From ice to water

Fallen weather towers, sunken scaffolds, and toppled tents.

The collapsed camp—“Swiss Camp”—might have been the premier base to monitor the impacts of a changing climate on the Greenland ice sheet, but in 2009, the camp’s own appearance revealed more than a thousand data readings.

“We don’t need to measure the changes—we can look at the camp and see the changes,” said former CIRES Director Konrad Steffen, a Swiss native who established the camp in 1990 and has been returning there every summer since.

Warming temperatures have gradually melted the camp’s foundations, causing it to collapse in a decidedly disorganized, “un-Swiss-like” manner. Weather towers, placed more than a decade earlier in 2 meters of ice, have toppled as their foundation has begun to disappear.

The scene, as well as more than 20 years of data, spells out a stark reality: The Greenland ice sheet is melting faster than it is replenishing.

“Over the years we have lost first 30 centimeters of ice, then 50 centimeters of ice, then a meter,” Steffen said. “Overall we have lost 6 meters—so the losses are very visual.”

Two decades of ogling ice

Steffen’s original intention in establishing the camp wasn’t to observe the impact of climate on ice-sheet melting. When he started his three-year research project in 1990, it was to study the interaction between the ice and the surrounding atmosphere in the vicinity of the “equilibrium line altitude”(ELA)—the elevation band on the ice sheet where the snowfall equals the annual snowmelt. To investigate the ELA, Steffen planned to spend three years measuring variables such as temperature and snow reflectivity and then dismantle the camp and continue his study at another equally icy location.

Fate, however, intervened.

In 1992, Mount Pinatubo erupted in the Philippines, killing 800 people and discharging millions of tons of sulfur dioxide into the atmosphere. The gas triggered a chain of reactions, and within two weeks, a cloud of aerosols shielded Earth from the sun. The planet cooled, and several feet of snow fell on Swiss Camp. “It was snowing all summer, and to remove the station, we had to shovel it out,” Steffen said. “We could not shovel fast enough.”

The Swiss researchers had signed a contract agreeing to remove every piece of the camp from the ice sheet at the end of the project, and as this was proving near impossible, Steffen, newly appointed at the University of Colorado, decided to accept responsibility for the camp and continue his research there.

Ice to Water

“It turned out to be a perfect place that represents a large portion of Greenland,” Steffen said. The camp is based on the gentle slope of the continent’s west coast—the same slope that comprises approximately 1,500 kilometers of the Greenland ice sheet.

Despite the fact that the camp has collapsed twice since 2008 and will have to be rebuilt again this summer, Steffen has continued recording key climate variables at the site these last 20 years. “It is the only camp, the only measurement that has existed that long on the ice sheet,” Steffen said.

During Steffen’s tenure on the ice, his measurements in Greenland have become invaluable to the scientific community as changes in climate have focused attention on the cryosphere.

While people might not notice an average temperature change of a degree in the mid-latitudes, in the polar regions, even minor temperature changes can have a significant impact. This is due to changes in the snow albedo, or reflectivity, he explains. As snow or ice melts, the surface of the ice sheet darkens, and this darker surface absorbs more of the incoming solar radiation, leading to increased melt. “That is why you see the changes much faster and amplified,” Steffen said.

By observing the Antarctic and Arctic and also glaciers outside of those regions, scientists can see the changes that are occurring, sometimes dramatically, each year.

Measuring the sensitivity of these regions to temperature changes allows researchers also to make predictions about changes that might happen elsewhere on the globe, Steffen said. “The polar regions are, for us, an early warning signal,” he said. “We can tell people, ‘This is what is happening here—if you wait a certain amount of time, this is what will happen in the lower latitudes also.’”

Early warning signs

The first canary cry to alert Steffen to the melting ice sheet was a fallen instrument tower in 1995, an exceptionally warm year. On his team’s return to camp, the researchers had to dig for a week to find the tower, which had since been buried beneath the winter’s snowfall. The tower’s collapse surprised Steffen. “If you build a tower in the ELA, you drill it 2 meters into the ice and assume it stays,” he said.

By the new millennium, the changes had become more visual as Steffen and the scientific community began to see an increase in the surface melting and runoff on the ice sheet. Over the last 20 years, Steffen has recorded an increase of 50 Watts per square meter in absorbed shortwave radiation on the ice. “The source is stable—the sun’s radiation is not increasing,” Steffen said. Neither has the atmosphere changed to allow more of the sun’s rays to reach Earth, he said. The culprit for the increased absorption is the albedo effect, by which the decrease in reflectivity, due to ice melt, has caused Greenland to absorb more of the sun’s rays. ”Fifty watts is huge,” he said, “many times bigger than the global warming signal from carbon dioxide.”

The initiator of this feedback loop was an increase in temperature. Over the last 20 years, Steffen has recorded a 4-degree Celsius (7.2-degree Fahrenheit) increase in the average temperature at the camp, nearly 2 degrees per decade. “It is probably one of the biggest warming signals we have on Earth,” he said.

The implications of these changes and the subsequent melting of the ice sheet are huge, Steffen said. As the ice sheet melts and sections of it calve off into the ocean, global sea level rises. With 10 percent of Earth’s population—about 600 million people—living in low-lying areas, such a rise could have significant impacts. Scientists now estimate that sea level will rise by nearly a meter by 2100.

While 1 meter is the estimated global sea level rise, certain regions could experience less sea level rise while other regions might see double that amount, Steffen said. Some of the areas that might see the largest sea level rise, such as Florida, are the most densely populated, he said.

Steffen’s first inkling to the possibility of this scenario came when he measured increasing temperatures in the region. He showed the results to his program manager, whose reaction was one of disbelief. “He said, ‘Go back and do the analysis again—it is not possible,’” Steffen said.

In spring 2012, when Steffen steps out of his helicopter and looks at the camp, the evidence will be staring him in the face.