Jonathan Lee Carrivick

Ice-marginal lakes are important components of glacierised landscapes, storing meltwater, influencing glacier dynamics, and regulating freshwater transfer to the ocean. Greenland (Kalaallit Nunaat) hosts a large concentration of ice-marginal lakes along the edge of the Greenland Ice Sheet, and its peripheral glaciers and ice caps. Here, we present a Greenland-wide remote sensing assessment of ice-marginal lakes between 2016 and 2025 to provide a comprehensive overview, and evaluate their role with ongoing glacier change. We identify 4038 lakes covering 4734.9 km², equivalent to 1 % of Greenland's ice-free land area. Lake number, area, and surface temperature show negligible change over the decade, indicating broadly stable conditions. However, in total these ice-marginal lakes store an estimated 462.5 Gt of meltwater, of which 67.0 Gt (14 %) has the potential to be rapidly released through glacial lake outburst floods (GLOFs). Our results demonstrate that ice-marginal lakes are a major and spatially heterogeneous component of Greenland’s meltwater system, functioning both as long-term water storages and as sources of episodic, high-magnitude outflow events. Their role remains under-represented in assessments of Greenland hydrology and freshwater fluxes, with implications for constraining Greenland’s contribution to global sea-level estimates.

Ice‑marginal lakes (IMLs) are increasing in number and size around the Greenland Ice Sheet and its peripheral glaciers. Yet consistent long‑term mapping of IML surface area and detection of sudden drainages, possibly as glacial lake outburst floods (GLOFs), remain unrealized. This study evaluated 10 spectral indices and 28 machine‑learning models to identify an optimal method for extracting IML surface area in Greenland. Performance was assessed using expert‑elicited pixel classifications and stratified random samples from six known GLOF‑producing IMLs. Spectral index performance varied substantially: the Water Ratio Index (WRI) and Icy Lakes Index (ILI) performed well across highly weighted metrics and produced the highest weighted rank-sum values (0.8990 and 0.8987). The widely used Normalized Difference Water Index (NDWI) performed poorly, scoring the third‑lowest weighted rank-sum value (0.7126). Machine‑learning models, developed using a clustering-to-random-forest methodology, generally outperformed spectral indices, with 10 models exceeding the best spectral index scores. The top performer, Model_1i, trained on Landsat 8’s seven surface reflectance bands and including lake ice pixels in the training data, achieved a weighted rank-sum value of 0.9327. An expert intercomparison dataset of 300 commonly interpreted pixels showed a mean agreement of 72% among experts, underscoring the need for rigorously trained and tested automated approaches. These combined results demonstrate that machine‑learning methods can provide the most consistent, scalable, and expert‑aligned approach for tracking Greenland IML areas and their potential drainages. Future work will apply the optimal model (Model_1i) to produce a Greenland‑wide, multi‑decadal database of IML dynamics that will, notably, be used for GLOF detection.

Ice-marginal lakes are increasingly widespread around the Greenland Ice Sheet (GrIS), but their influence on ice dynamics remains poorly constrained. Elsewhere, recent work has shown that ice-contact lakes are more thermally complex than previously thought, with potential implications for rates of melt undercutting and calving losses. Here, we assess the relationship between lake thermal regime and calving frequency at a lake-terminating outlet glacier in west Greenland using in situ observations collected during the summers of 2024 and 2025. Lake water temperature varied across the summer season, exhibiting a distinct warm phase during August characterised by a positive thermal gradient and brief period of stratification. Calving activity was dominated by waterline and collapse events, with event frequency peaking during the warm lake phase. Statistical modelling indicates that this was also the period when lake water temperature and calving frequency were most strongly associated. These findings suggest that intraseasonal changes in lake thermal structure may modulate calving behaviour, likely through enhanced melt undercutting. Overall, we highlight the potential for thermally driven calving to become an increasingly important mechanism of ice-loss at lake-contact margins of the GrIS with continued climate warming, and thus lake warming.

The environment in which a glacier terminates can strongly influence its behaviour, stability and future evolution, yet the relationship between terminus type and glacier dynamics at the global scale remains poorly constrained. Here we present a globally-complete classification of glacier termini distinguishing between land, lake, marine and shelf environments, and integrate it with datasets of glacier geometry, dynamics and climate. We show that although lake-, marine- and shelf-terminating glaciers comprise only 3.2% of glaciers globally, they account for over half of global glacier area and mass loss. We also show that lake- and marine-terminating glaciers flow, on average, 10% and 44% faster than land-terminating glaciers, respectively. Furthermore, specific (area-normalised) mass loss rates at lake-terminating glaciers are 57% greater than those at land- and marine-terminating glaciers. Our findings underscore the need for improved representation of non-land glacier termini in models of glacier evolution and sea-level rise, and suggest that distinguishing the environmental and geometric controls of termini on glacier dynamics remains an important challenge for future research.

Ice-marginal lakes are increasingly widespread around the Greenland Ice Sheet (GrIS), but their influence on ice dynamics remains poorly constrained. Elsewhere, recent work has shown that ice-contact lakes are more thermally complex than previously thought, with potential implications for rates of melt undercutting and calving losses. Here, we assess the relationship between lake thermal regime and calving frequency at a lake-terminating outlet glacier in west Greenland using in situ observations collected during the summers of 2024 and 2025. Lake water temperature varied across the summer season, exhibiting a distinct warm phase during August characterised by a positive thermal gradient and brief period of stratification. Calving activity was dominated by waterline and collapse events, with event frequency peaking during the warm lake phase. Statistical modelling indicates that this was also the period when lake water temperature and calving frequency were most strongly associated. These findings suggest that intraseasonal changes in lake thermal structure may modulate calving behaviour, likely through enhanced melt undercutting. Overall, we highlight the potential for thermally driven calving to become an increasingly important mechanism of ice-loss at lake-contact margins of the GrIS with continued climate warming, and thus lake warming.

Alaskan glaciers presently dominate contributions to global glacier mass loss and are projected to do so throughout the 21 ^st Century. Here we assess centennial-scale evolution and mass loss of 5289 Little Ice Age (LIA) glaciers by mapping geomorphological evidence of glacier extent and by reconstructing ablation area ice surfaces. We find that Alaskan glaciers have experienced extensive fragmentation and have lost at least 19 ± 2.8% total area since the local LIA maximum (year 1810) to year 2008. Individual glaciers had a median area loss of 32 ± 4.7%. Our ice surface reconstruction for LIA glacier ablation areas leads to a total volume loss estimate of at least 3345 ± 836 km ³ , equating to a mass loss of at least 2844 ± 711 Gt and a sea level equivalent of 8 ± 2 mm. Glacier mass balance since the LIA to 2008 was − 0.09 ± 0.02 m w.e. yr ^− 1 , which, compared with − 0.67 ± 0.13 m w.e. yr ^− 1 between 2000 and 2019, suggests a 7.4 ± 2.0 times acceleration across Alaska. Three quarters of Alaskan mountain regions shifted from near equilibrium mass balance between the LIA and 2008 (c. − 0.01 m w.e. yr ^− 1 ) to substantial mass loss (more negative than − 0.7 m w.e. yr ^− 1 ) between 2000 and 2019. Our Glacier Bay LIA icefield reconstruction evidences the greatest fragmentation, area, volume and mass loss of any known single LIA glacier globally. Our mapping, glacier reconstructions and mass loss findings will serve glacier evolution modelling, inform proglacial systems analysis, and support ecosystem services management especially within protected areas.

Although the Antarctic Peninsula has a similar climate to that of other regions hosting surge-type glaciers, only one glacier surge has been previously observed in this region. We examined ice surface velocity, elevation and terminus position changes of Antarctic Peninsula glaciers to identify glacier surges. This revealed only four surges from three glaciers, all on James Ross Island. Gourdon Glacier surged from 2005 to 2007 then again from 2013 to 2018, Kotick Glacier surged from 2013 to 2017 and Whisky Glacier surged from 2020 to 2024. All four surges were characterised by significant advances in glacier terminus position and, for the latter three surges where observations are more abundant, at least an order-of-magnitude speed-up accompanied by ice surface elevation gain in the terminal zone and drawdown of ice from above, as each surge progressed. The landform record and historical imagery suggest additional surges of Kotick Glacier and Gourdon Glacier may have occurred in the second half of the 20th century. Reanalyses, reconstructions and observations of air temperature suggest that atmospheric warming since 1940 has increasingly exposed these and neighbouring glaciers on the northern tip of the Antarctic Peninsula and its surrounding islands to conditions that are typical of surge-type glaciers globally. Climate projections indicate that future warming will expose more glaciers on the Peninsula to climatic conditions conducive to surging until the mid-20th century, after which the surge-conducive area remains steady under Shared Socioeconomic Pathway (SSP) 2-4.5 and declines under SSP5-8.5. This suggests that surges on the Antarctic Peninsula may become more common over the coming decades, motivating continued monitoring.

Although the Antarctic Peninsula has a similar climate to that of other regions hosting surge-type glaciers, only one glacier surge has been previously observed in this region. We examined ice surface velocity, elevation and terminus position changes of Antarctic Peninsula glaciers to identify glacier surges. This revealed only four surges from three glaciers, all on James Ross Island. Gourdon Glacier surged from 2005 to 2007 then again from 2013 to 2018, Kotick Glacier surged during 2013 to 2017 and Whisky Glacier surged from 2020 to 2024. All four surges were characterised by significant advances in glacier terminus position and, for the latter three surges where observations are more abundant, at least an order-of-magnitude speed-up and mass transfer from upper to lower parts of each glacier. The landform record and historical imagery suggest additional surges of Kotick Glacier and Gourdon Glacier may have occurred in the second half of the 20^th century. Reanalyses, reconstructions and observations of air temperature suggest that atmospheric warming since 1940 has increasingly exposed these and neighbouring glaciers on the northern tip of the Antarctic Peninsula and its surrounding islands to conditions that are typical of surge-type glaciers globally. Climate projections indicate that future warming will expose more glaciers on the Peninsula to climatic conditions conducive to surging until the mid-20th century, after which the surge-conducive area remains steady under Shared Socioeconomic Pathway (SSP) 2-4.5 and declines under SSP5-8.5. This suggests that surges on the Antarctic Peninsula may become more common over the coming decades, motivating continued monitoring.