The first comprehensive history of Arctic ice, carried out by a team of scientists from five countries, found that the recent retreat is the worst in thousands of years.
“The ice loss that we see today appears to be unmatched over at least the last few thousand years,” said Leonid Polyak, the lead research scientist at Byrd Polar Research Center at Ohio State University. For decades, scientists have strived to collect sediment cores from the difficult-to-access Arctic Ocean floor, to discover what the Arctic was like in the past. Their most recent goal: to bring a long-term perspective to the ice loss we see today.
Now, the team led by Ohio State University has re-examined the data from past and ongoing studies and combined them to form a big-picture view of the pole’s climate history stretching back millions of years.
Satellites can provide detailed measures of how much ice is covering the pole right now, but sediment cores are like fossil of the ocean’s history, said Polyak.
Sediment cores
“Sediment cores are essentially a record of sediments that settled at the sea floor, layer by layer, and they record the conditions of the ocean system during the time they settled. “When we look carefully at various chemical and biological components of the sediment, and how the sediment is distributed — then, with certain skills and luck, we can reconstruct the conditions at the time the sediment was deposited.”
For example, scientists can search for a biochemical marker that is tied to certain species of algae that live only in ice. While knowing the loss of surface area of the ice is important, Polyak said that this work can’t yet reveal an even more important fact: how the total volume of ice has changed over time.
“Underneath the surface, the ice can be thick or thin. The newest satellite techniques and field observations allow us to see that the volume of ice is shrinking much faster than its area today. The picture is very troubling. We are losing ice very fast,” he said.
“Maybe sometime down the road we’ll develop proxies for the ice thickness. Right now, just looking at ice extent is very difficult.” Their conclusion: the current extent of Arctic ice is at its lowest point for at least the last few thousand years.
During the summer of 2011, they hope to draw cores from beneath the Chukchi Sea, just north of the Bering Strait between Alaska and Siberia, which can provide a detailed history of interaction between oceanic currents and ice.