Cause of Antarctic ice gain identified

While the Antarctic ice sheet has lost mass at an average rate of about 140.5 billion metric tons a year over the past two decades, satellite data showed a striking reversal from 2021 to 2023, when the ice sheet gained 695 billion tons — the largest increase on record.

An international research team has now identified the mechanism behind the unusual gain, revealing a previously overlooked climate link between the tropics and the Antarctic ice sheet.

The study, conducted by researchers from institutes in China, the United States, Japan, Belgium and Hungary, was published in the journal Nature on Wednesday.

The researchers found that sustained warming in the tropical warm pool — a broad region where the western Pacific and eastern Indian oceans meet and sea surface temperatures are persistently high — sent large-scale atmospheric waves southward toward Antarctica. These waves carried unusually large amounts of moisture from the midlatitude Indian Ocean to Queen Mary Land and Wilkes Land in East Antarctica, resulting in persistent heavy snowfall.

The researchers used several types of evidence, including satellite measurements of changes in Earth's gravity, records of snowfall preserved in Antarctic ice cores and computer simulations of atmospheric circulation.

Wang Yunhe, first author of the study and an associate professor at the Institute of Oceanology of the Chinese Academy of Sciences, said such warming events in the tropical warm pool typically develop and persist for two to three years and occur roughly once in a decade. Similar, although smaller, fluctuations were observed around 2000, he said.

The team also examined what caused the unusual warming and snowfall. Their analysis showed that human-induced climate change accounted for only about 9 percent of the increase in snowfall, indicating that the event was driven mainly by natural fluctuations within the climate system rather than by greenhouse gas warming.

Wang, however, said the temporary increase in snowfall does not alter the Antarctic ice sheet's long-term trend.

"The West Antarctic ice sheet is still losing ice, and some outlet glaciers in East Antarctica are also threatened by ocean-driven ice shelf melting and accelerated ice flow," he said.

The findings help resolve a long-standing puzzle in Antarctic science: why the ice sheet's mass can fluctuate sharply over relatively short periods.

"Scientists have tried to explain the unusual fluctuations in Antarctic ice sheet mass," Wang said. "Most researchers have focused on the central and eastern tropical Pacific and its connection with West Antarctica, where climate signals are strongest and easiest to detect. We looked at the other side — the western Pacific warm pool and its connection with East Antarctica — and identified a pathway that had not previously been recognized."

In climate science, such a connection is known as a teleconnection, meaning that changes in one distant part of the climate system can influence weather and climate far away through atmospheric circulation.

The study identifies a previously underappreciated link between the tropical warm pool and the East Antarctic ice sheet, Wang said.

The finding provides a new framework for understanding short-term changes in Antarctic ice mass and could help guide future research into the climate of East Antarctica.