It happened in the last 18 years. It is a persistent decrease of the so-called multiannual ice. The Arctic lost a third of its volume. It is seasonal sea ice, which melts completely each summer instead of accumulating over the years. It is replacing the thicker multi-year ice. It is a trend of thinning sea ice.
New measurements
how was the snow depth of Arctic sea ice estimated? LIDAR and radar data were used. The study was published in Geophysical Research Letters.
“We didn’t expect to see this decrease,” said the study’s lead author, Sahra Kacimi. She is a polar scientist at the California Institute of Technology.
Scientists calculate the depth of snow and the height of floating ice above the sea surface. Previous estimates of ice thickness and snow depth from climate records were revised.
“Arctic snow depth, sea ice thickness, and sea ice volume are three very difficult measurements to obtain,” Ron Kwok said in a statement. He is a polar scientist at the University of Washington’s Applied Physics Laboratory. “The Arctic lost a third of its volume in just 18 years.”
Ice-free summers
The study used past records and new satellites to capture monthly changes in ice thickness and volume. The 18-year record showed a loss of about 6,000 cubic kilometers of winter ice volume. It is due to the shift from predominantly multi-year ice to thinner seasonal sea ice.
Older, multiyear ice tends to be thicker. Further downstream, the overall thickness and volume of Arctic sea ice is expected to decrease. “By mid-century we can expect ice-free summers in the Arctic,” Kacimi said.
“This is really old ice that we’re losing at a pretty scary rate,” Mallett said.
