In the entire history of mankind, we are wagering that nobody has ever said, "Look out! It's a runaway glacier! Run for your lives!" Nor has a newspaper headline ever read "Man run over by speeding glacier". Those events never happened and never will. However, there is concern about a real-life speeding glacier in Greenland, and the possible effects it may have on sea levels around the world. The glacier was studied as part of an effort sponsored by the NSF (National Science Foundation) and NASA, and the results were recently published in The Cryosphere.
According to researchers with DLR (the German Space Agency) and the University of Washington in Seattle, a glacier in Greenland-known as the Jacobshavn Glacier-has been moving at a rate of 10 miles per year. While this sounds trivial, consider that during the period from 2000 to 2010, moving at a slightly slower speed, this glacier alone contributed about 1 millimeter to the increase in sea level.
While that may also sound trivial, consider that there are estimated to be over 160,000 total glaciers in the world today. Of course, all of those glaciers are not the same size and do not necessarily have the same effect that the Jacobshavn Glacier is having near Greenland, but it does illustrate the point that even seemingly trivial changes in glacier movement and sea level may have large ramifications if taken in the aggregate.
How did the scientists determine this rate-with the finest available stopwatches and the world's most patient (and coldest) scientists? Not quite. The research team compared movements in satellite image data from the DLR's TerraSAR-X satellites. The speeds must be carefully calculated and averaged over time because the flow rates are understandably different in winter than in summer, but there is no question that the speed is increasing. The average speed of the Jacobshavn Glacier over the last few years is around 3 times the rate of the speed during the decade of the 1990s.
How does the speed affect sea level? The overall effect is that more of the ice sheet is released into the ocean. Jacobshavn Glacier directs the Greenland ice sheet toward the coast of Greenland into an ocean fjord (a narrow inlet surrounded by cliffs), where a portion of the ice melts and the rest is sent out into the ocean. As global warming causes the glacier to thin and the flow speed of the glacier changes, the location where the glacier begins to break up and form icebergs changes, as does the rate of the breakup. The breakup area moves closer inland because it has lost the ice in front that would slow the glacier down.
The Jacobshavn Glacier has another claim to fame aside from being the current world's fastest glacier-it is believed to be the glacier responsible for sinking the Titanic. Researchers will continue to monitor the Jacobshavn Glacier's movements and changes over time to continue to measure the effects of global warming in the area-and will hopefully report someday that it has lost one claim to fame by slowing down, indicating less global warming.