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.
How Antarctica began to melt
"The thought prior to our work is that Antarctica began to warm about 18,000 years ago, after the Northern Hemisphere had started to warm" about 24,000 years ago, says Fudge.
Climatologists debated exactly how the north triggered the south, though most agreed that the global ocean conveyor belt played a role, but they agreed that "Antarctica took its signal from the north to get it going." Fudge's team agrees that warming kicked into high gear 18,000 years ago, but they found evidence of warming in West Antarctica beginning between 2,000 and 4,000 years before the northern "trigger."
It now appears that both the northern and southern hemispheres were affected by orbital changes that made for longer summer days. In Antarctica, the increased sunlight melted the sea ice.