A pair of recent high-profile articles co-authored by an SIUC geologist report a new type of Antarctic deep-sea ecosystem and provide further evidence that the global warming going on today is attributable mainly to human activity rather than natural climate cycles.

Paleobiologist Scott Ishman, an associate professor of geology at SIUC, is one of about a dozen highly respected U.S. experts on Antarctica. He and his students have been part of a team led by Eugene Domack, a geologist at New York's Hamilton College, that has made several trips to study the breakup of parts of the Antarctic Peninsula's Larsen Ice Shelf in recent years.

They have wanted to determine whether the breakup is a unique event in recent geological history--implicating human causes for the current warming--or if it fits into a recurring pattern. Their findings were reported in the Aug. 4, 2005, cover story of Nature.

The article, under the headline: "A Long Shelf Life: Larsen-B Collapse Follows 10,000 Years of Stability," indicates that today's global warming is unnatural, is escalating at an unparalleled rate, and surpasses every such documented trend since the last great ice age some 10,000 years ago.

In mid-February 2005, Ishman and two undergraduate students in geology, Paul Dixon and Stephanie Dulgar, joined Domack and 14 other colleagues aboard the research vessel Lawrence M. Gould, which plied northwest Antarctica's Weddell Sea for a month during polar summer. It was Ishman's third expedition to this part of Antarctica and his seventh overall.

The scientists pulled cores of Antarctic seafloor sediment from an area formerly capped by the huge middle section of the shelf, labeled Larsen-B. (Larsen-A, the northernmost section, melted in the mid-1990s.) A sprawling, nearly 600-foot-thick sheet of ice, Larsen-B began shrinking in the late 1990s and collapsed in 2002, when a section the size of Rhode Island broke off and disintegrated.

"Recent warming in the Antarctic has really accelerated in the last 50 years," Ishman notes. "In that time, we've seen an average increase of 6.5 degrees Fahrenheit in the Antarctic ice shelf area, which is startling."

Ishman and his students determined what the region's environment was like in the past--and how to interpret what's happening with climate today--by studying fossilized shells of forams, single-celled marine creatures that are preserved in the sediment cores.

They have collected forams from various ecosystems to understand what environmental conditions are required by particular species. Identifying the species found in the sediment cores from Antarctica told them a lot about what the climate there was like when the fossilized specimens were alive.

Also, says Ishman, "In the cores we had--sediments deposited over the past 10,000 years--the forams were the same types of species throughout until very near the top." This indicates that the recent melting was not a cyclical occurrence.

"The global warming we're experiencing today is a matter of great concern because it's not part of any natural cycle we've observed in the last 10,000 years," he concludes.

Ice-pack conditions on the 2005 trip permitted the research team to get farther south along the peninsula than any ship had been able to get before. As a result, the team got a scientific bonus: their submersible video camera, which was photographing a glacial trough in an area formerly covered by Larsen-B, found a type of marine ecosystem previously unknown in Antarctica.

In this sunless habitat more than half a mile deep, mats of bacteria and populations of clams are thriving in near-freezing water that until recently was covered by the ice shelf. The organisms are apparently fueled by methane from underwater vents.

The surprising find was reported in the July 19, 2005, issue of Eos, a scientific journal published by the American Geophysical Union.

The team's discovery will enable biologists to learn more about life in extreme environments. They may need to hurry, though.

Without the protection of the ice shelf, the deep-water communities are now vulnerable to disturbance. Sediment is already beginning to cover some of the organisms, the team reports.

--by Paula Davenport, Media & Communication Resources, and Marilyn Davis, ed.