Cracks in ice shelves have appeared in disaster movies as ominous signs of global warming. One memorable instance occurs in The Day After Tomorrow when a paleoclimatologist is drilling ice cores at the Larsen Ice Shelf. The shelf breaks apart, leading to a series of cataclysmic climate events that disrupt the North Atlantic Ocean circulation. In July, a real- life crack appeared at Petermann Glacier in Greenland and has been growing steadily ever since. Two scientists, Andreas Muenchow and Keith Nicholls, are investigating the crack and hypothesize that it is caused by an increase in air and ocean temperatures.
Petermann Glacier connects the Greenland ice sheet to the Arctic Ocean at 81°N. It is approximately 43 miles long and nearly 10 miles wide. This is not the first crack or full break of ice at Petermann Glacier, according to a Washington Post article by Chris Mooney. Since 2010, entire slabs of the Petermann glacier have broken off.
In fact, during two occasions, the glacier lost an area of ice six times the size of Manhattan, according to Mooney. This loss raises enormous concern because the glacier serves to slow down the flow of ice downhill from the Greenland ice sheet into the ocean. For this reason, experts call Petermann a “floodgate.” If the glacier that sits behind Petermann melts, it could raise sea levels by about a foot.
A recent paper published in the Geophysical Research Letters describes this type of calving at Petermann as common. The authors explain that it is usually assumed that ocean-ice dynamics are not involved. However, evidence from the Pine Island Glacier in West Antarctica found that ocean forcing can play a role in the melting.
Muenchow and Nicholls expect similar dynamics are occurring with Petermann Glacier. They have been on several expeditions to the glacier in order to measure ocean temperatures underneath the shelf itself. They want to see if rising ocean temperatures are also detrimental to the glacier and causing the melting from below.
If warm ocean water were melting the base of the glacier, it would only accelerate the destruction of Petermann. While it is extremely difficult to know definitively, they hypothesize Petermann’s river and the channel beneath it are playing a role in the melting.
Data from 2015 and 2016 demonstrates that the temperatures of the warm Atlantic layer in the ocean have increased. With both air and ocean temperatures getting warmer, it is unclear how much longer Petermann Glacier will be intact, leaving frightening implications for the melting of the enormous glacier behind it. The crack in the Petermann Glacier and the possible ensuing events show that news from the ice can sometimes be just as scary as the scenes in disaster movies.