As expected, NASA satellite data shows the Antarctica sea ice coverage for the month of July was the smallest measured since continuous satellite monitoring began 45 years ago.
Map of sea ice extent surrounding Antarctica as of August 7, 2023, based on data from NASA's National Snow and Ice Data Center (NSIDC). The map also shows the historic average extent of the sea ice there. Image: NASA
Antarctica is currently immersed in the dead of winter.
It is a time when the ice sheets should be at their fullest, mostly not exposed to the sun much at all because of the inclination of the Earth’s axis this time of year. Yet this year, thanks to the overlap of the long-term warming trend caused by heat trapped by greenhouse gases close to the Earth’s surface, and unusually warm oceanic water conditions in the Southern Sea, the Antarctic ice had receded far from what it used to be only a few years ago.
According to satellite data provided by the National Aeronautics and Space Administration, Antarctic ice for July averaged just 5.2 million square miles (13.5 million square kilometers).
That coverage was roughly 772,000 square miles (2 million square kilometers) smaller than the average ice coverage of the polar “continent” from the period running from 1981 to 2010. That shrinkage is similar in size to the country of Mexico.
In most years sea ice melts in its summer months, shedding on average some 5.8 million square miles (15 million square kilometers) of coverage soon after the hottest months have passed, typically in the first few calendar months of the year. That same 5.8 million square miles typically regrows at a steady pace as the hours of sunlight shrink seasonally and the temperatures fall towards the peak of Antarctic’s winter. This year, however, that regrowth has been far slower than usual.
Antarctica's daily sea ice extent through August 7, 2023 (red) compared to the 2022 record low (orange) and the average extent from 1981 to 2010 (blue). Image: NASA
That slow rate of ice regeneration was present virtually everywhere within the South Pole region this year. The eastern Bellingshausen Sea, the Ross Sea in the northern parts, and the northeastern Weddell Sea all suffered the same much-lower-than-normal ice growth fate. Just one area, the Amundsen Sea, had above-average growth for this period.
The presence of far less sea ice in the mid-winter months in Antarctica is part of a decade-long trend which began in 2014. Just before that year the ice sheet areas around Antarctica had been growing for a few years, though without much understanding of all the factors that had caused that temporary blip in the long-term ice sheet shrinkage trend. Since 2014, however, the winter ice coverage there has diminished at an increasingly rapid clip. Prior to this year, satellite analysis measured a series of low ice coverage records being broken, first in 2017, then 2022, and now.
According to Claire Parkinson, a climate scientist who has been actively studying what is happening regarding Antarctica ice since 1983, it is a puzzle as to what is triggering the rapid decline of the ice sheets now.
“Both the increase in Antarctic sea ice prior to 2014 and its rapid decrease since are of great interest to scientists, without a consensus point-of-view on the drivers,” she said in an interview about this year’s unusually sharp decline in ice regrowth.
She also noted the current rate of ice coverage decline is accelerating, as expected.
One theory behind the lack of ice regrowth is that rapid ocean warming more generally in the Southern Hemisphere is having a stronger effect on ice melting than ever before. As the current El Niño global warming cycle of equatorial waters in the Pacific deepens, this could have implications for the Southern Seas that might push sea ice melting surrounding Antarctica to accelerate even further.
As this happens, with global heating accelerating more generally, that could cause more rapid outflows of fresh water into the ocean. The result would be faster sea level rise than expected and, with the ice mostly lost forever, could allow solar warming of the Southern Ocean itself to become more extreme.
NASA’s scientists say than increased ocean heat could be “playing a stronger role in limiting autumn and winter ice growth and enhancing spring and summer melting”. In doing so, it could be created yet another concerning climate feedback loop. It also could cause disruption in major ocean currents which surround Antarctica.
Together this could have implications in creating a more-powerful-than-usual southern polar vortex pattern below Australia, and a heat bubble generating southwards of the South American continent. Such a heat bubble has already created havoc in Chile and Argentina this summer, which together have experienced blisteringly hot temperatures earlier this month.