Below sixty degrees south, Antarctica experiences only one day (October to March) and one night (March to October) a year. During the warm season, the temperature at the South Pole may reach a balmy zero degrees Fahrenheit. Given the dark and the cold, it comes as no surprise that such a challenging part of the globe to study still keeps secrets from the scientists who know it best.
In a paper published in Geophysical Research Letters last month, Douglas S. Wilson of the Department of Earth Science and Marine Science Institute at the University of California worked with colleagues to reconstruct what Antarctica was like 34 million years ago.
The geological record and the theoretical models made by scientists both offered clues as to what the tip of the world must have looked like millions of years ago. Both agree that the global climate began to slowly change from warm to cool during the transition between the Eocene and Oligocene about 34 million years ago, but the two camps contradicted on certain points. The geological record indicated that there was a lot of ice at the planet’s poles. More ice, in fact, than the theoretical models could place. If there was so much ice, where did it all fit?
Antarctica’s transcontinental mountain range divides the continent into eastern and western land masses. Today’s Eastern Antarctica accounts for about 90% of Antarctica’s massive ice sheet. It holds millions of kilometers of deep ice, but it just wasn’t big enough to account for all the ice the geological record suggests existed 34 million years ago.
The surprise came when Wilson and his associates hypothesized that West Antarctica, small and hardly above sea level today, might have been very different at the end of the Eocene. From studying the nearby ocean sediments, they concluded that West Antarctica could have been hundreds of meters higher in elevation than it is today. Its mountains would have been ground to dust over millions of years by the heavy glaciers and eroded by flows of moving ice within the glaciers known as ice rivers. Recent studies have suggested that glacial ice erodes land even faster and more thoroughly than water or landslides.
This heightened elevation change drastically alters scientists’ vision of ancient Antarctica. It also changes their understanding about the formation of the great Antarctic Ice Sheet. Further removed from the ocean water, Western Antarctica probably not only supported the large amounts of missing ice, it probably hosted the ice sheet’s formation 20 million years earlier than previously thought.
This new insight into the timeline of the ice sheet does not only answer the mystery of the missing ice. It will help scientists learn more about the ecosystems of ancient Antarctica - it was home to temperate forests before the Eocene - and about the changes the entire globe underwent as temperatures shifted. The same information can assist in building accurate models of today’s ice levels, helping scientists understand what makes ice levels wax and wane, and predict what can be expected in the future.
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