Contribution of the Cryosphere to Sea Level Rise


Two new studies were recently published quantifying ice mass lost from the Greenland Ice Sheet (GrIS) and the Antarctic Ice Sheet (AnIS)[1] and mountain glaciers.[2] The GrIS/AnIS study is important because it combines 43 independent estimates of ice mass changes, from satellite measurements to arrive at estimates of ice sheet mass balance changes from 1972 for the GrIS and 1979 for AnIS. Combines, the two ice sheets "lost 11,309 ± 565 billion tonnes of ice between 1979 and 2023, with glacier dynamical imbalance driving 84% of the ice loss and surface mass balance the remainder." This change in total mass balance (TMB) equates to 31.4 ± 1.6 mm (1.24 ± 0.06 in) contribution to sea level rise since 1979. Now 1.24 in may not seem like a lot, but we have to remember that this accounting does not account for contributions from ice loss from mountain glaciers or other freshwater contributions to sea level rise. It also does not account for thermal expansion of the oceans. Accounting for all contributors, sea levels have risen by about 9 in since 1880.

The second study performs a similar analysis on mountain glaciers and found that these "Glaciers lost 408 ± 132 Gt of mass during the hydrological year 2025, equivalent to 1.1 ± 0.4 mm sea-level rise. Since 1975, glacier mass loss has totaled 9,583 ± 1,211 Gt, equivalent to 26.4 ± 3.3 mm of sea-level rise, with six of the highest mass-loss years on record occurring in the past seven years." I took the results of all 3 studies and set each to start at 1979 to calculate the cumulative total from all three from 1979 to 2023 (the years where all three overlap). Here's what I came up with:

The IMBIE study shows the change in TMB for the three major portions of Antarctica. There was a rebound in East Antarctica that causes a bump in Antarctica's TMB around 2022. Copernicus' data here is updated through 2024/25, and this updated data should put to rest the claim that Antarctica is reversing from mass loss to mass gain. That "reversal" has already reversed, and cumulative mass loss in 2025 is below 2022. In the graph below, I updated IMBIE's data through 2023 with data from Copernicus for 2024.
Predictably, the usual suspects on social media have been finding alternative ways to spin this. For instance, Matthew Wielicki has decide to reframe this data in terms of the percent of GrIS and AnIS that has been lost. In one post on X, he calculates that this is just 0.04% of the combined ice on GrIS and AnIS.


In actuality, 11,309 Gt is 0.046% of 24.38 million Gt that make up GrIS and AnIS, so to one significant figure that's about 0.05%, though Wielicki here entirely misses the point. The significance of these calculations has to do with closing the SLR budget and making better projections for future SLR from melting polar ice sheets. Essentially, all Wielicki has done is point out that there is ~2174x more ice to melt on these land masses than what has melted so far. So there's a lot more ice that can still contribute to future SLR. And if we lose all of it, we'll see ~65 meters (213 ft) of sea level rise. We're on pace to see more than 2 ft above 1880 levels by 2100, given current rates and acceleration, and that alone is a problem. To add insult to injury, in another post Wielicki calculated that it would take 120,000 years for both ice sheets to lose all their mass at current rates.


This again is wrong. Wielicki is assuming a linear trend, and even if I were to grant that, it would take about 93,000 years to lose all of the ice on Greenland and Antarctica. However, I downloaded the IMBIE data and plotted TMB anomalies from 1979 to 2023, setting 1979 to 0. Just look at the data. Mass loss from TMB is accelerating. Clearly a linear trend is going to severely underestimate how long it will take to lose both polar ice caps.
If I take the same data and plot the best fit quadratic through this same data, then we lose all of the ice on Greenland and Antarctica by ~3900 CE. That's less than 2000 years from now.
Now to be clear, I'm not predicting that we will lose all of this ice in the next 2000 years. This is a projection based purely on a best fit quadratic and not at all on the physics of how ice sheets melt. But clearly Wielicki is being rather foolish in making projections based on simple mathematical forecasts assuming a linear trend for data that is clearly showing accelerating mass loss. I'm quite confident that Wielicki understands exactly why he's wrong here, but he's selling a political narrative. He's not doing science.


Reference:

[1] Otosaka, I.N., Shepherd, A., Amory, C. et al. Mass balance of the Greenland and Antarctic ice sheets from the 1970s to 2023. Sci Data 13, 1301 (2026). https://doi.org/10.1038/s41597-026-08088-0

[2] The WGMS Network. Global glacier mass change in 2025. Nat Rev Earth Environ 7, 213–215 (2026). https://doi.org/10.1038/s43017-026-00777-z


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