The Unstable Giant: New Evidence of Greenland’s Fragile Future
Whilst US attacks on Greenland’s sovereignty create geopolitical instability, the island’s ice is rewriting the rules of global climate. No longer just a victim of warming, its an active participant.
In mid-July 2025, a massive heat dome settled over the Arctic, turning the Greenland ice sheet into a mirror of its own future. For three consecutive days, record-breaking temperatures caused more than 81% of the ice sheet’s surface to melt simultaneously, the highest extent ever recorded by satellites. But while these modern “melt spikes” grab headlines, it is the secrets emerging from beneath the ice that have scientists truly on edge. New data from the GreenDrill project and the discovery of ancient “geologic methane” leaking from retreating glaciers suggest the island is no longer just a passive observer of a warming world. Instead, it is becoming an active participant in its own demise, echoing a “Super-Interglacial” past when most of the 3,500m thick ice sheet simply ceased to exist.
Greenland is melting
According to data from NOAA’s 2025 Arctic Report Card1, the 2024/25 melt season was below average in terms of surface mass balance loss, the island ‘only’ lost 129 billion tonnes of ice, but it continued the trend of significant ice loss occurring every year for 29 years. The reason for the ‘limited’ loss (the average is 264 Gt), was record breaking snowfall across some regions, which made up for some of the overall melt, even though the ice discharge was above average. Ice discharge is the total volume entering the ocean as either water runoff or solid ice breaking from glacier fronts, floating out to sea as icebergs. 2024/25 ice discharge was 491Gt, higher than the average of 458Gt.
Putting those numbers into context, the island is losing ice mass at an average rate of 25 million tonnes per hour, that’s 6,900 tonnes per second. That’s hard to visualise. Ice discharge is even more difficult, at 52 million tonnes per hour or 14,500 tonnes per second. All of that is freshwater and it all flows into the Arctic and North Atlantic oceans, with knock-on consequences.
Although not a record breaker, the 2024/25 melt season was still extreme. A melt spike in mid-July saw over 80% of the ice sheet surface melting simultaneously. In addition, unusual late season melting continued into September. These late-season melting events are becoming more common, lengthening the melt season and increasing ice loss. The figure below shows the daily melt extent anomaly. Red areas indicate surface melting during the melting spike of July 2025.
One of the reasons why melting is increasing is the ice mass itself is warming up. Arctic Amplification is seeing the whole Arctic region warming up to 4 times faster than the global average. A 2024 study found that the ice and snow at 10m below the surface has warmed on average by 2.0ºC since 1998.23 Consequently, the cold reservoir of the Greenland Ice Sheet is being thermally eroded, requiring less springtime or summer warming to bring the surface to the melting point.
In addition to temperature and precipitation, surface reflectivity or albedo is a key driver of melt rate. Reflectivity of the surface can change dramatically in both directions, with fresh snowfall suddenly brightening the surface at any point in the year, or strong melting exposing darker ice and older snow, even initiating biological activity, all of which lower the reflectivity of the surface. The blue line in the graph below shows the high albedo following the fresh snow fall in early July 2025 followed by the darkening as the peak surface melt kicked in.
Black carbon and soot from forest fires, especially in northern Canada often settles on the ice surface and decreases the albedo. Algae growth on the surface also darkens it. This allows more heat to melt the surface rather than be reflected back out into space. The figure below shows the sequence from late July to mid August 2025 and the effect of snowfall on Albedo.
Dynamic Ice Loss - Crevasses and hydrofracturing
Although ice appears solid, it behaves like a highly viscous liquid. It flows slowly downhill driven by gravity. Channels form across the terrain creating the rivers of ice we know as glaciers. Every part of the Greenland ice sheet flows down to the surrounding seas via these glaciers. As they flow, huge stresses develop which creates cracks in the surface. These crevasses can start as small as 1mm in width, but grow as the glaciers speed up, negotiate corners and move towards the coast. They grow to meters wide even reaching 100m or more at the termination.
A study last year by Tom Chudley et al.4 used 3D surface mapping to measure crevasses across the whole island. For comparison the study compared data from 2016 and 2021 to understand if the increases in melting and discharge was linked to changes in crevasse behaviour. They found that from 2016 to 2021, there were significant increases in crevasse volume across fast-flowing sectors of the Greenland ice sheet. In the southeast of the ice sheet, an area that has been particularly vulnerable to ocean-induced acceleration and retreat in the past few years, crevasse volume increased by over 25% in the 5 years.
The study also highlighted how variable glacier flow and crevasse activity can be. One of the areas studied included the Sermon Kujalleq Glacier. This is the fastest flowing glacier on the planet reaching speeds of 50m per day. This glacier is responsible for an outsized proportion of the ice discharge for the whole island.
In 2016, responding to an influx of cold water from the north Atlantic ocean, the glacier slowed and thickened. As it did so, the crevasses on the surface began to close, offsetting increases across the rest of the ice sheet. This slowdown was short-lived though. Since 2018, Sermeq Kujalleq has once again reverted to acceleration and thinning in response to ongoing warming.
Crevasses also allow melt water from the surface to penetrate the glacier. Moulins form which drain the water through the ice. When it reaches the base, the water can act as a lubricant, allowing the glacier to move more easily over the ground, speeding it up.
Just like rivers, the flow in the centre of a glacier is often faster than at the edges. Crevasses also form on these margins, the high sheer areas between the fast and slow flowing zones. Recently these have also been growing as the glaciers accelerate, filling with meltwater and providing further lubrication to the ice flow.
The forces involved in ice flows and sub-glacial lakes are huge. A 2025 study reported on a subglacial lake in northern Greenland which drained upwards through the ice sheet under immense pressure, blasting an 85m deep crater on the surface and releasing 90 billion litres of water.5
Sometimes the meltwater drains into a crevasse, filling it with water. When this happens it can drive the crevasse even deeper by a process called hydrofracture. Crevasse depth is limited by the huge internal pressure of the ice at depth which acts to prevent the crack from spreading. These force acts as a break, but if the cracks are filled with water, the pressure of the water depth, resists the side pressure from the ice, keeping the fracture open, and allowing the movement stresses to drive the crack even deeper into the glacier.
Where the flow reaches the sea, crevasses form the initial fractures and break points from which icebergs can break off the front of the glacier. More crevasses increase the output of icebergs into the ocean and the rate of ice discharge. This in turn reduces the buttressing effect allowing the glacier to speed up, creating more crevasses in a feedback loop.
The New Permafrost Frontier and glacial fracking
When we think of permafrost, we tend to think about Arctic Canada and Siberia, but Greenland also contains significant amounts of frozen ground susceptible to warming and melting. As these degrade, methane is released into the atmosphere, providing more warming in another feedback loop. Evidence for degradation can be found in the significant greening of the island’s coastal regions. Satellite analysis shows a doubling of vegetation on Greenland over the last three decades6. Although green is generally good, it is also a strong indicator that ice covered and permafrost lands are being converted to wetlands. In fact the total area of wetland has quadrupled in this time.
In addition to organic methane release, geologic methane release is also a potentially growing emission source. Here methane, trapped in rocks and in the form of gas hydrates deep beneath the ice sheet, is liberated and flows out in melt rivers and ground springs as the ice retreats and the pressures drop. This methane then escapes to the atmosphere prompting further warming. A study published last year from neighbouring Svalbard, found methane concentrations in the melt river water up to 800 times higher than the atmospheric equilibrium level.7
Co-author Leonard Magerl said:
“Glaciers act like giant lids, trapping methane underground. But as they melt, water flushes through cracks in the bedrock, transporting the gas to the surface. You can think of as a natural ‘fracking’ process, or as we have called it: ‘glacial fracking’.”
In addition to climate feedbacks, melting permafrost causes significant infrastructure problems for local communities - and for any future mineral extraction, despite how optimistic politicians further south may feel.
Paleoclimate: The Lessons of MIS-11 and the Holocene
To understand where Greenland is going, we need to look to the past, and in particular periods of previous significant melting.
All through the current ice age back to the start of the Pleistocene 2.58 million years ago, ice sheets have grown and receded according to the Earth’s orbital patterns around the sun. Warm interglacials, like the recent Holocene have occurred roughly every 100,000 years for the last 800,000. One of these interglacials, the Hoxnian or MIS-11 is of particular interest when it comes to Greenland.
The Hoxnian was just over 400,000 years ago. It was an unusual interglacial in that it was very long lived, but with temperatures about the same as they are today (averaging at 1.5ºC above pre-industrial). This provides a clue as to how Greenland might react to the temperature regime we are driving it into.
In 1993 an ice core was drilled into the 3km thick ice near the centre of Greenland. Not only did it reach the bedrock beneath, it also collected a core of just over 1.5m of rock and soil from the base. This was analysed in a study published in 20248 when it was concluded that the samples were last exposed to air within 1 million years, most likely in the last 400,000 years, probably during the Hoxnian. The reason scientists think this is that sea level height at that time (4.5-6m contribution from Greenland) matches near total melt of the Greenland ice sheet.
The soil sample included vegetation fragments including a willow bud scale, over 100 spores from rock spiky-moss, poppy seeds, soil fungus and insect parts. Samples of angiosperm wood were also isolated. This paints a picture of a mainly ice free Greenland with a varied tundra ecosystem in a world with similar temperatures to today, but less than the temperatures expected this century.
More recently, new evidence published this month shows that the Prudhoe Dome ice cap in the northwest of Greenland, currently covered in 500m of ice, was ice free just 7,000 years ago.9 The drilling of the ice core also collected a 7m core of sediment and bedrock from the base.
The GreenDrill scientists used luminescence dating on the sediment. This technique measures when mineral grains were last exposed to sunlight. The results from these minerals proved the ground was open to the sky 7.1 (±1.1) thousand years ago during a warm period in the middle Holocene.
During that time, summer temperatures in the region were only 3°C to 5°C warmer than pre-industrial levels. This is a critical “mild” warming threshold that are close to being experienced today since Arctic Amplification means the region is warming up to 4 times faster than the global average, which is already at (or nearly at) 1.5°C. This is important, since if relatively modest warming was enough to erase a 500-meter-thick ice dome in the recent past, it suggests that Northwest Greenland is far more sensitive to temperature increases than previously thought, and prone to imminent melting leading to increased sea level rise.
The study also provides evidence of a tipping event in the recent past. The whole ice sheet is treated as a tipping element due to an elevation feedback. As the ice cap melts, the top is lowered into a lower altitude, with warmer air which promotes further melting, further lowering the altitude, and so on. At the same time, higher temperatures cause an increasing fraction of snowfall to fall as rain. Rain runs off the ice faster than snow and also lowers the surface albedo. Total precipitation also decreases, because a lower ice sheet induces less uplift, cooling and condensation of air. As a result, the accumulation of new ice is strongly reduced. The evidence of complete melting at Prudhoe shows this can happen at basically today’s temperatures.
Global Consequences: The North Atlantic Engine
There are two significant consequences to the melting of Greenland for the rest of the planet. The most obvious is sea level rise. Greenland contains enough ice to raise sea levels by 7.4 meters if it were all to melt. As the Prudhoe study shows, we are very close to reaching tipping points that would expedite this reality. This will of course take considerable time, centuries, to achieve full loss. However the rate of sea level rise in the near future and therefore the costs of adaptation are still highly relevant. Contributions of up to 1m within 75 years are possible.
This is higher than current IPCC estimates, however the models used in the last set of IPCC reports did not include any of the ice dynamics described here, or newly discovered changes in precipitation or wind patterns. When plausible worst case scenarios are used, as they should be in any sensible risk assessment, the prognosis is far worse than current policy is based on or could cope with.10
The second, and perhaps even more significant ramification of Greenland melt is its effect on the Atlantic Meridional Overturning Circulation or AMOC. The AMOC draws warm water into the North Atlantic where it maintains northern Europe’s temperate climate. It also keeps sea levels on the northeastern American coast about 1m lower than they would be otherwise. Globally it helps to situate the monsoon belts that provide irrigation for billions across Asia and north Amazonia. A more detailed review of the AMOC can be found in the footnotes.11
The AMOC is known to be weakening as a result of climate change. There is a direct influence on the temperature gradient between the equator and the Arctic which is getting smaller, but also meltwater from Greenland is freshening the seas, inhibiting the overturning current and weakening the deep water formation processes that drive the AMOC. With accelerated melting, the AMOC could weaken to a point where it would flip to an off state. The ramifications of this would be catastrophic. Scandinavia, the UK and northern mainland Europe would see tremendous drops in winter temperatures, while summer temperatures would continue to get warmer. Flooding would affect the East coast of the US as well as northern Europe and the monsoons that so many rely on would shift to currently arid areas. These are world economy and civilisation ending impacts.
The stability of Greenland is therefore of huge importance to the world, not for minerals, oil or to stroke the ego of a megalomanic, but for the stability of the planetary systems and the climate we all rely on.
NOAA Arctic Report Card 2025 - Greenland https://arctic.noaa.gov/report-card/report-card-2025/greenland-ice-sheet-2025/
Vandecrux, B. et al.: Recent warming trends of the Greenland ice sheet documented by historical firn and ice temperature observations and machine learning, The Cryosphere, 18, 609–631, https://doi.org/10.5194/tc-18-609-2024, 2024.
AMAP, 2024. AMAP Arctic Climate Change Update 2024: Key Trends and Impacts. Arctic Monitoring and Assessment Programme (AMAP), Tromsø, Norway. https://doi.org/10.21352/fz60-s852
Chudley, T.R., Howat, I.M., King, M.D. et al. Increased crevassing across accelerating Greenland Ice Sheet margins. Nat. Geosci. 18, 148–153 (2025). https://doi.org/10.1038/s41561-024-01636-6
See also the article in The Conversation: https://theconversation.com/the-greenland-ice-sheet-is-falling-apart-new-study-248926
Bowling, J.S., McMillan, M., Leeson, A.A. et al. Outburst of a subglacial flood from the surface of the Greenland Ice Sheet. Nat. Geosci. 18, 740–746 (2025). https://doi.org/10.1038/s41561-025-01746-9
Grimes, M., Carrivick, J.L., Smith, M.W. et al. Land cover changes across Greenland dominated by a doubling of vegetation in three decades. Sci Rep 14, 3120 (2024). https://doi.org/10.1038/s41598-024-52124-1
Kleber, G. E., Magerl, L., Turchyn, A. V., Schloemer, S., Trimmer, M., Zhu, Y., and Hodson, A.: Proglacial methane emissions driven by meltwater and groundwater flushing in a high-Arctic glacial catchment, Biogeosciences, 22, 659–674, https://doi.org/10.5194/bg-22-659-2025, 2025.
P.R. Bierman, H.M. Mastro, D.M. Peteet, L.B. Corbett, E.J. Steig, C.T. Halsted, M.M. Caffee, A.J. Hidy, G. Balco, O. Bennike, & B. Rock, Plant, insect, and fungi fossils under the center of Greenland’s ice sheet are evidence of ice-free times, Proc. Natl. Acad. Sci. U.S.A. 121 (33) e2407465121, https://doi.org/10.1073/pnas.2407465121 (2024).
Walcott-George, C.K., Brown, N.D., Briner, J.P. et al. Deglaciation of the Prudhoe Dome in northwestern Greenland in response to Holocene warming. Nat. Geosci. (2026). https://doi.org/10.1038/s41561-025-01889-9
Paice, C. M., Fettweis, X., and Huybrechts, P.: Positive feedbacks drive the Greenland ice sheet evolution in millennial-length MAR–GISM simulations under a high-end warming scenario, The Cryosphere, 20, 309–332, https://doi.org/10.5194/tc-20-309-2026, 2026.
Great piece!
Great essay Tom!