climate change

Ancient ice core holds climate future clues

U. COLORADO (US)—An international science team working on the North Greenland Eemian Ice Drilling (NEEM) project has hit bedrock after two summers of work, drilling down more than 1.5 miles in an effort to assess the risks of abrupt future climate change.

The team recovered ice from 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.

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.

While three previous ice cores drilled in Greenland in the last 20 years recovered ice from the period, the deepest layers were compressed and folded, making the data difficult to interpret.

NEEM has allowed researchers to obtain thicker, more intact annual ice layers near the bottom of the core that are expected to contain crucial information about how Earth’s climate functions, says Jim White, professor at the University of Colorado-Boulder and 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,” White says.

“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 formed over millennia in Greenland by compressed snow reveal information on past temperatures and precipitation levels, as well as the contents of ancient atmospheres, says White.

Ice cores from previous drilling efforts revealed temperature spikes of more than 20 degrees Fahrenheit in just 50 years in the Northern Hemisphere.

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.

A new National Oceanic and Atmospheric Administration study shows the first decade of the 21st century was the warmest on record for the planet.

The two meters of ice just above bedrock from NEEM, 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, White says.

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 isotopes, as well as atmospheric gas bubbles trapped in the ice and ice crystals to understand past variations in climate on a year-by-year basis.

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.

“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,” says project leader Dorthe Dahl-Jensen, director of the University of Copenhagen’s Centre of Ice and Climate.

Other U.S. institutions involved in the effort include Penn State, the University of California, San Diego, Dartmouth College, and Oregon State University.

Other nations involved in the project are Belgium, Canada, France, Germany, Iceland, Japan, Korea, the Netherlands, Sweden, Switzerland, and the United Kingdom.

The United States portion of the effort is funded by the National Science Foundation’s Office of Polar Programs.

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