What is a Rossby wave train? Scientists explain how Antarctica gained nearly 700 billion tons of ice – The surprising atmospheric pattern that disrupted normal weather, delivered extraordinary snowfall and and temporarily reversed the continent’s long-term ice loss

Antarctica has briefly defied its long-term ice-loss trend, gaining about 695 billion tons of mass between July 2021 and April 2023. Scientists now say the explanation did not begin at the South Pole. Instead, unusually warm tropical ocean waters thousands of miles away helped set off a chain of atmospheric changes that delivered exceptional snowfall to East Antarctica. The key player was a Rossby wave train, a large-scale atmospheric pattern capable of carrying the influence of distant weather disturbances across enormous distances. The new findings do not mean Antarctica has entered a lasting recovery. Researchers say the ice gain was temporary and largely reflected natural climate variability. Still, the study reveals how closely connected the tropics and polar regions can be – and why understanding those links matters for future sea-level projections.

WHAT IS A ROSSBY WAVE TRAIN?

A Rossby wave train is a sequence of large-scale atmospheric wave disturbances that propagates through the mid- and high-latitude circulation, allowing changes in tropical or midlatitude conditions to influence weather far downstream. In the new study, published in Nature on August 19, researchers found that persistent warming in the tropical warm pool during 2021–2023 helped excite a Rossby wave train that traveled toward high southern latitudes. The warm pool covers parts of the western Pacific and eastern Indian Ocean and contains some of the planet’s warmest waters. The waves helped reorganize atmospheric circulation over East Antarctica. Scientists identified a north-south pressure pattern, including higher pressure near the East Antarctic coast. That circulation change became an important link between tropical ocean warming and Antarctic snowfall.

HOW DID ANTARCTICA GAIN 695 BILLION TONS?

The research team, led by Yunhe Wang of the Institute of Oceanology, Chinese Academy of Sciences, combined satellite gravity observations, precipitation records, ice-core evidence and atmospheric modeling to investigate the unusual event. GRACE and GRACE-FO satellite measurements showed that Antarctica gained roughly 695 billion tons of mass during the 22-month period. Most of the increase occurred in East Antarctica, especially the Queen Mary Land and Wilkes Land region. The circulation pattern changed where moisture traveled. Researchers found that atmospheric rivers carried additional water vapor from the mid-latitude Indian Ocean toward East Antarctica. When that moisture reached the continent’s extremely cold environment, it fell as snow.

WHY THE ICE GAIN DOES NOT MEAN ANTARCTICA IS RECOVERING

The findings are striking, but scientists caution against interpreting them as evidence that climate change has been reversed. Antarctica continued to experience substantial ice loss in other regions, particularly West Antarctica, where ocean-driven melting remains a major concern. The study, published in Nature, was conducted by Yunhe Wang, Qinghua Ding, Xiaofeng Li, Thomas J. Ballinger, Yoshihiro Nakayama, Dániel Topál and Eric J. Steig. Their analysis suggests that similar prolonged warming events in the tropical warm pool occur roughly once a decade, making the 2021–2023 event unusual but not unprecedented. The researchers describe the tropical warm pool as a remote regulator of East Antarctic precipitation. Its influence can temporarily increase snowfall and slow overall ice loss, but it does not erase the continent’s longer-term vulnerability.

For climate scientists, the bigger lesson is that Antarctic ice changes cannot be understood by looking only at Antarctica. Distant ocean temperatures, atmospheric waves and moisture pathways can all influence the continent’s mass balance. Those connections will be important when scientists refine models and improve projections of future sea-level rise.