On February 21, 2023, Antarctic sea ice extent dropped to its lowest level since satellite observations began 45 years ago, marking the second year in a row with an ice area below two million km2. These worrisome findings raise the question of whether this change is merely a brief anomaly – since sea ice in the Southern Ocean is known to be highly variable, both seasonally and interannually – or an early sign of a transition to a long-term decline comparable to the current situation in the Arctic.
After the 2022 minimum of 1.924 million km2, massive heatwaves in mid-March contributed to further declines – particularly in East Antarctica and coastal areas – and since late May, the pace of seasonal ice growth had slowed dramatically, mostly due to anomalous northerly and northwesterly winds in parts of the eastern Pacific, western Atlantic, and central Indian Oceans that transported warm air southwards. Later in the year, the seasonal ice melt continued to increase in response to a stronger seasonal warming anomaly, culminating in the seasonal minimum of 1.788 million km2 measured in February.
According to an analysis published in the journal Ocean-Land-Atmosphere Research, this new record low could be a sign that Antarctic sea ice might enter a new regime, involving “a robust transition from long-term increasing Antarctic sea ice to decreasing sea ice, in which anthropogenic forcing outweighs natural variability.”
“Concern about a tipping point is enhanced by the fact that the latest generation of climate and earth system models projects a large decrease in Antarctic sea ice associated with increased greenhouse gases during the 21st century,” the authors explained.
If sea ice continues to dwindle at such a rate, Antarctica will likely witness more frequent climate extremes and severe instability of its ice shelves, phenomena that will disastrously impact the local food chains and wildlife populations, and have major global consequences such as sea level rise and carbon cycle feedback.
“The question is, has climate change reached Antarctica? Is this the beginning of the end? Will the sea ice disappear for good in the coming years in the summer?” asked Christian Haas, head of the Sea Ice Physics Research Section at the Alfred Wegener Institute for Polar and Marine Research in Germany.
However, since until now Antarctica’s response to climate change has been highly different from the Arctic’s, it is not yet clear how Antarctic sea ice will evolve during the following years. “The downward trend in sea ice may be a signal that global warming is finally affecting the floating ice around Antarctica, but it will take several more years to be confident of it,” concluded Ted Scambos, a senior research scientist at the Cooperative Institute for Research in the Environmental Sciences (CIRES).
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