U-Idaho’s Von P. Walden Studies Climate Change in One of the Coldest Places on Earth
By Tara Roberts
As a result, 97 percent of the massive Greenland Ice Sheet’s surface reached temperatures above the freezing point.
While rivers roiled over their banks on Greenland’s coast, the melt was gentler but still surprising 10,000 feet atop the ice sheet, where instruments at Summit Station recorded this remarkable event. The surface at Summit melted briefly before refreezing, leaving a thin, clear ice layer. Core samples show it was the first time in 124 years the surface melted there.
University of Idaho’s Von P. Walden, a geography professor, and a team of researchers from across the country have analyzed data gathered at Summit to understand exactly what happened during the melt event. Their research is the cover story for the April 4 edition of Nature, the world’s preeminent science journal. [Continue Reading...]
But Walden and his team’s work goes beyond that single event. Walden is principal investigator for the National Science Foundation-supported project formally known as the Integrated Characterization of Energy, Clouds, Atmospheric state and Precipitation at Summit, or ICECAPS.
Climate models over the past two decades have correctly predicted that the effects of increasing concentrations of carbon dioxide in the atmosphere would be first – and most dramatically – seen in the Arctic. Sea ice at the North Pole is decreasing faster than any model predicted, says Walden.
“It’s a surprise how fast the Arctic is actually changing,” says Walden, who has studied the Arctic atmosphere for close to 20 years.
The melt rate of the Greenland Ice Sheet is now at the upper limits of scientists’ predictions – and that has major global implications. The entire sheet holds enough water to increase ocean levels nearly 22 feet, and researchers say any major melt could affect ecosystems, climate processes and communities worldwide. Scientists believe that it is very likely Greenland has contributed to sea level rise over the past two decades, and that the rate of sea level rise from Greenland is increasing.
Scientists do not yet have a detailed picture of clouds’ net effects on ice sheets, sea ice and the Arctic climate. While satellites collect data above the clouds, few people other than Walden and the Summit team are studying the atmosphere’s role on the surface below.
“Clouds are still one of the greatest uncertainties in climate models we use to predict the future,” Walden says. “Even though the models are generally correct, we need better measurements to improve them.”
paper co-authored by Walden, U-Idaho doctoral student Christopher Cox and the ICECAPS team uses measurements of clouds over Greenland to explain the melt event last summer.
The paper’s authors used modeling techniques to demonstrate that cloud cover was a key component of the event. If the clouds over Greenland that day had been thicker, they would have reflected enough sunlight to keep the ice sheet below freezing. But clouds also play a role in warming the Earth’s surface by trapping infrared radiation.
“It’s kind of like the story of Goldilocks. If the sky had no clouds on July 11, it would have been too clear and cold to melt the surface. But if the clouds were too thick, it also would have been too cloudy and cold,” Walden says. “The thin, liquid water clouds were just right for melting the surface snow.”
The researchers showed Greenland was covered with thin, liquid-water clouds during the melt event, creating exactly the right conditions. These clouds occur frequently in the Arctic, Walden says, but researchers didn’t previously recognize their significance in terms of warming effects.
In addition to the Nature paper, the cover of the Bulletin of the American Meteorological Society’s February issue features a photograph of Summit Station with a green laser beam slicing across the starry Arctic sky.
Walden points out the image isn’t a digital trick – a person really can see the beam shooting from the station into the atmosphere. It’s ICECAPS’ lidar, or light detection and ranging system, which measures cloud height by calculating the beam’s travel time.
Alongside studying extreme events like the melt and seasonal cycles, the ICECAPS data allows researchers to better understand the big picture of atmospheric conditions in the Arctic. Summit Station features an uncommonly robust suite of instruments including lidar, Doppler radar, and tools that gather information on water vapor, heat energy and the atmosphere’s surface layer. In addition, a scientist who lives at the station releases weather balloons – accumulating data from more than 700 balloons annually.
“We’re able to get a first look at what really is occurring over the Greenland Ice Sheet,” Walden says.
An Arctic future
Walden plans to visit Summit Station this summer and hopes to extend the project. His team has submitted a proposal to conduct in-depth analysis of the ICECAPS data gathered over the past three years, and is proposing extending the experiment for another five years.
“Summit Station is really a unique place on the planet, and especially a unique place in the Arctic,” he says.
Jack McIver, U-Idaho’s vice president of research and economic development, said Walden’s studies in Greenland are just the beginning of a bright career.
“The university fosters the work of excellent faculty members like Von Walden,” McIver says. “His research achievements make him a rising star with a future of important contributions ahead of him.”
Walden, who has conducted research at Dome Concordia and South Pole Station in Antarctica and in the Arctic’s Eureka, Canada in addition to Greenland, expects to expand his polar investigations even further. He hopes to conduct a future field experiment over the Arctic Ocean, which won’t be an easy task.
And, Walden hopes his research reaches beyond the realm of science and into the lives of everyday people.
“What we’re doing in our own lives is affecting the planet,” he says. “We are at this point connected to the entire globe. We need to understand this system so we can make good decisions going into the future.”