Most of Antarctica's oldest ice is up in the eastern mountains, where cold air and steep terrain insulate the ice fields from the surrounding ocean and atmosphere. Climate researchers have focused on the 800,000-year climate record preserved there, discounting two previous ice cores taken in the west. One of the western cores was taken on a glacier, so its ice had moved away from the spot that the snow first fell; the other was taken at the edge of the Ross Ice Sheet, so its ice layers are vulnerable to ocean changes that can mask climate changes.
"So many good records came out of East Antarctica [that] the West Antarctic records have been forgotten a little bit," says Mr. Fudge, who is a graduate student in glaciology at the University of Washington.
But because West Antarctica is more influenced by storms and changes in sea ice, it's also much more sensitive to atmospheric changes – the very changes that make for a detailed and useful climate record.
In 2005, a team of scientists discovered the best of both worlds: a stable location in the west, which they found at the divide between two glaciers on the West Antarctic Ice Sheet (WAIS). Not only was the location right, but the WAIS Divide gets 3 feet of snow a year that then compacts down into about 9 inches of ice, which then compacts further and further over thousands of years, as it gets buried under tons of more snow and ice.
"This is basically the best site in Antarctica – in the Southern Hemisphere – to be able to look at the abrupt changes of the last glacial period," says Fudge.
With the ability to "zoom in" to the climate record – to look at changes from year to year instead of epoch to epoch – Fudge's team discovered that the timeline of warming and cooling, established from the eastern cores, wasn't telling the whole story.