By Kirsty Tinto & Mike Wolovick
As little as a few decades ago you could ask a scientist what it was like to monitor the changing ice in Antarctica and the response might have been “Like watching paint dry” — seemingly no change, with no big surprises and not too exciting. Well times have changed. The Ice Bridge Mission is deep into its third Antarctic season collecting data on the condition of the continental scale ice sheet and the floating sea ice that surrounds it, and has noted some exciting results.
On a recent survey flight, which was designed to be fairly routine flying back and forth across the main trunk of Pine Island Glacier, a large crack was spotted in the floating ice tongue in the front of the glacier — a crack large enough to bury a building 16 stories high. This means more changes are coming in the future of this active ice stream.
Pine Island Glacier has been under intense focus as one of the fastest moving, and rapidly thinning glaciers in Antarctica. The planned survey was a grid back and forth across the main trunk of Pine Island Glacier. The pilots refer to this kind of survey as “mowing the lawn.” This type of data collection is essential for putting together a more complete “picture” of the glacier surface, depth, and its underlying surface, and its “grounding line.” The grounding line, shown here as the white line running through the image of the survey plan, is the front edge of where the glacier is frozen all the way to the bottom surface beneath it. The glacier extends beyond the grounding line but as a “floating tongue” of ice.
Glacial tongues can be many meters thick, but because they rest on water they are susceptible to warming from the water below. It is not unexpected for sections of the tongues of glaciers to break off – in fact for this glacier scientists expect to see it occur about twice a decade (the last notable occurrence was in 2007). It is, however, impressive to see it actually developing, and to realize the scale of the crack as it begins – at least 50 meters deep, and up to 250 meters wide. Yes this is much better than watching paint dry.
Lamont-Doherty Earth Observatory has been a partner in this NASA led project collecting airborne gravity. The Ice Bridge Mission is designed to fill the gap between two satellite missions, IceSat I and IceSat II, collecting data on ice thickness in both polar regions. IceSat II is intended to be in orbit in another 4 to 5 years.