Using artificial intelligence techniques, a team of scientists discovered that at the height of the Antarctic summerin January, more than a half (57%) of all meltwater from Antarctic shelves remains in the form of slush (water-soaked snow).
This melting, which until now had not been quantified and is not taken into account in climate models, can profoundly affect the stability of ice shelves and accelerate sea level risewarns the study, led by the University of Cambridge (United Kingdom), and published this Thursday in Nature Geoscience.
Each summer, as the climate warms, water builds up on the surface of Antarctica’s floating ice shelves.
Previous investigations have shown that the surface water lakes defrosting can contribute to fracture and collapse of ice shelves, because the weight of water can cause ice to break up but the role of sleet in the stability of ice shelves is more difficult to determine.
“We can use satellite images to map meltwater lakes in much of Antarctica, but It’s hard to map sleet because it looks like other thingslike cloud shadows, when viewed from a satellite,” explains lead author Rebecca Dell of the Scott Polar Research Institute (SPRI) in Cambridge.
However, using machine learning techniques, “we can go beyond what the human eye can see and get a clearer picture of how sleet could be affecting the ice in Antarctica,” Dell says.
SATELLITE DATA
Using optical data from NASA’s Landsat 8 satellite, the team, along with researchers from the University of Colorado Boulder (United States) and the University of Delft (Netherlands), trained a machine learning model to get monthly records of sleet and water lakes of melting across 57 Antarctic ice shelves between 2013 and 2021.
Thus, they discovered that at the height of the Antarctic summer, more than half (57%) of the meltwater from the Antarctic ice shelves remains in the form of slush, and that the remaining 43% is meltwater.
“This slush has never been mapped on a large scale across all of Antarctica’s large ice shelves, so more than half of all surface meltwater has been ignored until now,” Dell says.
PLATFORM STABILITY
Meltwater affects the stability of floating ice shelves that line the Antarctic coast.
As the weather warms and melt rates increase in Antarctica, meltwater – whether in the form of lakes or slush – can get into ice cracks and fracture themwhich could lead to the collapse of the most vulnerable shelves, which in turn would cause ice from inland glaciers to spill into the ocean and contribute to sea level rise.
“Since sleet is more solid than meltwater, it will not cause hydrofracturing in the same way than lake water, but it is something we must take into account when predicting whether ice shelves will collapse or not,” says Ian Willis, co-author of the study at the University of Cambridge.
Furthermore, it also has a great effect on melt ratesBecause sleet and lakes are less white than snow or ice, they absorb more heat from the sun, causing more snowmelt.
This additional melting is not taken into account in climate modelswhich can lead to underestimating ice sheet melt projections and ice shelf stability.
“In the future, Places in Antarctica that currently have no water or sleet are likely to begin to change. As the climate continues to warm, more melting will occur, which could have implications for ice stability and sea level rise,” Willis concludes.
