Surface Lake Melt in Greenland Causing Ice Sheet to “Slip Away”
25.04.2012 - Ice & Snow, Arctic
According to results of a study by a team of researchers from the University of Colorado at Boulder, the Greenland Ice Sheet is slipping into the ocean at a faster rate due to “catastrophic lake drainages” – when huge amounts of meltwater from surface lakes on top of the ice sheet drain to the bedrock of the ice sheet and into the sea.
According to the researchers, the supraglacial lakes that form during the summer melt season have responded to recent increases in surface melting by draining more frequently.
Once the melt causes the lakes to grow large enough in size, the water pressure weighing on the ice sheet creates fractures beneath the lake and forms a vertical drainpipe-like system that channels the meltwater down to the bed of the ice sheet. During a drainage event, about 10,000 m3 of water is released over a period of two days. When the water reaches the base of the ice sheet, it lubricates the space between the ice sheet and the bedrock, causing the ice to slip towards the ocean more quickly.
The water can also carve out sub-glacial sewers, which route the meltwater towards the sea in such a way so as to avoid reaching the bedrock. This would slow down the ice sheet’s move towards the sea, as it avoids lubricating the base of the ice sheet.
“Catastrophic lake drainages” have been occurring more frequently as the climate has been warming. Over the last decade, they were 3.5 times more likely to happen during the warmest years when compared to the coldest years.
Published in the journal Remote Sensing of Environment, the study used satellite images along with state-of-the-art feature-recognition software that allowed the team of researchers to monitor over 1,000 lakes on an approximately 15,000 km2 section of the Greenland Ice Sheet over a 10-year period. The new software made it possible to determine lake size, as well as when the lakes appear and disappear during the melt season.
The project hopes to determine how catastrophic lake drainages from the ice sheet contribute to sea-level rise.