Arctic sentinels.

On a cloud-covered morning in April, Feiyue Wang trudges down the gangway of the Canadian research icebreaker CCGS Amundsen and joins three graduate students and a rifle-toting research technician on the ice below. They set out on snowmobiles across the snow-covered slab of ice adrift in the Beaufort Sea and stop at an untouched patch of the ice floe. They unload coolers, thermoses, a generator, and a variety of electric tools, as the hems of their jackets whip about in the wind. It's −15 degrees Celsius, and the winds are gusting to 30 knots. The technician strolls along the edge of the field site with the rifle slung over her shoulder and scans the horizon for polar bears. For most of the group, it's their first chance to be “on the ice” since they arrived. They've endured a full day of travel and another of safety drills and lab cleaning—Michel Gosselin, the chief scientist for this leg of the expedition, has made it clear that although their work is important, no science would be done until the labs are straightened up and bench top materials secured in case the ship had to suddenly dislodge from the ice floe. Samples of algae, zooplankton, water, and mud have piled up in the laboratories, which are passed on from one group to the next while the Amundsen is at sea. Despite the harsh conditions, the team works for hours without a break. They extract four-foot-long (~1.25-meter-long) ice cores from the floe and scoop up surface snow and seawater (see Figure 1). They will later analyze the samples in the onboard laboratories (see Box 1) to study the presence of mercury and other contaminants, tracing their paths from terrestrial and atmospheric sources to ocean waters and, ultimately, to marine mammals. Wang, an environmental chemist from the University of Manitoba in Winnipeg, Canada, and his collaborators believe that climate change may be behind a recent jump in mercury accumulation in beluga whales, ringed seals, and other marine mammals. Figure 1 Getting to the Core of Climate Change Box 1: Keeping It Clean One of the unique features of the Amundsen is its onboard clean lab, built solely for the study of mercury. The lab is nestled in a white shipping container that has been chained to the aft deck of the ship. Few people are allowed access to the clean room, and no one gets though the inner door without removing her heavy down coat and boots, and donning a white zip-up suit, booties, and a cap. Inside, machines cover the bench tops and are secured by a complex system of bungee cords and hooks. Should the Amundsen begin to move or be jostled by high winds, the equipment needs to stay in place. The clean room is stocked with equipment that can measure different mercury species in snow, ice, brine, and water samples in near–real time. “We used to ship the samples back to Winnipeg,” says Gary Stern, a researcher with the Department of Fisheries and Oceans and a professor at the University of Manitoba, “but that was always an issue. The possibility of contamination was high and you wouldn't know it until you got back.” The Amundsen is the research base for Canada's largest research project of the International Polar Year, the Circumpolar Flaw Lead System Study—a Can$40 million study of the impact of climate change on the Arctic ecosystem (see Figure 2). The researchers on board are especially interested in flaw leads, or polynyas, which are long watery gaps in the ice that open up when the mobile sea ice pulls away from the stationary coastal ice. Flaw leads can stretch for many kilometers and extend throughout the Arctic region, like oblong beads on a necklace. They are frequently covered with thin new ice, or nilas, in the winter, and have high levels of primary productivity during the warmer months. They are particularly sensitive to environmental change. The Amundsen is the first icebreaker to spend the winter in or close to the flaw lead. Figure 2 Canadian Coast Guard Ship Amundsen Flaw leads are expected to become more prevalent in the years ahead, as rising temperatures and melting sea ice create an increasingly ice-free Arctic. Flaw leads may be longer and wider and covered with thinner ice in the winter and early spring. “They're a proxy of what can happen in the future,” says Gosselin. By studying the flaw leads, researchers hope to understand how climate change might alter mercury cycling in the Arctic and how both may interact to affect the Arctic ecosystem.