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The Arctic is warming rapidly, significantly reducing the Greenland ice sheet (GrIS) surface mass balance (SMB) and raising its contribution to global sea‐level rise. Since these trends are expected to continue, it is essential to explore the GrIS SMB response to projected climate warming. We compare projections from three polar regional climate models, RACMO, MAR, and HIRHAM, forced by the Community Earth System Model CESM2 under a high‐end warming scenario (SSP5‐8.5, 1970–2099). We reveal different modeled SMB by 2100, including a twofold larger annual surface mass loss in MAR (−1735 Gt/yr) and HIRHAM (−1698 Gt/yr) relative to RACMO (−964 Gt/yr). Discrepancies primarily stem from differences in projected runoff, triggering melt‐albedo positive feedback and subsequent modeled ablation zone expansion. In addition, we find different responses of modeled meltwater production to similar atmospheric warming. Our analysis suggests clear avenues for model developments to further improve SMB projections and contribution to sea‐level rise. Plain Language Summary: We explore how three different polar climate models predict the future surface mass balance (SMB) of the Greenland ice sheet (GrIS), a major contributor to global sea‐level rise. Our results show that SMB projections among these models differ significantly by the end of the century. Differences primarily stem from how models convert meltwater into surface runoff toward the ocean, a crucial SMB component that directly contributes to sea‐level rise. Another key factor is the response of these models to climate warming, substantially affecting future melting rates. Our research highlights the need for further improvements of these climate models. By identifying and understanding the drivers behind model differences, we can improve SMB predictions and better estimate future global sea‐level rise. Key Points: With identical forcing, Greenland Ice Sheet surface mass balance from 3 regional climate models shows a two‐fold difference by 2100Different runoff projections stem from substantial discrepancies in projected ablation zone expansion, and reciprocallyThe response of meltwater production to similar atmospheric warming differs significantly among regional climate models [ABSTRACT FROM AUTHOR]

At least three primary iceberg calving styles have been identified in Greenland: serac collapse, which produces falling icebergs tens of meters in length; slab capsize, which produces rotating icebergs hundreds of meters in length; and tabular rifting, which produces kilometer‐scale icebergs. However, calving styles are mostly undocumented across Greenland. Here, we develop a method to disentangle the sizes of individual calving events and map the dominant calving style at glaciers, using the characteristic properties of step retreats in satellite‐derived terminus positions. At glaciers known to frequently produce calving teleseisms, step retreats greater than 200 m account for >80% ${ >} 80\%$ of net calved length since 2018. In contrast, at glaciers known to calve by serac failure, 200 m step retreats account <20% ${< } 20\%$ of net calving. Thus, terminus change timeseries can offer promising insight into the dominant calving styles at marine‐terminating glaciers. Plain Language Summary: Iceberg calving is ubiquitous at the ocean‐bounded edges of ice sheets. However, not all iceberg calving is the same: at least three distinct mechanisms govern the discharge of solid ice from the Greenland Ice Sheet. We show these are associated with a characteristic range of iceberg sizes. Because calving constitutes a major component of Greenland's continued mass loss, it is important that these distinct mechanisms be understood. We develop a method to identify which calving mechanisms are important at various glaciers. We do so by using satellite observations to estimate the lengths of terminus retreats producing icebergs at individual glaciers. Key Points: Greenland outlet glaciers with different calving styles have different characteristic retreat magnitudes in consecutive satellite imagesAt glaciers which frequently produce calving teleseisms, step retreats in terminus position are dominated by retreats >200 mThe distinct processes underlying different calving styles will likely necessitate several distinct calving laws [ABSTRACT FROM AUTHOR]

Pleistocene Ice Ages display abrupt Dansgaard-Oeschger (DO) climate oscillations that provide prime examples of Earth System tipping points--abrupt transition that may result in irreversible change. Greenland ice cores provide key records of DO climate variability, but gas-calibrated estimates of the temperature change magnitudes have been limited to central and northwest Greenland. Here, we present ice-core δ15N-N2 records from south (Dye 3) and coastal east Greenland (Renland) to calibrate the local water isotope thermometer and provide a Greenland-wide spatial characterization of DO event magnitude. We combine these data with existing records of δ18O, deuterium excess, and accumulation rates to create a multiproxy "fingerprint" of the DO impact on Greenland. Isotope-enabled climate models have skill in simulating the observational multiproxy DO event impact, and we use a series of idealized simulations with such models to identify regions of the North Atlantic that are critical in explaining DO variability. Our experiments imply that wintertime sea ice variation in the subpolar gyre, rather than the commonly invoked Nordic Seas, is both a sufficient and a necessary condition to explain the observed DO impacts in Greenland, whatever the distal cause. Moisture-tagging experiments support the idea that Greenland DO isotope signals may be explained almost entirely via changes in the vapor source distribution and that site temperature is not a main control on δ18O during DO transitions, contrary to the traditional interpretation. Our results provide a comprehensive, multiproxy, data-model synthesis of abrupt DO climate variability in Greenland. [ABSTRACT FROM AUTHOR]

Abstract: Meltwater from the Greenland Ice Sheet can alter the continental shelf/slope circulation and cross-shelf freshwater fluxes and limit deep convection in adjacent basins through surface freshening. We explore the impacts on the West Greenland Current and eastern Labrador Sea with different vertical distributions of the meltwater forcing. In this study, we present the results from global coupled ocean/sea ice simulations, forced with atmospheric reanalysis, that are mesoscale eddy-active (∼2–3-km horizontal spacing) and eddy-permitting (∼6–7-km horizontal spacing) in the study region. We compare the West Greenland Current in mesoscale eddy-active and eddy-permitting without meltwater to highlight the role of small-scale features. The mesoscale eddy-active configuration is then used to assess the change in the eastern Labrador Sea when meltwater is added to the surface or vertically distributed to account for mixing within fjords. In both simulations with meltwater, the West Greenland and West Greenland Coastal Currents are faster than in the simulation with no meltwater; their mean surface speeds are the highest in the vertical distribution case. In the latter case, there is enhanced baroclinic conversion at the shelf break compared to the simulation with no meltwater. When meltwater is vertically distributed, there is an increase in baroclinic conversion at the shelf break associated with increased eddy kinetic energy. In addition, in the eastern Labrador Sea, the salinity is lower and the meltwater volume is greater when meltwater is vertically distributed. Therefore, the West Greenland Current is sensitive to how meltwater is added to the ocean with implications for the freshening of the Labrador Sea. Significance Statement: Our goal is to understand how the flux of freshwater across the West Greenland continental slope into the Labrador Sea is modified by meltwater from the Greenland Ice Sheet. We compare the simulations of the ocean that capture key dynamics along the West Greenland continental slope that have no meltwater, meltwater added to the ocean surface, and meltwater distributed vertically to represent the mixing within fjords. When meltwater is added, the currents along the continental slope are faster, with the greatest increase when meltwater is vertically distributed. In that case, there is enhanced freshening of the Labrador Sea because modified density gradients generate more eddies. Proper representation of the vertical structure of meltwater is important for projecting the impact of freshwater on the subpolar North Atlantic.

Polar ice melt contributes to sea level rise. To understand this contribution, we need to examine the anomalous behaviors leading to significant snowmelts in polar regions, including the Greenland ice sheet. These regions are complex systems where various phenomena are represented by different sets of spatiotemporal data. Such data possess unique characteristics like spatial autocorrelation, heterogeneity, temporal nonstationarity, and multiple scales and resolutions. In this article, we provide a framework to analyze disparate datasets by forming spatial neighborhoods to capture local behaviors. We then perform graph deviation network-based anomaly detection for multivariate datasets within these neighborhoods. Although this study focuses on spatiotemporal data from Greenland as an example, the methodology is intended to be adaptable and relevant to other regions with similar data properties. Specifically, using spatiotemporal data from Greenland, we, first, integrate all subdomain data, including both spatial and temporal data. Second, create neighborhoods to preserve the spatial autocorrelation and heterogeneity present in the data. Third, apply graph deviation networks, a variant of graph neural networks, to locate anomalous regions with respect to snowmelt. We outline our findings in the Greenland region, evaluating anomalous patterns and validating them with ground truth findings from polar science domain experts. Our methodology allows for performing localized analysis on a Greenland-wide scale.

The coastal circulation around Southern Greenland transports fresh, buoyant water masses from the Arctic and Greenland Ice Sheet near regions of convection, sinking, and deep-water formation in the Irminger and Labrador Seas. Here, we track the pathways and fate of these fresh water masses by initializing synthetic particles in the East Greenland Coastal Current on the Southeast Greenland shelf and running them through altimetry-derived surface currents from 1993 to 2021. We report that the majority of waters (83%) remain on the shelf around the southern tip of Greenland. Variability in the shelf-basin exchange of the remaining particles closely follows the number of tip jet wind events on seasonal and interannual timescales. The probability of a particle exiting the shelf increases almost fivefold during a tip jet event. These results indicate that the number of tip jets is a close proxy of the shelf-basin exchange around Southern Greenland. [ABSTRACT FROM AUTHOR]

Introduction Noncommunicable diseases (NCDs) constitute a massive global burden and are the leading cause of death and disability worldwide. In Greenland, the prevalence of NCDs has historically been low. However, during the past approximately 70 years, life circumstances have changed dramatically resulting in increased life expectancy. Today, the proportion of inhabitants in Greenland ≥65 years has nearly tripled since the 1980s, and the prevalence of obesity and diabetes has increased rapidly within the past decades. The aim of this study was to describe the burden of selected NCDs in a primary care setting in Nuuk and compare it to a modern westernized suburban general practice in Denmark.Methods The study was performed as a cross sectional register-based study using data extracted from the electronic medical records (EMR) based on diagnosis codes from inhabitants living in Nuuk, Greenland, and a suburb in Denmark. Estimates of prevalence were age-standardized to the WHO world standard population.Results In both Nuuk and the Danish suburb, the highest prevalence was observed for hypertension (13.2% for both populations), followed by asthma (4.4 and 9.5%, respectively) and diabetes (4.3 and 2.9%, respectively). The age-standardized prevalences of diabetes, COPD, atrial fibrillation, and heart failure, were significantly higher in Nuuk, while seven NCDs including asthma, ischemic heart disease, arthritis urica, psoriasis, hyperthyreosis, hypothyreosis and osteoporosis were significantly higher in the Danish suburb.Conclusion In contrast to the disease pattern observed in Greenland in the last century, the prevalence of diagnosed NCDs in Nuuk is no longer rare. Thus, the overall prevalence of NCDs in the population of Nuuk is now comparable to or even higher than in the suburb in Denmark. This calls for increased focus on all NCDs in the primary healthcare system in Greenland and adaption of the primary healthcare services to a changed disease spectrum.

The surface elevation of the Greenland Ice Sheet is constantly changing due to the interplay between surface mass balance processes and ice dynamics, each exhibiting distinct spatiotemporal patterns. Here, we employ satellite and airborne altimetry data with fine spatial (1 km) and temporal (monthly) resolutions to document this spatiotemporal evolution from January 2003 to August 2023. To estimate elevation changes of the Greenland Ice Sheet (GIS), we utilize radar altimetry data from CryoSat-2 and EnviSat, laser altimetry data from the ICESat and ICESat-2, and laser altimetry data from NASA's Operation IceBridge Airborne Topographic Mapper. We produce continuous monthly ice surface elevation changes from January 2003 to August 2023 on a 1 km grid covering the entire GIS. We estimate cumulative ice loss of 4,352 Gt ± 315 Gt (12.1 ± 0.9 mm sea level equivalent) during this period, excluding peripheral glaciers. Between 2003 and 2023, the ice sheet land-terminating margin underwent a significant cumulative thinning of several meters. Ocean-terminating glaciers exhibited thinning between 20–40 m, with Jakobshavn Isbræ experiencing an exceptional thinning of nearly 70 m. This dataset of fine-resolution altimetry data in both space and time will support studies of ice mass loss and useful for GIS ice sheet modelling. To validate our monthly mass changes of the Greenland ice sheet, we use mass change from satellite gravimetry and mass change from the Input-Output method. On multiannual timescales, there is a strong correlation between the time series, with R values ranging from 0.88 to 0.92. [ABSTRACT FROM AUTHOR]

The Greenland Ice Sheet is highly sensitive to climate change, leading to significant retreat along its edges. This rapid ice loss contributes to rising sea levels and impacts the Earth's climate stability. Understanding the extent of recent glacier retreat is crucial in order to determine if it is unprecedented or within ranges of natural variability. Palaeoenvironmental studies aim to identify past glacial phases and landscape changes using advanced dating methods such as cosmic ray exposure (CRE) dating. In NE Greenland, CRE dating has helped establish the timing of glacial oscillations, yet a comprehensive understanding of glacial fluctuations during specific periods still needs to be developed. This study aims to chronologically constrain the postglacial landscape evolution of two NE Greenland valleys from the Young Sund–Tyrolerfjord area (74°N, 20–25°E) from the onset of deglaciation and throughout the Holocene to better understand glacial and postglacial changes. The chronological framework relies on 27 10Be cosmic‐ray exposure ages that constrain our interpretation of the geomorphological features in both valleys. Inconsistencies were observed in the ages dataset, highlighting potential bias associated with nuclide inheritance and post‐glacial dynamics. Despite limitations, the CRE results confirm the general pattern observed in NE Greenland: (i) major deglaciation and disconnection of glaciers from the main glacial systems during the Lateglacial and Early Holocene with a rapid but not homogeneous deglaciation within the range from ~14.3 to 11.9 ka; (ii) no evidence of glacial activity during the Middle Holocene, probably associated with the withdrawn position of the ice masses’ fronts; and (iii) glacier expansion during the Late Holocene, with a Little Ice Age advance as the last significant period of glacial regrowth. [ABSTRACT FROM AUTHOR]

Given the long response time of ice sheets, simulations of the Greenland ice sheet typically exceed the availability of input climate data to reliably simulate the fast processes underlying surface mass balance. Strong feedback processes are known to make the mass balance sensitive to inter- and intra-annual variability. Even simulations with climate models do not always cover the full period of interest, motivating bridging these gaps using relatively coarsely resolved climate reconstructions or temporal interpolation methods. However, both of these approaches usually only provide information about the climatological average but not variability. We investigate how this simplification impacts the surface mass balance using the BErgen Snow SImulator. The model was run for up to 500 years using the same atmospheric climatology but different synthetic variabilities. While changing inter-annual variations has an impact of less than 5 % on the surface mass balance of the Greenland ice sheet, neglecting intra-annual variability by using a daily climatology causes a 40 % change in mass balance. Decomposing the total effect into contributions from different input variables, the biggest contributor is precipitation followed by temperature. Using a daily climatology, a small amount of snowfall every day overestimates the albedo and thus surface mass balance (SMB). We propose a correction that re-captures the effect of intermittent precipitation, reducing the SMB overestimation to 15 %–25 %. We conclude that simulations of the Greenland surface mass and energy balance should be forced with a transient climate, in particular for models that are calibrated with transient data. [ABSTRACT FROM AUTHOR]

As the only remaining ice sheet in the Northern Hemisphere, the Greenland ice sheet (GrIS) plays a crucial role in influencing atmospheric circulations, particularly with its rapid melting under global warming. In this paper, the influences of GrIS topography and surface thermal conditions are investigated by a series of aquaplanet experiments. The results show that the GrIS topography induces stationary waves and favors more blocking events through the generation of negative potential vorticity (PV) anomalies, while it tends to suppress local storm activities through the induced stationary waves. The surface cooling center of the GrIS is found to strengthen the jet streams by enhancing the meridional temperature gradient and thermal wind, while it causes the PV and static stability to increase during near-Greenland blocking days, thereby disfavoring blocking onset. Altogether, the topography and surface thermal effects of GrIS appear to compete with each other so that the net effect would determine the final response. Nevertheless, nonlinearity is found in both GrIS-topography alone and GrIS-surface temperature alone experiments, where nonlinear responses of atmospheric circulation are detected when the GrIS topography height or surface temperature exceeds their critical values, respectively. Hence, through this study, the response of the blocking in the vicinity of Greenland to the combined effects of topography and surface thermal conditions may shed light on comprehending the underlying mechanism of blocking alteration in a changing climate. Significance Statement: Although there have been numerous observation-based studies showing that the blocking around Greenland has increased over the past few decades, which is a predominant driver in accelerating the Greenland ice sheet (GrIS) melting, the reasons for this change are still unclear. In addition, the impact of GrIS on blocking still needs investigation. Through idealized aquaplanet simulations, this study examines the effect of GrIS's topography and surface thermal conditions upon blocking onset. It suggests the nonlinearity of the blocking response in the vicinity of Greenland to the combined effects in the variation of the height and surface temperature of GrIS. This study will enhance our understanding of possible changes in blocking due to global warming. [ABSTRACT FROM AUTHOR]