The ice shelf has shrunk by 44% since 1997

Ice shelves are large ice sheets up to 1000 meters thick that float on the sea but are still connected to the land. They are fed by fast-flowing parts of the ice sheet that covers the Antarctic continent. Man-made global warming is considered a likely cause of ice shelf melting.

The ice shelf “exercises decisive control over the speed at which ice flows into the ocean,” scientists led by Benjamin Davison of the University of Leeds in Britain write in their work, which was published in the journal “Science Advances.” The ice sheets that extend into the sea are considered the Achilles heel of the Antarctic ice sheet: as the ice shelf melts, its supporting force decreases. This could cause the mighty ice sheet above the continent to lose mass faster and contribute more to global sea level rise.

100,000 satellite images analyzed
To understand the ‘health status’ of all Antarctic ice shelves from 1997 to 2021, the scientists analyzed more than 100,000 satellite images. To do this, they mainly used data from the European Space Agency’s (ESA) ‘CryoSat-2’ and ‘Sentinel-1’ satellites and the EU’s Copernicus Earth observation program, which observed Antarctica even in cloudy skies and for long periods of time. can keep an eye on. polar nights. Jan Wuite and Thomas Nagler from the Innsbruck company ENVEO calculated a continuous time series of monthly ice velocity maps of Antarctica based on ‘Sentinel-1’ data, which form the basis for calculating the ice mass flow and its change over time.

According to the analysis, between 1997 and 2021, 71 of the 162 Antarctic ice shelves lost volume, 29 of those areas gained mass and 62 did not change significantly. Of the melting ice shelves, 48 ​​have lost more than 30 percent of their original mass in just 25 years.

Strong regional differences
There were strong regional differences: almost all ice shelves on the western side of Antarctica recorded a decline. “On the eastern side, however, the variability is greater: some ice shelves have lost mass, while others have remained the same or even increased in mass,” Nagler told the APA.

According to the researchers, this has to do with sea temperatures and ocean currents around Antarctica: In the western half of Antarctica, warm ocean currents are rapidly attacking the ice shelf from below, “while much of East Antarctica is currently surrounded by a band of the cold water on the coast “is protected from the warm water nearby”.

Largest loss of ice on the Getz Ice Shelf
Some of the largest ice losses were observed on the Getz Ice Shelf, where 1.9 trillion tons of ice were lost during the study period. Only five percent of this was due to calving, that is, the breaking off of larger chunks of ice. Most of it melted at the base, lying in the seawater.

The picture is similar to that of the Pine Island Ice Shelf, which lost 1.3 trillion tons of ice during the study period – two-thirds of it from melting at its base. In contrast, the Amery Ice Shelf on the eastern side of Antarctica, surrounded by much colder seawater, has gained 1.2 trillion tons of ice.

67 trillion tons of meltwater
In 25 years, almost 67 trillion tons of meltwater ended up in the ocean. This is offset by an increase in ice of 59 trillion tons from the ice sheet, resulting in a net loss of about 7.5 trillion tons of ice. This could have significant consequences not only for the Antarctic ice system, but also for the global circulation of ocean currents.

The melting fresh water dilutes the salty seawater, making it take longer to sink. However, this sinking acts as an engine that powers the global ocean circulation system, which transports nutrients, heat and carbon.