Scientists have found a hidden reason why Antarctica may be melting faster

Scientists have studied the Fimbulisen ice shelf in East Antarctica. This region is generally considered colder and less vulnerable than West Antarctica. However, modelling has shown: even small inputs of warmer deep water can markedly increase melting if the glacier's lower surface has channels.

Details

Shelf glaciers are extensions of mainland glaciers that are already floating on water. By themselves, they don't make much direct contribution to sea level rise because they are already in the ocean. But they work as buttresses: they hold back the ice sliding from the mainland into the sea.

If this ice "backstop" thins and weakens, the glaciers behind it can move faster towards the ocean. This is what creates the risk of faster sea level rise.

The main mechanism the researchers described has to do with the shape of the lower surface of the ice shelf. If there are long channels at the bottom, they can change the movement of water under the ice. Small circulation cells form in these depressions, which keep warmer water close to the ice rather than allowing it to quickly move further away.

As a result, localised melting within such channels can increase by about an order of magnitude. So it's not just ocean temperature that matters, but also the geometry of the ice: the shape of the underside of the glacier determines where the ocean heat gets to and how destructive it becomes.

For the work, the team combined a detailed map of the underside of the Fimbulisen glacier with a high-resolution model of the ocean cavity beneath it. The researchers compared variants with a smoother ice base and one with a realistic canalised surface, and tested different conditions, from colder to slightly warmer water.

Why it matters

The study shows that some East Antarctica ice shelves may respond to ocean warming more strongly than expected. Even moderate infiltration of warm deep water can accelerate melting if water enters channels beneath the ice.

This has implications for climate models. The authors caution that current models may not adequately account for such small but important features of the undersurface of ice shelves. If this effect is underestimated, the sensitivity of glaciers to ocean warming may also be underestimated.

For coastal regions, this is important because sea level projections are used in infrastructure planning, coastal defence and climate change adaptation. Even small errors in assessing the resilience of Antarctic glaciers can have major consequences in the long term.

Background

Antarctic ice shelves melt mostly from below, where ocean water comes into contact with them. The more actively warm water penetrates beneath a glacier, the faster it loses mass and the weaker it holds back mainland ice.

Previous research has previously shown that channels beneath ice shelves may be important for localised melting and exchange of water beneath the ice. The new work adds an important element to this picture: the channels may not just be a consequence of melting, but may increase the glacier's sensitivity to slight ocean warming.

That said, the findings do not mean that Antarctica will "melt soon" or that sea levels will rise dramatically in the coming years. It is about a mechanism that may make some glaciers less resilient and that needs to be better factored into forecasts.

Source

The study Channelised topography amplifies melt-sensitivity of cold Antarctic ice shelves is published in Nature Communications in 2026. The authors studied the Fimbulisen ice shelf in East Antarctica and showed that channels on the underside of the glacier can trap warm water and enhance melting from below.