Melting ice shields in the Antarctic will raise the sea level
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Scientists warn that Antarctica may have passed the climatic turning point of the return, with growing evidence that a sudden decline in the formation of sea ice has been associated with the human caused warming of the ocean.
For decades, the level of Antarctic sea ice remained relatively stable, despite the increase in global temperature. But this suddenly changed in 2016, when the degree of sea ice began to drop sharply.
In February 2023, Antarctic sea ice set a new minimum of records, the third record summer for low sea ice in just seven years. In September 2023, there was also a record maximum for Antarctic sea ice.
Climate models have long predicted the loss of sea ice to accelerate in the Antarctic, but the speed and magnitude of the decrease since 2016 have found scientists -climatologists by surprise and Researchers tried to explain the shiftThis week, scientists met in Royal Society in London to discuss whether the recent changes in the climate -renewal of the liable moment are presented.
Natural variability in the climate and weather cannot explain the sudden transition, says Marilyn Rafael At the University of California, Los -Angels.
Satellite records for measuring sea ice began only in 1979. The use of data on proxy from the Antarctic weather stations, Rafael and its colleagues expanded the time series before the beginning of the 20th century.
They came to the conclusion that, based only on historical data, the probability of a minimum of sea ice in 2023 was less than 0.1 percent. “We really look at extreme behavior in terms of sea ice,” she said in a presentation at a meeting of royal society.
A sudden decline in ice formation has distinctive features of the climate point, says Alexander Haumann At the Institute of Alfred Veener in Germany. He told the delegates that the change occurred suddenly, influenced the entire continent and will have a huge impact on the wider climate and ecology of Antarctica.
“Now we see that the entire Antarctic sea ice is in general,” he said New scientist At the meeting. “And the changes that we observe are very long -term and, in the visible, are preserved in the system for a long time.”
The minimum length of the Antarctic sea ice last summer was much lower than the historical level
NASA scientific visualization studio
Hauman says that the “superimposed changes” in the sea ice system are to blame, and now the studies that appear show that ocean water warming is behind a sudden decrease. The oceans in the world absorbed about 90 percent of excess heat, captured in the atmosphere as a result of human activity.
In the Antarctic, warm, deep ocean waters are usually contained by a layer of cold fresh water separate from mixed surface waters. But New study of Hauman and his colleagues It assumes that changes in the speed of wind and salinity in the Southern Ocean have significantly weakened this border layer since 2015, which leads to greater effects of warmer, deep ocean water to the surface, which leads to ice loss. This deep ocean water was heated as a result of climate change, Studies showField
Hauman says that natural variability in the climatic system may have caused changes in the salinity of the ocean and winds, but warns that this has released the consequences caused by a man of warming stored in the deep water of the ocean. In fact, this may mean the influence of ocean water warming is currently felt in Antarctica, where he limits the formation of new sea ice.
Recent changes in circulation can only be addressed by damping the effect of lifting or sudden change in the salinity of the Southern Ocean, for example, through a sudden influx of fresh water from melting a huge glacier, says Haumann. But any future systemic response is very vague, he says.
The consequences of this recent move can be catastrophic. Antarctica’s sea ice helps stabilize glaciers and ice shields on Earth. Without adequate formation of sea ice, their melting indicators will accelerate, which can cause an extremely global increase in sea level. It is assumed that the ice cover of the Antarctic contains enough water to increase the global sea level by 58 metersField
The loss of antarctic sea ice will affect the brightness of the surface of the earth, since the water of the dark ocean absorbs more heat from the sun than reflecting white ice, which will lead to further warming.
Meanwhile, hundreds of carbon gigatons stored in the deep waters of the South Ocean can also be released into the atmosphere through increased deep water up, up, up Studies suggestField
Scientists are just beginning to understand how such climate feedback effects could play in the AntarcticAfter decades of fighting inaccurate models and low -resolution models.
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