Covering roughly 660,000 square miles beneath layers of ice up to two miles thick, the Greenland ice sheet holds enough frozen fresh water that, if it all melted, sea levels around the world would rise by an estimated 24 feet. That figure alone places Greenland among the most consequential single features on the planet for coastal cities everywhere, even though a full melt remains a process that would unfold over centuries rather than years under current warming trends.
The Second-Largest Ice Mass on Earth
Only the Antarctic ice sheet holds more frozen water than Greenland’s, and together the two ice sheets contain the overwhelming majority of the planet’s fresh water locked away as ice. Greenland’s ice built up gradually over hundreds of thousands of years as snowfall compacted into thick layers of glacial ice, forming a dome-shaped mass that presses down on the bedrock beneath it and flows slowly outward toward the coast through a network of outlet glaciers, some of which drain directly into fjords along the island’s western and southeastern coasts. Beneath the ice, the weight of the sheet has pressed the underlying bedrock down over thousands of years, meaning much of Greenland’s interior actually sits below sea level today and would only rebound slowly upward over centuries after the ice above it disappeared.
Enough Water to Raise Every Coastline
NASA’s ongoing satellite monitoring estimates that a complete melt of the Greenland ice sheet would raise global sea level by roughly 7.4 meters, or about 24 feet, an amount that would reshape coastlines on every inhabited continent, according to the data maintained on NASA’s ice sheet vital signs page. That total does not include the far larger volume of ice held in Antarctica, which alone could raise sea level by tens of additional meters if it were to melt entirely, underscoring how much of the world’s potential sea level rise remains locked in polar ice rather than already in the ocean.
Losing Mass Faster Than It Gains
Satellite gravity measurements have tracked the Greenland ice sheet losing mass at an accelerating pace over the past two decades, as warmer air and ocean temperatures increase surface melting and speed up the flow of outlet glaciers that drain ice into the sea. Some individual glaciers, including Jakobshavn Isbræ on Greenland’s west coast, have been documented moving and thinning at rates that surprised researchers when continuous satellite tracking became available, offering a more direct picture of how quickly a major ice stream can respond to a warming ocean. Summer melt seasons in particular have grown longer and more intense across large portions of the ice sheet’s surface in recent decades, with meltwater now reaching areas of the high interior that historically stayed frozen even through the warmest months.
A Process Measured in Centuries, Not Years
Even with mass loss accelerating, scientists generally describe a complete melt of the Greenland ice sheet as a process that would take many centuries to unfold fully, since the sheer volume of ice involved and the physics of how ice sheets respond to warming both act as natural brakes on the pace of change. That timeline does not make the current trend inconsequential; even a partial loss of Greenland’s ice contributes measurably to the sea level rise already being recorded at tide gauges and by satellite altimeters around the world each year.
A Darkening Surface That Feeds Its Own Melt
Some of the acceleration in Greenland’s ice loss has been linked to feedback loops that make melting easier to sustain once it starts. Fresh, bright snow reflects most sunlight back into space, but as the surface melts and exposes older, darker ice, or as soot and algae darken the snowpack, the surface absorbs more solar energy and melts faster still. Meltwater pooling on top of the ice sheet during summer months can also drain down through cracks called moulins to the base of the glacier, where it can lubricate the boundary between ice and bedrock and speed the flow of ice toward the ocean.
Why Greenland Draws Continuous Monitoring
Because of the scale of sea level rise locked away in its ice, Greenland has become one of the most closely monitored landmasses on the planet, tracked through a combination of satellite gravity missions, radar altimetry, and repeated field expeditions that measure surface melt, ice thickness, and glacier flow speed directly. That sustained monitoring effort is what allows scientists to say with confidence not just how much water the ice sheet could eventually contribute to the ocean, but how quickly that contribution is actually beginning to arrive, and how that pace compares with earlier projections made only a decade or two ago. Each new mission added to that monitoring effort has generally refined the picture further, narrowing the uncertainty around how much the ice sheet is likely to contribute to sea level rise over the coming decades.
This article was produced with the assistance of AI and reviewed by Morning Overview editors.
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