Enormous lakes atop the Greenland ice sheet have a behavior of abruptly vanishing: One second they’re there, and the following they’re quickly draining by holes within the ice.
Some scientists imagine these occasions can improve the speed at which ice is being misplaced into the ocean. That’s a giant concern for Greenland, the place soften charges are at the moment on the quickest they’ve been in 12,000 years—and nonetheless dashing up.
Until lately, scientists believed these drainage occasions occur nearly fully throughout the summer season, when the ice is melting and the lakes are rising. It appeared much less probably throughout the winter, when a lot of the ice needs to be refreezing.
But new proof suggests they’ll occur all 12 months spherical.
A new study, printed Wednesday within the journal The Cryosphere, finds proof for at the least six winter drainage occasions between 2014 and 2017.
The research depends on a particular form of radar information often called “backscatter”—it’s basically a measurement of the waves mirrored again to the satellite tv for pc emitting the radar sign. Backscatter tends to be greater with objects which are extra reflective, reminiscent of snow and ice. That means a liquid lake ought to produce much less backscatter than a frozen floor.
The researchers, Corinne Benedek and Ian Willis of the University of Cambridge, first combed the information to search out lakes on high of the Greenland ice sheet. Then, they seemed for cases wherein backscatter over these lakes abruptly elevated throughout the winter months. That would recommend that the liquid water in these lakes shortly drained away, leaving their frozen lake beds behind.
They discovered six examples, all happening between November and February.
Additional information offered further proof for at the least three of those occasions. The researchers used a particular imaging technique to estimate the way in which the lakes modified in quantity after they drained, demonstrating that they actually did shrink.
The research means that Greenland’s lakes don’t all the time refreeze within the winter. Some of them clearly retain some liquid water.
The subsequent query is how widespread these winter drainage occasions actually are.
“We know now that drainage of lakes during the winter is something that can happen, but we don’t yet know how often it happens,” stated Willis in a press release.
They additionally aren’t completely certain what’s inflicting the winter drainage occasions.
In the summer season, scientists imagine that lakes could exert rising stress on the ice as they develop larger. This added stress can ultimately trigger cracks to open up within the ice. Other research have advised that the motion of the ice sheet itself, because it shifts and slides on high of the bedrock, could cause new cracks to kind. More analysis is required to determine what occurred to the winter lakes.
Scientists are nonetheless determining precisely how speedy drainage occasions have an effect on the Greenland ice sheet, each in summer season and winter.
When lakes drain, the liquid water usually rushes straight to the underside of the ice sheet. Some research recommend that this could have a form of lubricating impact, making it simpler for the ice to slip over the bedrock beneath it. When that occurs, some specialists say, it might probably pace up the speed at which melting glaciers crumble into the ocean.
There’s nonetheless some debate about it. Some scientists imagine that different processes could steadiness it out in the long term.
The U.N. Intergovernmental Panel on Climate Change’s final main report, printed in 2014, advised that drainage occasions could briefly pace up the move of ice the place they happen however that the impact is short-lived. It additionally means that if these occasions grow to be extra widespread over time—a chance, as melting will increase on the floor of the ice sheet—than the slipping impact could subside.
In both case, determining simply how usually these occasions are occurring is a crucial step. It may also help scientists make higher projections about the way forward for the Greenland ice sheet because the Arctic continues to heat.
“We don’t yet know how widespread this winter lake drainage phenomenon is, but it could have important implications for the Greenland ice sheet, as well as elsewhere in the Arctic and Antarctic,” Willis stated.
Reprinted from E&E News with permission from POLITICO, LLC. Copyright 2021. E&E News supplies important information for vitality and atmosphere professionals.