Icy mile leads to climate future

U. COLORADO (US)—An international drilling project in Greenland has set a record, recovering more than a mile of ice core. By offering clues to the past, the ice is expected to help scientists better assess the risks of abrupt climate change in the future.

The project, known as the North Greenland Eemian Ice Drilling, or NEEM, is being undertaken by 14 nations, with the University of Colorado at Boulder as the lead U.S. institution.

The goal is to retrieve ice from the last interglacial episode known as the Eemian Period that ended about 120,000 years ago. The period was warmer than today, with less ice in Greenland and 15-foot higher sea levels than present—conditions similar to those Earth faces as it warms in the coming century and beyond, says CU-Boulder professor Jim White.

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

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, explains White.

Radar measurements taken through the ice sheet from above the NEEM site indicate the Eemian ice layers below are thicker, more intact and likely contain more accurate, specific information, he says.

“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,” says White. Ice cores exhumed during previous drilling efforts revealed abrupt temperature spikes of more than 20 degrees Fahrenheit in just 50 years in the Northern Hemisphere.

The NEEM team reached a depth of 5,767 feet in early August, where ice layers date to 38,500 years ago during a cold glacial period preceding the present interglacial, or warm period.

The team hopes to hit bedrock at 8,350 feet at the end of next summer, reaching ice deposited during the 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.

Increased warming has a host of potentially harmful 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.

“Evidence from ancient ice cores tell us that when greenhouse gases increase in the atmosphere, the climate warms,” says  White. “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.”

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 explains.

“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.”

Contributing to the study are researchers from Oregon State University, Penn State, the University of California at San Diego, and Dartmouth College. Nations involved in the project include the United States, Belgium, Canada, China, Denmark, France, Germany, Iceland, Japan, Korea, the Netherlands, Sweden, Switzerland, and the United Kingdom.

University of Colorado at Boulder news: www.colorado.edu/news