U. COLORADO (US) — Cameras mounted on unmanned aircraft flying over the Arctic are doing double duty by assessing declining sea ice and pinpointing seals that have hauled up on ice floes.
The project is the first to use aircraft to monitor ice and seals in remote areas without putting pilots and observers at risk.
The Arctic is rapidly warming as a result of human-produced greenhouse gases and sea ice loss is impacting Arctic marine and terrestrial mammals, researchers say.
“Because ice is diminishing more rapidly in some areas than others, we are trying to focus on what areas and types of ice the seals need for their survival,” says Peter Boveng, leader of the Polar Ecosystems Program at the National Oceanic and Atmospheric Administration’s Alaska Fisheries Science Center.
“By finding the types of ice they prefer, we can keep track of that ice and see how it holds up as the Arctic sea ice extent shrinks,” says Elizabeth Weatherhead of the University of Colorado at Boulder.
Four species of Arctic seals are of particular interest: the bearded, ringed, spotted, and ribbon seals, because each rely in some way on sea ice for breeding, resting, and as a safe haven from predators.
The unmanned aircraft, the “Scan Eagle,” was launched in May and June of 2009 from the NOAA vessel McArthur II over the Bering Sea west of Alaska. The drone has a 10-foot wingspan and is owned and operated by the University of Alaska.
The image recognition software was developed by Boulder Labs Inc. in Boulder, Colo., and was used to automate the identification of seals in 27,000 images that were collected during the flights.
“The results show that the seals have distinct preferences for specific types of ice, demonstrating that ice extent is not the only factor affecting seal populations,” Weatherhead says.
The Scan Eagle flights lasted from two to eight hours and flew at altitudes ranging from 300 to 1,000 feet.
While the amount of ocean and ice scanned by the unmanned aircraft was small—it flew 3- to 5-mile-long transects over the Bering Sea—the researchers were eager to see whether the image recognition system would work for characterizing both the ice and the seals. “The answer was a resounding yes,” Weatherhead says.
Sizing up ice
The analysis of sea ice by the team included edge-to-area calculations of ice floes as well as ice floe size and distribution.
“There is an incredible variety of ice and we are trying to come up with mathematical ways to describe it,” she says. “One thing that really interests us is how broken up the ice is in particular areas.”
According to CU-Boulder’s National Snow and Ice Data Center, the total loss of Arctic sea ice extent from 1979 to 2009 was an area larger than the state of Alaska. Scientists believe the Arctic may become ice-free during the summers within the next several decades.
This month, NOAA’s Fisheries Service proposed to list the Arctic ringed seal as threatened under the Endangered Species Act because of diminishing sea ice and snow cover.
Arctic ringed seals do not come ashore, but use sea ice for whelping, nursing, and resting. Ringed seal pups are born in snow caves on the ice, and their survival can be affected by snow depths and the timing of spring snowmelt and ice breakup.
“Biologists are thrilled about the image recognition software because it could change the way we monitor seal populations,” says Weatherhead.
“We can send an unmanned craft out from a ship, collect 4,000 images, and have them analyzed before dinner. This is a great example of physicists working closely with biologists who are concerned with the health of seal populations.”
Typically, seals appear in less than 1 percent of the images, says Weatherhead. But on the ice floes or ice edges where they are found, the software can help researchers identify seals by species.
In the future, researchers might be able to identify the relative age and gender for some seal species. The software could even be adjusted to look for polar bears and their tracks.
The team wants to combine its results with forecasts not only of future sea ice extents, but also of future ice characteristics that will allow for predictions regarding the impacts of changing and disappearing ice types on seal populations.
Researchers from the University of Alaska contributed to the study.
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