Glacier retreat
Iceland's glaciers are losing roughly ten billion tonnes of ice a year, and most of that comes from the very glacier that holds the country's best-known ice caves. Here is what that actually means for a trip.
The glaciers are shrinking fast, and less ice eventually means fewer caves. But ice caves are not disappearing this season — new ones form every year, and the 2026 season produced them as usual.
Two things are true at once, and travel writing usually picks one. The long-term trend is serious and well documented. The short-term reality is that caves keep forming, because the process that makes them does not depend on the glacier being healthy — it depends on the glacier melting.
Iceland's glaciers lose around 10 billion tonnes of ice per year, with 85 to 90 percent of that coming from Vatnajökull and its outlet glaciers.
Glaciers cover roughly 11 percent of Iceland, about 11,400 square kilometres, and Vatnajökull alone accounts for around 7,900 of that. Vatnajökull National Park states that outlet glaciers have retreated exceptionally fast since 2000, and that their mass loss is among the highest recorded anywhere in the world.
| Measure | Figure |
|---|---|
| Annual ice loss, all Icelandic glaciers | ~10 billion tonnes |
| Share from Vatnajökull and its outlets | 85–90% |
| Skeiðarárjökull retreat, 2015–2023 | 500–1,000 m on average |
| Typical outlet retreat since 1995 | 50–100 m per year, sometimes more |
| Projected volume loss by 2100 | Around half |
The Icelandic Meteorological Office's Þorsteinn Þorsteinsson has described the pattern for Skeiðarárjökull as retreat of one to two kilometres between 1925 and 1950, a slight advance from the 1960s to the 1980s, and rapid retreat again since 1995.
It slowed between 2012 and 2020, and that pause has now ended.
Monitoring by the Iceland Glaciological Society across around 130 locations found that the comparatively slower loss of the 2010s has given way to rates comparable with the 1995 to 2011 period. The most pronounced retreat was recorded on outlet glaciers of Vatnajökull, Langjökull and Mýrdalsjökull — which is to say, all three of the glaciers holding the caves on this site.
Heinabergsjökull shortened by around three kilometres over two years following an extensive break-up in summer 2025. Not everything is uniform, though: Gígjökull was recorded as advancing slightly over the same period.
In 2019 Iceland held a funeral for Okjökull, the first glacier officially declared dead because of climate change.
Okjökull once covered around 38 square kilometres on the Ok volcano in western Iceland. By 2014 it had shrunk below one square kilometre — too small and too thin to move under its own weight, which is the definition of a glacier. A bronze plaque now marks the site, addressed to the future.
It matters here because it makes the trend concrete. A glacier is not simply a large block of ice; it is ice heavy enough to flow. When it stops flowing, it stops being a glacier, and it stops forming caves.
Not soon, and not evenly. Less ice means fewer caves eventually, but the caves themselves are a product of melting, so more melt does not immediately mean fewer caves.
This is the counter-intuitive part. Ice caves form because meltwater carves channels through the glacier. A warming glacier produces more meltwater, not less, so in the short term the machinery that produces caves is running harder than ever.
The constraint is volume and stability. Caves need a thick, cold body of ice to form inside and to hold a roof up. As outlet glaciers thin and retreat, there is less ice for caves to form within, and what forms is more likely to be low, fragile or short-lived. Fjallsárlón's own guides put it plainly: if Vatnajökull shrinks substantially, the number of ice caves shrinks with it, simply because there is less ice to hold them.
Caves are more variable year to year, access routes shift, and some tours now involve longer walks than they used to.
It is a fair question and at least one traveller raised it in a review of a tour on this site.
A visitor with an environmental background wrote after a Vatnajökull cave tour that, having heard from park rangers how fast the glaciers are retreating, they were left uneasy about hundreds of people a day being brought onto the ice, and noted the glacier is impressive even from the viewing points further back.
Honestly: the direct physical impact of visitors walking on a glacier is negligible compared with atmospheric warming. The larger footprint is the flights and the driving. That does not make the discomfort unreasonable, and anyone who feels it has real options — the lagoon and Diamond Beach are free and require no tour, and glacier viewpoints show the retreat clearly from solid ground.
You do not need a scientist to point it out. At Jökulsárlón and Skaftafell the evidence is marked on the ground.
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