Climate Change

Antarctica’s sea ice is at its lowest extent ever recorded

High temperatures and warm air from north may be responsible: Experts

By Rohini Krishnamurthy
Published: Wednesday 26 July 2023
As of July 25, 2023, Antarctica’s sea ice extent was about 14.2 million square kilometres, which should be closer to 16.7 million sq km normally. Photo: iStock

As the northern hemisphere shatters new temperature records, Antarctica in the southern hemisphere is also bearing the brunt of warm temperatures.

Despite it being peak winter in the southern hemisphere, the sea ice cover in Antarctica has deviated from the 1991-2020 average by over six standard deviations (SD). One SD is a measure of how much an observation deviates from the mean. 

An SD value of 6.4 is really well outside of a value that we would expect to see, or closer to a 1 in 100 chance of occurring with a population of 43 years’ worth of data,” Howard Diamond, Climate Science Programme Manager at the United States’s National Oceanic and Atmospheric Administration air resources laboratory, told Down To Earth.

Read more: Mega iceberg released 158 billion tonnes of water into ocean

As of July 25, 2023, the sea ice extent was about 14.2 million square kilometres. The normal amount of sea ice for this time of year, Diamond explained, should be closer to 16.7 million sq km.

In June 2023, the sea ice extent was 11.02 million square kilometres, deviating by 18.13 per cent from the 1991-2020 mean. This value is ranked the smallest in the last 45 years, according to the National Snow and Ice Data Center.

Antarctica lost about 2.6 million square kilometres of sea ice compared to the long-term average of the satellite era, the United Nations’ World Meteorological Organization highlighted.

“Despite sea ice levels being low this year, they are still growing (as you can see in my first two plots), but just more slowly than all the other years in the record since 1979,” Diamond explained.

The first graph (top) represents the anomaly and the second shows the sea ice extent. Source: Howard Diamond, Climate Science Programme Manager at NOAA's Air Resources Laboratory

Typically, the Southern Ocean that encircles Antarctica freezes to form sea ice every year, reaching its maximum at the end of winter, which is September or early October in the Southern Hemisphere. 

In the summer months, which last from December to February, the sea ice melts due to warmer temperatures and longer hours of sunlight.

From years to 2012 to 2014, satellites observed new record highs for winter sea ice extent in September. But since 2015, there has been a significant drop.

Read more: Climate change 'hitting harder and sooner' than forecast: Report

Further, temperatures in and around Antarctica are up to 2.0-3.0°C above normal in the surface waters around Antarctica and up to 4.0°C above normal on land, per data collated by Diamond.

Further, the lack of sea ice is causing temperatures to warm further. The bright surface of sea ice is known to reflect incoming sunlight into space.

“Without sea ice, the ocean absorbs sunlight and gives off heat to the atmosphere, keeping the atmosphere warmer than it would be over sea ice,” Walt Meier, senior research scientist at National Snow and Ice Data Center, University of Colorado, told DTE.

Winds from the north are transporting warm air to Antarctica. “This could be contributing to the low ice condition,” he added.

There is currently no data on the current impacts of the record low sea ice extent on marine life. But the heat does not bode well for wildlife accustomed to low temperatures.  

Read more: Anthropocene in the Arctic

Meier warns that if this trend continues, we could see large impacts in the coming years. For example, warmer ocean waters can melt and thin glaciers and ice shelves that extend over the ocean without sea ice, Meier explained.

Over time, he added, the ice and parts of the floating shelves could become destabilised and glaciers may break up. “Ultimately, this can allow more ice on land to flow into the ocean and melt, which raises the sea level,” he noted.

The global mean sea level has already gone up by 21–24 centimetres since 1880, according to National Aeronautics and Space Administration.

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