SAN FRANCISCO, CALIFORNIA—A continually warming Arctic is having profound impacts across the top of the planet and beyond, according to a government report released here today at a meeting of the American Geophysical Union. The effects include weather disruptions, disappearing snow, and lands greening as temperatures rise. But some of the biggest changes are happening in warming Arctic seas, with the future of northern fisheries hanging in the balance.
The latest version of the Arctic Report Card, first released in 2006, showed that warming trends remain largely consistent in the Arctic, which is warming, on average, twice as fast as the rest of Earth. Snow cover on land was below the average of the previous 3 decades; for the 10th straight year, June featured record lows over land in the North American and Eurasian sectors of the Arctic. Loss of sea ice and the melting of the Greenland Ice Sheet slowed, though summer temperatures on the ice sheet set records.
This year offered new insight into the future of the Arctic marine ecosystem, one of the biggest question marks as the region warms. The first task is to get a handle on all the factors that explain why the Arctic, mostly ocean, is warming up so fast. A couple of factors are warm air coming in from the tropics and replacement of white sea ice—which reflects heat back into the atmosphere—with dark, absorbent water. A new clue may be in the water itself, says Kathy Crane, an oceanographer with the National Oceanic and Atmospheric Administration (NOAA) in Silver Spring, Maryland, which published the report. Ships studying currents have recently identified new flows of warm water entering the Arctic through the Bering Strait on the Pacific side and the Norwegian Sea on the Atlantic side. “We not only have the solar radiation, but we have these currents to bring water in laterally,” she says.
All of this warming could have a dramatic impact on the region’s fish. The Bering Sea, between Alaska and Russia, and the Chukchi and Laptev seas, off eastern Siberia, saw summer temperatures 4°C higher than the average of the previous 3 decades. This, along with acidifying waters, could spell doom for many species, for example crustaceans whose shells may dissolve. And warming temperatures can have an uncertain impact on Arctic fish, says Jim Ianelli, a fisheries biologist with NOAA in Seattle, Washington. Alaska pollock, an important fish commercially, was thought to benefit, on average, from warm conditions, which may stimulate the ecosystem as a whole. But new findings suggest that cold temperatures are important, too: Cool waters in the fall and winter encourage the growth of nutritious microorganisms that young fish need to grow. With waters projected to continue to warm, NOAA now projects a likely decline in the amount of Alaska pollock by 2050.
2014 showed the promise of a new, productive Arctic Ocean as well: In the Kara and Laptev seas off Siberia, for example, satellites measured higher than normal levels of chlorophyll, which strongly suggests increased growth of crucial marine plants like algae.
The Barents Sea was colder than usual in 2014, but the trend since 1981 is warming. That may be why scientists have seen cod and other fish from the northern Atlantic migrating north from Barents Sea fisheries into the Arctic Ocean. “It’s very much a concern in Norway and among the Russians, who worry the fish may be leaving fisheries,” says Crane, who helped lead the report. Crane, with NOAA, says that satellite measurements are adequately monitoring parameters like sea ice and vegetation on tundra from space. “But they don’t tell us what’s happening inside the Arctic Ocean. For that we need continuous and improved measurements.”
For the first time, NOAA included details about how the warming Arctic may be linked to weather further south—even causing cold weather in North America and Europe. January and March of this year included “periods of strong connection” between the pole and mid latitude, according to the report. The “polar vortex,” which separates arctic and tropical air, weakened, the report said, allowing warm air to flow north in January, when Alaska saw temperatures 10°C warmer than usual. Meanwhile, frigid arctic air dipped low into eastern North America and Russia, and winter months were 5°C colder than average. Emerging science about these linkages has spurred NOAA to focus its Arctic research program on the problem, Crane says.