Greenland ice core to help assess risks of abrupt climate change

An international team of scientists working on the North Greenland Eemian Ice Drilling project hit bedrock July 27 after three summers of work, drilling down more than 1.5 miles in an effort to better understand the nature of abrupt climate changes in the past.

Led by Denmark and the United States, the team recovered ice spanning the Eemian interglacial period from about 115,000 to 130,000 years ago, a time when temperatures were 3.6 to 5.4 degrees Fahrenheit above today’s temperatures and sea level was 15 feet higher.

While three previous deep ice cores drilled in Greenland in the last 20 years recovered some ice from the warm Eemian, intergalacial period, the deepest layers in these ice cores were compressed and folded, making the entire Eemian climate record difficult to interpret. Just prior to reaching bedrock, the NEEM drilling managed to penetrate what appears to be a continuous Eemian sequence and even some ice that was deposited during the glacial period prior to the Eemian. This ice is expected to contain crucial information about how Earth’s climate functions, said University of Colorado-Boulder Professor Jim White, lead U.S. investigator on the project.

"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."

Annual ice layers recorded in the Greenland ice reveal information on past temperatures and precipitation levels, as well as the contents of ancient atmospheres, said White. Ice cores from previous drilling efforts revealed abrupt temperature changes of more than 20 degrees Fahrenheit in just 50 years in the Northern Hemisphere.

White said the new NEEM ice cores will more accurately portray past changes in temperatures and greenhouse gas concentrations throughout 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, University of Copenhagen’s Centre of Ice and Climate. The National Science Foundation’s Office of Polar Programs funded the U.S. portion of the effort.

Todd Sowers, senior research associate, Penn State, will measure the isotopic composition of methane trapped in bubbles throughout the NEEM ice core. The isotope data, along with corresponding concentration data, provide important information that will help sort out changes in the sources of methane over time and their relation to abrupt climate change.

The two meters of ice just above bedrock from NEEM -- which is located at one of the most inaccessible parts of the Greenland ice sheet -- go beyond the Eemian interglacial period into the previous ice age and 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.

The cores samples are being studied in detail using a suite of measurements, including stable water isotopes that reveal information about temperature and moisture changes back in time. The team is using state-of-the art laser instruments to measure the water isotopes, as well as atmospheric gas bubbles trapped in the ice to understand past variations in climate on a year-by-year basis, said White.

The NEEM facility includes a large dome, a drilling rig to extract four-inch diameter ice cores, drilling trenches, labs and living quarters. The U.S. 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 include Oregon State University, the University of California, San Diego and Dartmouth College.

Additional information and photos on the NEEM effort can be found on the web at http:// www.neem.ku.dk.