Deep beneath the Antarctic ice, there’s something astonishing – liquid water. Latest estimates suggest that the south polar icecap hides over 350 subglacial lakes, buried thousands of metres below the surface. And we’re not talking puddles here, but significant bodies of water: East Antarctica’s Lake Vostok has a surface area of around 14,000 square kilometres, making it one of the largest lakes in the world.
How Do Subglacial Lakes Form?
It may seem counter-intuitive to find liquid water beneath enormous thicknesses of ice on the planet’s coldest continent, but in fact it isn’t really so surprising. Antarctica, after all, was a continent long before it was covered in ice, and the land which underlies the frozen surface has been shaped, over millions of years, in just the same way as the rest of the Earth.
Underneath the ice, therefore, the topography is characterised by mountains and valleys, a glaciated landscape whose original river valleys were gouged out into deep troughs by the power of glaciers as the ice cap formed. And, just as elsewhere – in places like England’s Lake District or the Finger of New York State – these ice-carved troughs are places where water collects and forms ice.
So, how come the lakes are liquid water rather than solid ice? Put simply, the answer is a combination of two factors.
- Firstly, the earth itself is giving out heat as the radioactive materials within it decay: although levels of heat are low, they are sufficient to melt the ice.
- Secondly, the thick layer of ice overlying the lakes provides insulation, preventing the heat from being lost.
Between them, these two mechanisms combine to maintain huge quantities of water in a liquid state – as subglacial lakes.