Beneath Antarctica's icy surface, meltwater can reach the bedrock and speed up the movement of the ice. Direct observations carried out on the Langhovde Glacier in East Antarctica confirm this mechanism for the first time on the continent.
An international team drilled several boreholes more than 550 meters deep through the glacier. Cameras and pressure sensors were then lowered to its base. These measurements provide a view of an area inaccessible to satellites.
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During periods of intense melting and after a rainfall event in January 2022, the water accumulated beneath the ice saw its pressure rise sharply. It then bore more than 90% of the weight exerted by the ice above.
This pressure reduces contact between the glacier and the ground. Friction decreases, which facilitates the sliding of the ice mass toward the sea. The researchers measured a speed increase of between 10 and 20%.
The glacier also lifted slightly during these episodes. This movement provides additional evidence of the lubricating effect of pressurized water. The phenomenon was already well documented in Greenland but remained uncertain in Antarctica.
The result does not mean that all Antarctic glaciers will react in the same way. Langhovde is a particular coastal glacier subject to local conditions. However, it demonstrates that surface water can directly alter the dynamics of Antarctic ice.
Surface melting is expected to increase in certain regions of the continent with climate warming. More water could then seep into cracks and reach the bedrock. This process would add to the already known effects of warming ocean waters.
Antarctica stores a considerable amount of frozen water. Its evolution is therefore decisive for projections of sea level rise.
New measurements will be needed on other glaciers to determine the true extent of the phenomenon. They will also help identify areas where surface melting could enhance the transport of ice toward the ocean.