Warming up Greenlandic ice sheet takes no point in returning

Nearly 40 years of satellite data from Greenland show that glaciers on the island are shrinking so much that even if global warming stopped today, the ice sheet would continue to shrink.

The finding, published today, August 13th. In the magazine Nature Communication Earth and Environment, means that the glaciers of Greenland have been passed a tipping point of sorts, whereby the snowfall that fills the ice sheet every year cannot keep up with the ice flowing through the glaciers into the ocean.

“We observed these observations remotely to study how ice discharge and accumulation varied,” said Michalea King, lead author of the study and a researcher at Byrd Polar and Climate Research Center at Ohio State University. “And what we found is that the ice that is extracted in the ocean is the snow that accumulates on the surface of the ice sheet.

King and other researchers analyzed monthly satellite data of more than 200 large glaciers that drain into the ocean around Greenland. Their observations show how much ice breaks in icebergs or melts from the glaciers in the ocean. She also shows the amount of snowfall each year – the way these glaciers are replenished.

The researchers found that, through the 1980s and 90s, snow obtained by accumulation and ice melting or calving of glaciers was mostly in balance, leaving the ice sheet intact. By those decades, the researchers found, the ice sheets generally lost about 450 gigatons (about 450 billion tons) of ice each year from flowing outlet glaciers, which were replaced by snowfall.

“We measure the ice sheet’s pulse – how many ice glaciers rotate at the edges of the ice sheet – which increases in summer. And what we see is that it was relatively stable until a large increase in ice to the ocean. in a short period of five to six years, “King said.

The researchers’ analysis found that the baseline of that pulse – the amount of ice that was lost each year – began to increase gradually around 2000, causing the glaciers to lose about 500 gigatons each year. Snowfall did not increase at the same time, and in recent decades the rate of ice loss of glaciers has remained about the same – meaning that the ice sheet has lost ice faster than it has replenished.

“Glaciers are susceptible to seasonal melting as long as we could observe it, with spikes in the summer in the ice,” she said. “But in early 2000, you start to superimpose this season’s meltdown on a higher baseline – so you’ll get even more losses.”

Before 2000, the ice sheet would have about the same chance of winning or losing mass every year. In today’s climate, the ice sheet will gain mass in just one out of every 100 years.

King said large glaciers across Greenland have receded on average about 3 kilometers since 1985 – “that’s a lot of distance,” she said. The glaciers are shrinking back enough that many of them are sitting in deeper water, which means more ice is in contact with water. Warm ocean water melts glaciers, and also makes it difficult for glaciers to grow back to their previous positions.

This means that even if humans were somehow miraculously able to stop climate change in their tracks, ice lost from glaciers that drain ice to the ocean would probably still win the ice from the snow accumulation, and it ice sheet would shrink for a while.

“Glacier retreat has thrown the dynamics of the entire ice sheet into a constant state of loss,” said Ian Howat, a co-author on paper, professor of earth sciences and distinguished university scholar at Ohio State. “Even if the climate remained the same or even got a little colder, the ice sheet would still lose mass.”

Shrinking glaciers in Greenland are a problem for the entire planet. The ice that melts or breaks out of Greenland’s ice sheets ends up in the Atlantic Ocean – and, eventually, all the oceans in the world. Ice from Greenland is a leading contributor to rising sea levels – last year enough ice melted or broke off the Greenland ice sheet to increase the oceans by 2.2 millimeters in just two months.

The new findings are bleak, but King said there are silver linings.

“It’s always a positive thing to learn more about glacier environments, because we can only improve our forecasts for how fast things will change in the future,” she said. “And that can only help us with adaptation and mitigation strategies. The more we know, the better we can prepare.”