New research, published in the journal Nature Climate Change has revealed that circulation in the southern ocean is compromising the East Antarctic ice sheet, a dangerous finding for the world’s coastal cities. The ice sheet is massive, and its stability was never in doubt for decades. But no more, as in Greenland and West Antarctica, warm water is melting the underbelly of the marine extensions of glaciers in the region.
The decay from below had caused the first East Antarctica ice shelf (Glenzer and Conger glaciers) to completely disintegrate rather than shedding an iceberg, a natural phenomenon in the Antarctic.
The study by lead authors Laura Herraiz Borreguero, Alberto Naveira Garabato, and Jess Melbourne-Thomas focused on the Aurora Subglacial Basin, which is primarily anchored below sea level and drained by the Totten Glacier. Totten is a highly vulnerable glacier to warming water. Totten has ice-carved fjords over one mile deep, where warm water can now pulse, wreaking havoc on the stability of Totten, which holds 10.66 feet of sea level rise. The study revealed — “warm water replacing the colder dense shelf water.”
The authors write in The Conversation:
We examined 90 years of oceanographic observations off the Aurora Subglacial Basin. We found unequivocal ocean warming at a rate of up to 2℃ to 3℃ since the earlier half of the 20th century. This equates to 0.1℃ to 0.4℃ per decade.
The warming trend has tripled since the 1990s, reaching a rate of 0.3℃ to 0.9℃ each decade.
So how is this warming linked to climate change? The answer relates to a belt of strong westerly winds over the Southern Ocean. Since the 1960s, these winds have been moving south towards Antarctica during years when the Southern Annular Mode, a climate driver, is in a positive phase.
The phenomenon has been partly attributed to increasing greenhouse gases in the atmosphere. As a result, westerly winds are moving closer to Antarctica in summer, bringing warm water with them.
The East Antarctic ice sheet was once thought to be relatively stable and sheltered from warming oceans. That’s in part because it’s surrounded by very cold water known as “dense shelf water”.
Part of our research focused on the Vanderford Glacier in East Antarctica. There, we observed the warm water replacing the colder dense shelf water.
The movement of warm waters towards East Antarctica is expected to worsen throughout the 21st century, further threatening the ice sheet’s stability.
The calving event occurred faster than predicted when the ice separated on July 16, 2022.
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Europes Copernicus satellite found the lowest sea ice in the satellite record for the months of June, July continuing in August.
The Copernicus Climate Change Service (C3S) found Antarctic sea ice extent reached 15.3 million square kilometers (5,900,000 square miles)—some 1.1 million km2, or seven percent, below the 1991-2020 average for July.
This was the lowest ice cover for July since satellite records began 44 years ago, and followed record low Antarctic sea ice levels for June too.
C3S said the low ice values continued a string of below-average monthly extents observed since February 2022.
The service said in its monthly bulletin the Southern Ocean saw "widespread areas of below-average sea ice concentration" last month.
Somewhere in Antarctica.