Venu Menon
Wellington, November 13,2023
It is not all bad news from Antarctica.
While warming ocean temperatures are melting the ice sheet from below the surface leading to a long-term trend of significant ice sheet loss, very heavy snowfall during 2022 has resulted in an overall gain in Antarctica’s ice mass.
This is the first time a net gain in Antarctica’s ice mass has been recorded since satellite measurements began in 2003.
Climate report
This is among the key findings of the latest State of the Climate report, an annual review of the world’s climate, compiled by the National Centres for Environmental Information, affiliated to the National Oceanic and Atmospheric Administration (NOAA) in the US, and published as a supplement to the Bulletin of the American Meteorological Society. It is based on contributions by scientists from around the world.
The report, published last month, confirmed that greenhouse gases, global sea levels, and ocean warming all peaked in 2022.
Said Dr Kyle Clem, lead editor of the report’s chapter on Antarctica and the Southern Ocean and a lecturer in climate science at Victoria University of Wellington: “An unprecedented heatwave hit East Antarctica in March 2022, pushing temperatures in the cold, high elevation interior to a new all-time high.”
This resulted in “significant surface melting along the East Antarctica coast,” which was followed shortly after by the “collapse of the critically unstable Conger Ice Shelf,” Dr Clem said.
Warmer temperatures resulted in a record drop in sea ice around Antarctica last year, causing “a rapid retreat of upstream glaciers.”
Sea ice has continued to deplete in 2023.
Antarctica ice mass
Yet, despite the ice sheet loss due to warming ocean temperatures, Antarctica has recorded a gain in ice mass, thanks to heavier than normal snowfall during 2022.
“While 2,100 gigatonnes (Gt) of glacial ice was lost, heavy snowfall associated with atmospheric rivers added an estimated 2,400 Gt of surface mass to the continent. This meant Antarctica gained approximately 300 Gt of mass,” Dr Clem said.
Snowfall vs melting
He added: “This is remarkable and highlights the complex interplay of snowfall versus melting in Antarctica in a warming world.
“A warmer world will both melt ice and increase snowfall intensity, potentially even leading to more rainfall events.”
While global sea levels were rising due to ocean warming and ice loss, “the ice gain on the continent meant Antarctica actually contributed a sea level reduction of a little under 1mm.”
The report traced many of the events on the Antarctic continent in 2022 to two “strong atmospheric conditions that dominated the region.”
The first was “a deep low in the Bellingshausen, Amundsen and Ross Seas,” while the second was “a strong blocking high in the southwest Pacific.”
“These conditions resulted in a persistent warm northerly flow together with an unusually high number of atmospheric rivers – long bands of moisture- laden air,” said Dr Clem.
Ozone layer
The report recorded the sighting of an abnormally long-lasting hole in the ozone layer above Antarctica.
“The Antarctic ozone hole is still a prominent feature of the Southern Hemisphere during the spring and summer. In 2022, it developed again during August and September and didn’t break up until December 16, marking one of the longest-lived ozone holes on record,” Dr Clem noted.
But there was cause for relief.
“However, its total size was near-average and it had a slower-than-average growth rate, which are signs of continued ozone recovery,” Dr Clem said.
Venu Menon is an Indian Newslink reporter based in Wellington
