The melting of glaciers has accelerated over the past two decades. Is it possible to make predictions for the future?
Seattle – In the next 200 years, the Pine Island Glacier in Antarctica alone could contribute a good five centimeters to the rise in global sea levels.
By the end of the century it could possibly be two centimeters, as American researchers report in the journal “Science Advances”. The melting of the glacier currently accounts for around 40 percent of ice loss in West Antarctica, which is particularly hard hit by the melting of the Antarctic ice, explains Ian Joughin’s team from the University of Washington in Seattle.
The Pine Island Glacier pushes ice into the Amundsen Sea in western Antarctica. There are wind patterns there that change over the course of decades and that drive sometimes more, sometimes less warm deep water to the estuary areas of glaciers. This resulted in considerable uncertainties in the predictions of the contribution of Antarctica to sea level height, explain the scientists.
Using measurement data from 2017, Joughin and colleagues simulated the melting of the glacier in a computer model for the next 200 years. They carried out 30 simulations each for melting rates of 57, 75, 100 and 125 billion tons of ice per year. “Despite the complexity of the model, a single value, the 200-year average melt rate, almost completely predicts the contribution of the Pine Island Glacier to sea level over the next 200 years,” the researchers say. This discovery could greatly simplify the calculation of future ice losses from similar glaciers.
This connection is possibly due to the special shape of the Pine Island Glacier: It is fed from a large catchment area, but is relatively narrow towards the sea due to the shape of the landscape. In the narrow place, the movement of the ice accelerates, just as water flows faster in narrower passages. Where the glacier meets the sea, the ice shelf on the water is also relatively narrow. “While our hypothesis was confirmed for one glacier, it probably applies to other glaciers with narrow shelves,” the study authors write. This should clarify further investigations.
Joughin and colleagues assume that the Pine Island Glacier and other glaciers in this bay of the Amundsen Sea will lose a great deal of ice beyond 200 years. Over several centuries this could lead to a complete collapse of the West Antarctic ice sheet.
The melting of the glaciers in the Antarctic and on Greenland has accelerated in the past two decades, scientists reported in April 2021 in the journal “Nature”. In the first five years of this period it was 227 billion tons of ice, in the last five years 298 billion tons.
The globally melting glacier ice contributed about 21 percent or 0.74 millimeters per year to the observed rise in global sea levels. dpa
