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Melting Antarctic land ice raises global mean sea level when ice that was resting on land flows into the ocean. The effect is not the same as melting floating sea ice or ice shelves, and the resulting rise is not identical at every coast. Antarctica lost 2,670 ± 530 gigatons of ice and contributed 7.4 ± 1.5 millimeters to global mean sea-level rise from 1992 to 2020, according to the IPCC’s 2021 assessment.
How Antarctic ice loss raises sea level
The Antarctic Ice Sheet is a vast mass of ice grounded on land. Its mass changes through a balance: snowfall adds ice, while surface melting and the flow of ice into the ocean remove it. When grounded ice is lost to the ocean, it adds water and raises global mean sea level. Greater snowfall can partly offset those losses. The IPCC describes this accumulation-and-loss balance in its sea-level change FAQ.
Why ice shelves matter indirectly
Ice shelves are extensions of the ice sheet that float on the ocean. Because they already displace seawater, their own melting has little direct effect on sea level. But shelves can buttress, or restrain, the grounded glaciers feeding them. If a shelf thins or breaks up, grounded ice may flow into the ocean faster, increasing sea-level rise.
Sea ice is a different case
Sea ice forms from ocean water, so its melting is not equivalent to transferring grounded Antarctic ice into the ocean. The sea-level contribution discussed here is principally about the Antarctic land ice sheet and the mass it loses.
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How much has Antarctica contributed so far?
The IPCC’s 2021 assessment estimates that Antarctica lost 2,670 ± 530 gigatons of ice from 1992 through 2020, contributing 7.4 ± 1.5 millimeters to global mean sea-level rise. That is a measured contribution over a specified period, not the total rise in sea level.
For context, global mean sea level rose 0.20 meters (likely range: 0.15–0.25 meters) from 1901 to 2018, and its rate of rise was 3.7 millimeters per year (likely range: 3.2–4.2) from 2006 to 2018, according to the IPCC’s 2021 assessment. Those global totals include multiple causes; they should not be attributed entirely to Antarctica.
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The IPCC’s 2019 assessment found that Antarctic mass loss during 2007–2016 was three times the loss during 1997–2006. This comparison describes those historical periods; it is not a current annual rate or a forecast for 2026.
Will sea level rise equally around the world?
No. Global mean sea level is an average, not a prediction for every shoreline. The IPCC’s 2019 assessment says regional sea-level changes from land-ice loss and variations in ocean warming and circulation can differ from the global mean by about ±30%. The local relative change also depends on whether the land itself is rising or sinking.
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That means a global mean figure cannot be used by itself as a site-specific coastal forecast. Regional ocean behavior, the geographic pattern—or “fingerprint”—of land-ice loss, and vertical land motion all affect what a particular place experiences. The IPCC discusses local relative sea level and these regional differences in its Special Report on the Ocean and Cryosphere chapter on sea-level rise.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.How much could sea level rise by 2100?
Projections depend on the emissions scenario and are stated relative to a baseline. The IPCC’s 2019 assessment projected the following global mean sea levels by 2100, relative to 1986–2005:
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| Scenario | Global mean rise by 2100 | Likely range |
|---|---|---|
| RCP2.6 | 0.43 m | 0.29–0.59 m |
| RCP8.5 | 0.84 m | 0.61–1.10 m |
These are scenario-conditioned global projections, not precise forecasts for an individual coast and not estimates of Antarctica’s contribution alone. Under RCP8.5, the same assessment placed Antarctica’s contribution as high as 28 centimeters at the upper end of the likely range by 2100.
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The IPCC identifies uncertainty about when ice shelves may be lost and how far ice-sheet instabilities may develop. Limited observations, incomplete understanding of atmosphere–ocean–ice interactions, and models that do not fully represent some ice-sheet processes all affect projections. The IPCC also assessed, with low confidence, that processes involving ice-shelf loss and instability could push Antarctic contributions above the likely range on century and longer timescales.
Uncertainty does not mean the direction of change is unknown. The IPCC says global sea level will continue rising for centuries as the ocean takes up heat and ice sheets lose mass, and will remain elevated for thousands of years. It does not mean the rate of rise will stay constant: the pace can change as emissions, ocean responses, and ice-sheet dynamics evolve.
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