Mythbusters: is Antarctica really growing?

Polly Stevens discusses the commonly held belief that in spite of global warming, Antarctica is actually gaining mass.

Polly Stevens
30th October 2020
The idea that Antarctica is experiencing ice expansion is commonly cited as an argument against global warming: how can the frozen land mass be growing when the climate is supposedly warming at an unprecedented rate? But is there any truth in the climate denier’s favourite piece of evidence: is Antarctica really growing? 

The answer is - technically - no. While the interior of East Antarctica is slightly gaining mass due to increased snowfall in a warming climate, ice loss from West Antarctica means that, overall, the continent is losing land ice at an accelerating rate. Scientists estimate that between 1992 and 2017, Antarctica lost 2 720 billion tonnes of ice, equating to a sea level rise of 0.3mm/yr. 

So where has the myth of the continent’s expansion come from? The answer lies not in Antarctica, but in what surrounds it: sea ice. Formed in salt water during winter and almost entirely melting during summer, sea ice surrounding Antarctica has experienced long term growth since the start of satellite observations in 1979, prompting the misconception that it is the continent itself that is expanding. However, unlike land ice, when sea ice melts, global sea levels do not measurably change. 

As to the causes of this growth in sea ice in an ocean warming at an unprecedented rate of 0.17°C per decade, there are several theories. A drop in ozone levels over Antarctica may have strengthened cyclonic winds which create open areas of water, known as polynyas, in turn increasing sea ice production. Ocean circulation is also likely to have played a role: increased rain and snowfall due to higher air temperatures leads to ocean stratification as freshwater is deposited at the surface, reducing heat transportation from deeper water and melting of floating sea ice. 

In summary, Antarctic sea ice is a complex manifestation of the variable impact of climate change on the planet. But in any case, our focus should lie on the principle message that Antarctica is sending us, in the form of an unprecedented rate of continental ice melt with the potential to raise sea levels by 6.5m in the next century.

Featured image: Pxfuel

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