Von Walden took a tentative step forward on a snow-covered ice floe and found himself waist deep in freezing water. After a moment, he was able to push himself back up onto solid ice, saved by his Arctic immersion survival suit – part snowmobile suit, part life preserver – and quick reflexes. A visiting scientist on the Norwegian research vessel Lance (“lan-sa”), he’d awoken that morning to find the ship surrounded by open water, and 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 middle of the ocean walking around on this raft of ice, and if anything compromised that you’d be floating!”
Walden, a professor of Civil and Environmental Engineering at Washington State University’s Laboratory for Atmospheric Research, had joined the Norwegian Young Sea Ice Cruise, a six-month expeditionary study of drifting Arctic sea ice, earlier that month. In January of 2015, researchers from the Norwegian Polar Institute sailed the Lance to 83°N 21°E, a point in the middle of the Arctic Ocean 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.
“They actually made us swim in the Arctic Ocean with these suits on to get a feeling of what it’s like. It’s absolutely freezing,” he said. “We swam about 30 feet, and could barely move after that, it’s so cold. So you have an impression in your mind that you do not want to go in this ocean.”
“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.”
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 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 reduced ice cover could lead to increased Arctic amplification, say the researchers.
“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 radiate reflected 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.”