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In the depths of the Southern Hemisphere, the borders of one of Antarctica’s vast ice sheets are succumbing to warm waters. As the Earth’s temperature rises, larger quantities of warm water are caressing West Antarctica’s ice shelves, the colossal extensions of ice at the end of glaciers. These massive shelves act as barriers, preventing land-based ice from flowing more rapidly into the open sea. Consequently, as the shelves diminish and weaken, more land ice is channelled towards the ocean, ultimately contributing to the swelling of sea levels. Although reducing emissions from fossil fuels could mitigate this melting process, the extent of its effectiveness has been unclear to scientists.
British researchers have crunched the numbers and arrived at a disconcerting verdict: a certain degree of accelerated melting is essentially inevitable. Even if nations were to cap global warming at 1.5 degrees Celsius (2.7 Fahrenheit), the thinning of these ice shelves would persist. Maintaining temperatures below 1.5 degrees Celsius represents the loftiest ambition of the Paris Agreement, but it currently appears improbable to attain.
The findings, published in the journal Nature Climate Change on Monday, are giving more grim predictions for the ice in western Antarctica. Two of the region’s fastest-retreating glaciers, Thwaites and Pine Island, have been shedding substantial volumes of ice into the ocean for several decades. Scientists are striving to determine when greenhouse gas emissions might push the West Antarctic ice sheet past a “tipping point” beyond which its collapse becomes precipitous and difficult to reverse, jeopardizing coastlines worldwide in the ensuing centuries.
Nevertheless, curtailing emissions of heat-trapping gases still holds the potential to prevent even more extensive losses of Antarctic ice from contributing to sea-level rise. The East Antarctic ice sheet, which contains approximately ten times the volume of ice as the West Antarctic counterpart, is generally considered less susceptible to global warming, although recent research has challenged this view.
The researchers initially utilized computer simulations to estimate the changes in ocean temperature and subsequent ice-shelf melting that occurred in the 20th century. They then contrasted these findings with potential scenarios under various global warming trajectories for the 21st century, ranging from highly optimistic to unrealistically pessimistic. Their analysis revealed that the water at depths of 200 to 700 meters (650 to 2,300 feet) below the surface of the Amundsen Sea is set to warm at more than three times the rate in the coming decades compared to the last century, with little sensitivity to emissions trends.
Even if global warming is constrained to 1.5 degrees Celsius relative to preindustrial conditions, temperatures in the Amundsen Sea would only partially stabilize after approximately 2060. In contrast, under the most catastrophic emissions trajectory, ocean warming would accelerate even more rapidly after 2045.
It’s important to note that variations in this region’s water temperatures are influenced not only by human-induced atmospheric warming but also by natural climate oscillations like El Niño.
The study is unlikely to provide the definitive outlook on the destiny of the West Antarctic ice shelves. Scientists have been collecting data on the melting in this region since only 1994, and due to the challenges of gathering measurements in such extreme conditions, data remains limited.
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