Extreme melting across the Greenland Ice Sheet

Changes in the atmosphere are driving extreme melting across the Greenland Ice Sheet. By looking at satellite images, we found that the summers of 2012, 2019, and 2023 were unusual: the ice reflected much less sunlight than it normally does. When ice reflects less light, it means the surface is getting darker and absorbing more heat, which causes it to melt even faster.

As shown in the figure below, the maps in the top row (A-C) display these sunlight reflection levels for each of the three years. The areas without a gray background show where conditions were more than one standard deviation away from the average. You can see these extreme low-reflectance values spread across the entire ice sheet during these summers.

We used wind and air pressure data (shown in the bottom row, G-I) to track where the air masses causing this melting came from. We also found that temperatures near the ground (middle row, D-F) were unusually high during these summers, especially in 2012 and 2023.

Interestingly, we found that two very different weather patterns can cause this extreme melting. In 2019, the weather was dry and clear, which allowed the sun to beat down on the darker edges of the ice sheet. However, in 2012 and 2023, it was cloudy and wet. In those years, the clouds acted like a blanket, trapping heat and causing even the bright, snowy center of the ice sheet to melt.

Top Row (A-C): Shows how much sunlight the ice reflected. Darker areas indicate the ice was absorbing more heat than usual.

Middle Row (D-F): Shows air temperatures near the surface, combining satellite data with readings from weather stations on the ground.

Bottom Row (G-I): Shows wind patterns and air pressure high in the atmosphere, which help explain where the warm air came from.

Areas without a gray background show conditions that were unusually extreme (more than one standard deviation away from the average).