Migrating Supraglacial Lakes on the Greenland Ice Sheet May Cause Major Melting

It turns out that Greenland's ice loss and its impact on rising sea levels may have been greatly underestimated. Scientists have found that migrating, supraglacial lakes could trigger future ice loss which, in turn, may add to rising sea levels.

Scientists previously assumed that the impact of supraglacial lakes were small. Supraglacial lakes are located on the glacial surface. They're darker than ice, and so absorb more of the sun's heat. Now, scientists have found that these lakes will migrate farther inland over the next half century and potentially alter the ice sheet flow in dramatic ways.

"Supraglacial lakes can increase the speed at which the ice sheet melts and flows, and our research shows that by 2060 the area of Greenland covered by them will double," said Amber Leeson, one of the researchers, in a news release.

In order to understand the impacts of these lakes, the researchers used observations of the Greenland ice sheet and estimates of future ice melting drawn from a climate model. With this data, the scientists drove simulations of how meltwater will flow and pool on the ice surface to form supraglacial lakes.

So what did they find? As Arctic temperatures rise, supraglacial lakes will spread further inland. Water draining from these lakes won't drain to the oceans as efficiently as today. Instead, the water draining could lubricate the bottom of the ice sheet more effectively as it seeps through cracks in the surface. This, in turn, may cause the ice sheet to speed up.

The findings reveal that as temperatures warm, these lakes could have a major impact on the rate of melting. This, in turn, could mean that the ice sheet's disappearance could speed up in the future.

"Because ice losses from Greenland are a key signal of global climate change, it's important that we consider all factors that could affect the rate at which it will lose ice as climate warms," said Andrew Shepherd, co-author of the new study. "Our findings will help to improve the next generation of ice sheet models, so that we can have greater confidence in projections of future sea-level rise. In the meantime, we will continue to monitor changes in the ice sheet losses using satellite measurements."

The findings are published in the journal Nature Climate Change.