Scientists have identified more than 50 new lakes of liquid water lying under the Greenland Ice Sheet.
Antarctica hides some 470 lakes beneath its ice but this latest UK/US study proves the northern polar region also has its share.
They are nothing like as big, however. The largest down south, Lake Vostok, is 250km long. The biggest subglacial lake in Greenland is just 6km long.
Extensive areas of water can pool under a kilometres-thick ice sheet for a number of reasons.
Pressure from above and geothermal heat from below can maintain a liquid; surface meltwaters will also drain to the bed and collect in hollows.
Researchers are interested in finding such lakes because they say something about the hydrology (water network) underlying an ice sheet and the way it moves.
Water acts as a lubricant, and as the world warms, modelling how quickly ice might slide towards the ocean will inform projections of future sea-level rise.
Greenland’s ice would increase global ocean height by 7m if it were all to melt.
BBC
