For decades, Antarctica’s ice sheet has been melting fast, pushing sea levels higher with each passing year. The losses were relentless, particularly in West Antarctica and the vulnerable glacier basins of East Antarctica.

But in an unexpected twist, scientists observed a dramatic reversal: between 2021 and 2023, the Antarctic Ice Sheet gained mass — for the first time in decades. This anomaly, driven by unusual precipitation patterns, is reshaping how scientists understand the icy continent’s role in the climate crisis.

Data from NASA’s GRACE and GRACE-FO missions have been pivotal in tracking the Antarctic Ice Sheet’s mass changes over time. For nearly two decades, the data told a grim story. From 2002 to 2010, Antarctica lost ice at a rate of 73.79 gigatons per year, a figure that surged to 142.06 gigatons annually between 2011 and 2020. Most of this loss came from West Antarctica and the Wilkes Land-Queen Mary Land (WL-QML) region in East Antarctica.

Then, between 2021 and 2023, the trend took a surprising turn. Antarctica saw a net gain of 107.79 gigatons of ice per year — marking a rare period of recovery. This gain was especially pronounced in four East Antarctic glacier basins — Totten, Moscow, Denman and Vincennes Bay — which had previously been losing mass due to reduced surface accumulation and faster ice discharge. These glaciers, once indicators of accelerating loss, shifted course and began accumulating ice again.

The implications for sea-level rise are significant. Between 2002 and 2010, the AIS added about 0.20 mm per year to global sea levels. That number rose to 0.39 mm per year from 2011 to 2020. But in 2021-2023, Antarctica’s mass gain helped offset sea-level rise by 0.30 mm per year. Researchers attribute this anomaly largely to increased snowfall over the continent.

Still, the gains may be temporary. The same four glaciers that rebounded recently are among Antarctica’s most unstable. Their total collapse could push sea levels up by more than 7 meters. As scientists continue to monitor these hotspots, the recent GRACE data has provided an unprecedented look at how quickly — and unpredictably — the ice sheet can change.