The Greenland Ice Sheet is one of the great immovable giants of Earth’s cryosphere—home to the second-largest body of ice on the planet and a key contributor to global sea level. Understanding how it has changed from the Last Glacial Maximum (LGM) to the present helps scientists put today’s rapid melting into long-term context.
Where Greenland Sat at the Last Glacial Maximum
About 26,000–20,000 years ago, during the Last Glacial Maximum, global ice volume reached its peak. Ice sheets like the Laurentide over North America and the vast Eurasian Ice Sheet dominated much of the Northern Hemisphere, pushing sea levels down by more than 120 meters compared with today.
In Greenland, the ice sheet was significantly larger than its modern form. Reconstructions indicate that ice extended all the way to, and in places beyond, the modern continental shelf edge and was substantially thicker than today’s sheet. Some areas of the present coastal margin were buried under ice more than 1500 meters thicker than modern levels, and overall the ice cover was more extensive around the island.
At the LGM, the Greenland Ice Sheet was part of a global glacial system. Its sheer volume contributed a substantial fraction of global ice, holding back ocean water in massive continental glaciers and shaping global climate through its influence on albedo (surface reflectivity) and atmospheric circulation.
Greenland Today: A Melting Giant
Fast-forward to the present: the Greenland Ice Sheet still dominates the island, covering roughly 1.7 million square kilometers—about 80% of Greenland’s land surface—and contains enough frozen water to raise sea levels by about 7.3 meters if it were to melt entirely.
But unlike the steady state of the late Pleistocene, the modern ice sheet is rapidly losing mass. Satellite gravity observations from missions like GRACE and GRACE-FO show Greenland shedding hundreds of billions of tonnes of ice every year—much faster than in past decades. Between 2002 and 2025, average ice loss was around 264 gigatons per year, contributing to measurable sea level rise. Web radar, satellite altimetry, and field observations confirm that most of this loss comes from increased surface melting and iceberg calving as ocean and air temperatures rise.
In recent years, despite variability (for example, 2024 saw slightly lower net ice loss), the overall trend remains one of significant mass decline, with the last year of verified net ice gain still back in the mid-1990s.
LGM vs Today: A Tale of Ice Extent and Climate Drivers
The contrast between the LGM and today is stark:
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Extent & Thickness: During the LGM, the ice sheet was larger and thicker, covering a greater area and pressing outward to continental shelves. Today it is reduced in extent and thinning at margins, especially where glaciers contact warming oceans.
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Climate Context: The LGM was driven by natural orbital forcing and cold global temperatures. Modern changes are driven by rising greenhouse gases and rapid warming, particularly in the Arctic, where temperatures are increasing faster than the global average.
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Ice Sheet Dynamics: During deglaciation after the LGM, ice retreated over thousands of years as Earth warmed naturally. Today’s melt is happening on decadal timescales—a much faster pace with profound implications for sea level and climate feedbacks.
Scientists also note that parts of Greenland may have been ice-free during past interglacials, and sediment preserved beneath the ice suggests episodes of significant retreat even before the present warm period.
Understanding how Greenland responded in the past provides crucial insight into how sensitive the ice sheet might be to current and future warming—especially as modern climate change pushes the ice toward states not seen since the last deglaciation.