Satellites put Greenland and Antarctic ice loss at 12.5 trillion tons since 1979

Greenland and Antarctica have lost about 12.5 trillion tons, or 11.3 trillion metric tons, of ice since 1979, according to a study published on 16 September in the journal Scientific Data. The figure is enough frozen water, the authors said, to stack ice five feet deep across the contiguous United States. Converted to liquid it is about 11.3 quadrillion litres. That water has raised global mean sea level by about 3.1 centimetres, or just over an inch, on top of other sources of rise.

The collaboration, associated with the European Space Agency’s ice-sheet mass-balance work, used 27 satellite missions and 45 independent surveys. Earlier IMBIE assessments started in the 1990s. Extending the record back to 1979 is the paper’s main addition. Lead author Ines Otosaka of Northumbria University said 84 percent of the lost ice came from glaciers discharging into the ocean, with only 16 percent from surface melting driven by warmer air. Warm water eating the ice from below and at the sides is the dominant mechanism.

The rates have climbed. Greenland lost about 60 to 66 billion metric tons a year in the 1980s and about 264 to 291 billion tons a year in the 2010s, depending on the rounding in different summaries of the same dataset. Antarctica’s annual loss rose from about 53 billion tons to more than 222 billion tons over the same span. Greenland accounts for a slightly larger share of the sea-level increment, about 0.7 inches of the 1.2-inch combined rise cited in one briefing. Together the two ice sheets now contribute about a quarter of observed global sea-level rise.

Otosaka pointed to Jakobshavn glacier in Greenland as a working example, retreating up to 50 metres, or 164 feet, a day in recent measurements. Co-author Andrew Shepherd warned that the extra water puts another six to nine million people at risk of coastal flooding and erosion. A slower stretch between 2020 and 2023, tied to weather variation, does not cancel the multi-decade trend. Otosaka said the long-term driver remains warming oceans speeding discharge, and that tipping points remain a live concern.

The distinction between surface melt and discharge is the practical takeaway. Air-temperature headlines miss most of the mass budget. If 84 percent of the loss is ice sliding and calving because the ocean is warmer, then cutting summer heat waves over the ice sheet, while useful, does not stop the main leak. Ocean heat is slower to reverse than a single season’s air anomaly. That is why the authors describe the result as bad news for the next increment of sea level, even if surface melt has quiet years.

Coastal planners already work with centimetres. Three extra centimetres from the ice sheets since 1979 is a measured slice of a larger rise that also includes glacier melt outside the poles and thermal expansion of seawater. The paper does not forecast a collapse date. It does document that both sheets are now losing ice several times faster than they did in the 1980s, and that the ocean, not the sky, is doing most of the work.