Back in 2008, a similar study could not fully grasp the mechanisms that cause the icy bottoms of the lakes found in the Greenland Ice Sheet to suddenly crack and drain a full lake in as much as 24 hours.
The 2008 study from the Woods Hole Oceanographic Institution (WHOI) in collaboration with the University of Washington stood as the basis for the new research that added scientists from the MIT as well as the University of Tasmania.
Together, they sent an unprecedented number of GPS units surrounding North Lake, found in the southwest Greenland Ice Sheet. The 16 GPS units provided the necessary data to solve the mystery of the super-sized cracks and lake disappearance.
The ice movements in the North Lake region of the Greenland Ice Sheet were recorded before and during, as well as after the major lake draining that occurred in in each summer from 2011 to 2013.
The gathered data indicated that prior to the icy bottom cracking and leading to the major spill, the ice surrounding the lake shifted upwards and then slipped horizontally. The process was caused by water melted by the rising temperatures. The water had begun to infiltrate the intricate moulins system connected to the ice sheet base at a considerable distance.
The more water accumulated here through the vertical conduits, the ice sheet started floating which in turn created considerable tension at the icy lake bottom. The sudden cracks are a simple way of relieving stress accumulated.
The immense volume of water then starts playing its role by exerting pressure on the created crack, widening it and infiltrating through the same moulins all the way to the base of the ice sheet. This creates a vicious circle that is called hydrofractures.
They are responsible for draining as much as 11 billion gallons of water in 90 minutes. This was the case of North Lake in particular.
Each year, a high number of lakes form on the Greenland Ice Sheet during spring and summer. With the rising global temperatures, it is expected that hydrofractures will become a more common phenomenon which will lead to ice sheet movements and certain rising of sea levels.
The research results were published in the journal Nature on June 4th.
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