low clouds over the GrIS west coast that warm radiatively the GrIS surface during the melt season. Polar low circulation transports moisture and low clouds from the sea to the west of Greenland up over the GrIS west coast through the melt season. The concomitance of the increasing presence of low cloud in fall over the Baffin Sea due to seasonal sea‐ice retreat and a maximum occurrence of Polar low circulation in September results in a maximum of low cloud fraction (∼14% at 2.5 km above sea level) over the GrIS west coast in September. These low clouds warm radiatively the GrIS west coast surface up to 80 W/m2 locally. This warming contributes to an average increase of 10 W/m2 of cloud surface warming in September compared to July on the GrIS west coast. Overall, this study suggests that regional atmospheric processes independent from North Atlantic transport may also influence the GrIS melt. Plain Language Summary: The melting of Greenland plays a major role in the global sea level rise. The west coast of Greenland has contributed to 22% of Greenland mass loss between 2002 and 2021, making it a hotspot for Greenland mass loss. Clouds modulate the energy that reaches the surface of Greenland and, therefore, might accelerate or decelerate surface melt. To explain what leads to cloud presence over Greenland, previous studies focused on the connection between the mid‐latitudes and the Greenland cloud cover. Using a combination of satellite cloud observation and models, we highlight that a low‐pressure system over the Arctic brings moisture and low clouds from the sea west of Greenland to the Greenland west coast. Then, we assess the strong surface warming effect of these low clouds. Overall, our study demonstrates that local Arctic processes lead to formation of low clouds where Greenland melts. Key Points: The Greenland Ice Sheet (GrIS) west coast by itself represents 22% of the GrIS mass loss over the last two decadesA polar low promotes the presence of low clouds over the GrIS west coast during the melt seasonThe cloud surface radiative warming on the Greenland west coast is +10 W/m2 larger in September than July due to these low clouds [ABSTRACT FROM AUTHOR]

Glacial fjord circulation determines the import of oceanic heat to the Greenland Ice Sheet and the export of ice sheet meltwater to the ocean. However, limited observations and the presence of both glacial and coastal forcing—such as coastal‐trapped waves—make uncovering the physical mechanisms controlling fjord‐shelf exchange difficult. Here we use multi‐year, high‐resolution, realistically forced numerical simulations of Sermilik Fjord in southeast Greenland to evaluate the exchange flow. We compare models, with and without a plume, to differentiate between the exchange flow driven by shelf variability and that driven by subglacial discharge. We use the Total Exchange Flow framework to quantify the exchange volume transports. We find that a decline in offshore wind stress from January through July drives a seasonal reversal in the exchange flow increasing the presence of warm Atlantic Water at depth. We also find that including glacial plumes doubles the exchange flow in the summer. Our results show that the plume‐driven circulation is more effective at renewal with a flushing time 1/3 that of the shelf‐driven circulation near the fjord head. Plain Language Summary: Glacial fjords are narrow coastal inlets with a glacier at the landward edge. The flow of water within fjords plays a crucial role in exchanging heat and freshwater between the glacial ice and ocean. The circulation of water is driven, in part, by melting at the ice surface which falls through cracks in the ice and enters the fjord near the sea bed. The meltwater is less dense than ocean water causing it to rise as a plume before leaving the fjord close to the surface. However, fjord circulation is also impacted by storms close to the coast and offshore wind. We used a model of a fjord in Greenland to isolate and study the effects of coastal winds and meltwater on fjord circulation. Our model experiments reveal that weaker than average winds can lead to warmer water within the fjord. Also, we find that the circulation speed doubles with the addition of meltwater and a plume. These results increase our understanding of fjord circulation. Key Points: We present a set of realistically forced, multi‐year numerical simulations of Sermilik Fjord in GreenlandThe shelf‐driven circulation is tied to along‐shelf wind stress and drives a reversal in the exchange flow as winds intensify in SeptemberThe plume‐driven circulation is more effective at renewal with a flushing time 1/3 that of the shelf‐driven circulation near the fjord head [ABSTRACT FROM AUTHOR]

The Northeast Water Polynya is a significant annually recurring summertime Arctic polynya, located off the coast of Northeast Greenland. It is important for marine wildlife and affects local atmospheric and oceanic processes. In this study, over 40 years of observational and reanalysis products (ERA5 and ORAS5) are analyzed to characterize the polynya's climatology and ascertain forcing mechanisms. The Northeast Water Polynya has high spatiotemporal variability; its location, size and structure vary interannually, and the period for which it is open is changing. We show this variability is largely driven by atmospheric forcing. The polynya extent is determined by the direction of the near‐surface flow regime, and the relative locations of high and low sea‐level pressure centers over the region. The surface conditions also impact the oceanic water column, which has a strong seasonal cycle in potential temperature and salinity, the amplitude of which decreases with depth. The ocean reanalyses also show a significant warming trend at all depths and a freshening near the surface consistent with greater ice melt, but salinification at lower depths (∼200 m). As the Arctic region changes due to anthropogenic forcing, the sea‐ice edge is migrating northwards and the Northeast Water Polynya is generally opening earlier and closing later in the year. This could have significant implications for both the atmosphere and ocean in this complex and rapidly changing environment. Plain Language Summary: Polynya's are areas of open water surrounded by sea ice. These features are important for marine wildlife and can impact how the atmosphere and ocean interact. The Northeast Water Polynya is one example from the Arctic. Each summer, it appears off the coast of Northeast Greenland. In this research we use data from the last 40 years to study this polynya. We find that its location, size and structure varies from year to year. The period for which it is open each year also changes. We conclude that these differences are due to changes in the wind direction near the surface. Winds that flow from south to north over the region are linked to a larger polynya. Winds that flow from north to south are linked to a smaller polynya. With climate change, the Northeast Water Polynya is opening earlier and closing later in the year. In the future, this polynya may no longer form as it does now, which will impact the local environment and wildlife. Key Points: A climatological study of the Northeast Water Polynya reveals spatial, interannual and decadal variabilityThe summertime polynya extent closely correlates to near‐surface winds, largely dictated by the orientation of the pressure gradient across Fram StraitBetween 1980 and 2022, the duration of the Northeast Water Polynya, and associated oceanic warming, increased [ABSTRACT FROM AUTHOR]

The Northeast Greenland shelf is a broad Arctic shelf located between Greenland and Fram Strait. It is the principal gateway for sea ice export and sea ice‐associated freshwater from the Arctic Ocean. Sea ice thickness has decreased by 15% per decade since the early 1990s and meteoric freshwater discharge has increased. The consequence of changing sea‐ice and freshwater conditions in the region on ocean dynamics and the biological system remains unknown. Determining the source(s) of freshwater is important to be able to understand how the area will react to future upstream change. Here we present a synoptic survey of the Northeast Greenland shelf and slope with observations of hydrography, the nutrients nitrate, phosphate and silicate, and conservative tracers δ18O, δ2H, and total alkalinity during late summer 2017. We compare these to previously published values, including those which identify Pacific and Atlantic water, the Siberian shelf seas, and the six largest Arctic rivers. We show that a major source of freshwater on the Northeast Greenland shelf during late summer 2017 is the Laptev Sea and find no conclusive evidence of Pacific Water. Our observations indicate a direct link between Northeast Greenland hydrology and processes occurring on Eurasian shelves. Plain Language Summary: The Northeast Greenland shelf is a shallow marine environment between Greenland and the adjacent Fram Strait, where a large fraction of the Arctic Ocean freshwater is exported into the North Atlantic. To predict the regional response to climate change, it is important to determine what the remote sources of freshwater on the shelf are and how these influence mixing. We compare the chemistry of the water found at different locations on the shelf with those found in other areas of the Arctic Ocean to determine where it comes from and conclude that most of the water on the Northeast Greenland shelf in late summer of 2017 is from the Laptev Sea, while surface waters have subsequently been modified by sea ice melt. Key Points: Northeast Greenland Winter Water is fresher than in the 1990sThe cold halocline layer is a brine‐enhanced mixture of river discharge and Atlantic WaterThe river discharge is primarily sourced from the Laptev Sea [ABSTRACT FROM AUTHOR]

Observed and model‐projected sea ice loss enhances warming in the Arctic. We investigate to what extent warming on Greenland can be attributed to changes in the sea ice cover in different parts of the Arctic. Using Climate Model Intercomparison Project phase 5 model projections of the future, we perform multilinear regressions to separate the simulated warming on Greenland in two parts; one following global warming and one following regional sea ice changes. This reveals the magnitude and spatial pattern of warming on Greenland, which can be attributed to sea ice loss in different Arctic regions. The results indicate that the impact of sea ice loss is largely confined to the coastal parts of Greenland. We find the strongest links to sea ice loss in adjacent regions; remote regions only have a limited impact. Overall, warming attributable to sea ice variability is a minor contribution but can be a dominant signal locally in coastal regions. Plain Language Summary: The observed decline of the Arctic sea ice cover is projected to continue with continued global warming. Sea ice loss contributes to amplified warming in the Arctic region, which could increase melting on the Greenland Ice Sheet and thereby contribute to global sea level rise. Here, we study the long‐term warming impact from sea ice loss using data from 10 climate models covering the period 1850–2300. Our aim is to isolate the warming contribution from sea ice loss and study how it varies across Greenland for sea ice loss in different parts of the Arctic. The results indicate that sea ice loss occurring near Greenland has a warming impact along the adjacent coasts but only a limited impact on the central, more elevated ice sheet. Sea ice loss occurring in more remote parts of the Arctic has no substantial impact on Greenland. Finally, our analysis suggests that sea ice loss provides a minor contribution to Greenland warming overall, but it can be a dominant effect locally in coastal areas. Key Points: Warming in coastal parts of Greenland can in part be attributed to nearby sea ice lossOnly a limited part of the warming on central Greenland can be attributed to sea ice lossSea ice loss in more remote regions has a minor impact on Greenland warming [ABSTRACT FROM AUTHOR]

Sediment cores from 13 lakes in a 1500 km transect along the eastern North American Arctic contain up to four superposed stratified interglacial units. All 13 lakes contain one unit with sediment similar in character and mass to Holocene gyttja, with 14C ages >40 ka, luminescence ages 90 to 120 ka, and pollen assemblages that require nearly complete Laurentide deglaciation, supporting a Last Interglacial (LIG; MIS 5e) age. Two lakes preserve an older interglacial, with luminescence ages suggesting an MIS 7 age. Four adjacent lakes record a thin, stratified organic unit between the LIG and Holocene units with 14C ages >50 ka, that is probably from late in MIS 5. Temperature estimates from biotic proxies suggest LIG summer temperatures 4–6°C above mid‐20th century values; pollen, chironomids and DNA document a poleward expansion of woody plants and invertebrate species during the LIG, supporting arguments that positive feedbacks native to the Arctic amplified insolation‐driven summer temperature increases. The stratigraphic succession implies the Laurentide Ice Sheet remained intact with sea level below ‐40 m from ~115 ka to ~11 ka, and places new constraints on the interpretation of cosmogenic radionuclide inventories in erratic boulders older than the Holocene throughout this region. [ABSTRACT FROM AUTHOR]

During the past four decades significant decrease in Arctic sea ice and a dramatic ice mass loss of the Greenland Ice Sheet (GIS) has been coincident with global warming and an increase in atmospheric CO2. In Northeast Greenland significant mass loss from the outlet glaciers Nioghalvfjerdsbræ (79NG) and Zachariæ Isstrøm (ZI) and intensive seasonal breakup of the local Norske Øer Ice Barrier (NØIB) have also been observed since 2000. In order to better understand the processes driving these modern changes, studies of paleoclimate records are important and of major societal relevance. A multiproxy study including organic‐biogeochemical and micropaleontological proxies was carried out on a marine sediment core recovered directly in front of 79NG. Data from Core PS100/270 evidenced a strong inflow of warm recirculating Atlantic Water across the Northeast Greenland shelf from the early Holocene between ~10 and 7.5 ka. An overall high in phytoplankton productivity occurred within a stable sea ice margin regime, accompanied by 79NG retreat most probably triggered by peak solar insolation and changes in the local ocean circulation. Enhanced basal melt of the underside of 79NG at ~7.5 ka then led to the total disintegration of the ice shelf. The released freshwater would have driven water column stratification and promoted the formation of the local landfast ice barrier, which is shown by lowered biomarker values and foraminifera abundances toward the end of the early Holocene. Near perennial sea ice conditions with short summers and 79NG retreat to the inner fjord then prevailed from ~7.5 to ~0.8 ka. Key Points: Multiproxy record allowed reconstruction of NEG ice sheet retreat and sea ice history from the last deglaciation to the late HoloceneIncreased inflow of warm recirculating Atlantic Water linked to retreat and disintegration of the 79NG between 10 and 7.5 kaExtended to even perennial sea ice conditions were predominant on the inner NE Greenland shelf since 7.5 ka [ABSTRACT FROM AUTHOR]

The presence of warm Atlantic water on the Greenland continental shelf has been connected to the accelerated melting of the Greenland Ice Sheet, particularly in the southwest and southeast shelf regions. Results from two high‐resolution coupled ocean‐sea ice simulations that utilized either the 1/10° Parallel Ocean Program (POP) or the 1/12° HYbrid Coordinate Ocean Model (HYCOM) are used to understand the flux of heat on and off the southern Greenland shelf. The analysis reveals that the region of greatest heat flux onto the shelf is southeast Greenland. On the southwestern shelf, heat is mainly exported from the shelf to the interior basins. We identify differences in the shelf break current structure and on‐shelf heat content between the two simulations. Just south of the Denmark Strait, there is a seasonally persistent pattern of multi‐day variability in the cross‐shelf heat flux in both simulations. In the POP simulation, this high‐frequency signal results in net on‐shore heat flux. In the HYCOM simulation, the signal is weaker and results in net off‐shelf heat flux. This variability is consistent with Denmark Strait Overflow eddies traveling along the shelf break. Plain Language Summary: Melting of the Greenland Ice Sheet has been accelerating in recent decades because of rising ocean and air temperatures. Warm ocean water in the deep basin from the subtropical North Atlantic is separated from the ice sheet margin (glacier termini in the Greenland fjords) by the shallower continental shelf region. In this study we compare two simulations of the ocean and sea ice that represent the currents and eddying motions around Greenland realistically. We identify how and where heat is moved on and off the southern Greenland shelf and consider the results to be robust when they are common to both simulations. Warm water mainly moves onto the southeast shelf and off the southwest shelf; the currents on the shelf transport the warm water around the southern tip of Greenland. Near the Denmark Strait we identify oscillations in the warm water crossing onto the shelf that are associated with the presence of Denmark Strait Overflow eddies. On average, these eddies move heat onto the shelf in one model and off the shelf in the other. Understanding how warm water reaches the shelf allows us to better understand how the ocean contributes to the melting of the Greenland Ice Sheet. Key Points: Cross‐shelf heat flux is strongest over the southeast continental shelf in both POP and HYCOM ocean modelsDenmark Strait Overflow eddies traveling along the shelf break drive multi‐day oscillations of on‐shelf heat fluxOn‐shelf heat fluxes along the wide sector of the southeast Greenland shelf are associated with the mean flow in HYCOM and eddies in POP [ABSTRACT FROM AUTHOR]

The Greenland ice sheet is expected lose at least 90% of its current volume if ice sheet summer temperatures warm by around 1.8 °C above pre‐industrial. Geoengineering by stratospheric sulfate aerosol injection might slow Greenland ice sheet melting and sea level rise by reducing summer temperature and insolation; however, such schemes could also reduce precipitation and affect large‐scale climate drivers such as the Atlantic Meridional Over‐turning Circulation (AMOC). Earlier work found that AMOC increased under geoengineering and that might lead to greater mass loss from Greenland than under greenhouse gas forcing alone. We simulated Greenland ice sheet climates using four Earth system models running the stratospheric sulfate aerosol injection experiment GeoMIP G4 and the CMIP RCP4.5 and RCP8.5 greenhouse gas scenarios that were then used to drive the surface energy and mass balance model, SEMIC. Simulated runoff is 20% lower under G4 than RCP4.5, while under RCP8.5 it is 17% higher. The mechanism is through increased Arctic sea ice concentration and reduced humidity leading to surface cooling of the ablation zone. Reduced absorption of outgoing longwave radiation caused by hydrological cycle weakening dominates associated decreases in precipitation under geoengineering and stronger AMOC than under RCP4.5. An ice dynamics model simulates 15% lower ice losses under G4 than RCP4.5. Thus, total sea level rise by 2070 from the Greenland ice sheet under G4 geoengineering is about 15–20% lower than under the RCP4.5 scenario. Plain Language Summary: Mass loss from the Greenland ice sheet is expected to raise sea levels by tens of centimeters this century and far more in the further future. Rising seas are one of the most damaging aspects of the warming climate, affecting hundreds of millions, and costing $ trillions by 2100, and geoengineering might be one approach that could be used against this threat. But the North Atlantic climate is a complex region where the flux of warm tropical waters is being reduced by greenhouse warming, which geoengineering would reverse. Hence, how Greenland would likely respond is a key factor in deciding the potential utility of doing geoengineering. We examine the impact of stratospheric aerosol geoengineering on both the surface ice sheet water runoff (which accounts for half of present‐day ice loss) and the dynamic loss of ice from fast‐flowing glaciers that are being accelerated by warming ocean currents (accounting for the other half). We find that aerosol injection equivalent to about ¼ Pinatubo volcanic eruption per year can slow mass loss from Greenland by 15–20% compared with greenhouse gas forcing alone, mainly due to reduced surface melting. Key Points: We examine the impact of stratospheric aerosol geoengineering on both the surface ice sheet water runoff and the dynamic loss of iceAerosol injection of ¼ 1991 Pinatubo volcanic eruption per year slows mass loss by 15–20% mainly due to reduced surface meltingIncreased Arctic sea ice and reduced humidity cool the ablation zone sufficiently to overcome a slightly increased AMOC relative to RCP4.5 [ABSTRACT FROM AUTHOR]

The calving of glaciers regularly produces tsunami‐like waves that pose a serious threat to coastal environments. Those strong waves are not only able to move ice mélange and redistribute icebergs, growlers, or sea ice across a fjord but also flood and remodel neighbouring cliffs and beaches. Here, we analyze over 90 years (1929–2023) of coastal zone changes that occurred in front of Eqip Sermia. We show that calving waves play a dominant role in transforming the lateral moraine and forming a beach and spit system south of the glacier front. Part of the former moraine has transformed into a boulder‐dominated spit, which closed the lagoon over the years. By multidecadal analysis, we also detected a significant erosion of unconsolidated cliffs located on the opposite side of the bay (~0.53 m per year between 1985 and 2023). In addition, we demonstrate that even a single event (one calving wave) can remodel a beach surface by entrainment of up to 1.8‐m‐diameter boulders and the erosion of the beach surface by washing away sand and gravel from rocky outcrops. Our study constitutes important progress toward modes of paraglacial coastal evolution in regions characterized by rapidly retreating calving glaciers. [ABSTRACT FROM AUTHOR]

Humboldt Gletscher is a 100‐km wide, slow‐moving glacier in north Greenland which holds a 19‐cm global sea level equivalent. Humboldt has been the fourth largest contributor to sea level rise since 1972 but the cause of its mass loss has not been elucidated. Multi‐beam echo sounding data collected in 2019 indicate a seabed 200 m deeper than previously known. Conductivity temperature depth data reveal the presence of warm water of Atlantic origin at 0°C at the glacier front and a warming of the ocean waters by 0.9 ± 0.1°C since 1962. Using an ocean model, we reconstruct grounded ice undercutting by the ocean, combine it with calculated retreat caused by ice thinning to floatation, and are able to fully explain the observed retreat. Two thirds of the retreat are caused by undercutting of grounded ice, which is a physical process not included in most ice sheet models. Plain Language Summary: Humboldt Gletscher is the widest glacier in Greenland, slow moving, and terminating in shallow waters in its southern half, but grounded 200 m deeper than previously known in its northern half, with a submarine trough extending more than 100 km inland. The glacier has been retreating at 0.6 km/year and contributing significantly to sea level rise. We attribute the retreat to undercutting of grounded ice by warmer ocean waters combined with a retreat caused by ice thinning to floatation sooner due to glacier speed up. The glacier, which hosts an ice volume equivalent to a 19‐cm global sea level, will remain a major contributor to sea level rise this Century. Key Points: The 100‐km wide Humboldt Gletscher holds a 19‐cm sea level rise equivalent, lost 161 billion tons of mass, and retreated 13 km since 1972Warm waters at 0°C flood a 350–400 m deep trough on its northern flank that remains below sea level more than 100 km inlandWe explain the glacier retreat as 70% from ocean‐induced undercutting and 30% from thinning‐induced retreat [ABSTRACT FROM AUTHOR]

Stable oxygen isotope records from central Greenland suggest disproportionally large long‐term surface air temperature (SAT) variability during the Last Glacial Maximum (LGM) relative to preindustrial times. Large perturbations in mean atmospheric circulation and its variability forced by extensive Northern Hemisphere ice sheet coverage have been suggested as cause for the enhanced Greenland SAT variability. Here, we assess the factors driving Greenland SAT variability during the LGM by means of dedicated climate model simulations and find remote forcing from the Pacific of critical importance. Atmospheric teleconnections from the Interdecadal Pacific Oscillation (IPO), a multidecadal oscillation of sea surface temperature in the Pacific Ocean, strongly intensify under LGM conditions, driving enhanced surface wind variability over Greenland, which in turn amplifies SAT variability by anomalous atmospheric heat transport. A major role of the IPO in forcing Greenland SAT variability also is supported by a number of models from the Paleoclimate Modeling Intercomparison Project Phase III. Plain Language Summary: Stable oxygen isotope records, a proxy for the local surface air temperature (SAT), from central Greenland indicate disproportionally large reductions in the multidecadal variability from the Last Ice Age (Last Glacial Maximum, LGM; about 21,000 years before present) to modern times. A climate model simulates the changes in multidecadal Greenland SAT variability as inferred from the proxy data. The enhanced variability during the LGM is largely remotely driven by the Interdecadal Pacific Oscillation (IPO), a multidecadal oscillation of sea surface temperature (SST) in the Pacific Ocean. Atmospheric teleconnections from the IPO strongly intensify under glacial conditions, driving enhanced surface wind variability over Greenland and through atmospheric heat transport the SAT variability. Key Points: Oxygen isotope records and climate modeling show large reductions in Greenland surface temperature variability from the LGM to modern timesAtmospheric teleconnections from the Interdecadal Pacific Oscillation intensify under glacial conditionsGreenland surface temperature is forced by atmospheric heat transport and sea ice linked to the Interdecadal Pacific Oscillation [ABSTRACT FROM AUTHOR]

Along the coastal areas of northwest Greenland, sea ice is crucial to people's livelihoods. People in the region have long depended on hunting marine mammals such as seals; walrus; narwhal, beluga, fin, and minke whales; and polar bears, as well as fishing for fjord cod, Greenland halibut, salmon, and Arctic char. Terrestrial animals such as reindeer and Arctic foxes have also been of some importance, as have musk ox in some areas. However, the effects of a changing climate on the marine environment are stark, immediate, and tangible. Ice is melting, and coastal waters are warming. Sea ice, glaciers, coastlines, and seas have become sites and objects for new forms of environmental governance shaped by ideas of unique and fragile ecosystems under threat at a moment of planetary crisis. Conservation organizations frame the Arctic as a zone of climate change crisis and have launched campaigns—underpinned by narratives of ruination—to protect what are termed last areas of ice. However, Inuit organizations are also working to ensure that environmental governance and conservation policymaking do not exclude local communities in the region and are campaigning for protected marine areas in which wildlife management systems and community‐based monitoring take note of indigenous rights and incorporate indigenous knowledge. This article is categorized under: Science of Water > Water and Environmental ChangeHuman Water > Rights to WaterHuman Water > Water GovernanceWater and Life > Conservation, Management, and Awareness [ABSTRACT FROM AUTHOR]

Greenlandic fjords, located between the ice sheet and the ocean, are dynamic systems that can sustain highly variable levels of primary productivity and are sensitive to climate change. In our current climate trajectory, meltwater discharge is expected to significantly increase but its long‐term effects on fjord productivity are still poorly constrained. Paleo‐archives can offer valuable insights into long‐term effects. Here, we present two marine sediment core records from Nuup Kangerlua, Southwest Greenland. Our goal is to better understand to what extent, and on what time‐scales, climate fluctuations and associated glacier dynamic changes have impacted fjord productivity over the past ca. 3300 years. Our multiproxy records include diatom fluxes and assemblage composition, sediment biogeochemistry, and grain‐size distribution. Our study reveals that fjord productivity is tightly linked to regional climate variability; relatively higher productivity levels coincided with mild climate periods whereas the climate cooling of the last millennium led to a decrease in productivity. The diatom records suggest that lower productivity is associated with shorter or less intense summer blooms, increased sea‐ice cover and/or a stratified water column. Diatom assemblages demonstrate cold sea‐surface conditions around 1600 CE that might be linked to local advance of glaciers. Cold conditions and decreasing productivity culminated at 1850 CE, when glaciers in the fjord retreated and high glacial meltwater discharge would have altered the fjord hydrography, likely leading to limited nutrient availability. Our long‐term records support the idea that changing climate and cryosphere conditions have a non‐linear impact on the productivity of Greenlandic fjords. Key Points: Diatom assemblages record multiannual to multidecadal changes in the timing, magnitude, and composition of phytoplankton bloomsFjord productivity is linked to climate variability and to associated changes in marine‐terminating glaciersHigher fjord productivity coincided with warmer climate periods while the lowest productivity was recorded at the end of the Little Ice Age [ABSTRACT FROM AUTHOR]

We mapped the terminus position for every marine‐terminating glacier in the Northern Hemisphere for 2000, 2010, and 2020, including the Greenland Ice Sheet, to provide the first complete measure of their variability. In total, these 1,704 glaciers lost an average of 389.7 ± 1.6 km2 a−1 (total 7,527 ± 31 km2) from 2000 to 2020 with 123 glaciers becoming no longer marine‐terminating over this period. Overall, 85.3% of glaciers retreated, 2.5% advanced, and the remaining 12.3% did not change outside of uncertainty limits. Outlet glaciers of the Greenland Ice Sheet are responsible for 61.9% of total area loss, although their rate of retreat was 34% less in 2010–2020 than 2000–2010. Glaciers with the largest area loss terminate in ice shelves or ice tongues, are surge‐type, have an unstable basal geometry, or have an unusually wide calving margin. Plain Language Summary: North of the equator, 1,704 glaciers touched the ocean in 2000. Here, we present the first analysis to document the frontal position of every one of these glaciers in 2000, 2010, and 2020. We found that 85.3% retreated and are now reduced in area. Only 2.5% of glaciers advanced or increased in area. The remaining 12.3% did not change within uncertainty limits. Total area losses were 389.7 ± 1.6 km2 per year (total 7,527 ± 31 km2) over the 20‐year period. Glaciers flowing from the Greenland Ice Sheet accounted for over 60% of total area losses. We found wide variations in the response of glaciers to similar changes in air and ocean temperature and sea ice concentrations, showing that environmental conditions alone cannot explain why some glaciers retreated more than others. Instead, unique glacier characteristics are the most important factor in controlling the variability of terminus retreat. Glaciers with floating ice at their front (ice shelves or ice tongues), those that undergo periodic changes in their flow velocity (surges), those which have a weak connection to their beds, and glaciers that are unusually wide, experienced the largest area loss from 2000 to 2020. Key Points: There were 1704 marine‐terminating glaciers in 2000 in the Northern Hemisphere, of which 85.3% retreated and 2.5% advanced from 2000 to 2020Tidewater glaciers lost a total area of 7,527 ± 31 km2 from 2000 to 2020, with the Greenland Ice Sheet responsible for 61.9% of total lossesVariations in retreat are best explained by glacier characteristics: ice shelves/tongues, surging, basal geometry, and calving width [ABSTRACT FROM AUTHOR]

Increased freshwater input to the Subpolar North Atlantic from Greenland ice melt and the Arctic could strengthen stratification in deep convection regions and impact the overturning circulation. However, freshwater pathways from the east Greenland shelf to deep convection regions are not fully understood. We investigate the role of strong wind events at Cape Farewell in driving surface freshwaters from the East Greenland Current to the Irminger Sea. Using a high‐resolution model and an atmospheric reanalysis, we identify strong wind events and investigate their impact on freshwater export. Westerly tip jets are associated with the strongest and deepest freshwater export across the shelfbreak, with a mean of 37.5 mSv of freshwater in the first 100 m (with reference salinity 34.9). These wind events tilt isohalines and extend the front offshore, especially over Eirik Ridge. Moderate westerly events are associated with weaker export across the shelfbreak (mean of 15.9 mSv) but overall contribute to more freshwater export throughout the year, including in summer, when the shelf is particularly fresh. Particle tracking shows that half of the surface waters crossing the shelfbreak during tip jet events are exported away from the shelf, either entering the Irminger Gyre, or being driven over Eirik Ridge. During strong westerly wind events, sea ice detaches from the coast and veers toward the Irminger Sea, but the contribution of sea ice to freshwater export at the shelfbreak is minimal compared to liquid freshwater export due to limited sea ice cover at Cape Farewell. Plain Language Summary: The Atlantic circulation brings warm surface waters from the tropics to the poles, where deep, cold waters are formed and brought back to the tropics, thus redistributing heat across the Atlantic. Climate change leads to increased melt of the Greenland ice sheet and a freshening of the Arctic Ocean. If this additional freshwater reaches regions where deep waters are formed, it could weaken this deep water formation and consequently the Atlantic circulation. Since this could lead to large‐scale climate impacts, we need to better understand the pathways between freshwater sources and these regions. The present study investigates wind‐driven freshwater export from the east Greenland shelf to the Irminger Sea, southeast of Greenland. We find that strong westerly winds are associated with surface waters export offshore, with part of the exported waters entering the Irminger Sea. How much freshwater enters the Irminger Sea and the possible impact on deep water formation are subject to further research. Key Points: Westerly winds at Cape Farewell drive enhanced transport of surface waters across the shelfbreak and extend the salinity front offshoreWesterly tip jets lead to the strongest export and can impact the water column up to 100 m deep, especially over Eirik RidgeSea ice at Cape Farewell veers eastwards in response to westerly winds, but export at the shelfbreak is minimal compared to liquid export [ABSTRACT FROM AUTHOR]

The ultimate demise of the Laurentide Ice Sheet (LIS) and the preceding and succeeding oceanographic changes along the western Labrador Sea offer insights critically important to improve climate predictions of expected future climate warming and further melting of the Greenland ice cap. However, while the final disappearance of the LIS during the Holocene is rather well constrained, the response of sea ice during the resulting meltwater events is not fully understood. Here, we present reconstructions of paleoceanographic changes over the past 9.3 Kyr BP on the northwestern Labrador Shelf, with a special focus on the interaction between the final meltwater event around 8.2 Kyr BP and sea ice and phytoplankton productivity (e.g., IP25, HBI III (Z), brassicasterol, dinosterol, biogenic opal, total organic carbon). Our records indicate low sea‐ice cover and high phytoplankton productivity on the Labrador Shelf prior to 8.9 Kyr BP, sea‐ice formation was favored by decreased surface salinities due to the meltwater events from Lake Agassiz‐Ojibway and the Hudson Bay Ice Saddle from 8.55 Kyr BP onwards. For the past ca. 7.5 Kyr BP sea ice is mainly transported to the study area by local ocean currents such as the inner Labrador and Baffin Current. Our findings provide new insights into the response of sea ice to increased meltwater discharge as well as shifts in atmospheric and oceanic circulation. Key Points: Sea ice on the Labrador Shelf mainly follows the solar insolation and meltwater input from the decaying Laurentide Ice SheetSea ice increased following the Lake Agassiz outburst and Hudson Bay Ice Saddle Collapse between 8.5 and 8.2 Kyr BPLow sea ice conditions during the Holocene Thermal Maximum were replaced by an increase following the Neoglacial cooling trend [ABSTRACT FROM AUTHOR]

Climate warming is rapidly reshaping the Arctic cryosphere and ocean conditions, with consequences for sea ice and pelagic productivity patterns affecting the entire marine food web. To predict how ongoing changes will impact Arctic marine ecosystems, concerted effort from various disciplines is required. Here, we contribute multi‐decadal reconstructions of changes in diatom production and sea‐ice conditions in relation to Holocene climate and ocean conditions off northwest Greenland. Our multiproxy study includes diatoms, sea‐ice biomarkers (IP25 and HBI III) and geochemical tracers (TOC [total organic carbon], TOC:TN [total nitrogen], δ13C, δ15N) from a sediment core record spanning the last c. 9,000 years. Our results suggest that the balance between the outflow of polar water from the Arctic, and input of Atlantic water from the Irminger Current into the West Greenland Current is a key factor in controlling sea‐ice conditions, and both diatom phenology and production in northeastern Baffin Bay. Our proxy record notably shows that changes in sea‐surface conditions initially forced by Neoglacial cooling were dynamically amplified by the shift in the dominant phase of the Arctic Oscillation (AO) mode that occurred at c. 3,000 yr BP, and caused drastic changes in community composition and a decline in diatom production at the study site. In the future, with projected dominant‐positive AO conditions favored by Arctic warming, increased water column stratification may counteract the positive effect of a longer open‐water growth season and negatively impact diatom production. [ABSTRACT FROM AUTHOR]

The Iceland and Greenland Seas are a crucial region for the climate system, being the headwaters of the lower limb of the Atlantic Meridional Overturning Circulation. Investigating the atmosphere–ocean–ice processes in this region often necessitates the use of meteorological reanalyses—a representation of the atmospheric state based on the assimilation of observations into a numerical weather prediction system. Knowing the quality of reanalysis products is vital for their proper use. Here we evaluate the surface‐layer meteorology and surface turbulent fluxes in winter and spring for the latest reanalysis from the European Centre for Medium‐Range Weather Forecasts, i.e., ERA5. In situ observations from a meteorological buoy, a research vessel, and a research aircraft during the Iceland–Greenland Seas Project provide unparalleled coverage of this climatically important region. The observations are independent of ERA5. They allow a comprehensive evaluation of the surface meteorology and fluxes of these subpolar seas and, for the first time, a specific focus on the marginal ice zone. Over the ice‐free ocean, ERA5 generally compares well to the observations of surface‐layer meteorology and turbulent fluxes. However, over the marginal ice zone, the correspondence is noticeably less accurate: for example, the root‐mean‐square errors are significantly higher for surface temperature, wind speed, and surface sensible heat flux. The primary reason for the difference in reanalysis quality is an overly smooth sea‐ice distribution in the surface boundary conditions used in ERA5. Particularly over the marginal ice zone, unrepresented variability and uncertainties in how to parameterize surface exchange compromise the quality of the reanalyses. A parallel evaluation of higher‐resolution forecast fields from the Met Office's Unified Model corroborates these findings. [ABSTRACT FROM AUTHOR]