West Antarctic Ice Sheet Froze 20 Million Years Earlier Than Thought

Parts of the Antarctic ice sheet may be far older than we once thought. Scientists have discovered that the West Antarctic ice sheet probably existed 20 million years earlier than was once believed. The finding changes our understanding of the history of Earth's global ice sheets.

In our distant past, warm greenhouse conditions kept even the coldest reaches of our planet ice-free. About 34 million years ago, though, these conditions changed as Earth transitioned to a cool icehouse climate. Yet previous computer simulations were unable to produce the amount of ice that geological records suggest existed at the time because the neighboring East Antarctica alone could not support it. Now, scientists may have discovered this missing ice.

Records show that ice growth in the northern hemisphere only started about three million years ago. This rules it out as the possible source of the missing ice. Instead, scientists turned to West Antarctica. Previous research actually showed that the bedrock in this region was much higher in elevation at the time of global climate transition than it is today. This higher land mass probably allowed it to host a large ice sheet much earlier than previously realized.

"Our new model identifies West Antarctica as the site needed for the accumulation of the extra ice on Earth at that time," said Douglas S. Wilson, one of the researchers, in a news release. "We find that the West Antarctic Ice Sheet first appeared earlier than the previously accepted timing of its initiation sometime in the Miocene, about 14 million years ago. In fact, our model shows it appeared at the same time as the massive East Antarctic Ice Sheet some 20 million years earlier."

Both West Antarctica and Greenland are major players when it comes to sea level rise today. This makes understanding their history and what may cause them to melt (or freeze) crucial when developing future climate models.

"We feel it is important for the public to know that the origins of the West Antarctic Ice Sheet are under increased scrutiny and that scientists are paying close attention to its role in Earth's climate now and in the past," said Bruce Luyendyk, one of the researchers, in a news release.

The findings are published in the journal Geophysical Research Letters.