
McMurdo Station, near the site where the sediment core was obtained. (credit: US Antarctic Program)
Antarctica wasn't always the barren ice world that we now know. In the distant past, plate tectonics placed it at warmer latitudes. But more recently, even after it adopted its southern location, high global temperatures severely limited the ice on Antarctica. That started to change as the period known as the Eocene came to a close and global temperatures dropped. But the precise details of how the continent went white are a challenge to determine.
Now, a large international team of researchers has obtained a sediment core from just offshore of the East Antarctic ice sheet that captures key events in the glaciation of the continent. And because it provides relatively precise indications of when things happened, it's possible to line it up with other global records. Combined, the records indicate that there were two key transitions: one where an ice cap began to form and a second when it expanded to meet the ocean.
Both of these events appear to have been tied to the level of atmospheric carbon dioxide. And in each case, we've been on a path toward reversing them before the century is out.
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