Image: Sarah Das Woods Hole Oceanographic Institution
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Summary
Greenland’s ice sheet is the second-largest in the world behind Antarctica, covering 1.71 million km2; ~79% of its surface area. It contains ~10% of the frozen freshwater on Earth, the equivalent of ~6-7m of sea-level rise if it all melted.
It’s been losing more ice than it gains (from snow) for almost 30 consecutive years. Ice loss contribution to sea level rise doubled (Video 4). It lost 105bn tonnes of ice 2024-25.
The models used by the Intergovernmental Panel on Climate Change predict a sea level rise contribution from Greenland of around 10 centimeters by 2100, with a worst-case scenario of 15cm. But that prediction is at odds with what field scientists are witnessing from the ice sheet itself. – Alun Hubbard Professor of Glaciology, University of Tromsø, 2022
Many ice sheet scientists now believe that exceeding even 1.5°C will be sufficient to melt large parts of Greenland. – UNESCO State of the Cryosphere 2024
Six narwhals outfitted with transmitters explored East Greenland waters for 3 years, bringing back data showing that warm Atlantic water is reaching glaciers located deep within East Greenland’s fjords.
The 500m thick Prudhoe Dome ice sheet, which covers ~2,500km2, melted some 7,000 years ago when temperatures in the Northern Hemisphere were warmer. This implies it could melt suddenly and rapidly in today’s climate, contributing around 75cm to sea level rise.
Hurricanes are now delivering rain to Greenland, accelerating snow and ice melt, as longer and extreme summer temperatures are accelerating the loss of Arctic sea ice. This is destabilizing the jetstream, resulting in even less snowfall in a feedback effect.
What’s covered on this page:
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- Maps of Greenland: with and without ice and where it’s thawing
- Glossary of terms: ice sheet | marine ice sheet | ice shelf | outlet glacier | grounding line
- The ‘Great Greenland Meltdown’ 2008 – 2025
- More information |impact on Jetream | impact on sea levels | State of the Crysphere reports 2022-2025
- References and further reading
Glossary of terms
- Ice sheet: continental glaciers that have joined together to cover the surrounding land in an area greater than 50,000 km². There are only three in the world: Greenland, and two in Antarctica: the West Antarctic Ice Sheet (WAIS) the East Antarctic Ice Sheet (EAIS). The existence of these ice sheets are why we are still in an Ice Age.
- Marine ice sheet: an ice sheet whose base is on ground below sea level. This makes it particularly vulnerable to undercutting by warming waters.
- Outlet glacier: drains inland glaciers/ice sheets through gaps in the surrounding topography. If an outlet glacier reaches the coast (some terminate inland) it can become an:
- Ice shelf: a tidewater (coastal) glacier or ice sheet that flows down to a coastline and onto the ocean surface, where it floats.
- Grounding line: the point where the bottom or ‘basal’ (bottom) side of a glacier leaves land and extends out over the ocean.
The Great Greenland Meltdown
In 2008, a year before the 2009 IPCC Report stating that any melting from Greenland would not greatly contribute to sea level rise, a staggering volume of ice on the leading edge (front) of the Jakobshavn Glacier (Map 1) was filmed as it carved spectacularly in just 75 minutes (Video 1).
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Extract from the documentary ‘Chasing Ice’. The footage has not be slowed; the sheer scale of the icebergs breaking off Jakobshavn Glacier, which drains about 40% of Greenland’s icecap (Map 1), gives that impression.
Two years later, a single iceberg 260km² x 213m deep broke off the Petermann Glacier (Map 1). By then, multiple Arctic researchers had been pointing out changes happening across Greenland. This bottom up melting was and continues to occur because relatively warm water originating from the Irminger Sea near Iceland erodes the underside of ice shelves (in some places over 2km deep), thinning them from below.
Continued undercutting allows more water to travel further under the ice shelf, eroding it and thinning it until it’s detached from the grounding line and the ice begins to float. As the thinning glacier becomes more buoyant, instead of being part of a solid ice mass, it’s forced up and down with the tides. These forces travel up the length of the glacier, ultimately causing the leading edge to break at the weakest point. Because the glacier is thinner at the front, the slope is steeper so the glacier speeds up due to gravity, allowing huge volumes of ice to surge downstream and into the sea (Fig. 1).
The Jakobshavns Effect is a group of positive feedback mechanisms which allow Jakobshavns Glacier to literally pull ice out of the Greenland Ice Sheet at a rate exceeding 7 km/a across a floating terminus 800 m thick and 6 km wide. The pulling power results from an imbalance of horizontal hydrostatic forces in ice and water columns at the grounding line of the floating terminus.…A small imbalance of forces caused by some perturbation can cause a substantial non-linear response. – Prof. Terry Hughes, ‘The Jakobshavns Effect’ 1978
Because of their much lower albedo, these lakes were absorbing more heat than the surrounding ice, causing more warming and hence further melting in a feedback effect. However, it was assumed that the water would refreeze in winter, and any water that fell into crevasses would refreeze. But in 2002, researchers had identified a process by which meltwater lakes on the surface of Jakobshavn Glacier were exploiting crevices in the ice to lubricate the base of the glacier, which explained why it was moving so fast (Fig. 3).
The meltwater finds crevasses in the ice, whereupon it drains down moulins (Videos 2 & 3) that it scours out like a drill into the heart of glacier. The image at the top of this page also shows the scale of these moulins.
When this happens on marine glaciers or ice shelves once the water reaches the base of the ice, the ice shelf is effectively turned into Swiss cheese and rapidly breaks up.
Whereas when this happens to glaciers sitting on land the outcome is different. If the glacier is on land that slopes downhill inland, when the meltwater reaches the bottom of the glacier, it lifts the glacier and/or joins with ocean water that has reached this point, adding to the melting and undercutting from below.
Where the glacier is on land that slopes downhill towards the ocean, the meltwater lubricates the glacier like a water slide, making it flow faster, which in turn opens or widens more crevasses, allowing yet more meltwater lakes to drain, and so on in a feedback effect. When this warm buoyant freshwater reaches the submerged terminus (front) of the glacier, it scours it from below, then shoots hundreds of metres up the terminus. In some instances it erupts at the surface in a churning jaccuzi-like swirl of mud and ice.
Each year since 2015, the (NASA) team has dropped about 250 probes into the ocean around the edge of Greenland. They’ve found the toasty water—up to 10°C or more—nosed up to the end of glaciers around the island most of the time in most of the places…As they flew low over the leading edge of the massive Helheim glacier, aiming to drop a probe through a hole in the in the mélange of giant bergs floating at the glacier’s snout, they saw water roiling up through the hole “like a bubbling cauldron,” says Willis. When the probe pinged back data, it showed a warm wall of water extending straight down 2,000m to the bottom of the fjord: A solid wall of water ready to melt the glacier. – National Geographic, 2019
