Researchers have observed extremely high rates of melting at the bottom of the Greenland Ice Sheet, caused by huge quantities of meltwater falling from the surface to the base. As the meltwater falls, energy is converted into heat in a process like the hydroelectric power generated by large dams.
An international team of scientists, led by the University of Cambridge, found that the effect of meltwater descending from the surface of the ice sheet to the bed – a kilometre or more below – is by far the largest heat source beneath the world’s second-largest ice sheet, leading to phenomenally high rates of melting at its base.
The lubricating effect of meltwater has a strong effect on the movement of glaciers and the quantity of ice discharged into the ocean, but directly measuring conditions beneath a kilometre of ice is a challenge, especially in Greenland where glaciers are among the world’s fastest-moving.
This lack of direct measurements makes it difficult to understand the dynamic behaviour of the Greenland Ice Sheet and predict future changes. With ice losses tied to both melting and discharge, the Greenland Ice Sheet is now the largest single contributor to global sea-level rise.
Now, in a study published in the Proceedings of the National Academy of Sciences, the Cambridge-led team has found that the gravitational energy of meltwater forming at the surface is converted to heat when it is transferred to the base through large cracks in the ice.