The melting of the ice in Western Antarctica began in the 1940s: this is indicated by analyzes of core samples carried out on the Thwaites glacier, one of the largest in the world.
According to the study led by Julia Wellner of the University of Houston and published in the journal of the United States Academy of Sciences, PNAS, an abrupt change occurred starting from 1945, promoted by the El Nino phenomenon recorded between 1939 and 1942 .
We know with certainty that Antarctica's ice has been melting at very high rates since the 1970s, but knowing what was happening further back in time is rather difficult due to the lack of precise data, in particular the absence until then satellite images.
Precisely for this reason, a fundamental contribution comes from core sampling, i.e. sampling of ice layers which allows the evolution of the ice cap to be reconstructed, but with less precision than satellite data.
The new data comes from the Thwaites glacier, by far one of the largest in the world, whose complete melting is estimated to raise the seas by about 65 centimetres.
Core samples from the region indicate that the Thwaites began a gradual retreat as early as 9,400 years ago, but an abrupt change occurred starting from the 1940s.
A change that could be associated with the occurrence of El Nino between 1939 and 1942, the periodic climatic phenomenon that originates in the Pacific and which also has profound influences on the rest of the planet.
The massive arrival of warmer water currents in the Antarctic region may have triggered an accelerated melting of the ice, the effects of which continue today.
“A significant implication of our findings is that, once ice sheet retreat has begun, it can continue for decades even if no further deterioration has occurred,” said James Smith, a marine geologist at the British Antarctic Survey and co-author of the study.
“It is possible – he continued – that the changes we see today on the Thwaites and Pine Island glaciers, and potentially in the entire Amundsen Sea basin, were essentially set in motion in the 1940s.”
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