Scientists calculated that the most rapidly changing Antarctic region, the Bay of the Amundsen Sea, lost more than 3 billion tonnes of ice over a 25-year period.
To get an idea of what this amount represents, if all the lost ice accumulated on the surface of London, it would be more than 2 km high. If it covered Manhattan, it would be 61 km high, the equivalent of 137 Empire State Buildings stacked on top of each other.
Twenty large glaciers form the Amundsen Sea Reservoir in West Antarctica, which is about three times the size of Spain, and play a key role in contributing to the level of the world’s oceans. The snow and ice here hold so much water that if it all melted, global sea levels could rise by more than a meter.
He study, published in Nature Communications calculated the “mass balance” of the Amundsen Sea Reservoir, which describes the balance between the mass of snow and ice gained by snowfall and lost by calving, which is when icebergs form at the mouth of a glacier and fall into the sea. When calving occurs faster than snow accumulation, there is a total loss of ice mass that contributes to sea level rise.
The results show that West Antarctica experienced a net reduction of 3.331 million tons of ice between 1996 and 2021, representing a contribution of more than nine millimeters to global sea levels. Changes in temperature and ocean currents are believed to have been the most important factors in ice loss. According to scientists, there is no evidence that the process will be reversed anytime soon.
The importance of extreme snowfall
Using climate models that show how air currents move around the world, the scientists identified that the Amundsen Sea Reservoir experienced several extreme snowfall events during the 25-year study period. During this period, there were periods of heavy snowfall and periods of low snowfall or “snow drought”.
The researchers took these extreme events into account in their calculations. Surprisingly, they found that these events accounted for up to half of the ice variation over certain periods, and therefore play a key role in the Amundsen Sea Basin’s contribution to sea level rise during certain periods.
For example, between 2009 and 2013, models revealed a period of persistently low snowfall, or “snow drought”. The lack of nutritious snowfall caused the ice sheet to lose ice, thus contributing 25% more to sea level rise than in years of average snowfall.
In contrast, during the winters of 2019 and 2020, heavy snowfalls occurred. Scientists estimated that this heavy snowfall mitigated the Amundsen Sea Reservoir’s contribution to sea level, reducing it to about half of what it would be in an average year.
The new piggy glacier
Loss of ice from the region over the last 25 years has caused the Pine Island Glacier, also known as the PIG, to retreat. As it retreated, one of its tributary glaciers broke away from the main glacier and rapidly accelerated. The UK Antarctic Place Names Committee has therefore renamed the tributary glacier Piglet Glacier so that it can be unambiguously located and identified in future studies. Satellite observations showed that the newly named Piglet Glacier accelerated its ice velocity by 40%, while the largest PIG retreated to its smallest extent on record.
Satellites like the European Space Agency’s Copernicus Sentinel-1, which uses sensors that “see” through clouds even during the long polar night, have transformed scientists’ ability to monitor remote regions and monitor incredibly rapid changes taking place in Antarctica. The result is studies like this one.
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Source: University of Leeds
