Von Walden took a tentative step forward on a snow-covered ice floe and found himself waist deep in the Arctic Ocean. He was immediately shocked by the freezing cold water in spite of his Arctic immersion survival suit. Part snowmobile suit, part life preserver, the suit kept his head above water, but the cold was penetrating. “We swam about 30 feet in training, and could barely move after that, it’s so cold,” Walden said. “So you do not want to go in this ocean.” He pushed himself back up onto solid ice, and continued his work.
Walden, a geophysicist at Washington State University’s Laboratory for Atmospheric Research, had joined the Norwegian Young Sea Ice Cruise earlier that spring. In January of 2015, researchers from the Norwegian Polar Institute sailed the Lance (“lan-sa”) to 83°N 21°E, a point more than 1500 miles north of Oslo. Once there, they tethered the ship to an ice floe to drift with the ice pack. The Lance served as the expedition’s base, and the ice around it became a floating research camp.
Walden had been a visiting scientist on the Lance for a little over six months. The crew had woken that morning to find the ship surrounded by open water, ice sheets rapidly breaking up around them. “That whole day we started getting equipment off the ice,” he told me. “It was just like Swiss cheese. You’re in middle of the ocean walking around on this raft of ice, and if anything compromised that you’d be floating!”
“You’re out there working on this very thin veneer of ice, and you just have this really strange feeling that there is a mass of water – thousands of feet of water – beneath you, and you’re just walking around on the ocean.” – Von Walden, Washington State University
At the American Geophysical Union (AGU) fall 2016 meeting in San Francisco, the researchers reported an alarming discovery: thinning Arctic sea ice is melting even during the winter months. Sea ice usually reflects solar radiation back into space, but with melting snow and ice replaced by darker open water, much of that radiation is absorbed. While there isn’t enough data yet to know definitively, the researchers reported that reduced ice cover could lead to increased Arctic amplification.
“One of the major results we found is that when high winds would come from the major weather systems, it pushed the ice around, and that would cause mixing in the ocean,” said Walden. “Warmer water, from about 40 meters down, was getting mixed up and we actually saw a couple inches of ice melt in the winter. That means the ice isn’t growing at a time when it should be growing. We were really making the first measurements of processes in the new Arctic.”
Walden was one of more than a dozen scientists from around the globe who visited the Norwegian researchers during the expedition. A specialist in remote atmospheric sensing, he brought a number of instruments to take cloud measurements, including a ceilometer to measure cloud height and a LIDAR, which beams a laser at clouds to determine their properties and composition. Under the right conditions, he could determine whether the clouds were icy, liquid, or a combination of both.
The composition of clouds affects a important phenomenon in climate science known as cloud radiative forcing. Dense clouds at lower elevations will generally reflect solar radiation and cool the surface of the Earth. High, thin clouds allow solar radiation to pass through, and reflect radiation back to the surface, warming it. When liquid clouds are present, they have a significant impact on the surface temperature, particularly during the Arctic winter when there is no sunlight.
“We saw these liquid layers even in the winter,” said Walden. “We just happened to be there during a very stormy winter, with an anomalous jet stream, where the ship was right under the storm track. So we had an opportunity to observe what happened in the atmosphere, the ice, and the ocean as these major storms passed over the ship. The thinner sea ice is more susceptible to these storms. It breaks up more easily, and it is smaller in volume, so it takes less to melt it.”
While Walden was on the Lance, the ship was tethered to an ice floe. Onboard, one had no sense that the ship was drifting, he said, but working on the ice was altogether different. “You’re out there working on this very thin veneer of ice, and you just have this really strange feeling that there is a mass of water – thousands of feet of water – beneath you, and you’re just walking around on the ocean,” he said.
“Put yourself out there,” he said. “It’s really calm and clear, it’s cold and dark, and then one of these storms comes through and the conditions just completely change. Surface temperature rises from -40 F to freezing and the winds are over 50 mph. It’s an all-out blizzard, and it’s snowing hard, and the high winds push the ice around like a sailboat being pushed across the water.”
Walden has been doing polar fieldwork since 1990. He’s been to Antarctica a half dozen times, to the South Pole four times, and currently has an experiment at the top of the Greenland ice sheet.
“I’ve been to a lot of cold places, but this was my first experience on sea ice,” he said. “It was the most exciting and exhilarating field experiment of my life.”