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Antarctic ice-sheet projections estimate how much Antarctica may contribute to global mean sea-level rise under specified climate scenarios. They do not, by themselves, forecast how many centimetres sea level will rise at a particular coast. Local relative sea level depends on the ice sheet’s geographic fingerprint, other climate and ocean processes, and how the land moves.
What the Antarctic projections actually measure
The IPCC’s Sixth Assessment Report gives likely Antarctic Ice Sheet contributions to global mean sea-level rise by 2100 of:
| Climate scenario | Antarctic contribution to global mean sea-level rise by 2100 |
|---|---|
| SSP1-2.6 | 0.03–0.27 m (3–27 cm) |
| SSP2-4.5 | 0.03–0.29 m (3–29 cm) |
| SSP5-8.5 | 0.03–0.34 m (3–34 cm) |
These are assessed likely ranges for Antarctica’s component of global mean change, conditional on each emissions scenario—not projections for a particular city. The ranges reflect uncertainty in the Antarctic response as well as the scenario assumptions. The upper end is not a prediction that the outcome is most likely to reach that value. See the IPCC AR6 Chapter 9 for the assessment.
Why the local effect varies
An ice sheet’s mass attracts nearby ocean water through gravity. When Antarctica loses mass, that pull weakens and water is redistributed. The changing ice load also deforms Earth’s solid surface; changes in Earth’s rotation contribute to the spatial pattern. Together, these effects produce a sea-level fingerprint: sea level can fall near the melting ice source and rise more than the global average in some distant regions.
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NASA gives California and Florida as examples of regions where the sea-level effect generated by Antarctic melting can be up to 52% greater than its average effect around the world. That is an illustrative regional result, not a multiplier to apply to every coast or a forecast for every location. NASA explains the pattern in “Evidence of sea level ‘fingerprints’”; NASA/JPL also describes the mechanism in “The Fingerprints of Sea Level Rise”.
Global mean rise is not local relative sea level
Global mean sea-level contribution describes the average ocean response attributed to a source such as Antarctic ice loss. Local relative sea-level change is the change in sea surface compared with the land at a particular place. It includes the fingerprint and other regional and local influences.
A local estimate therefore needs a specified place, time horizon, and reference baseline, plus a regional projection that combines relevant contributors. Those may include Greenland and glacier mass loss, ocean and atmospheric effects, the solid-Earth response, and vertical land motion. The IPCC’s Chapter 13 on sea-level change discusses the range of processes involved.
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1Repair Windows errors before they cause bigger problems2Scan for outdated or missing drivers - takes under a minute3Clear out junk files and repair common Windows errorsWhat these figures can—and cannot—answer
They can
- Compare assessed Antarctic contributions to global mean sea-level rise under SSP1-2.6, SSP2-4.5, and SSP5-8.5 by 2100.
- Show that Antarctic mass loss is one contributor to sea-level rise and that its future response is uncertain.
- Help motivate regional analysis that accounts for gravitational and solid-Earth fingerprints.
They cannot, on their own
- Tell you how many centimetres of relative sea-level rise a named town, neighbourhood, or property will experience.
- Provide a complete local projection combining Antarctica with other ice sources, regional ocean and atmospheric processes, and land movement.
- Give a local flood probability, inundation depth, or date when a threshold will be crossed.
Even a local sea-level projection is not a flood forecast by itself. Flood risk depends on the site and on the event being assessed; a sea-level change number alone does not specify the chance or depth of inundation.
How to use a local projection responsibly
- Choose the location and baseline. Use a projection for the relevant coastal area and check the reference period against which change is measured.
- Match the time horizon and scenario. Keep the scenario attached to each figure; the IPCC’s Antarctic ranges are specifically for 2100 and differ by SSP.
- Check what the estimate includes. Look for treatment of ice-sheet fingerprints, other land ice, ocean and atmospheric effects, and solid-Earth response or vertical land motion.
- Separate sea-level change from flood risk. For inundation or flood questions, use information that addresses local exposure and the particular event, not a global-average contribution alone.
NASA’s sea-level visualization can help illustrate the fingerprint mechanism, but NASA notes that its Antarctic solid-Earth feedback simulation is not fully representative of all processes affecting sea-level rise. Treat it as an illustration, not a complete local forecast: NASA/JPL VESL simulation.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Historical context: observed Antarctic loss
The IPCC assessed that Antarctica lost 2,670 gigatonnes of ice from 1992 to 2020, equivalent to 7.4 mm of global mean sea-level rise. The assessed ranges were 1,800–3,540 gigatonnes of ice loss and 5.0–9.8 mm sea-level equivalent. These figures describe an observed historical period, not a future projection or a local coastal change estimate. Source: IPCC AR6 Chapter 2.
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