Huge lakes atop the Greenland ice sheet have a behavior of all of a sudden vanishing: One second they’re there, and the subsequent they’re quickly draining by holes within the ice.
Some scientists consider these occasions can enhance 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.
Till lately, scientists believed these drainage occasions occur nearly solely in the course of the summer time, when the ice is melting and the lakes are rising. It appeared much less doubtless in the course of the winter, when a lot of the ice must be refreezing.
However new proof suggests they will occur all 12 months spherical.
A new study, printed Wednesday within the journal The Cryosphere, finds proof for at the very least six winter drainage occasions between 2014 and 2017.
The examine depends on a particular type of radar information often called “backscatter”—it’s primarily a measurement of the waves mirrored again to the satellite tv for pc emitting the radar sign. Backscatter tends to be increased with objects which can be extra reflective, reminiscent of snow and ice. Meaning a liquid lake ought to produce much less backscatter than a frozen floor.
The researchers, Corinne Benedek and Ian Willis of the College of Cambridge, first combed the information to search out lakes on prime of the Greenland ice sheet. Then, they regarded for cases by which backscatter over these lakes all of a sudden elevated in the course of the winter months. That may counsel that the liquid water in these lakes rapidly drained away, leaving their frozen lake beds behind.
They discovered six examples, all going down between November and February.
Extra information supplied further proof for at the very least three of those occasions. The researchers used a particular imaging methodology to estimate the best way the lakes modified in quantity after they drained, demonstrating that they actually did shrink.
The examine means that Greenland’s lakes don’t all the time refreeze within the winter. A few of them clearly retain some liquid water.
The subsequent query is how widespread these winter drainage occasions actually are.
“We all know now that drainage of lakes in the course of the winter is one thing that may occur, however we don’t but understand how typically it occurs,” stated Willis in an announcement.
Additionally they aren’t completely positive what’s inflicting the winter drainage occasions.
In the summertime, scientists consider that lakes could exert rising strain on the ice as they develop greater. This added strain can ultimately trigger cracks to open up within the ice. Different research have urged that the motion of the ice sheet itself, because it shifts and slides on prime of the bedrock, may cause new cracks to kind. Extra analysis is required to determine what occurred to the winter lakes.
Scientists are nonetheless determining precisely how fast drainage occasions have an effect on the Greenland ice sheet, each in summer time and winter.
When lakes drain, the liquid water typically rushes straight to the underside of the ice sheet. Some research counsel that this will have a type of lubricating impact, making it simpler for the ice to slip over the bedrock beneath it. When that occurs, some consultants say, it may possibly velocity up the speed at which melting glaciers crumble into the ocean.
There’s nonetheless some debate about it. Some scientists consider that different processes could steadiness it out in the long term.
The U.N. Intergovernmental Panel on Local weather Change’s final main report, printed in 2014, urged that drainage occasions could briefly velocity up the move of ice the place they happen however that the impact is short-lived. It additionally means that if these occasions turn into extra frequent over time—a risk, as melting will increase on the floor of the ice sheet—than the slipping impact could subside.
In both case, determining simply how typically these occasions are occurring is a vital step. It might probably assist scientists make higher projections about the way forward for the Greenland ice sheet because the Arctic continues to heat.
“We don’t but understand how widespread this winter lake drainage phenomenon is, however it might have essential implications for the Greenland ice sheet, in addition to elsewhere within the Arctic and Antarctic,” Willis stated.
Reprinted from E&E News with permission from POLITICO, LLC. Copyright 2021. E&E Information gives important information for vitality and surroundings professionals.