The summer of 2021 actually started out not badly for the Greenland Ice Sheet: cool and snowy. However, this only delayed the melting period, which finally began at the end of July with exceptionally high temperatures and large ice losses within a few days with full force. However, that was only one of several notable events on the Arctic island this year, as the “Polar Portal Season Report 2021” sums up.
The heat wave at the end of July ensured that 60 percent of the area of the ice sheet began to melt; On July 28, the Nerlerit weather station in East Greenland recorded a new high of 23.4 degrees Celsius. Two and a half weeks later, on August 14, a low pressure area finally moved across Greenland, which ensured that it rained even on one of the highest points of the ice sheet at 3,216 meters above sea level. The average annual temperature there is minus 30 degrees Celsius, and even in summer the values rarely exceed the dew point. Scientists had never observed rain on site before.
During the past 2000 years, scientists analyzed ice cores and detected nine melt events at this altitude on the ice sheet: three of them in the last ten years. In total, Greenland lost almost 400 billion tons of ice in 2021, which is slightly above the average for the past 40 years. It also marks the 25th year in a row that the island lost more ice than it formed. Since 1986 the losses have now totaled around 5500 gigatons.
With this supply of meltwater, Greenland alone contributed more than ten percent to the average global rise in sea levels of twelve centimeters. Most of the melt has taken place since the turn of the millennium. And climate change is affecting more and more parts of the island, the areas with regular melt have been expanding for years and reaching higher regions of Greenland. This is a self-reinforcing process: the thinner the glacier masses become, the easier it is for them to melt because they are at lower altitudes with higher average temperatures. It is therefore feared that the Greenland ice sheet has either already reached its tipping point or is about to reach it, at which point the melt is practically irreversible.