When ice grounded on Antarctica’s land flows into the ocean, it raises global mean sea level. NASA estimates that Antarctica lost about 135 gigatons of ice per year during 2002–2025, adding roughly 0.4 millimeters per year to global sea-level rise. Floating ice shelves do not raise sea level much as they melt, but their loss can let land ice move into the ocean faster. The amount Antarctica may add by 2100 depends partly on future emissions, and local sea-level changes will not match the global average everywhere.
Why Antarctic land-ice loss raises sea level
Antarctica’s ice sheet is mostly ice resting on bedrock. When grounded ice flows past the coast and enters the ocean, it adds water to the sea. NASA’s satellite-based indicator, using GRACE and GRACE Follow-On observations through 2025, estimates an average Antarctic ice loss of about 135 gigatons per year from 2002 to 2025, equivalent to about 0.4 millimeters per year of global mean sea-level rise. This is an observed average over that period, not a forecast of the future rate. NASA’s Ice Sheets indicator
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Why melting floating shelves still matters
Ice shelves are extensions of glaciers that float offshore. Their direct melting has little effect on sea level, much as melting an ice cube already floating in a glass does not make the glass overflow. But shelves can brace the glaciers behind them. When warm ocean water melts a shelf from below, the shelf thins and may break apart, reducing that restraint and allowing grounded ice to flow faster into the ocean.
NASA JPL scientist Helene Seroussi explains: “The water melts the ice shelves from below which can cause them to thin and break off.” NASA’s Kelly Brunt, an ICESat-2 scientist at NASA’s Goddard Space Flight Center and the University of Maryland, uses the floating-ice analogy to distinguish shelf melt from land ice entering the sea. NASA’s explanation of glacial ice loss
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Why West and East Antarctica differ
West Antarctica
West Antarctica has been the dominant source of observed Antarctic ice-sheet mass loss in recent decades. The IPCC reports that losses from West Antarctic outlet glaciers outpaced increased snow accumulation and dominated Antarctic ice-sheet losses since 1992; the losses were mainly induced by melting beneath ice shelves. Much of West Antarctica’s bedrock lies below sea level. In places where the bed slopes downward inland, retreating grounding zones can bring thicker ice into contact with ocean water, making continued retreat a concern. IPCC Sixth Assessment Report, Working Group I, Chapter 9
East Antarctica
East Antarctica is generally higher, and most of its bedrock lies above sea level. That does not mean the region is wholly stable: some sectors have lost mass. Its future contribution remains an important uncertainty in assessing Antarctica as a whole. NASA on warming seas and melting ice sheets
How much Antarctica could add by 2100
The IPCC’s 2021 Sixth Assessment Report gives likely ranges for the Antarctic contribution to global mean sea-level rise by 2100 under three emissions pathways. These figures are Antarctica’s contribution alone, not projections for total global sea-level rise.
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Outbyte PC Repair FREERepair Windows errors before they cause bigger problemsFix Now →Outbyte Driver Updater FREEScan for outdated or missing drivers - takes under a minuteDriver Scan →| Emissions pathway | Antarctic contribution by 2100 |
|---|---|
| SSP1-2.6 | 0.03–0.27 m |
| SSP2-4.5 | 0.03–0.29 m |
| SSP5-8.5 | 0.03–0.34 m |
The ranges overlap substantially: they are not precise point predictions, and the spread reflects uncertainty in how the ice sheet will respond. The highest pathway has the widest upper bound, but the ranges do not mean every outcome within them is equally likely. Total global sea-level rise also includes thermal expansion as ocean water warms, melting glaciers outside Antarctica, Greenland ice loss, and changes in water stored on land. IPCC AR6, Chapter 9
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Will sea level rise by the same amount everywhere?
No. Global mean sea level is an average, while the change experienced at a particular coast depends on regional ocean conditions and local land movement as well as the distribution of ice loss. The IPCC’s 2019 Ocean and Cryosphere report describes regional departures of about ±30% around global mean sea-level rise due to the combined effects of thermal expansion, ocean dynamics, and land-ice loss. That is a general regional pattern, not an Antarctic-only estimate or a value for any specific coastline. IPCC Special Report on the Ocean and Cryosphere, Technical Summary
A reliable local estimate therefore requires a location-specific projection and information about whether the land itself is rising or sinking. NASA’s Sea Level Change Portal links to an AR6 Sea Level Projection Tool and a Sea Level Explorer for exploring projections by location; the Antarctic ranges above should not be applied directly to an individual city or coast.
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