There are few frontiers in the world that can still be said to be unexplored. One of these terra incognita is the land beneath Antarctica’s ice sheets. Buried under kilometres of ice is a fascinating realm of canyons, waterways and lakes, which is only now being mapped in detail.
There are more than 400 known lakes in this harsh environment, and more are being discovered as technology advances. This water beneath the ice lubricates the interface between the ice sheet and its rocky bed, and thus controls the flow and behaviour of the ice itself.
Under such a large volume of ice, how is it possible for water to exist at all without freezing? The answer is pressure: when a large weight of ice is pushed onto water, it can stay liquid at temperatures well below the normal freezing point. What’s more, the large body of ice actually insulates the bed and protects it from the very cold air temperatures above.
The liquid water is created by heat from the Earth’s interior and from the friction generated as ice flows over the bedrock, which can melt the underside of the ice sheet. It is this water that flows into the subglacial lake basins and eventually into the ocean.
Huge Water Features
A tour around this subglacial landscape would take you first to the largest lake under the ice: Lake Vostok. At 12,500 square kilometres and with an average depth of 430 metres, Lake Vostok is the world’s sixth-largest lake by volume, but as it lies beneath some 3.5km of ice, it’s not easy to visit.
Using ice-penetrating radar and seismic techniques, scientists have mapped Lake Vostok to understand its origins. They have found that it may be up to 15 million years old. The lake has circulation patterns driven by freezing and thawing of the overlying ice, and even has small lunar tides.
Lake Vostok was discovered decades ago, but what is thought to be the second-largest lake under the ice sheet was first observed only this year. It is in Princess Elizabeth Land, East Antarctica, known as the “last pole of ignorance” because until recently it was virtually unmapped.