Editor TLN
16 Jan. () –
The collapse of the entire West Antarctic ice sheet is not inevitable: the rate of ice loss varies based on regional differences in atmospheric and oceanic circulation.
An international team of researchers has combined satellite imagery and climate and ocean records to obtain the most detailed understanding yet of how the West Antarctic ice sheet is responding to climate change. containing enough ice to raise global sea level by 3.3 meters.
The researchers, from the University of Cambridge, the University of Edinburgh and the University of Washingtonfound that the rate and extent of ice destabilization along the West Antarctic coast varies based on regional climatic differences.
Their results, published in the journal Nature Communicationsshow that while the West Antarctic ice sheet continues to recede, the rate of retreat slowed in a vulnerable region of the coast between 2003 and 2015. This slowdown was due to changes in the temperature of the surrounding ocean, caused by in turn due to variations in offshore wind conditions.
Home to the vast and unstable Pine Island and Thwaites glaciers, the West Antarctic sea ice sheet sits on a land mass 2,500 meters below the ocean surface. Since the early 1990s, scientists have observed a sharp acceleration in melting, receding, and speed of melting in this area, which is partly attributed to human-induced climate change in the last century.
Other scientists have previously indicated that this type of response in a low-lying landmass could be the start of an irreversible collapse of the entire ice sheet, called sea ice sheet instability, which would continue regardless of any other climatic influences.
According to Dr Frazer Christie of the Scott Institute for Polar Research in Cambridge and lead author of the paper, “It is widely believed that once a sea ice sheet passes a certain tipping point, there will be a response runaway”. “Nonetheless, Questions remain about the extent to which ongoing climate changes continue to regulate ice losses along the entire West Antarctic coast.”
Using observations collected by a suite of satellites, Christie and his colleagues found pronounced regional variations in the way the West Antarctic ice sheet has evolved since 2003 due to climate change, with the rate of retreat in the South Antarctic Sea sector. Amundsen having decreased significantly compared to the neighboring and much faster sector of the Bellingshausen Sea.
By analyzing climate and ocean records, the researchers linked these regional differences to changes in the strength and direction of offshore surface winds.
In this part of Antarctica, the prevailing winds come from the west. When these westerly winds get stronger, they stir up the warmer, saltier water in the deep ocean, that reaches the Antarctic coast and increases the rate of melting of the ice.
“But between 2003 and 2015, off the coast of the Amundsen Sea sector, the intensity of the prevailing westerly winds decreased,” Christie explains. it’s a statement. “This meant that deeper, warmer water couldn’t penetrate, and we saw a remarkable change in the corresponding behavior of glaciers across the region: a clear reduction in the rate of melting and loss of ice mass”.
What was the cause of the weakening of the winds and, therefore, of the reduction in snowmelt? The researchers found that the main cause was an unusual deepening of the Amundsen Sea low-pressure system, which led to less intrusion of warm water. This system is the key atmospheric circulation pattern in the region, and the location of its center of pressure -near which the greatest changes in the strength of the offshore winds occur- It is usually located offshore from its homonymous coast during most of the year.
Farther from this center of pressure, the researchers found that the accelerated response of glaciers flowing from the Bellingshausen Sea sector can be explained by relatively more undisturbed winds, allowing for comparatively more persistent ocean-driven melt.
Ultimately, the study illustrates the complexity of the interactions between ice, ocean and atmosphere that drive short-term changes in West Antarctica, And it raises important questions about how quickly the frozen continent will evolve in a warming world.
