The summer of 2021 actually started not bad 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, this was only one of several remarkable events on the Arctic island this year, as the Polar Portal Season Report 2021 summarizes.
The heat wave at the end of July, for example, caused the melting to occur on 60 percent of the area of the ice sheet; on July 28, the weather station of Nerlerit in east Greenland recorded a new maximum temperature of 23.4 degrees Celsius. Two and a half weeks later, on August 14, a low pressure area finally moved over Greenland, which caused it to rain even on one of the highest points of the ice sheet at an altitude of 3216 meters. There is an average annual temperature of minus 30 degrees Celsius, and even in summer the values rarely exceed the dew point. Scientists had never observed rain on site before.
Over the past 2000 years, scientists have been able to demonstrate nine melting events in this altitude on the ice shield on the analysis of ice drilling nuclei: three of them in the past ten years. Overall, Greenland lost almost 400 billion tons of ice in 2021, which is a little above the average of the past 40 years. It also marks the 25th year in a row, in which the island lost more ice than new was formed. Since 1986, the losses have been added up at around 5,500 gigatons.
Through this supply of meltwater, Greenland alone contributed more than ten percent to the average global sea level rise of twelve centimeters. Most of the melting took place since the turn of the millennium. And climate change is affecting more and more parts of the island, the areas with regular melting 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 they melt because they are located at lower altitudes with higher average temperatures. It is therefore feared that the Greenland ice sheet has either already reached its tipping point or will soon reach it, at which the melt is practically irreversible.
