Faster Glaciers Drove 84% of 11.3-Trillion-Tonne Polar Ice Loss
A record combining 42 estimates from 27 satellite missions finds that Greenland and Antarctica lost 11.309 trillion tonnes of ice from 1979 to 2023. Faster glacier discharge caused 84% of the loss, but the historical reconstruction does not determine how quickly future sea level will rise.
Greenland and Antarctica lost 11.309 trillion tonnes of ice between 1979 and 2023, according to the longest reconciled satellite record yet assembled for both ice sheets. The loss raised global mean sea level by 31.4 millimetres, while faster glacier discharge into the ocean accounted for 84% of the total.
The 30-second summary
- What happened? An international team combined 42 independent estimates built from 27 satellite missions to reconstruct nearly half a century of polar ice-sheet change.
- Why does it matter? Greenland and Antarctica now account for about a quarter of global sea-level rise, and their behaviour is the largest uncertainty in longer-term projections.
- What is the catch? The record ends in 2023 and does not forecast future loss. A slowdown after 2020 reflects snowfall and milder summers, not evidence that the long-term decline has reversed.
Key Number: 84% of the combined ice loss came from glaciers flowing faster and discharging more ice into the ocean, rather than reduced surface mass balance.
Three ways to weigh an ice sheet
Satellites cannot place Greenland or Antarctica on a scale. Researchers instead compared changes in surface height measured by altimeters, variations in Earth's gravity measured by gravimetry, and estimates that subtract snowfall and other gains from ice flowing across the grounding line.
The Ice Sheet Mass Balance Inter-comparison Exercise standardized and reconciled these approaches. Its dataset includes 23 estimates for Greenland and 19 for Antarctica, drawing on missions from early Landsat observations to CryoSat, the Copernicus Sentinels and the GRACE gravity satellites. The team extended Greenland's record to 1972 and Antarctica's to 1979.
The loss accelerated after the 1990s
Greenland lost 6.215 trillion tonnes from 1972 through 2023. Its average annual loss rose from about 60 billion tonnes in the 1980s to 264 billion tonnes in the 2010s. Antarctica lost 4.780 trillion tonnes between 1979 and 2023, with annual losses increasing from roughly 48 billion tonnes in the 1980s to 202 billion tonnes in the 2010s.
The combined 1979 to 2023 loss carried an uncertainty of 565 billion tonnes. It contributed 31.4 plus or minus 1.6 millimetres to sea level, enough to expose an estimated six million to nine million additional people to annual coastal flooding or erosion.
Why glacier speed matters
Surface melting is only part of the balance. Outlet glaciers move solid ice from land into the ocean, and warmer water can thin their floating margins or attack ice near the grounding line. Once resistance weakens, inland ice can flow faster. Antarctica's net loss in this record came entirely from ice dynamics, while dynamics produced 67% of Greenland's loss.
This mechanism is why measurements beneath Greenland's ice are important. NewTqnia previously covered the robot swarm gathering data where glaciers meet the Atlantic. The wider climate context also includes natural feedback emissions that could amplify future warming.
Before we overstate the result
This is a reconstruction of past mass change, not a prediction that the same rate will continue. The methods disagree most in East Antarctica, where limited ice-thickness measurements near grounding lines increase uncertainty. The assessment also excludes thinning and retreat of floating ice shelves except where those changes alter grounded-ice mass.
From 2020 to 2023, unusually high snowfall in East Antarctica and less intense Greenland summer melt reduced net losses. The researchers describe this as short-term variability: West Antarctic discharge still increased, and the longer record remains one of accelerating loss since the 1990s.
What comes next
Future missions including CRISTAL and ROSE-L are expected to sharpen measurements of ice thickness and flow. The practical test is whether the extended record can reduce uncertainty in sea-level models enough to improve coastal planning, especially for high-end scenarios involving unstable ice-sheet retreat.
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