120,000-year-old Ice Yields Clues to Climate of a Warmer Earth

More than a mile of ice core was pulled from the Greenland ice sheet by scientists this summer, setting a new record for single-season deep ice-core drilling.

The researchers, from 14 countries and led by the University of Copenhagen, are on a quest to recover ice formed 120,000 years ago, the last time our planet was in a period of warm climate such as the one many scientists think we are now entering.

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Pushing an ice core out of the drill.

Photo courtesy NEEM ice core drilling project

“Evidence from ancient ice cores tell us that when greenhouse gases increase in the atmosphere, the climate warms,” says University of Colorado at Boulder Professor Jim White, who is leading the U.S. research contingent. “And when the climate warms, ice sheets melt and sea levels rise.

“If we see comparable rises in sea level in the future like we have seen in the ice-core record, we can pretty much say good-bye to American coastal cities like Miami, Houston, Norfolk, New Orleans and Oakland.”

“If we see comparable rises in sea level in the future like we have seen in the ice-core record, we can pretty much say good-bye to American coastal cities like Miami, Houston, Norfolk, New Orleans and Oakland.”

This year’s drilling operation reached a depth of 1,758 meters (5,767 feet) in early August, where ice layers date to 38,500 years ago during cold glacial period preceding the present interglacial, or warm period.

“The team hopes to hit bedrock at 2,545 meters (8,350 feet) at the end of next summer, reaching ice deposited during warm Eemian period that lasted from roughly 130,000 to 120,000 years ago before the planet began to cool and ice up once again,” says a statement about the project released by the National Science Foundation yesterday.

The goal of the North Greenland Eemian Ice Drilling (NEEM) project is to retrieve ice from the the Eemian Period.

Annual ice layers formed over millennia in Greenland by compressed snow reveal information on past temperatures and precipitation levels and the contents of ancient atmospheres, said White, who directs CU-Boulder’s Institute of Arctic and Alpine Research. “Ice cores exhumed during previous drilling efforts have revealed abrupt temperature spikes of more than 20 degrees Fahrenheit in just 50 years in the Northern Hemisphere.”

The period was warmer than today, with less ice in Greenland. That led to 15-foot (5-meter) higher sea levels than present–conditions similar to those Earth faces as it warms in the coming century and beyond, White says.

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This MODIS Terra image, acquired August 23, 2006, shows the southern portion of Greenland. The Greenlandic ice cap covers about 80 percent of the island’s surface. Photo courtesy NASA

While three previous Greenland ice cores drilled in the past 20 years covered the last ice age and the period of warming to the present, the deeper ice layers representing the warm Eemian, and the period of transition to the ice age were compressed and folded, making them difficult to interpret, he says.

“Radar measurements through the ice sheet from above the NEEM site have indicated the Eemian ice layers below are thicker, more intact and likely contain more accurate, specific information.

“Every time we drill a new ice core, we learn a lot more about how Earth’s climate functions,” White said. “The Eemian period is the best analog we have for future warming on Earth.”

Increased warming on Earth has a host of potentially deleterious effects, including changes in ecosystems, wildlife extinctions, the growing spread of disease, potentially catastrophic heat waves and increases in severe weather events, according to scientists.

While ice cores pinpoint abrupt climate change events as Earth has passed in and out of glacial periods, the warming trend during the present interglacial period is caused primarily by human activities like fossil fuel burning, White says.

“What makes this warming trend fundamentally different from past warming events is that this one is driven by human activity and involves human responsibility, morals and ethics.”

The NEEM project is led by the University of Copenhagen’s Centre of Ice and Climate directed by Professor Dorthe Dahl-Jensen. The U.S. and Denmark are the two leading partners in this project. The U.S. effort is funded by the National Science Foundation’s Office of Polar Programs.

The project began in 2008 with the construction of a state of the art facility, including a large dome, the drilling rig for extracting three-inch in-diameter ice cores, drilling trenches, laboratories and living quarters. The official drilling started in June 2009.

The United States is leading the laboratory analysis of atmospheric gases trapped in bubbles within the NEEM ice cores, including greenhouse gases like carbon dioxide and methane.

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

Changing Planet

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