Antarctica Gained a Record 695 Billion Tons of Ice, Study Finds

A persistent patch of unusually warm tropical ocean water set off a chain of atmospheric changes that boosted snowfall over East Antarctica, temporarily adding about 695 billion tons of mass to the Antarctic Ice Sheet, a study published in the journal Nature on August 19 has found. The gain, recorded during 2021-23, is the largest Antarctic mass increase observed by the GRACE satellite missions.

Over the past two decades, Antarctica has lost ice at an average rate of about 140.5 billion tons a year, making the ice sheet a major source of uncertainty in sea-level-rise projections. Researchers led by the Institute of Oceanology, Chinese Academy of Sciences (IOCAS) combined gravity satellite data, ice-core snow records and circulation simulations to trace the reversal.

The team found that sustained warming of the "tropical warm pool," where the tropical western Pacific meets the eastern Indian Ocean and holds some of the planet's warmest water, generated a Rossby wave train, a large-scale pattern of atmospheric waves carrying weather changes across vast distances. This produced a north-south pressure dipole: unusual low pressure south of Australia and unusual high pressure along the East Antarctic coast. That pattern rerouted moisture, strengthening atmospheric rivers, narrow corridors carrying huge amounts of water vapor, toward East Antarctica, producing heavy snowfall over the Queen Mary Land-Wilkes Land region.

Human-caused warming accounted for only about 9% of the observed snowfall increase, the researchers calculated, showing natural tropical variability, not general global warming, mainly drove the event. Similar warm-pool heating episodes occur roughly once a decade, leading the authors to call the region a remote "regulator" of East Antarctic ice mass.

Despite the record gain, the researchers stressed that the event was temporary and does not reverse the ice sheet's long-term decline. The West Antarctic Ice Sheet continues losing mass, and some East Antarctic outlet glaciers remain vulnerable as warm ocean water melts their ice shelves from below, speeding up ice flow.