Polar ice sheets lost 11.3 trillion metric tons since 1979, study finds

About 12.5 trillion tons — or 11.3 trillion metric tons — of ice from Greenland and Antarctica has melted since 1979, enough frozen water to blanket the continental United States five feet deep, according to the most comprehensive satellite assessment of polar ice loss ever assembled. The findings, published Wednesday in the journal Scientific Data, underscore how accelerating ice loss from the planet's two largest ice sheets is reshaping the global outlook for sea-level rise.nbcnews+1

Speeding Glaciers, Not Surface Melting, Are the Primary Driver

The study, known as the Ice Sheet Mass Balance Inter-comparison Exercise (IMBIE), was led by Dr. Inès Otosaka and Professor Andrew Shepherd at Northumbria University and Dr. Tyler Sutterley of the University of Washington. The team combined 42 independent satellite surveys drawn from 27 missions, some reaching back to 1972 for Greenland.eurekalert

One of the most striking findings is that 84% of the combined ice loss was driven not by surface melting but by glaciers accelerating and discharging more ice into the ocean. "More than four-fifths of the ice lost was discharged into the ocean by faster-flowing glaciers, rather than melted at the surface — which tells us the long-term trend is being driven by the dynamic response of the ice sheets to a warming ocean," Otosaka told Gizmodo.phys+2

The two ice sheets now account for roughly one-quarter of all global sea-level rise. The total melt pushed ocean levels up by about 1.2 inches (3.1 centimeters) since 1979, with Greenland contributing the larger share.esa+1

An Accelerating Trend With Brief Respite

Ice losses have climbed steeply since the 1990s. Greenland's rate of loss rose from about 60 billion tonnes per year in the 1980s to 264 billion in the 2010s, while Antarctica's rose from 48 billion to 202 billion over the same span. West Antarctica's ice discharge, led by Pine Island and Thwaites glaciers, has increased in every decade of the record.eurekalert

A temporary slowdown between 2020 and 2023 — driven by record snowfall over East Antarctica and milder Greenland summers — partially offset losses, but scientists caution this is a short-term fluctuation. "Three centimetres of sea level rise may sound small, but that puts another six to nine million people at risk of coastal flooding and erosion," Shepherd said.eurekalert