Greenland's ice sheet is melting at the fastest rate in centuries
This past month, earth science professor Erich Osterberg published a paper proving that the melt rates of the Greenland ice sheet are the highest they have been since A.D. 1550. The study was published in Geophysical Research Letters and is entitled “Ice Core Records of West Greenland Melt and Climate Forcing.”
According to the study, Greenland is 1.2 degrees Celsius warmer today than in the 1890s, consistent with the larger trend of climate change caused by the substantial release of greenhouse gases into the atmosphere by human industrial practices. Melt rates are often influenced by ocean temperature fluctuations and changes in the number of summer high-pressure systems; however, it is highly likely that the warming of Greenland’s climate and the associated temperature increase of the sea surface are acting as the most significant influencing factors, Osterberg said.
Osterberg conducted his research using ice cores, which form due to meltwater that trickles down under the snow and refreezes. Summer ice layers are buried under fresh snow each winter, preserving the history of snowmelt.
According to Gabriel Lewis GR’19, who assisted Osterberg in his study, these ice cores can be found as far down as 30 meters, or 100 feet. In total, seven ice cores were collected from Western Greenland during the first year of the study, each containing the history of ice melt dating back to 1966.
After transporting these ice cores back to Dartmouth, Osterberg and his team were able to determine that there has been an increase in the amount of ice layers since the 1990s, indicating that there has been a significant increase in summer melting. This data is supported by computer models and satellites, which demonstrate the Greenland ice sheet’s decrease in size and increase in surface melt within the past 20 to 30 years, according to the study.
“The first two to two and a half weeks were extremely frustrating,” Osterberg said. “We’d never [traversed the ice sheets on snowmobiles] before, so we had to sort of shake everything down and figure out what worked well and what didn’t ... and then we hit our stride.”
Both Osterberg and Lewis described an incident on their first day of research in which a fuel barrel for their snowmobile was punctured, leaking gasoline into their sled. They resorted to fixing the rupture with chewing gum, they said.
“We were covered in gasoline and we collected no data,” Lewis said. “We got back to camp that night and had to reevaluate how we were going to do things — it was all uphill from there.”
After this setback, the research team successfully collected and transported seven ice cores during the first year and nine during the second.
Lewis, who was present during both years to maintain procedural consistency, called the second year a “victory lap,” and said the team returned to Greenland with “the mentality that the project had already succeeded.”
According to research published by the National Academies of Sciences, at the current rate of rise, the world’s oceans will be on average two feet higher at the end of the century than they are now. Since 1993, more than three-quarters of this rise has been due to melting ice sheets in Greenland and Antarctica.
“What I think is special about our records is that all these other datasets just go back into the 1980s or 70s, but our record goes back 450 years,” Osterberg said. “We’re able to show that, yes, the melting we thought was happening is happening, but also that it’s extremely unusual, and I think that’s where our research says something new.”
Lewis said that the density of snow has increased, and that many climate models do not take that into account because they are based on invalid data from the 1990s.
He added that the research team is working with climate model scientists to update the models for a more accurate prediction of temperature and sea level rise.
Environmental studies professor Lauren Culler, who is not a part of Osterberg’s research team, said she appreciates Osterberg’s ability to get direct measurements of the melt that satellite data has been demonstrating for decades.
The fact that “these two vastly different methods [of collecting data] yield similar patterns is not only important for confirming increasing melt events, but also in increasing our confidence that remote sensing methods do indeed work quite well,” Culler said.
Climate change is becoming an increasingly pressing issue, making a globally-coordinated human response even more necessary, Osterberg said.
“We’ve seen, after tragedies like the Parkland shooting, that when young people decide that they want their voices to be heard, they have a huge impact,” he said. “Everybody who is concerned about climate change needs to do a better job of voicing their opinion of what needs to change and trying to express that opinion through the ballot box.”
Osterberg also emphasized that Dartmouth students should “be conscious of how much carbon they’re using in ... life decisions that stick with [them] for decades,” adding that students can make a long-term impact on their personal carbon footprints.
Correction appended (April 15, 2018): This article has been updated to clarify a comment by Osterberg about learning to traverse ice sheets on snowmobiles.