A NASA mission flying over Antarctica discovered a new rift in the ice shelf of Pine Island Glacier. The glacier could soon calve a large iceberg, the first such event since 2007. Across the 29 kilometre stretch that NASA flew over in October, the rift is around 73 metres wide and in some places up to 58 metres deep. It is widening by two metres per day. When the iceberg finally breaks off, its surface will be around 803 square kilometres, larger than the area of Toronto.
Iceberg calving occurs when a fracture forms through the thickness of an ice sheet. An iceberg breaks off the main sheet, eventually splitting into smaller pieces and melting as it is carried away. Understanding the calving process is important to glaciologists, but until this NASA flight, no one had ever observed an active calving rift.
Pine Island transports more ice from the West Antarctic ice sheets to the sea than any other glacier. It is also the fastest-moving glacier on the continent. Scientists have been interested in it for some time, but it is difficult to reach over land. The NASA mission Operation IceBridge, the largest airborne campaign ever conducted over the polar regions, collected the data.
The mission is designed to bridge the gap between the Ice, Cloud, and Land Elevation Satellite (ICESat), which stopped collecting data in 2009, and ICESat-2, which is scheduled to launch in 2016. IceBridge carries out two surveys a year, once each over Greenland and Antarctica. NASA still has some satellites operating over Antarctica, but only IceBridge’s close-range, high-resolution measurements provide information on the interaction between ice, bedrock, and ocean currents.
IceBridge will provide a three-dimensional view of Arctic and Antarctic ice sheets, helping scientists to understand their behaviour and how they affect the sea level. “At a time when glaciers and ice sheets are showing rapid changes, we need consistent data that shows how and why that change is happening,” said Michael Studinger, a scientist on the project.
The shelf rift is unrelated to climate change, NASA scientists say. Pine Island calves a new iceberg of about the same size every few years in a natural cycle. However, the glacier is thinning at an accelerating rate as a result of climate change. It lost 7 billion tonnes of ice in 2005, and 46 billion in 2010. NASA labels it “one of the most significant climate change response trends” observed worldwide. In 2009, UK researchers estimated that if the current acceleration of melting holds constant, the entire glacier could be afloat in 100 years.
Possible side effects of this include: doom.
illustration by Jeff kent