The Arctic has entered a new era. The region has shifted to conditions of warmer air and water, less ice cover on the sea and more vegetation growing on land, says an international team of scientists in this year’s Arctic Report Card from the US National Oceanic and Atmospheric Administration (NOAA).
Unlike less frequent studies, the annual report card allows scientists to “capture changes as we learn about them,” says Monica Medina, principal deputy undersecretary for Oceans and Atmosphere at NOAA. She adds that the reports provide a baseline of understanding from which “we can have a better sense of the trends and changing conditions.”
A big part of the change is the diminishing range of the sea ice covering the Arctic through the summer months. “This year’s end of summer ice extent was the second smallest in the 32-year satellite record,” says Don Perovich, a geophysicist with the US Army Corps of Engineers Cold Regions Research and Engineering Laboratory (CRREL).
A record low for sea ice was observed in 2007. The report’s authors say there are now enough observations since that year’s dramatic decline to show that longer periods of open Arctic waters are becoming the norm. The melting ice and rising carbon dioxide levels are also making the Arctic ocean less salty and more acidic, the report finds. But water chemistry is not the only thing changing.
“We’ve always expected physical changes in Arctic to come first but in previous report cards we’ve had mixed signals when it comes to the ecosystem or the biodiversity,” says Mike Gill of the Circumpolar Biodiversity Monitoring Programme of the Arctic Council Conservation of Arctic Flora and Fauna.
This year, however, “we are starting to detect a response from these ecosystems to those physical changes,” says Gill.
With thinner and less ice covering the sea, more light shines into the ocean (see More light under ice). The additional solar energy promotes further melting and increased productivity at the base of the marine food chain. “These increases are particularly strong in the eastern Arctic where production has increased 70% in the Kara sea and 135% in the eastern Siberian sea,” says Karen Frey, a geographer at Clark University in Worcester, Massachusetts.
Species at the top of the food chain are affected in a different way: Loss of pack ice on the Chukchi Sea has hindered the ability of both polar bears and walruses to hunt.
“For polar bears, 7 of 19 subpopulations appear to be declining in number, with trends in two of the populations linked to reductions in sea ice,” says Frey. This summer, thousands of walruses hauled out of the water onto land in Alaska, a first for that time of year and a major risk to the animals.
“With those haul outs you get moralities related to stampedes of animals and crushing of pups,” says Sue Moore, oceanographer with NOAA’s National Marine Fisheries Service.
Some marine mammals may benefit from the changes. Gray whales that migrate into the Arctic for feeding can stay there longer, says Moore.
The winners and losers dichotomy also exists for vegetation. “The winners appear to be the taller shrubs species,” says Howie Epstein, ecologist at the University of Virginia. Vegetation without root systems like mosses and lichens are the potential losers, stuck in understory and over-shaded by the shrubs that are dominating the canopy, says Epstein.
“The Arctic is clearly experiencing the impacts of a prolonged and intensified warming trend,” says Richter-Menge. The effects reach well beyond its waters.
“Given the projection of continued warming, it is very likely, indeed expected, that these changes will continue in years to come, with increasing climatic, physical, biological and socioeconomic impact,” she says.
As the northern ice cap melts, the regions untapped resources become more accessible (see Scientific challenges in the Arctic: Open water). Medina notes that the report card can also influence many impending decisions for the Arctic and its resources, including whether or not to explore the region for oil and gas deposits.
Image credit: US Fish & Wildlife Service