Richard Musgrove
Dr Richard Musgrove is a zoologist and science journalist. He writes for Cosmos and Double Helix.
Chinese researchers were surprised to find growth in coastal glaciers in East Antarctica two years ago, prompting them to remind the scientific community to pay more attention to the region.
Antarctica is losing about 136 billion tonnes of ice per year, with Greenland almost double that, at 267 billion tonnes, says NASA. These two ice sheets hold two thirds of the freshwater on Earth, and their melting – because of ongoing anthropogenic global heating – is pushing sea levels higher.
Complete glacier collapse could contribute to 7m of sea level rise, says Dr Wei Wang of Shanghai’s Tonji University.
Sea levels have risen by about 225mm since 1880, including 101mm since 1993, suggesting ice melt is accelerating, contributing to a predicted rise of 2.2m over the next 75 years.
Images from NASA’s satellites show thinning ice sheets and retreating glaciers in Antarctica, which have contributed about a third of the estimated 63mm mm of global sea level rise since 2002.
But melting of these vast ice sheets is not as simple as the vanishing ice cube in that gin and tonic. Antarctica is almost twice the size of Australia and 98% covered in ice to an average depth of around 2.2km, and in some places 4.8km.
The Shanghai team used the NASA data to explore changes in Antarctica’s Ice Sheet (AIS) between April 2002 and December, 2023.
Lead author Dr Wei Wang says they focussed on four glacier basins (Denman; Moscow; Totten; and Vincennes Bay) in the East Antarctic Ice Sheet (EAIS).
Around 74 billion tonnes of ice disappeared each year from 2002 to 2010, and almost twice that, 142 billion tonnes, was lost each year between 2011 and 2020.
This lines up with the temperatures experienced in the frozen south. Professor John Turner of the British Antarctic Survey says that temperatures on the Antarctic Peninsula rose by around 3.2°C in the second half of the 20th century, more than 3 times the global average, a rise only matched in the Arctic.
In Vincennes Bay and Denham losses were “intense” says Wang, as they suffered about 72.5% surface melt and 27.5% ice loss.
More melting causes instability in the ice sheets, which leads to more ice loss. Dr Nicole Schlegal, of NASA’s Sea Level Change Team says, “When polar ocean temperatures rise, then you have thinning in those ice shelves, but you can have other things occur when the ice shelves are also affected by the atmosphere.
“So, when you have more melting on the surface because the temperatures of the atmosphere are going up, in addition to the ocean-driven melting, then that can help create instabilities and cracks. And then you can have increased ice loss due to calving, which is when a portion of the ice shelf breaks away.”
Dr Alex Gardner, also of NASA’s Sea Level Change Team, says “Once you start thinning the ice, you start to put more ice into the ocean,” he said. “That leads to more thinning and that leads to more loss, more thinning, more loss. And then all of a sudden, you can have the collapse of an entire ice sheet.”
Wang says “strangely the AIS froze up a little until 2023,” because more snow fell. The gain was 107 billion tonnes.
Wang concludes that the scientific community should pay more attention to such coastal glacier basins. “Complete disintegration” of the four glaciers in East Antarctica could trigger global sea level rise of more than 7m, he says.
The paper was published in Science China Earth Sciences
Antarctica’s ice melt threatens the planet
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