Abstract The retreat and acceleration of Greenland’s marine-terminating glaciers are linked to enhanced submarine melting driven by ocean warming. Despite the significance of these ice-ocean interactions, observations of ice-front proximal waters remain limited due to logistical challenges. Buoyant subglacial meltwater plumes entrain deep, warm Atlantic waters during their ascent. Using a plume model, we demonstrate that when these plumes reach the surface in deep fjords (>400 m), their surface temperatures can serve as a proxy for subsurface ocean temperature variability. Here, we optimise and validate a Landsat sea surface temperature algorithm for Arctic waters using in situ measurements, with an accuracy of ∼0.4°C for Landsat 5, 7, 8 and 9. Applying this method, we analyse plume surface temperatures at Sermeq Kujalleq (Store Glacier) from 1985 to 2024 and compare Landsat-derived plume surface temperatures with plume model simulations forced by in situ measurements and four ocean reanalysis products. The Landsat-derived plume surface temperatures are of the correct magnitude and reveal trends consistent with expected interannual ocean variability. While large seasonal variability and confounding physical processes still make it difficult to isolate the subsurface signal, our 40 year record suggests that plume surface temperatures could become a useful proxy for subsurface ocean change.
Abstract The Milne Ice Shelf was, until recently, a relatively stable ice shelf on the north coast of Ellesmere Island. In summer 2020, it underwent a major calving event, losing 43% of its surface area from its northern, ocean edge. A mass balance network across the ice shelf indicates that this calving was preceded by a mean annual surface mass balance of −0.40 ± 0.13 m water equivalent from 2008 to 2019, but with large inland-to-ocean variability. Individual stake measurements indicate that ablation is highest at the rear of the ice shelf, furthest from the ocean, while summer air temperature and shortwave radiation are lower towards the front of the ice shelf, where snow accumulation is greatest. The ice shelf shifts to a state of strongly negative mass balance in years with >200 cumulative positive degree-days, which occurred half the time over the study period. The mass balance gradient may help explain the 2020 calving pattern, as sustained thinning and fracture near the rear of the ice shelf may have reduced structural integrity, weakening the mechanical connection to the seaward section prior to its detachment.
The Canadian Arctic Archipelago constitutes a primary source of contemporary sea-level rise from glaciers and ice caps, yet glacier-scale, multi-decadal records on Baffin and Bylot Islands remain limited. This study reconstructs long-term elevation and volume change for seven glaciers, six in Auyuittuq National Park and one in Sirmilik National Park, using 1958/59 imagery from the Canadian National Air Photo Library. Historical digital elevation models were reconstructed using TanDEM-X for vertical ground control and PlanetScope imagery for horizontal ground control, with ArcticDEM supporting final co-registration and on-ice elevation-change analysis. Uncertainty was quantified from stable-terrain residuals, with normalized median absolute deviation values of 2.08 $2.08$2.08–4.07 $4.07$4.07 m. Specific geodetic mass balances for the Auyuittuq glaciers ranged from minus 0.22 $-0.22$−0.22 to minus 0.35 $-0.35$−0.35 m w.e. aminus 1 $^{-1}$−1 for 1959–2021/22, while Fountain Glacier averaged minus 0.35 $-0.35$−0.35 m w.e. aminus 1 $^{-1}$−1 for 1958–2022. Cumulative ice-volume change totalled minus 4.76 times 109 $-4.76 \times 10^{9}$−4.76×109 m3 $^{3}$3, equivalent to minus 4.05 plus or minus 0.29 $-4.05 \pm 0.29$−4.05±0.29 Gt. Auyuittuq glaciers shortened by 7 $7$7–16 percent sign $16\%$16% and lost 9 $9$9–28 percent sign $28\%$28% of their area. Spatial variability reflects glacier hypsometry, with lower-elevation glacier areas showing greater sensitivity to atmospheric warming. These results provide new glacier-scale geodetic mass-balance estimates for the Canadian Arctic Archipelago based on archival photogrammetry, although density assumptions that omit firn evolution require further refinement when estimating mass change.
Supraglacial lake drainages create spatially finite regions of reduced basal friction, slippery patches, at the ice-bed interface that perturb local stresses in the overlying ice, potentially sufficiently to trigger cascading hydrofracture-driven lake drainage events. We derive analytical solutions for the perturbed stress response to such slippery patches using the shallow shelf approximation and validate these solutions against 2d full-Stokes numerical simulations for Newtonian $n=1$ and Glen $n=3$ rheologies, spanning a range of flow parameters. The stress perturbation magnitude scales as $\rho g \alpha \ell/4$, linear in surface slope $\alpha$ and patch length $\ell$, and decays exponentially into the ice away from the patch over a decay lengthscale $(2Bh/C)^{n/(n+1)}$, dependent on ice thickness $h$, rheological parameters $n, B$, and basal sliding coefficient outside the patch, $C$. The stress decay lengthscale increases with larger ice thickness and smaller basal traction. Combining stress magnitude and decay lengthscale, we define an absolute coupling length as the distance over which the perturbed stress remains above a given threshold, which is largest in the Greenland ablation zone. We discuss implications of these results for the magnitude and spatial reach of stress communication among lake drainage events, especially under a warming climate.
Abstract Sea ice develops a porous structure as impurities from sea water are rejected during freezing. This study revisits factors regulating noble gas inclusion in sea ice and, for the first time, parameterizes the bulk sea ice–sea water partition coefficient ( k iw )—the ratio of concentrations in sea ice to sea water—as a function of ice properties. Ten sea-water freezing experiments were conducted in a gas-tight chamber to quantify gas partitioning. Experimental k iw spanned k iw, helium = 1.31–1.90, k iw, neon = 0.29–1.34, k iw, krypton = 0.12–0.67, k iw, xenon = 0.12–0.66 and k iw, salt = 0.15–0.49, reflecting variations in ice growth rates and properties. Partitioning trends were analyzed against ice temperature, salinity and growth rate ( n = 10) and brine porosity ( n = 8). Bulk sea-ice salinity was the statistically strongest indicator of k iw and predicted >70% of variability in k iw, krypton and k iw, xenon . Doubling ice salinity (e.g. from 5 to 10) increased k iw by 140–150% for krypton and xenon. Neon did not exhibit statistically significant trends in k iw with ice properties, likely due to its small size and low solubility facilitating bubble nucleation and/or crystal lattice inclusion. Gases larger than the ice-Ih cavity radius showed nearly identical k iw , consistent with firn diffusion models.
Abstract Despite advances in global glacier modeling, notable uncertainties remain in part due to model overparameterization. We develop a novel Bayesian inference framework to calibrate the Python Glacier Evolution Model (PyGEM) against spatially distributed surface elevation change data. The utility of this framework is demonstrated using a 1994–2021 airborne laser altimetry record for 185 glaciers in Alaska, which altogether represent over half of the region’s glacier area. Calibration against these data reduces parameter uncertainty by 5–18% and lowers the mean absolute error in hindcast surface elevation change by 0.18 m a −1 (15% compared to prior models). Model projections for these 185 glaciers estimate mass loss ranging from 43 plus or minus $ \pm $ ± 17% to 67 plus or minus $ \pm $ ± 27% depending on the emissions scenario. The projections highlight considerable subregional variability ranging from a median glacier mass loss of 57–99% by the end of the century for Lake Clark, Denali, Kenai Fjords, and Glacier Bay national parks, compared to 28–51% lost for Wrangell–St. Elias National Park and Preserve. As additional spatially distributed elevation change datasets become available in Alaska and elsewhere, the framework presented here is well suited to further refine model calibration and improve projections, while remaining flexible to incorporate additional glacier change observations as they become available.
Abstract If crevasse fields deliver meltwater to the bed of the Greenland ice sheet, it would affect seasonal ice flow speeds and total mass balance. The best current automated tool to map crevasse fields extends only a few dozen kilometers inland. To address this gap, we develop MimiNet, a neural-network-based tool that identifies surface crevasse fields. We train MimiNet on Sentinel-1 scenes across a 629 km 2 area in Pâkitsoq, central-western Greenland, and use it to locate crevasse fields annually over 2015–24. We find that the crevassed area varied from a minimum of 106 ± 5 km 2 in 2019 to a maximum of 144 ± 6 km 2 in 2016, with no overall trend over the 10 year study period. We find some evidence that seasonal ice velocity anomalies in crevasse fields are higher than those in moulin-drained areas in the late melt season. This may suggest that the subglacial drainage system under crevasse fields remains inefficient all summer, and thus that at least some Pâkitsoq crevasse fields deliver meltwater to the bed. Interannual variability in ice dynamics may drive the observed variability in crevassed areas; we expect crevasse extent to become more variable in time as ice flow speeds and their variations, amplify under climate change.
Abstract Temperate glaciers, characterized by ice at the pressure-melting point and the coexistence of solid and liquid water, are generally considered unsuitable as natural archives because meltwater undermines the paleoclimatic signals they hold. Historically, ice-core studies have favored cold glaciers. However, the ongoing atmospheric warming is driving many formerly cold portions of glaciers toward temperate conditions. As such, the relevance of temperate ice as potential paleoclimate archives is increasing. Assessing its ability to record environmental signals has become a priority for ice-core science. This review synthesizes more than 70 years of research on temperate ice cores, tracing the evolution of scientific approaches from pioneering efforts in the 1950s to recent projects across the globe. The behavior of ice-core proxies—including soluble and insoluble impurities, water stable isotopes, gases, radionuclides and organic compounds—is discussed in the context of meltwater-related post-depositional processes. By compiling and comparing evidence from diverse settings, this work highlights both the challenges and the emerging opportunities for retrieving meaningful information from temperate glaciers. Understanding how climatic and chemical signals are modified, preserved or lost in rapidly transforming glaciers is essential for sustaining the role of ice-core science in a warming world.
