Antarctic: Ice loss has increased sixfold

Presumably stable East Antarctic contributes more to the melting of ice than assumed

Antarctic glaciers continue to pick up speed, here is a view of Mount Baldfour and the Flemiong Glacier on the Antarctic Peninsula © NASA / Joe MacGregor
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Rapide Schmelze: In the last 40 years, ice loss in the Antarctic has increased dramatically. In 1979, the annual mass loss was still 40 billion tons, in 2017 it is already 252 billion tons per year, as revealed by the most comprehensive mass balance of the southern continent so far. Worryingly, parts of this ice melt are also part of the East Antarctic - a previously considered stable area, as the researchers report.

The Antarctic covers the coldest places on earth, yet the ice is melting in the largest ice reservoir on our planet. More and more of the ice shelves break off enormous ice sheets, most recently on the Larsen C Ice Shelf. Warm deep water penetrates there by notches in the underground far below the glacier tongues. In parts of the West Antarctic, the melting of ice could therefore even be irreversible, researchers fear.

From 40 to 252 gigatons per year

A new record of the Antarctic ice loss and defrost rate has now been set up by Eric Rignot of the University of California at Irvine and his team. For their study, they evaluated satellite data and data from test aircraft on snowfall, glacier movement and ice shrinkage from the period from 1979 to 2917. They also determined the loss of ice in 18 regions and 176 ice basins of the Antarctic ice cap.

Comparison of ice loss per decade from 1979-1989 and 2009-2017. Rignot et al., PNAS / CC-by-sa 3.0

The result: In the last 40 years, the loss of ice in the Antarctic has increased six-fold, as the researchers report. Between 1979 and 1990, the South Continent lost around 40 billion tons of ice a year. By contrast, in the period from 2009 to 2017, it was already 252 billion tons per year. "Every decade, ice loss is now 280 percent of pre-2001 levels, " says Rignot and his colleagues.

Out of balance

The data shows that even the partially abundant snowfall, especially in the east of the continent can not compensate for the loss of ice: "We find that the Antarctic ice sheet during our entire study period was no longer in equilibrium with the snowfall accumulation ", The researchers report. "" This also applies to the East Antarctic. "Display

Due to the melting of the ice, the Antarctic has contributed about 14 millimeters to the global sea level rise since 1979, as Rignot and his team calculated. "During this time, the loss of mass concentrated in the areas that were the most exposed to the warm, subglacial deep water, " the researchers explain.

East Antarctica is more sensitive than expected

The West Antarctic accounts for the largest share of ice shrinkage, contributing 63 percent of total ice loss, according to the analysis. The Antarctic Peninsula accounted for 17 percent of the total decline. However, the East Antarctic, which has long been considered stable, also has a surprisingly high share: it contributed around 20 percent to ice loss, as Rignot and his team determined. A large part of this East Antarctic melt took place here in the Wilkes Land on the east coast of the continent.

"The Wilkes-land area of ​​the eastern Antarctic is apparently more sensitive to climate change than has been traditionally assumed. Thus, our observations contradict the notion that the East Antarctic ice sheet is stable and immune to change, "says Rignot. "This is important to know because this area contains more ice than the West Antarctic and the Antarctic Peninsula combined." (Proceedings of the National Academy of Sciences, 2019; doi: 10.1073 / pnas.1812883116)

Source: University of California Irvine

- Nadja Podbregar