Tropical Warming Drove a Record, Temporary Ice Gain in East Antarctica

Between 2021 and 2023, the Antarctic Ice Sheet gained about 695 billion tons of mass, the largest increase recorded by the GRACE satellites, according to a new study in Nature. Researchers led by the Institute of Oceanology of the Chinese Academy of Sciences (IOCAS) traced much of the gain to sustained warming thousands of miles away in the tropical western Pacific and eastern Indian Ocean, which altered atmospheric circulation and sent more moisture toward East Antarctica.

The finding stands out against Antarctica's longer-term trend: over the past two decades, the ice sheet has lost mass at an average rate of about 140.5 billion tons per year, making its future contribution to sea-level rise a major source of uncertainty. The temporary gain did not reverse that decline, the researchers said, but it revealed how conditions in the tropics can influence Antarctic snowfall over several years.

The team combined gravity-satellite observations, ice-core snow-accumulation records, water-vapor tracking and atmospheric circulation simulations to trace the 2021-23 event. They found that sustained warming in the tropical warm pool triggered a wave pattern in the atmosphere that reshaped circulation over East Antarctica, redirecting moisture from the midlatitude Indian Ocean toward the continent and increasing the number of moisture-carrying atmospheric rivers reaching it. The resulting heavy snowfall was concentrated in the Queen Mary Land-Wilkes Land region.

The researchers found that human-caused warming accounted for only about 9% of the observed snowfall anomaly, meaning the tropical ocean pattern, not global warming directly, was the main driver of the event. Similar periods of sustained tropical warm-pool warming occur roughly once a decade, the study found, suggesting the link between the tropics and East Antarctic snowfall could recur. Despite the temporary gain, the West Antarctic Ice Sheet continues to lose ice, and some East Antarctic outlet glaciers face faster melting driven by warm ocean water.