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Abstract. Over recent decades, the Greenland Ice Sheet (GrIS) has lost mass through increased melting and solid ice discharge into the ocean. Surface meltwater features such as supraglacial lakes (SGLs), channels and slush are becoming more abundant as a result of the former and are implicated as a control on the latter when they drain. It is not yet clear, however, how these different surface hydrological features will respond to future climate changes, and it is likely that GrIS surface melting will continue to increase as the Arctic warms. Here, we use Sentinel-2 and Landsat 8 optical satellite imagery to compare the distribution and evolution of meltwater features (SGLs, channels, slush) in the Russell–Leverett glacier catchment, southwest Greenland, in relatively high (2019) and low (2018) melt years. We show that (1) supraglacial meltwater covers a greater area and extends further inland to higher elevations in 2019 than in 2018; (2) slush – generally disregarded in previous Greenland surface hydrology studies – is far more widespread in 2019 than in 2018; (3) the supraglacial channel system is more interconnected in 2019 than in 2018; (4) a greater number and larger total area of SGLs drained in 2019, although draining SGLs were, on average, deeper and more voluminous in 2018; (5) small SGLs (≤0.0495 km2) – typically disregarded in previous studies – form and drain in both melt years, although this behaviour is more prevalent in 2019; and (6) a greater proportion of SGLs refroze in 2018 compared to 2019. This analysis provides new insight into how the ice sheet responds to significant melt events, and how a changing climate may impact meltwater feature characteristics, SGL behaviour and ice dynamics in the future.
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This content will become publicly available on January 1, 2027
A nine-year record of slush on the Greenland Ice Sheet
Abstract. Surface melt on the Greenland Ice Sheet has intensified in recent decades, accelerating mass loss. Slush, i.e., water-saturated snow or firn, is a key component of the ice sheet's surface hydrological system, yet its extent and behaviour remain poorly constrained. We present the first classification of slush across the Greenland Ice Sheet, using Sentinel-2 imagery and a random forest classifier to generate a nine-year dataset spanning 2016–2024. Over this period, slush covered a mean seasonal extent of 2.8 % of the ice sheet (∼ 48 100 km2), ranging from 1.1 % (∼ 18 700 km2) in 2018, the lowest-melt year, to 5.1 % (∼ 88 500 km2) in 2019, the highest-melt year. Slush was most extensive in the southwestern and northern basins and most recurrent in the northern and northeastern basins; across these regions, its distribution was associated with bare ice, low-permeability ice slabs and, potentially, finer-scale firn heterogeneity. Slush was the dominant mapped surface meltwater feature by area: in 2019, its extent was nine times the reported combined area of supraglacial lakes, channels, and water-filled crevasses. The mean elevation of the upper slush limit broadly covaried with slush extent, with both increasing during high-melt years. Slush extent and occurrence were associated with higher snowmelt and lower firn air content, while a first-order upper-bound estimate suggests that additional energy absorption associated with slush could produce a mean melt equivalent of 12.4 Gt yr−1 if fully converted to melt. As the ice sheet warms, slush is likely to play an increasingly important role in the surface hydrological system, and its explicit representation in surface energy-balance and hydrological models is required to better constrain future ice-sheet mass-balance projections.
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- PAR ID:
- 10706257
- Publisher / Repository:
- Copernicus
- Date Published:
- Journal Name:
- The Cryosphere
- Volume:
- 20
- Issue:
- 8
- ISSN:
- 1994-0424
- Page Range / eLocation ID:
- 4345 to 4365
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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