Tropical Ocean Warming Triggered Record Antarctic Ice Gain, Scientists Discover

Between 2021 and 2023, East Antarctica accumulated roughly 695 billion tons of ice—the largest gain the GRACE satellite missions have ever recorded. The event was sudden, substantial, and temporary. It also arrived with an explanation that reaches halfway around the world.

For the past twenty years, Antarctica has shed ice at a steady clip of about 140.5 billion tons per year. That relentless loss is one reason climate scientists watch the continent so closely; how fast the ice disappears will shape how high the oceans rise. But for those two years, the pattern reversed. Researchers from the Institute of Oceanology of the Chinese Academy of Sciences set out to understand why, assembling satellite gravity measurements, ice-core records of accumulated snow, and atmospheric circulation models to trace the source of the moisture that fell as snow across East Antarctica's Queen Mary Land and Wilkes Land regions.

The answer began in the tropics. The tropical warm pool—that band of ocean where the western Pacific meets the eastern Indian Ocean, home to some of Earth's warmest water—experienced sustained warming during 2021 and 2023. That warming did not stay local. Instead, it triggered what atmospheric scientists call a Rossby wave train, a large-scale undulation in the atmosphere capable of transmitting weather patterns across vast distances. The wave traveled toward the high southern latitudes and reorganized the air circulation around Antarctica itself, creating what researchers describe as a north-south dipole: unusually low pressure south of Australia paired with unusually high pressure along the East Antarctic coast.

This pressure arrangement redirected the flow of moisture through the atmosphere. Atmospheric rivers—narrow channels that can transport enormous quantities of water vapor—began funneling moist air from the midlatitude Indian Ocean directly toward East Antarctica. When that moisture-laden air reached the cold continent, it fell as snow, heavy and sustained, adding mass to the ice sheet across the region. Computer simulations of atmospheric circulation confirmed that the tropical warming directly drove both the circulation shift and the resulting snowfall increase.

The researchers also tested how much of this snowfall anomaly could be attributed to human-caused climate change—the general increase in atmospheric moisture that comes with global warming. They found it accounted for only about 9 percent of the observed increase. The event, in other words, was primarily a natural climate oscillation, not a signature of anthropogenic forcing.

Yet the discovery carries a larger implication. The team's analysis suggests that comparable periods of sustained tropical warm pool warming occur roughly once per decade. This makes the tropical warm pool, in their framing, a kind of remote regulator—a distant climate switch that can influence how much snow falls on Antarctica and how much mass the ice sheet gains or loses over periods of several years. It is a long-distance connection: conditions in the tropics reshaping atmospheric circulation in ways that ultimately matter for a continent at the bottom of the world.

The researchers are careful to note that this 695-billion-ton gain, striking as it is, does not alter Antarctica's long-term trajectory. The West Antarctic Ice Sheet continues to lose mass. Outlet glaciers in East Antarctica remain vulnerable to warm ocean water melting ice shelves from below, accelerating ice flow into the sea. The temporary reprieve is just that—temporary. But it reveals a previously underrecognized pathway through which distant tropical conditions can influence Antarctic ice-sheet behavior, offering new ground for understanding how the continent's ice will respond to future climate shifts.