Core Contingent

Multi-year Antarctic mission could provide precise 80,000-year climate timeline

After four years, an international team of scientists drilling into the West Antarctic Ice Sheet (WAIS) has nearly reached the halfway point of its mission to core 3,500 meters (11,483 feet) into the ice.

Participants in the WAIS Divide project include Scripps Institution of Oceanography at UC San Diego graduate student Anais Orsi. Orsi, a member of the lab of Scripps geoscientist Jeff Severinghaus, returned to campus in January after a two-month stint on the sheet and said the cores yielded by the project could help scientists better understand ice shelf collapses and other headline-grabbing events by creating a more precise timeline of climate from a 80,000-year record frozen in the ice.

"The most important thing we want from these ice cores are precise temperature and carbon dioxide records that are co-dated," said Orsi.

The biggest payoff will not come until possibly 2011 when the corer breaks through the last of the ice and reaches the sediment that would have been on the seafloor before the ice sheet formed. The scientists know the total thickness of the ice and that each 22 centimeters (9 inches) or so equal one year's worth of compressed snowfall in the upper layers. However the dating of fossil remnants trapped in the sediment is needed to establish an accurate start date for the formation of the ice sheet.

With that, the researchers can understand how stable the ice sheet is and better predict the situations that lead to ice sheet collapses and other prominent signs of climate change. Unlike cold and sunny east Antarctica and the continent's central mountains, the ice sheet remains relatively unstudied, said Orsi.

"That's what's waiting for us at the end," said Orsi. "If you're missing this one big part of the puzzle, it hard to make predictions."

In the meantime, more than 40 individual projects are underway as part of WAIS Divide, including Orsi's — an investigation of how the continent responded to the so-called Little Ice Age, a period of cooling between the years 1300 and 1800. Orsi said she could have conclusions by the end of the year -- before she returns to the ice sheet for another austral summer of coring.

Get a taste of life in the field all this month in the Photo of the Week feature of explorations as WAIS Divide researchers share their images of work and play at the bottom of the world.

—Robert Monroe

March 2009