The Greenland and Antarctic ice sheets together lost 11,309 ± 565 billion tonnes of ice between 1979 and 2023, according to a new reconstruction that combines 42 independent satellite-based estimates of ice-sheet mass change. Most of that loss, 84%, came from changes in ice flow and discharge rather than reduced snowfall and surface melting. The combined loss corresponds to 31.4 ± 1.6 millimeters of global sea-level rise.
The assessment brings together measurements from 27 satellite missions, covering changes in ice velocity, surface elevation and Earth’s gravitational field. The researchers also incorporated estimates from regional climate models to separate total mass change into two broad components: changes at the ice surface, such as snowfall and melt, and changes in the movement and discharge of ice.
The resulting dataset extends farther back than the previous Ice Sheet Mass Balance Inter-comparison Exercise, or IMBIE, assessment. For Greenland, the record begins in 1972. For Antarctica, it begins in 1979.
The researchers assembled 23 Greenland mass-balance estimates and 19 for Antarctica. The Greenland set includes six estimates based on satellite altimetry, 14 based on satellite gravimetry and three based on the input-output method. The Antarctic set contains five altimetry estimates, 13 gravimetry estimates and one input-output estimate.
Each individual record was converted to a common monthly measure of the rate of mass change. The researchers then combined estimates within each measurement technique and, finally, combined the three technique-specific records into a single reconciled time series.
The approach also accounts for Greenland’s peripheral glaciers and ice caps, which are not included in some of the original satellite estimates. The researchers estimate that these peripheral glaciers and ice caps lost mass at an average rate of 8.0 ± 0.5 billion tonnes per year from 1972 to 2023, accounting for about 7% of Greenland’s ice loss. Their estimated loss increased from 4.4 ± 0.8 billion tonnes per year in the 1990s to 18.9 ± 1.3 billion tonnes per year in the 2010s.
The researchers did not make an equivalent correction for Antarctic peripheral glaciers and ice caps because available estimates there disagree substantially. One estimate indicated little change, another estimated a loss of 20.9 ± 4.9 billion tonnes per year from 2010 to 2018, and a separate satellite-altimetry estimate gave a loss of 3.5 ± 0.4 billion tonnes per year over the same period.
Greenland’s losses accelerated sharply
Greenland was close to mass balance in the 1970s, but its losses increased over the following decades.
The average rate of mass loss was 60 ± 19 billion tonnes per year in the 1980s and 57 ± 25 billion tonnes per year in the 1990s. It then increased to 192 ± 19 billion tonnes per year in the 2000s and 264 ± 18 billion tonnes per year in the 2010s.
During the 2010s, reduced surface mass balance accounted for a larger share of Greenland’s annual loss than changes in ice dynamics. Surface mass balance includes gains from snowfall and losses from processes such as surface melting and runoff. The study estimates a surface-mass-balance anomaly of −141 ± 24 billion tonnes per year during that decade, compared with an ice-dynamical anomaly of −123 ± 30 billion tonnes per year.
The pattern changed again from 2020 through 2023. Greenland lost ice at a rate of 199 ± 29 billion tonnes per year. Dynamic ice losses remained at roughly the same pace as during the 2010s, while the rate of surface-mass loss fell to about half its 2010s level.
The researchers note that the 2010s included several extreme summer melt events associated with record mass-loss years. No comparable extreme events occurred during the final four years of the record, and surface-mass-balance losses returned to a level similar to that of the 2000s.
Across the full 1972–2023 record, Greenland lost an estimated 6,215 ± 467 billion tonnes of ice, equivalent to an average loss of 119 ± 9 billion tonnes per year. The researchers attribute 67% of that cumulative loss to increased ice discharge and 33% to reduced surface mass balance.
West Antarctica dominates the Antarctic loss
Antarctica followed a different pattern. Its overall mass loss was dominated by West Antarctica, where ice discharge increased in every decade examined.
West Antarctic ice discharge rose from 29 ± 7 billion tonnes per year in the 1980s to 163 ± 12 billion tonnes per year in the 2010s. During 2020–2023, the estimated rate remained high, at 162 ± 34 billion tonnes per year, while the dynamic component reached −215 ± 34 billion tonnes per year relative to the study’s reference-period surface mass balance.
The Antarctic Peninsula also underwent substantial changes. Its mass loss reached 32 ± 5 billion tonnes per year in the 2000s, about four times its estimated rate during the 1990s. The researchers associate the increase since the early 2000s with ice-shelf collapse, citing previous research on the region.
But the Peninsula’s mass balance changed markedly in the final four years of the record. From 2020 to 2023, it was close to balance, with increased snowfall accumulation estimated at 22 ± 2 billion tonnes per year and reduced ice discharge estimated at 11 ± 11 billion tonnes per year.
East Antarctica behaved differently again. Its average mass trend over the 45-year record was 1 ± 9 billion tonnes per year, indicating little net change within the uncertainty. But exceptionally high snowfall in 2022 and 2023 produced an estimated mass gain of 92 ± 63 billion tonnes per year during 2020–2023.
That recent gain in East Antarctica offset some of the continuing losses from West Antarctica. As a result, the Antarctic Ice Sheet’s overall rate of mass loss during 2020–2023 was more than three times smaller than its rate during the 2010s.
Over the entire 1979–2023 Antarctic record, the ice sheet lost 4,780 ± 513 billion tonnes of ice. The researchers estimate that this contributed 13.3 ± 1.4 millimeters to global sea-level rise.
In the study’s partitioning of the Antarctic mass balance, surface mass balance made a net positive contribution over the full record, while ice dynamics produced the net loss.
Most of the combined loss came from ice dynamics
Putting the two ice sheets together, the researchers estimate that 11,309 ± 565 billion tonnes of ice were lost from 1979 through 2023.
The estimated contribution to global sea level was 31.4 ± 1.6 millimeters.
The partitioning shows a clear difference between the two broad processes. Increased glacier dynamical imbalance accounted for 84% of the combined ice loss, while reduced surface mass balance accounted for the remaining 16%.
That overall figure hides substantial changes through time and major differences between regions. Greenland’s surface losses became particularly important during the 2010s, while Antarctica’s net loss over the full record was attributed to ice dynamics in the study’s reconstruction.
The different measurement methods mostly agree in Greenland
A central purpose of the assessment was to determine how consistently different satellite techniques measure ice-sheet mass change.
For Greenland, the three technique groups were in relatively close agreement during their common 2002–2023 period. Their rates of mass loss had a standard deviation of 24 billion tonnes per year, and the reconciled estimate was 236 ± 12 billion tonnes per year.
For Antarctica, the corresponding reconciled mass-loss rate over 2002–2021 was 169 ± 17 billion tonnes per year. But the spread between the three techniques was much larger, with a standard deviation of 70 billion tonnes per year.
The disagreement was especially pronounced in East Antarctica. There, the three methods did not even agree on the sign of the mass change. Their maximum difference was 111 ± 19 billion tonnes per year between the input-output and altimetry estimates.
For 2021, the final year in which all three techniques overlapped in East Antarctica, the input-output estimate indicated a mass loss of 210 ± 73 billion tonnes per year, while the altimetry and gravimetry groups indicated mass gains of 99 ± 124 and 166 ± 50 billion tonnes per year, respectively.
The researchers caution that Antarctica’s reconciled estimate gives relatively high weight to the single available input-output estimate because there is only one such dataset in the Antarctic compilation. They say this could produce a small underestimation of mass gains in East Antarctica.
They point to limited measurements of ice thickness near the grounding line as one possible source of the discrepancy. In several East Antarctic regions, including Enderby Land, Princess Elizabeth Land, Dronning Maud Land and Wilkes Land, more than 60% of the grounding line lacks an ice-thickness measurement within 5 kilometers of its actual location.
The new record differs from the previous IMBIE assessment
The researchers also compared their reconstruction with the previous IMBIE mass-balance assessment covering 1992–2020.
For Greenland, the two assessments produced rates of mass loss of 180 ± 12 and 169 ± 16 billion tonnes per year, respectively, and the researchers report that they agree within their uncertainties.
For Antarctica, however, the new assessment gives a higher mass-loss rate: 140 ± 13 billion tonnes per year compared with 92 ± 18 billion tonnes per year in the previous assessment.
The differences are not uniform across Antarctica. The researchers report statistically significant differences between the two assessments for the Antarctic Ice Sheet as a whole and for the Antarctic Peninsula, with p-values of 0.01 and 0.03, respectively.
The Antarctic Peninsula shows one of the clearest changes between the assessments. In the 1992–2018 period, the new altimetry-aggregated estimate gives a mass-loss rate of 20 ± 3 billion tonnes per year, compared with 6 ± 1 billion tonnes per year in the earlier assessment. The researchers attribute this difference primarily to substantially updated altimetry datasets and the inclusion of more teams providing measurements at finer temporal resolutions. They report that the updated altimetry estimate is now closer to the gravimetry and input-output estimates, with all three techniques agreeing at the Peninsula.
The remaining differences at Greenland, West Antarctica and East Antarctica arise from the inclusion of new and updated participant datasets, while the Greenland assessment also now systematically includes its peripheral glaciers and ice caps.
The uncertainties remain largest in some Antarctic regions
The researchers tested agreement not only between different measurement techniques but also among estimates using the same technique.
For Greenland, input-output estimates had a median difference of 21 billion tonnes per year and a standard deviation of 48 billion tonnes per year during their 1986–2021 overlap. Gravimetry estimates had a median difference of 20 billion tonnes per year and a standard deviation of 43 billion tonnes per year during 2018–2022. Altimetry estimates showed larger differences, with a median difference of 64 billion tonnes per year and a standard deviation of 51 billion tonnes per year over 2011–2018.
Antarctica had only one input-output estimate, so that group could not be compared internally. Among gravimetry estimates, disagreements were largest in East Antarctica and smallest in the Antarctic Peninsula. The same general pattern appeared among altimetry estimates.
Despite these differences, the researchers report that most individual annual mass-balance estimates fell within the uncertainty range of the final reconciled estimate. The proportions were 93% for Greenland, 88% for Antarctica as a whole, 87% for the Antarctic Peninsula, 90% for East Antarctica and 94% for West Antarctica.
The final dataset covers July 1, 1971, through December 31, 2023, for Greenland and January 1, 1979, through December 31, 2023, for Antarctica and its major subregions. It provides both annual rates and cumulative changes in total mass, surface mass balance and ice dynamics, along with their uncertainties.
The study was published in Scientific Data.
