Photo Credit: Ted Scambos

A helicopter hovers over the back deck of the research vessel NATHANIEL B. PALMER during one of the expeditions for the LARISSA project. Research before and during the IPY project has suggested the Larsen B Ice Shelf collapsed as a result of rising air temperatures and melting at the ice surface.

Surface melt

Study suggests Larsen B Ice Shelf collapsed from the top down

Newly published research on the geologic history of the Antarctic Peninsula, specifically an area where a large, floating ice shelf disintegrated in the early 2000s, indicates that the cataclysmic break-up was primarily a result of rising air temperatures and melting at the ice surface.

The recent findings support the idea that a warming of the ice surface and its after-effects – such as the development of melt ponds and crevasses, or cracks, in the surface of the ice that allow warmer water to infiltrate downward into the ice – could cause such a dramatic collapse.

The findings were published in the Sept. 11 edition of the journal Science.

The under-cutting of the bottom of an ice shelf by relatively warm ocean water also causes ice shelves to collapse, and scientists have demonstrated such occurrences in Antarctica and Greenland.

But the new study indicates that most changes at the base of the Larsen B Ice Shelf on the Antarctic Peninsula, the portion of Antarctica that extends northwards toward South America, had already occurred at the end of the last ice age.

“Now, we can recognize two distinct mechanisms for the destabilization of ice shelves,” said Eugene Domack, a lead author on the paper and a professor of geological oceanography at the University of South Florida, in a press release . “This research gives us at least two ‘devils’ to worry about.”

The research involved an international team of researchers and focuses on the 2002 disintegration of the Larsen B, a slab of ice the size Rhode Island and located on the eastern coast of the Antarctic Peninsula.

The research was supported by the Division of Polar Programs within the National Science Foundation’s Geosciences Directorate . Parts of the findings were supported by a program called LARISSA, for LARsen Ice Shelf System, Antarctica. The project was funded by the NSF during the 2007-08 International Polar Year, a global campaign to study the polar regions in unprecedented detail.

Scientists with the LARISSA project participated in several research cruises to the Antarctic Peninsula to collect data about the area’s response to past climate changes and to examine more recent behavior after the ice shelf disappeared. Samples had also been collected by Domack and colleagues during research cruises in 2005 and 2006.

The new work has major implications for the study of ice-sheet dynamics, which are important in understanding how the vast Antarctic ice sheets will behave, as global temperature increase. The Antarctic Peninsula is one of the fastest-warming places on the planet, with temperatures increasing by about a half-degree Celsius per decade since the 1950s.

Ice shelves play a vital role in the behavior of the enormous mass of freshwater ice that covers the Antarctic continent, acting as dams that regulate the flow of ice into the sea. The Antarctic ice sheet contains enough freshwater to raise global sea level by about 60 meters.

Earlier this year, researchers published findings indicating that such a collapse may have begun in another part of Antarctica, a process that is expected to take centuries to complete. However, the potential response of the ice sheet to increases in air temperature can be much faster.

Co-authors on the Science paper include: M. Rebesco, E. Domack, F. Zgur, C. Lavoie, A. Leventer, S. Brachfeld, V. Willmott, G. Halverson, M. Truffer, T. Scambos, J. Smith, E. Pettit.