The new result is significant, explains team member Adrian Jenkins, because the timescales needed for atmospheric warming to penetrate key water masses are centuries or longer, which would suggest that ice sheets are relatively immune to recent climate change. However, if temperature increases in the atmosphere are accompanied by changes in atmospheric circulation, then ice sheets could be affected much sooner. The model suggests that any changes in the atmosphere, be they natural or anthropogenic, that alter regional winds will affect how ocean heat is delivered to Antarctica's ice shelves and floating glacier tongues.

The researchers used a version of the Miami Isopycnic Coordinate Ocean Model adapted for domains that include ice shelves. This was coupled to a dynamic/thermodynamic sea ice model, forced with surface pressure – from which surface winds were derived – and temperature from NCEP/NCAR reanalyses.

Jenkins stresses, however, that the results are a simply a "hindcast". "We have offered one possible explanation for glaciological changes that have been observed," he told environmentalresearchweb. "However, we have not made any predictions about the future and have stressed that our results show decadal variability rather than a long-term trend."

He adds that it is not yet possible to extract a trend from the variability or say whether it is entirely natural or related to anthropogenic forcing.

The Amundsen Sea is an important location for climate change studies. Indeed, a US cruise early next year, led by team member Stan Jacobs of the Lamont-Doherty Earth Observatory, will continue oceanographic observations on the Amundsen Sea Continental Shelf and deploy instruments for year-round ocean monitoring. The UK will participate thanks to the Natural Environment Research Council's autonomous underwater vehicle, Autosub-III, which will be used to directly measure ocean properties beneath the floating ice shelves, explains Jenkins.

"These results should provide us with more information on the variability of ocean forcing on ice shelves and the processes by which the warmth of ocean waters leads to melting," he adds. "This will help improve our model representation of the continental shelf and floating ice shelves."

The team is now running its model at higher resolution and extending the length of the integrations.

The work was reported in Geophysical Research Letters.