Warm Seas Drove Most of 11.3 Trillion Tonnes of Ice Loss

Greenland and Antarctica lost 11,309 billion tonnes of ice from 1979 to 2023, 84% of it from glaciers dumping ice into a warmer ocean.

The Ice Sheet Mass Balance Inter-comparison Exercise, backed by the European Space Agency and NASA, combined 42 independent satellite estimates from 27 missions. That ice raised global sea level by 31.4 millimetres. Most of it left because outlet glaciers sped up after warm water thinned their floating fronts, a process that trails air warming by decades.

The Ocean Took Four-Fifths of the Ice

Inès Otosaka, the Northumbria University ice scientist who led the study, said the longer record shows what actually moves the sheets. Surface melt is the part people picture. The ledger says glacier flow did the heavy work.

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.

Inès Otosaka, ice scientist, Northumbria University, IMBIE briefing

The 11,309 billion tonnes of ice (11.3 trillion tonnes) is the combined 1979 to 2023 total, with an uncertainty of 565 billion tonnes. Glacier flow accounted for 84% of that loss. Reduced snowfall and extra surface melt, grouped as surface mass balance, accounted for the other 16%.

Antarctica’s entire net loss was from ice discharge. Greenland was mixed: 67% from increased discharge and 33% from a weaker surface budget across 1972 to 2023. Eric Rignot, an ice scientist at the University of California, Irvine and a co-author, said the ice sheets are melting away fast, polar regions are being melted, and sea level is rising worldwide.

If that volume were stacked across the continental United States it would sit about 5 feet (1.5 metres) deep. The leftover ice on land is still vast, which is why 31.4 millimetres can sound small. The risk sits in how the lost slice left: marine glaciers speeding up where the bed slopes inland, a path that does not wait on the next hot summer.

Greenland’s Annual Loss Crossed 264 Billion Tonnes

Greenland sat close to balance in the 1970s, with snowfall roughly matching what left. Loss then climbed, decade by decade, and the 2010s were the peak in this record.

GREENLAND LOSS BY DECADE

Greenland’s 2000s rate was three times the 1980s figure. The 2010s rate, 264 ± 18 billion tonnes a year, was more than four times the 1980s rate and the first decade in which surface losses beat glacier discharge on that island. Repeated extreme summer melt marked those years. From 1972 to 2023 Greenland lost 6,215 ± 467 billion tonnes, a mean of 119 ± 9 billion tonnes a year.

Antarctica rose from about 48 billion tonnes a year in the 1980s to 202 billion in the 2010s, more than four times as fast. Of the 31.4 millimetres already added, ESA’s split is 1.81 centimetres from Greenland and 1.33 centimetres from Antarctica for 1979 to 2023. Antarctica’s own total is 4,780 ± 513 billion tonnes, or 13.3 ± 1.4 millimetres. The two ice sheets now supply about a quarter of global sea-level rise.

Jakobshavn Glacier in Greenland is now retreating by as much as 50 metres (164 feet) a day, Otosaka said. That is ice leaving as a moving cliff, not as a puddle on the surface.

What the 2020 to 2023 Dip Did Not Reverse

Loss slowed in the last four years of the survey. East Antarctic snow and quieter Greenland summers cut the headline rate. West Antarctic glaciers did not join the pause.

WHAT CUT THE HEADLINE RATE

• East Antarctic snow: Record snowfall in 2022 and 2023 produced a mass gain of 92 ± 63 billion tonnes a year over the last four years, against a 45-year East Antarctic trend of 1 ± 9 billion tonnes a year.
• Milder Greenland summers: Surface losses ran at about half the 2010s pace, and Greenland’s total rate fell to 199 ± 29 billion tonnes a year, with no repeat of those extreme melt summers.
• West Antarctic flow: Ice discharge there rose a further 38% in the same four years, but extra snowfall offset the extra outflow on the continent-wide books.

Antarctica’s 2020 to 2023 loss rate was more than three times smaller than in the 2010s. On the Antarctic Peninsula, losses had already jumped to 32 ± 5 billion tonnes a year in the 2000s, four times the 1990s, after ice shelves collapsed. Otosaka said the study stops at 2023, but measurements since then show the faster trend has picked back up. Rignot called the three-year lull just a bump in the record, with the long rise tied to climate.

The dip is the sort of short weather run that invites a wrong reading of the 11.3 trillion tonnes as a closed event. IMBIE reports net mass after winter snow, not the seasonal melt that returns. A thin slice of the ice still sitting on land can still lift the ocean, and it did.

31.4 Millimetres Already Puts Millions in the Flood Path

Andrew Shepherd, head of Northumbria’s School of Geography and Natural Sciences and founder of IMBIE, put the millimetres in human terms.

Just over 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. With the ice sheets set to lose much more ice in the decades ahead, global assessments like IMBIE are vital to protecting communities impacted by climate change.

Andrew Shepherd, IMBIE founder, Northumbria University

That 6 to 9 million figure is for the 3.14 centimetres already added by these two sheets, on top of other climate factors raising the ocean. Shepherd also said the ice-sheet changes are tracking decades behind global warming, so they can be expected to continue for decades more, even if heating of the planet stopped. Hundreds of millions of people live in low-lying coastal areas that sit inside that lag.

Air-temperature targets do not switch off water already in contact with glacier fronts. The 31.4 millimetres is committed water. The next decades of discharge are the part still being priced.

Why Ice-Sheet Instability Still Swings the Forecasts

West Antarctica’s ice discharge rose in every decade of the satellite record, led by Pine Island and Thwaites glaciers, from 29 ± 7 billion tonnes a year in the 1980s to 163 ± 12 billion tonnes a year in the 2010s. Warm ocean water reaches the underside of ice shelves that brace those glaciers. When the brace thins, grounded ice speeds up. On beds that deepen inland, retreat can feed itself.

Otosaka said the largest changes are in these abrupt flow processes, which can trip runaway thresholds. The IMBIE paper notes that ice sheets are the largest source of uncertainty in future sea-level rise, and that high-end estimates by 2150 increase by a factor of 2.6 once ice-sheet instability is included. That is the same family of ice-sheet instability in sea-level projections assessed in the IPCC Sixth Assessment, and it is why high-end sea-level projections to 2150 fan out so widely once low-confidence ice processes are switched on.

WHERE EXPERTS DISAGREE

• David Holland, New York University: The NYU ice scientist, who was not on the study, said most of the ice loss is dynamical, which is what you would expect in an ice-sheet instability collapse scenario. Independent methods, he said, give greater confidence, and the upward trend is real.
• Ted Scambos, University of Colorado: The ice scientist, also outside the team, called Antarctic mass-loss wild cards a clear and present danger, but many decades in the future, and said society is smart enough to know the future but not prudent enough to act on the knowledge.

Holland is reading the same 84% flow share as a collapse signature now. Scambos places the worst Antarctic surprises further out. Both treat the ocean path, not a hot-air lid, as the live risk.

Landsat, GRACE and CryoSat Rebuilt a 50-Year Ledger

Earlier IMBIE assessments started in the 1990s. This one pulls in NASA and early Landsat velocity maps so Greenland runs from 1972 and Antarctica from 1979. In years with poor coverage between Landsat-1/2 and Landsat-4/5, discharge was interpolated and the error bar widened.

THE HALF-CENTURY RECORD

1. 1972: Greenland velocity mapping begins in the Landsat archive, with the reconciled mass-balance dataset opening on 1 July 1971.
2. 1979: Antarctic coverage becomes wide enough for a continental discharge estimate, starting 1 January 1979.
3. 1990s: Losses begin to climb after the quieter 1970s and 1980s.
4. 2010s: Peak decade rates, 264 ± 18 billion tonnes a year in Greenland and 202 billion in Antarctica.
5. 2020 to 2023: East Antarctic snow and milder Greenland summers cut the combined rate; West Antarctic discharge keeps rising.
6. 16 September 2026: The IMBIE team publishes the Scientific Data record through 2023.

Tyler Sutterley of the University of Washington Applied Physics Laboratory, an IMBIE co-lead, said the longer record, the larger pool of teams, and better error checks make this the most robust mass-balance assessment so far. Diego Fernández, head of ESA’s science section, said missions such as CryoSat-2 and the Sentinels have to be sustained if the climate data record is to hold.

🫠 Half a century of satellite data shows 11 trillion tonnes of ice loss 🫠

The longest satellite data record of ice-sheet change ever assembled reveals that Greenland and Antarctica have lost a staggering 11 trillion tonnes of ice since the 1970s, driving global sea level up by… pic.twitter.com/HL40xYyVZu

— ESA's CryoSat mission (@esa_cryosat) September 16, 2026

THREE WAYS THE SATELLITES COUNT ICE

• Altimetry: Radar and laser height repeats, from CryoSat-2, ICESat-2 and the Sentinels, converted to mass with a firn-density model.
• Gravimetry: GRACE and GRACE-FO weigh the ice by tracking Earth’s gravity field, after glacial isostatic adjustment is removed.
• Input-output: Ice speed at the grounding line times ice thickness, minus the surface budget from regional climate models.

On the overlapping 1992 to 2020 window, Greenland matches the previous IMBIE assessment within error (180 ± 12 versus 169 ± 16 billion tonnes a year). Antarctica does not: this dataset finds 140 ± 13 billion tonnes a year against 92 ± 18 before. More loss, not less, once the older Landsat years and extra teams are in.

Otosaka has already looked past 2023 and found the faster trend has resumed. The ocean that took four-fifths of the ice is still at the cliff.

Frequently Asked Questions

How Far Back Does the New Ice-Sheet Record Go?

Greenland’s reconciled series runs from 1 July 1971 through 31 December 2023, with the paper treating 1972 as the start of usable Landsat velocity cover; Antarctica runs from 1 January 1979 through 31 December 2023. In years with no or poor velocity maps, ice discharge was linearly interpolated and the uncertainty was increased with the gap length.

How Does This IMBIE Update Compare With the 1992 to 2020 Assessment?

The previous IMBIE consensus put the two ice sheets at 21.0 ± 1.9 millimetres of global mean sea-level rise between 1992 and 2020. The new overlap still agrees for Greenland, but Antarctica’s loss rate is higher (140 ± 13 against 92 ± 18 billion tonnes a year), so the longer ledger is not a quiet extension of the old one.

What Share of Greenland’s Ice Loss Came From Surface Melt?

Over 1972 to 2023, 33% of Greenland’s 6,215 ± 467 billion tonnes came from a reduced surface mass balance and 67% from extra ice discharge. The 2010s were the first decade in which surface losses exceeded discharge on that ice sheet, before milder summers in 2020 to 2023 cut surface losses by about half.

How Much Ice Equals One Millimetre of Sea-Level Rise?

About 360 billion tonnes of ice, once melted, raise global mean sea level by roughly 1 millimetre. That is the conversion IMBIE uses to turn the 11,309 ± 565 billion tonnes into 31.4 ± 1.6 millimetres, and Antarctica’s 4,780 ± 513 billion tonnes into 13.3 ± 1.4 millimetres.