subglacial lake

Satellite image of subglacial Lake Vostok in Antarctica. Image credit: NASA A subglacial lake is a lake that is found under a glacier, typically beneath an ice cap or ice sheet. Subglacial lakes form at the boundary between ice and the underlying bedrock, where liquid water can exist above the lower melting point of ice under high pressure. Over time, the overlying ice gradually melts at a rate of a few millimeters per year. Meltwater flows from regions of high to low hydraulic pressure under the ice and pools, creating a body of liquid water that can be isolated from the external environment for millions of years.

Since the first discoveries of subglacial lakes under the Antarctic Ice Sheet, more than 400 subglacial lakes have been discovered in Antarctica, beneath the Greenland Ice Sheet, and under Iceland's Vatnajökull ice cap. Subglacial lakes contain a substantial proportion of Earth's liquid freshwater, with the volume of Antarctic subglacial lakes alone estimated to be about 10,000 km, or about 15% of all liquid freshwater on Earth.