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In the Northern Hemisphere, ~1500 glaciers, accounting for 28% of glacierized area outside the Greenland Ice Sheet, terminate in the ocean. Glacier mass loss at their ice-ocean interface, known as frontal ablation, has not yet been comprehensively quantified. Here, we estimate decadal frontal ablation from measurements of ice discharge and terminus position change from 2000 to 2020. We bias-correct and cross-validate estimates and uncertainties using independent sources. Frontal ablation of marine-terminating glaciers contributed an average of 44.47 ± 6.23 Gt a−1 of ice to the ocean from 2000 to 2010, and 51.98 ± 4.62 Gt a−1 from 2010 to 2020. Ice discharge from 2000 to 2020 was equivalent to 2.10 ± 0.22 mm of sea-level rise and comprised approximately 79% of frontal ablation, with the remainder from terminus retreat. Near-coastal areas most impacted include Austfonna, Svalbard, and central Severnaya Zemlya, the Russian Arctic, and a few Alaskan fjords. As glaciers terminate into the ocean, mass is lost through frontal ablation where the ice meets the ocean. Here the authors estimate decadal frontal ablation from 2000 to 2020 of 1496 glaciers in the Northern Hemisphere, and find that frontal ablation makes up 79% of ice discharge to the ocean. [ABSTRACT FROM AUTHOR]

The once-contiguous Ellesmere Ice Shelf, first reported in writing by European explorers in 1876, and now almost completely disintegrated, has rolling, wave-like surface topography, the origin of which we investigate using a viscous buckling instability analysis. We show that rolls can develop during a winter season (~ 100 d) if sea-ice pressure (depth-integrated horizontal stress applied to the seaward front of the Ellesmere Ice Shelf) is sufficiently large (1 MPa m) and ice thickness sufficiently low (1–10 m). Roll wavelength initially depends only on sea-ice pressure, but evolves over time depending on amplitude growth rate. This implies that a thinner ice shelf, with its faster amplitude growth rate, will have a shorter wavelength compared to a thicker ice shelf when sea-ice pressure is equal. A drawback of the viscous buckling mechanism is that roll amplitude decays once sea-ice pressure is removed. However, non-Newtonian ice rheology, where effective viscosity, and thus roll change rate, depends on total applied stress may constrain roll decay rate to be much slower than growth rate and allow roll persistence from year to year. Whether the viscous-buckling mechanism we explore here ultimately can be confirmed as the origin of the Ellesmere Ice Shelf rolls remains for future research. [ABSTRACT FROM AUTHOR]

The physical, sedimentological, mineralogical and elemental geochemical properties of sediment cores AMD1803‐02BC and 01PC from the Cape Norton Shaw Inlet were investigated to reconstruct glacial sediment discharges from southeastern Manson Icefield and document the impact of ice–ocean interactions on the sediment dynamics and opening of the North Water Polynya (NOW) in northwestern Baffin Bay since the last deglaciation. Laminated glaciomarine sediments rich in quartz and feldspar are observed prior to 11 cal. ka BP and were probably deposited by hyperpycnal currents triggered by the local retreat of the southern margin of the Innuitian Ice. Detrital proxies suggest that Early Holocene sediment dynamics were mainly influenced by sea ice and iceberg rafting and meltwater discharges related to the deglaciation of eastern Smith (~11 to 10.65 cal. ka BP) and Jones (~10.7 cal. ka BP) sounds. This also provides an upper limit to the timing of formation of the NOW. The high detrital carbonate contents during 8.8 to 6.6 cal. ka BP confirm that enhanced carbonate‐rich sediment export from Nares Strait to northern Baffin Bay occurred during and after the deglaciation of Kennedy Channel (8.8 to 8.2 cal. ka BP). Canadian Shield sediment inputs have dominated since 6.6 cal. ka BP, indicating that sedimentation is mainly influenced by Cape Norton Shaw glacier discharges. The lower level of sedimentation recorded in core 01PC during the Middle to Late Holocene suggests an accelerated landward retreat of the Cape Norton Shaw glaciers in response to warmer marine conditions. During the Neoglacial period, higher sedimentation rates and detrital proxies in the cores suggest increased glacial erosional processes, probably associated with the long‐term declines in boreal summer insolation and glacier growth. Finally, mineralogical and grain‐size data in core 02BC support the idea that increased Arctic atmospheric temperatures have had an important influence on the glacial dynamics during the industrial period. [ABSTRACT FROM AUTHOR]

Over the last two decades, Trinity, Wykeham, Ekblaw, and Cadogan glaciers have retreated and been identified as the primary sources of iceberg flux from Prince of Wales (POW) Icefield, Ellesmere Island, accounting for ∼83% of total solid ice discharge. In this study, we used a total of 167 Radarsat‐2 Synthetic Aperture Radar scene pairs collected between 2009 and 2019 to derive winter surface velocities of these four major basins of the POW Icefield. Over this period both Cadogan and Ekblaw glaciers underwent multiyear acceleration and deceleration limited to their lower parts, consistent with characteristics of "pulse‐type" glaciers. Trinity and Wykeham glaciers are currently the fastest flowing glaciers in the CAA and are grounded below sea level for ∼40 km up‐glacier from their termini. Both glaciers underwent multiyear repeating periods of velocity acceleration between 2009 and 2019 which coincided with significant thinning at their termini. As of 2017, Trinity and Wykeham were each within ∼10 m of flotation over their lowermost 4 km. We also identified a shift in flow since 2014 on Trinity and Wykeham, after which winter flow rates began to propagate up‐glacier and were nearly identical to flow rates observed throughout the rest of the year, indicating that seasonal variability in flow has become less apparent in recent years. Our findings suggest that Trinity and Wykeham glaciers have transitioned to a flow type dominated by dynamic thinning, which is strongly influenced by subglacial topography and may be susceptible to instability of the glacier front and large‐scale collapse. Plain Language Summary: Trinity, Wykeham, Ekblaw, and Cadogan are the four primary glacier basins on the Prince of Wales (POW) Icefield, and are responsible for the majority of solid ice discharged from it. Previous work on tidewater glacier dynamics in the Canadian Arctic has mainly focused on quantifying surface velocities and ice fluxes to the ocean, but less research has been undertaken on the physical processes controlling variability in glacier flow. Here, we use remote sensing methods to measure changes in ice flow, surface elevation, and terminus buoyancy to identify the processes controlling glacier motion in this region. We find that ice flow of the four major glaciers on the POW Icefield are strongly controlled by their underlying bed topography. Trinity and Wykeham glaciers are two of the fastest flowing glaciers in the Canadian Arctic and appear to have recently entered a period of instability at their termini, which, if they continue at the current rates of thinning, could lead to their large‐scale acceleration, retreat, and collapse. Key Points: We report updated winter velocity and surface elevation change estimates for four major basins on the Prince of Wales IcefieldFlow for Trinity, Wykeham, Cadogan, and Ekblaw glaciers is strongly influenced by bed topographyVelocity changes, surface thinning, and terminus buoyancy resulted in instability and near flotation of the termini of Trinity and Wykeham glaciers [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]

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A total of eight floating glacier tongues have shrunk in area by >85% from the Yelverton Bay region of Northern Ellesmere Island since 1959, with unusually large losses since 2005. To better understand the causes of these losses, this study undertakes the first examination of ice tongue changes in this region, including an assessment of changes in surrounding marine ice (i.e. sea ice, sikussak and mélange), and atmospheric and oceanographic forcings. From 1959 to 2017, the total ice tongue area decreased by 49.07 km2, with the majority of this loss occurring from 2005 to 2009 (34.68 km2). The loss of ice tongues since 2005 occurred when open water replaced multi-year landfast sea ice (MLSI) and first-year sea ice in the regions adjacent to the ice tongues. These changes were accompanied by an increase in mean annual mid-depth (i.e. 100 and 200 m) ocean temperatures from −0.29°C from 1999 to 2005 to 0.67°C from 2006 to 2012. Despite the recent return of ocean temperatures to below pre-2006 levels, atmospheric summer temperatures have continued to rise (+0.15°C decade−1 between 1948 and 2016), with open water continuing to occur. Without the sustained presence of MLSI in this region the ice tongues are unable to stabilize, making it unlikely that they will re-form in the current climate. [ABSTRACT FROM AUTHOR]

Since the 1960s, warming air and sea surface temperatures have led to decreasing sea ice extent and longer periods of open water in the Canadian Arctic Archipelago (CAA), together with changes in glacier discharge patterns. An important question, therefore, is whether there is a relationship between changing sea ice conditions, glacier dynamics, and iceberg production in this region. Using synthetic aperture radar (SAR) (Radarsat-1, Radarsat-2, and ALOS PALSAR) and optical (Landsat 7 and 8) satellite imagery, iceberg plume events and sea ice break-up/freeze-up dates between 1997 and 2015 are investigated for 40 tidewater glaciers around the Prince of Wales (POW) Icefield, Ellesmere Island. Results show a clear relationship between the presence of sea ice and the production of icebergs, with ~49% of total iceberg plume events occurring during the 3–4 month long summer open water season and ~51% of events when sea ice was present the remaining 8–9 months of the year. There is no clear evidence of recent increases in iceberg production on a regional basis, but on a local, individual glacier scale there has been a connection between periods of increased iceberg plume events and: (a) acceleration in the surface velocity of Trinity and Wykeham glaciers; (b) increase in terminus retreat rates for glaciers which have not accelerated in flow speed over the past ~5–10 years. Comparisons with ocean temperature, surface air temperature from NCEP-NCAR reanalysis, and tidal data showed no clear relationship with iceberg plume events. [ABSTRACT FROM AUTHOR]

This study presents detailed observations of calving behavior variability from daily oblique photographs acquired over a five-year period (2007-2011) covering the terminus of Rink Isbræ, a major West Greenland outlet glacier. The evidence suggests that calving at Rink is characterized by two styles with distinct temporal and spatial footprints. The first style is characterized by frequent small magnitude events, which show clear seasonal variability with a marked increase in frequency immediately following ice mélange breakup and a peak in July. The second style is characterized by the sporadic detachment of kilometer-sized tabular icebergs with no clear seasonal signal. We suggest that two sets of mechanisms control calving variability at this location, namely (1) melt-driven processes enhancing submarine undercutting and (2) mechanically driven buoyant flexure. The presence of sea ice and/or ice mélange in the fjord presents an additional factor limiting calving in the winter. [ABSTRACT FROM AUTHOR]

Declining sea ice area in the Canadian Arctic has gained significant attention with respect to the prospect of increased shipping activities. To investigate relationships between recent declines in sea ice area with Arctic maritime activity, trend and correlation analysis was performed on sea ice area data for total, first-year ice (FYI), and multi-year ice (MYI), and on a comprehensive shipping dataset of observed vessel transits through the Vessel Traffic Reporting Arctic Canada Traffic Zone (NORDREG zone) from 1990 to 2012. Links to surface air temperature (SAT) and the satellite derived melt season length were also investigated. Between 1990 and 2012, statistically significant increases in vessel traffic were observed within the NORDREG zone on monthly and annual time-scales coincident with declines in sea ice area (FYI, MYI, and total ice) during the shipping season and on a monthly basis. Similarly, the NORDREG zone is experiencing increased shoulder season shipping activity, alongside an increasing melt season length and warming surface air temperatures (SAT). Despite these trends, only weak correlations between the variables were identified, although a step increase in shipping activity is apparent following the former summer sea ice extent minimum in 2007. Other non-environmental factors have also likely contributed to the observed increase in Arctic shipping activity within the Canadian Arctic, such as tourism demand, community re-supply needs, and resource exploration trends. [ABSTRACT FROM AUTHOR]

For much of the 20th century, multiyear landfast sea ice (MLSI) formed a permanent ice cover in Yelverton Bay, Ellesmere Island. This MLSI formed following the removal of ice shelf ice from Yelverton Bay in the early 1900s, including the well-documented Ice Island T-3. The MLSI cover survived intact for 55-60 years until 2005, when >690 km2 (90%) of MLSI was lost from Yelverton Bay. Further losses occurred in 2008, and the last of the Yelverton Bay MLSI was lost in August 2010. Ground penetrating radar (GPR) transects and ice cores taken in June 2009 provide the first detailed assessment of MLSI in Yelverton Inlet, and indeed the last assessment now that it has all been replaced with first-year ice. A detailed history of ice shelf, glacier, and MLSI changes in Yelverton Bay since the early 1900s is presented using remotely sensed imagery (air photos, space-borne optical, and radar scenes) and ancillary evidence from in situ surveys. Recent changes in the floating ice cover here align with the broad-scale trend of long-term reductions in age and thickness of sea ice in the Arctic Ocean and Canadian Arctic Archipelago. [ABSTRACT FROM AUTHOR]

Synthetic aperture radar (SAR) satellite imagery was used to reconstruct the change in limnological conditions adjacent to an Arctic ice shelf by examining the backscatter values of coastal ice in mid-winter scenes. High SAR backscatter values (>− 6 dB) suggest that an ice-dammed lake was present adjacent to the south coast of Petersen Bay from 1992 until 2005. Following a large calving event of the adjacent Petersen Ice Shelf (− 8.07 km 2 ) in August 2005, the lake drained through a region where the ice shelf had separated from the coastline. This loss of freshwater and replacement of lake ice with sea ice along the southern coast of Petersen Bay were confirmed from analyses of ice core samples and conductivity–temperature–depth (CTD) profiles. The exception to this pattern was one distinct area where terrestrial streams entered the edge of Petersen Bay and freshwater continued to collect from 2006 to 2008. However, this ephemeral area of freshwater has not reformed since 2009 due to the persistence of open water events in Petersen Bay (observed in optical satellite imagery), which likely facilitated mixing of freshwater with sea water. Based on the continued break-ups of Petersen Ice Shelf and the frequency of open water events, it is unlikely that this ice-dammed lake will reform. The results of this study underscore the utility of SAR for reconstructing past hydrographic conditions in the water column below. [ABSTRACT FROM AUTHOR]