Thinning of the Greenland ice sheet. Is it affected by the shape of a glacier?

Scientists at the Universities Space Research Association and their colleagues at NASA, the University of Texas and others have proven that the slope of the bedrock beneath glaciers around the Greenland ice sheet can either release ice. further into the country or stopped.

Glaciers are usually rivers of ice flowing over the seabed and draining into the ocean. They escape and become thin as the climate warms and this thinning spreads further inland towards the center of the ice sheet.

Recently, by studying the topography of 141 outer glaciers around Greenland, scientists have gained a better understanding of which glaciers could have a significant effect on the glaciers. the Greenland Ice Sheet has contributed to sea level rise in the coming decades. They found that the properties of steep bedrock, known as “knickpoints”, can effectively stop the spread of ice thinning. This often occurs in areas where the topography of the bed is mountainous. In contrast, in more temperate terrain areas where hilltops are less present or less steep, glaciers can spread ice thinning far into the interior, away from of the sea. The results were published in Geophysical Research Letters.

Denis Felikson, scientist at the Universities Space Research Association at NASA Space Flight Center, and lead author of the study, “Several small glaciers flow over a calm landscape in northwestern Greenland that allows thinning ice spread to the center of the ice sheet. These glaciers may have such a large role to play, that little attention has been paid to future sea level rise than the most famous and studied glaciers. ”

Glaciers that flow through a calm landscape, or have no crack place at all, are found to have gradual glaciers. There is interest in such glaciers, and they are concerned that, despite their size, their potential to allow thinning extends hundreds of kilometers inland, eroding the heart of the ice sheet.

Researchers have concluded that by allowing the thinning of ice sheets to spread far into the country, these smaller glaciers will provide no knick points on the ice sheet. continue to lose ice over a longer period than the largest glaciers flowing on a cliff with hill points.

“Scientists have only recently been able to identify the steep changes in topography using digital elevation models to design a landscape under ice. Without that capability, the research team would not have been able to find the conclusions, ”said Felikson. The bed-shaped digital elevation model, called Dataset BedMachine – a high-resolution model of the bed under the Greenland ice sheet – surrounded by using aerial data from NASA’s Operation IceBridge, was crucial for this research.

Using NASA remote sensing data, scientists were able to determine if the thinning of the ice sheet could continue upstream from the boundary of a glacier ocean by computing one meter based on the shape of the ice sheet. glacier at all points on glacier flow line. This helped them to identify a resting place between glacial ice up and down the river. “Ice beneath the hilly area tends to thin out from the edge of the glacier. But thinning does not extend upstream and therefore does not affect the interior of the ice sheet. This means that some parts of the Greenland ice sheet are more sensitive to what happens at the edge than other parts, ”says Felikson.

“Glaciers can have an impact on sea level rise, not because they are large and dense, but because they have access to more ice and can eat away,” Felikson said. “It will take them a long time to respond, but over the long term they can make a significant contribution to sea level rise, just as the large glaciers do.

According to Felikson, “We are seeking confirmation from models for the theoretical limitations on attenuation we have found, and hope that future modeling efforts will further test how ice thinning spreads on ice- streams. ”

This research was funded by NASA under a NNX12AP50G grant and by the Gale White Fellowship at the University of Texas Institute of Geophysics.