Research could show why Northern Hemisphere temperatures spiked 20 degrees in just 50 years in long-ago interglacial era
By Bob Berwyn
SUMMIT COUNTY — Scientists from the University of Colorado at Boulder are part of an international team that recently hit bedrock after drilling down more than 1.5 miles deep into the North Greenland ice cap.
The drilling took two summers to complete, CU said in a recent press release on the project.The research is part of an effort to assess the risks of abrupt future climate change.
Led by Denmark and the United States, the team recovered ice from the Eemian interglacial period from about 115,000 to 130,000 years ago, when global average temperatures were 3.6 to 5.4 degrees above today’s readings. During the Eemian — the most recent interglacial period on Earth — there was substantially less ice on Greenland, and sea levels were more than 15 feet higher than today.
As part of the project, the researchers want to determine how much smaller the Greenland ice sheet was 120,000 years ago when the temperatures were higher than present, as well as how much and how fast the Greenland ice sheet contributed to sea level.
Previous drilling has also recovered ice core samples from the Eemian age, but the deepest layers were compressed, making it hard to interpret the data. The intact samples are expected to reveal crucial information about how Earth’s climate functions, said CU-Boulder Professor Jim White, lead U.S. investigator on the project.
Core samples can show what the atmosphere was like when the ice was formed. In this case, the research team hopes to find clues as to how and why northern hemisphere temperatures spiked more than 20 degrees in a short span of just 50 years.
The two meters of ice just above bedrock go beyond the Eemian interglacial period into the previous ice age. They contains rocks and other material that have not seen sunlight for hundreds of thousands of years, said White. The researchers expect the cores to be rich in DNA and pollen that can tell scientists about the plants that existed in Greenland before it became covered with ice.
“Scientists from 14 countries have come together in a common effort to provide the science our leaders and policy makers need to plan for our collective future,” said White, who directs CU-Boulder’s Institute of Arctic and Alpine Research and is an internationally known ice core expert. “I hope that NEEM is a foretaste of the kind of cooperation we need for the future, because we all share the world.”
White said the new NEEM ice cores will more accurately portray past changes in temperatures and greenhouse gas concentrations in the Eemian, making it the best analogue for future climate change on Earth.
An international study released by the National Oceanic and Atmospheric Administration last week showed the first decade of the 21st century was the warmest on record for the planet.
The NEEM project involves 300 scientists and students and is led by Professor Dorthe Dahl-Jensen, director of the University of Copenhagen’s Centre of Ice and Climate. The United States portion of the effort is funded by the National Science Foundation’s Office of Polar Programs.
“We expect that our findings will increase our knowledge on the future climate system and increase our ability to predict the speed and final height of sea level rise during the Eemian,” said Dahl-Jensen.
The vast majority of climate scientists attribute rising temperatures on Earth to increased greenhouse gases pumped into the atmosphere as a result of human activity. The Intergovernmental Panel on Climate Change concluded that temperatures on Earth could rise by as much as 10 degrees F above today’s temperatures in the next century, primarily due to atmospheric greenhouse gases.
The NEEM facility includes a large dome, a drilling rig to extract 3-inch in diameter ice cores, drilling trenches, labs and living quarters. The United States is leading the laboratory analysis of atmospheric gases trapped in bubbles within the cores, including greenhouse gases like carbon dioxide and methane.
Other nations involved in NEEM include Belgium, Canada, France, Germany, Iceland, Japan, Korea, the Netherlands, Sweden, Switzerland and the United Kingdom. Other U.S. institutions involved in the effort include Oregon State University, Penn State, the University of California, San Diego and Dartmouth College.
Other CU-Boulder participants include postdoctoral researcher Vasilii Petrenko and doctoral student Tyler Jones. White also is a professor in CU-Boulder’s geological sciences department.