When the Antarctic Geological Drilling Program begins its second drilling campaign this month, scientists will be looking for a "Rosetta Stone" in their sediment cores that will tie together decades of paleoclimate research in Antarctica and the rest of the world to get a more complete picture of how the Antarctic ice sheets responded to past times of global warmth.
The Rosetta Stone, of course, is the tablet found in northern Egypt in 1799 that provided the key to deciphering ancient Egyptian hieroglyphics. The "Rosetta Stone" target for ANDRILL scientists in this fall's Southern McMurdo Sound Project is the warmest part of the middle Miocene, a time between 14 million and 15 million years ago when the Earth was much warmer than today, and for an extended period.
This year's ANDRILL project will drill for rock cores beneath sea ice with a goal of bridging the geological gap between cores drilled by two previous projects in the Ross Sea area. ANDRILL's McMurdo Ice Shelf Project recovered an Antarctic-record 1,285 meters of rock core last year, representing geologic time from the present day to approximately 13 million years ago. ANDRILL's predecessor, the Cape Roberts Project in the late 1990s, drilled core that represents the period from 17 million to 40 million years ago.
The geological target this year is the past 17 million years of Earth history, including the 4 million-year gap between the earlier projects, especially the warm middle Miocene period.
According to geologist David Harwood of the University of Nebraska-Lincoln, understanding what happened in the warm period is especially important as Earth's climate continues to warm.
"If we can identify time periods in Antarctica when we had minimal ice and minimal ocean freezing, we can then look at that particular interval of time -- and hopefully several examples from those intervals of time -- and see how the rest of the world responded. This will provide evidence to confirm or reject a lot of interpretations that have been suggested and linked to Antarctica," he said.
Harwood, a professor of geoscience at UNL and research director for ANDRILL's Science Management Office at UNL, is co-chief scientist for the Southern McMurdo Sound project along with Fabio Florindo of Italy's National Institute for Geophysics and Volcanology in Rome. Richard Levy is staff scientist for the ANDRILL Science Management Office.
In the past, Harwood said, when scientists working in different parts of the world noted changes in their data, they often deduced that these must be due to changes in the ice on Antarctica. But after this year's ANDRILL project, he said scientists will be able to make those connections with more certainty.
"We are going to have a clearer record, an archive of past glacial and warm events, so that we can tie together the history we've documented in Antarctica, with records from the rest of the world and develop a standard paleoclimate event history," Harwood said. "It will be a Rosetta Stone for the rest of Antarctica and the rest of the world. It will lay out a reference section of paleoenvironmental change."
Furthermore, understanding Antarctica's climate history in the face of global warming is critical, Harwood said, because the amount of sea ice that surrounds Antarctica is a crucial factor in driving Earth's climate. When sea ice forms, it pushes the salt out, creating a mass of cold, salty, dense water that sinks to the bottom of the ocean, creating deep ocean currents that affect ocean circulation and the distribution of heat worldwide.
An advance team from Webster's Drilling of Porirua, New Zealand, Antarctica New Zealand, Raytheon Corp. and New Zealand's Victoria University arrived in Antarctica in late August to set up the 40-ton-drill rig at a site in McMurdo Sound some 25 miles from the research bases on Ross Island at McMurdo Station (United States) and Scott Base (New Zealand). More than 60 scientists and technicians and eight educators in the ANDRILL Research Immersion for Science Educators (ARISE) program representing the ANDRILL partner nations of Germany, Italy, New Zealand and the United States will travel to Antarctica in October to participate in the drilling season, and a seismic survey to develop potential future drilling projects. The seismic survey team will include UNL undergraduate student Jake Carnes, a senior geology major from DeWitt, Neb.
Harwood said there are some significant logistical differences with this year's project compared to last year's. For one, the drill site is more than twice as far from McMurdo and Scott than last year's drill site, so the drillers and some of the scientists will live at a camp at the site, while the rest of the scientists will work in the labs at McMurdo. Also, this year's drill site is on sea ice that is only 8 meters thick, compared to the 85-meter-thick ice shelf at last year's site. The thinner ice required divers from Raytheon to go under the ice to inflate giant balloons that provide additional buoyancy to support the weight of the drill rig. More importantly, the sea ice will also begin melting as the Southern Hemisphere enters its spring season. That means that there will be only about a six-week window for drilling from mid-October to the first of December before the rig will have to be pulled off of the sea ice.
"We're hoping that time will be gained by the drillers being more familiar with the rig this year, but it really will be a race against time to keep the core coming in good shape -- to keep getting down the hole," Harwood said. "The constant work effort will be taxing on people.
"Our target depth is 1,000 meters. We had such a phenomenal drilling season last year that even if we get 75 percent of what was drilled last year, I'd be happy."
ANDRILL is a multinational collaboration involving more than 150 scientists from Germany, Italy, New Zealand and the United States. Its purpose is to recover sediment core samples from the McMurdo Sound region of Antarctica to develop a detailed history of the Antarctic climate and the expansion and contraction of Antarctica's ice sheets and ice shelves over the past 20 million years.
Operations and logistics for ANDRILL are managed by Antarctica New Zealand. Scientific research, education and outreach, and media efforts are administered and coordinated through the ANDRILL Science Management Office, led by Frank Rack, ANDRILL executive director, at the University of Nebraska-Lincoln.
- University of Nebraska-Lincoln