Arctic sea ice is at its record low in the recent geologic history, says an international study.
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 — the ice loss that started in the early 20th Century and sped up during the last 30 years — appears to be unmatched over at least the last few thousand years,” said Leonid Polyak, a research scientist at Byrd Polar Research Centre 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 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, said the university.
Satellites can provide detailed measures of how much ice is covering the pole right now, but sediment cores are like fossils of the ocean's history, said Mr. Polyak. “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.
Scientists can search for a biochemical marker that is tied to certain species of algae that live only in ice. If that marker is present in the sediment, then that location was likely covered in ice at the time, he explained. While knowing the loss of surface area of the ice is important, Mr. Polyak said this work cannot yet reveal an even more important fact: how the total volume of ice — thickness as well as surface area — 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.
