Satellite data reveal how the new record low Arctic sea ice extent, from Sept. 16, 2012, compares to the average minimum extent over the past 30 years (in yellow). Image: Flickr/NASA/Goddard Scientific Visualization Studio
The dramatic retreat of Arctic sea ice in recent years is changing disease patterns, altering the local food web and lowering the region's ability to reflect sunlight, according to two new studies.
The research in Science and Nature Climate Change, although on two different topics, fits into a growing body of knowledge about the side effects of ice loss. The papers also come as scientists say that Arctic ice extent could be near historic lows this year, even if it does not break last year's record.
This year "will without a doubt" rank in the top five lowest levels of ice extent ever recorded in the satellite era, and there is a good possibility that 2013 could rank second in terms of recorded ice lows, said Walt Meier, a scientist at the National Snow & Ice Data Center.
"It's kind of remarkable that it's as low as it is [this year], given that the weather conditions were not terribly optimal for ice loss," Meier said.
Distinctive weather patterns in 2013—such as extensive cloud cover in some areas—brought lower temperatures to the Beaufort and Chukchi sea regions, keeping ice loss off pace from last year, he said. Arctic ice will not reach its annual minimum until September, and "anything can happen" before then, but it would be unusual for there to be two record-breaking years in a row, he said.
Continuing a long-term retreat
What is important, Meier said, is that 2013 fits into the long-term trend of significant ice retreat and ice thinning from the 1970s and 1980s, despite year-to-year weather variations. The last six years have witnessed the six lowest minimum extents since satellite observations began in 1979, according to the National Oceanic and Atmospheric Administration.
"Even though some Arctic locations haven't been as warm this year, you can still melt through 3 feet of the ice, whereas in the past, you might have needed to melt through 6 or 8 feet of ice in that area," Meier said.
This ongoing ice retreat is spawning a variety of changes in the Arctic ecosystem, from increased parasites in caribou herds to a growth in annual tundra fires in Alaska, according to the assessment in Science last week, which reviews prior data.
Declining ice can change the timing of phytoplankton blooms, throwing off the feeding cycles of animals along the feed chain, it states.
Some changes are well-known, such as declines in polar bear populations and stresses to walruses being forced out of their shallow feeding grounds as ice retreats into deeper waters. Ice loss can cause less genetic diversity among animals like arctic foxes that use the ice as a travel pathway, while also creating the opposite effect with other species.
"Observed hybridization between polar bears and grizzly bears may be the result of increasing inland presence of polar bears as a result of prolonged ice-free seasons," the assessment notes.
Other changes are less visual. Diseases like phocine distemper virus, now present in eastern Arctic seals, may now "spill over" to western species because of the loss of ice, according to the review. On the other hand, some changing disease patterns could be beneficial— arctic foxes may not be able to carry rabies to Svalbard via an ice trek as they have in the past, for example.
Jedediah Brodie, a scientist at the University of British Columbia and study co-author, said a next step of research is determining which ecological changes in the Arctic are completely a result of ice loss, as opposed to climate change factors such as temperature increases.
"Most of the studies that we reviewed found plausible and even likely links between sea ice and things like polar bear breeding success, seal breeding success, plankton communities, and even climates in coastal terrestrial systems. But without actual experiments, we can't prove that sea ice is 100 percent the driver of those things," he said.