East Antarctica Far More Vulnerable to High Emissions: Could Add Up to Five Meters Sea-Level Rise by 2300

Nature, 10 August 2022

Under a high-emissions scenario, ice loss could accelerate across the East Antarctic Ice Sheet and generate several meters of sea-level rise within just a few centuries; but this substantial loss could be avoided if temperatures remain within the “well below 2°C” limit of the Paris Agreement.

This comprehensive review study found that in recent decades, glaciers are rapidly thinning across several regions of East Antarctica due to increasingly warm ocean currents eroding the base of the ice sheet. In particular, ice loss has likely accelerated by a factor of ten in the massive Wilkes Land region of East Antarctica over the past decade; and the huge Denman Glacier is now experiencing ice shelf melt rates comparable to the highest rates in West Antarctica.

Evidence from the “paleo record” highlights the sensitivity of East Antarctica’s three main subglacial basins (Aurora, Wilkes, and Recovery) to previous warm periods, which had climate conditions similar to today. During the early to mid-Miocene (24-14 million years ago), the East Antarctic Ice Sheet experienced its largest ice loss as sea surface temperatures peaked around 11-17°C above present, and produced tens of meters of sea-level rise from these three main basins, which are much larger than those in West Antarctica. With current emission trends, average mid-Miocene atmospheric CO2 concentrations could be reached by 2100. The most recent period when CO2 concentrations last exceeded today’s current levels around 400 ppm was the Mid-Pliocene (3.5-3 million years ago). Mid-Pliocene atmospheric temperatures were about 2-4°C warmer than present, and the Aurora and Wilkes basins both substantially retreated, resulting in several meters of sea-level rise above today.

Climate projections indicate surface melt and rainfall on East Antarctic ice shelves will increase over the next century, further increasing the vulnerability of this region to rapid thinning. If temperatures remain well below 2°C however, East Antarctica might only contribute 0.6 meters to global sea-level rise by 2300, slowing to 0.7 meters by 2500. Under a high-emissions scenario, East Antarctica could contribute 3 meters of sea-level rise by 2300 and nearly 5.5 meters by 2500. Of greater concern, projections incorporating “marine ice cliff instability” processes, which involve the collapse of deep ice cliffs and intense fracturing along the edge of the continent, warn that East Antarctica could produce 5 meters of sea-level rise as early as 2300.

These findings underscore the necessity of strictly upholding nationally determined contributions and other pledges, especially prior to 2030; and preferably to keep global temperatures within the 1.5°C limit, according to an interview with lead author Chris Stokes. Reducing emissions is the only way to avoid substantial ice loss and keep the East Antarctic Ice Sheet’s sea-level contribution well below a meter over coming centuries. As the authors conclude, “The fate of the world’s largest ice sheet remains very much in our hands.”

https://www.nature.com/articles/s41586-022-04946-0