NASA satellite measurements have contributed to the first ever study focusing on the current status of 11 species of Arctic marine mammals, all of which depend on sea ice to survive. The study, which revealed details on ice loss in the region, made use of more than 35 years of archived satellite data.
Arctic sea ice experiences growth in the fall and winter months, and melts during the spring and summer. In recent decades, the period of melting has grown steadily longer, leading to a general shrinking of sea ice volumes – something that affects many marine mammal species.
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The study, which was funded by NASA, the Greenland Institute of Natural Resources and the Danish Ministry of the Environment, focused on the impact of that drop in sea ice on a specific group of marine mammals. The research team used microwave measurements of the ice taken by NASA and Department of Defense satellites in an uninterrupted stream since 1978.
During the study, the Arctic Ocean was divided into 12 regions, using the satellite data to calculate the beginnings and ends of the melt and growth seasons. With the calculations ranging from 1979 to 2013, it was found that the melt season has grown longer by between five and 20 weeks.
The volume and behavior of the ice is critical for survival of the species being studied, specifically beluga whales, walruses, polar bears, narwhal and bowhead whales, and six different species of seal. For example, the seals use the sea ice as platforms when giving birth during specific weeks of the spring, while walruses use it for transport and as resting points between bouts of feeding.
The ongoing loss of ice is disrupting these natural behaviors, a key example being how walruses are now hauling out on land in Russia and Alaska, sometimes resulting in the trampling of their young.
While most of the species studied were found to be negatively affected by the sea ice trend, things aren't so bad for the Arctic whale, with the loss of ice and change in melt/growth patterns opening up new habitats for the species and increasing feeding season length.
"This research would not have been possible without support form NASA," says Kristin Laidre, the lead author of the study and polar scientist with the University of Washington in Seattle. "NASA backed us on research to the biodiversity and ecology of Arctic marine mammals, as well as the development of metrics for the loss of sea ice, their habitat."
Looking forward, the research team believes that high-resolution satellite data might be useful in studying how the marine mammals interact with their changing habitat, helping us better understand certain behavior, such as why narwhals congregate in specific areas during the winter.
The results of the study were published in the journal Conservation Biology.