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- Title
Polar Low Circulation Enhances Greenland's West Coast Cloud Surface Warming.
- Authors
Lac, Jean; Chepfer, Hélène; Arouf, Assia; Shupe, Matthew D.; Gallagher, Michael R.
- Abstract
Mass loss of the Greenland Ice Sheet (GrIS) plays a major role in the global sea level rise. The west coast of the GrIS has contributed 1,000 Gt of the 4,488 Gt GrIS mass loss between 2002 and 2021, making it a hotspot for GrIS mass loss. Surface melting is driven by changes in the radiative budget at the surface, which are modulated by clouds. Previous works have shown the impact of North Atlantic transport for influencing cloudiness over the GrIS. Here we used space‐based lidar cloud profile observations to show that a polar low circulation promotes the presence of low clouds over the GrIS west coast that warm radiatively the GrIS surface during the melt season. Polar low circulation transports moisture and low clouds from the sea to the west of Greenland up over the GrIS west coast through the melt season. The concomitance of the increasing presence of low cloud in fall over the Baffin Sea due to seasonal sea‐ice retreat and a maximum occurrence of Polar low circulation in September results in a maximum of low cloud fraction (∼14% at 2.5 km above sea level) over the GrIS west coast in September. These low clouds warm radiatively the GrIS west coast surface up to 80 W/m2 locally. This warming contributes to an average increase of 10 W/m2 of cloud surface warming in September compared to July on the GrIS west coast. Overall, this study suggests that regional atmospheric processes independent from North Atlantic transport may also influence the GrIS melt. Plain Language Summary: The melting of Greenland plays a major role in the global sea level rise. The west coast of Greenland has contributed to 22% of Greenland mass loss between 2002 and 2021, making it a hotspot for Greenland mass loss. Clouds modulate the energy that reaches the surface of Greenland and, therefore, might accelerate or decelerate surface melt. To explain what leads to cloud presence over Greenland, previous studies focused on the connection between the mid‐latitudes and the Greenland cloud cover. Using a combination of satellite cloud observation and models, we highlight that a low‐pressure system over the Arctic brings moisture and low clouds from the sea west of Greenland to the Greenland west coast. Then, we assess the strong surface warming effect of these low clouds. Overall, our study demonstrates that local Arctic processes lead to formation of low clouds where Greenland melts. Key Points: The Greenland Ice Sheet (GrIS) west coast by itself represents 22% of the GrIS mass loss over the last two decadesA polar low promotes the presence of low clouds over the GrIS west coast during the melt seasonThe cloud surface radiative warming on the Greenland west coast is +10 W/m2 larger in September than July due to these low clouds
- Subjects
GREENLAND; POLAR vortex; GREENLAND ice; ICE sheets; CLOUDINESS; SEA level; SEA ice
- Publication
Journal of Geophysical Research. Atmospheres, 2024, Vol 129, Issue 11, p1
- ISSN
2169-897X
- Publication type
Article
- DOI
10.1029/2023JD040450