If all ice melts: the global flood map and what disappears underwater

01How much sea level would rise

Sea level rise is an increase in the level of the world's oceans due to the effects of global warming. The two primary mechanisms are thermal expansion of ocean water as it warms and the addition of water from melting land ice, including glaciers and ice sheets. If all land ice on Earth were to melt, global sea level would rise by approximately 70 meters, or about 230 feet, though this scenario would require thousands of years under current warming trajectories.

The major contributors to a total ice melt scenario are the Antarctic ice sheet, which contains enough ice to raise sea level by about 58 meters, and the Greenland ice sheet, which could contribute about 7 meters. Mountain glaciers and smaller ice caps add roughly 0.5 meters combined. The East Antarctic ice sheet is by far the largest single reservoir, containing roughly 53 meters of potential sea level rise. The question is not whether all ice will melt, which is a long-term extreme scenario, but how much and how fast sea level will rise under realistic warming trajectories.

02Which major cities would be submerged

If all land ice melted and sea level rose by approximately 70 meters, most of the world's coastal cities would be submerged. Cities at or near current sea level, including New York, Miami, New Orleans, Shanghai, Mumbai, Jakarta, Bangkok, Tokyo, London, Amsterdam, and Copenhagen, would be underwater. The inundation would not be uniform, as local factors including land subsidence, ocean currents, and gravitational effects of ice mass loss cause regional variation in sea level change.

The impact on coastal cities would be catastrophic and irreversible on human timescales. Entire metropolitan areas would need to be abandoned or protected by extraordinary engineering measures. The economic loss would be incalculable, as a large fraction of global infrastructure, population, and economic activity is concentrated in coastal zones. While the complete melt scenario is a theoretical extreme, even partial sea level rise of one to two meters by 2100 would force significant adaptation and potential abandonment of low-lying areas.

03The redrawn coastlines of continents

A 70-meter sea level rise would fundamentally redraw the coastlines of every continent. In North America, the entire Atlantic seaboard would retreat inland by hundreds of kilometers in some areas. Florida would largely disappear, the Gulf Coast would move far inland, and California's Central Valley would become a vast inland sea. In Asia, Bangladesh would be almost entirely submerged, large parts of Vietnam and Thailand would be lost, and China's eastern coast would retreat dramatically.

In Europe, the Netherlands would be entirely underwater, Denmark would be reduced to islands, and the Baltic coast would shift far inland. In Africa, the coastlines would change less dramatically due to steeper coastal topography, but low-lying areas including parts of Egypt's Nile Delta and West African coastal cities would be submerged. In South America, the Amazon basin would see significant incursion, and the Río de la Plata would expand far inland. Australia would gain an inland sea in the Murray-Darling basin. The geography of the planet would be unrecognizable.

04How many people would be displaced

Approximately 40 percent of the global population lives within 100 kilometers of a coast, and roughly 10 percent lives in low-lying coastal zones less than 10 meters above sea level. A complete ice melt scenario with 70 meters of sea level rise would displace well over a billion people, potentially several billion, depending on population distribution at the time. The internal displacement within individual countries would be enormous, creating refugee crises of unprecedented scale.

Even under more realistic scenarios of one to two meters of sea level rise by 2100, hundreds of millions of people would be affected. The displacement would not be evenly distributed. Low-lying island nations, including Maldives, Tuvalu, and Marshall Islands, face existential threat even under modest sea level rise. Bangladesh, with a population of over 170 million in a low-lying delta, is particularly vulnerable. The economic and humanitarian cost of mass coastal displacement would reshape global politics and economics.

05The impact on food production areas

Sea level rise would inundate some of the world's most productive agricultural land. River deltas, which are among the most fertile farming areas, are also among the lowest-lying. The Nile Delta, the Mekong Delta, the Ganges-Brahmaputra Delta, and the Mississippi Delta are all critical food production regions that would be partially or entirely submerged under significant sea level rise. The loss of these areas would reduce global food production at a time when population growth and climate stress are already straining food systems.

Beyond direct inundation, sea level rise causes saltwater intrusion into coastal aquifers and soils, degrading agricultural productivity even in areas not directly flooded. The combination of lost land, degraded water supplies, and increased coastal flooding would create cascading effects on food security, agricultural economics, and rural livelihoods. The impact would be felt globally through food prices and supply chains, but the most severe effects would be concentrated in the regions that lose their primary agricultural base.

06What the new geography looks like

The geography of an ice-free Earth would be fundamentally different from the world we know. Beyond the submerged coastlines, the absence of the Antarctic and Greenland ice sheets would change global albedo, ocean circulation patterns, and regional climates. The exposed land under the ice sheets, particularly in Antarctica, would become available for potential habitation, though the climate would remain harsh. The redistribution of water mass would affect Earth's rotation and gravitational field, creating regional variations in sea level that differ from the global average.

The new geography would also feature changed river systems, new inland seas, and altered weather patterns. The geological processes that shape coastlines, including erosion and sediment deposition, would operate on the new coastlines over centuries and millennia. The map of the world would need to be redrawn from scratch, with new trade routes, new political boundaries, and new patterns of human settlement. While this extreme scenario is distant, understanding it helps frame the trajectory of current climate change and the importance of limiting warming.

07How this connects to current climate projections

The complete melt of all land ice is an extreme scenario that would require sustained warming over thousands of years. Current scientific projections indicate that under continued high emissions, sea level could rise by 0.5 to 1 meter by 2100, with potential for higher levels if Antarctic ice sheet instability accelerates. The question is not whether all ice will melt but how quickly partial melting occurs and how societies adapt to the resulting changes.

The connection between the extreme scenario and current projections is important because it illustrates the stakes. Every fraction of a degree of warming commits the planet to additional sea level rise that will persist for centuries or millennia. The decisions made about emissions in the coming decades will determine how much ice melts, how much sea level rises, and how many coastal communities can be preserved. The complete melt scenario is a warning about the long-term consequences of unchecked warming, not a prediction of near-term outcomes.