If all of Earth’s ice were to melt, the world map would be dramatically transformed. Coastlines would be erased, and vast inland areas would submerge under an expanded ocean. This hypothetical scenario would redraw continental boundaries and reshape human civilization, resulting in a planet strikingly different from today.
Earth’s Frozen Reservoirs and Potential Sea Level Rise
Earth’s freshwater ice is primarily stored in the Antarctic and Greenland Ice Sheets. The Antarctic Ice Sheet, covering nearly 14 million square kilometers, holds an immense volume of ice, estimated to be between 26.5 and 30 million cubic kilometers, accounting for approximately 61% to 90% of all freshwater ice on Earth. If this entire mass were to melt, global sea levels could rise by an estimated 57.9 to 70 meters (190 to 230 feet).
The Greenland Ice Sheet, the second largest, spans about 1.7 million square kilometers. Its complete melting would contribute an additional 7.2 to 7.4 meters (20 to 24 feet) to global sea levels. Smaller glaciers and ice caps worldwide would contribute another 0.32 to 0.43 meters (about 1.6 feet).
The total melting of all land-based ice on Earth would result in a global sea level rise of approximately 70 meters (230 feet). These ice sheets and glaciers together contain over 68% of the planet’s total freshwater. This increase would inundate vast expanses of low-lying land.
Reshaping Coastlines: A Global Overview
A 70-meter sea level rise would fundamentally redraw the world map, transforming continental outlines. Entire continental shelves, currently shallow extensions of land beneath the sea, would disappear beneath the expanded oceans. This massive inundation would significantly shrink Earth’s total land area.
River estuaries would expand, with the ocean extending far inland. In North America, the Atlantic seaboard and Gulf Coast would vanish, and Florida would disappear. San Francisco’s hills would become islands, and California’s Central Valley would transform into a vast bay. The Gulf of California would stretch northward.
South America would see the Amazon and Paraguay River Basins become expansive Atlantic inlets, erasing coastal Uruguay and most of Paraguay. Australia would lose much of its coast, forming a large inland sea. Antarctica, without its ice, would appear as an archipelago of islands, as much of its bedrock is below sea level. Greenland would also be exposed as a landmass.
Vulnerable Regions and Major City Submergence
A dramatic sea level rise would devastate low-lying regions and coastal population centers. The Netherlands and most of Denmark would be entirely submerged. Bangladesh, a densely populated nation, would be almost completely wiped off the map, displacing an estimated 62 million people. Many small island nations would cease to exist.
Iconic cities, currently global economic and cultural hubs, would be lost to the encroaching waters. London and New York City would vanish. Shanghai would be largely submerged. Other urban centers facing inundation include Venice, Barcelona, Rome, Tokyo, Hong Kong, and Bangkok.
The scale of human displacement would be immense. Billions of people, potentially up to 40% of the world’s population, would be forced to relocate to higher ground. Approximately 634 million people currently reside in coastal areas at or below 10 meters above sea level. Such a rearrangement of populations would present unprecedented challenges.
Broader Planetary Consequences
The melting of all Earth’s ice would trigger broader planetary consequences. Ocean currents, which distribute heat and nutrients globally, would be significantly disrupted. These currents, part of a system known as the thermohaline circulation, are driven by differences in water density, influenced by temperature and salinity. The massive influx of freshwater from melting ice sheets would reduce ocean surface water salinity, making it less dense. This decreased density would interfere with the natural sinking process of cold, salty water in polar regions, which is a key driver of deep ocean currents.
Evidence suggests a weakening of major current systems, including the Atlantic Meridional Overturning Circulation (AMOC). A slowdown or cessation of these currents would alter heat distribution, leading to regional cooling in areas like Western Europe and North America. Such changes would also impact nutrient mixing in the oceans, affecting marine ecosystems and fisheries.
The planet’s climate patterns would be profoundly altered. Ice and snow reflect solar radiation, regulating Earth’s temperature. As ice melts, darker land and ocean surfaces absorb more solar energy, leading to further warming in a feedback loop. This could result in more extreme weather events, including changes in rainfall patterns, increased frequency of hurricanes, and render tropical regions uninhabitable due to extreme heat. The long-term disappearance of glaciers would also reduce freshwater availability for human consumption, agriculture, and hydroelectric power generation, necessitating unprecedented societal adjustments due to displacement and food supply disruption.