The findings, which appear in the December issue of the Geological Society of America Bulletin, are significant because they likely will fuel renewed debate about the severity of the greenhouse effect, according to Hamilton College Associate Professor of Geology Eugene Domack, a lead investigator for the study.
"These data take us one step closer to finding the geological fingerprint for greenhouse warming," Domack said.
The data reported in this study correlate closely with well-known cycles that reveal variations in the output of the sun's energy over the past 2,500 years. An unprecedented rise in the mean annual temperature for Antarctica -- 2.5 degrees Celsius over the past 50 years -- is inconsistent with the cycle and has led scientists to hypothesize about the role of greenhouse gases in altering the natural variability of the system.
To help test the hypothesis, Domack has received a National Science Foundation grant to extend scientists' knowledge of the paleohistory of the region from 2,500 years to 14,000 years. The grant, Domack's fifth from the NSF in the past decade, will fund an expedition in March 1998 to collect and then analyze sediment cores in the Belingshausen Sea. Approval to drill the site was based on research conducted in Antarctica by former Hamilton undergraduate students, including 1993 graduate Matt Kirby.
Domack said the recent warming trend in the Antarctic has led to significant environmental changes in the region, including increases in melting across ice shelves and reductions in the annual coverage of sea ice. The ecosystem may also be affected. Scientists have documented changes in the distribution of penguin species and some plants.
"The area is clearly responding environmentally to what is the highest mean temperature increase of any region on earth," Domack said, "but we have to conduct additional research to pinpoint the cause."
Over the past decade, Domack's research in Antarctica has advanced scientists' understanding of the paleohistory of the region. Specifically, the data he and his students have collected and analyzed have helped scientists compare modern changes in the region to historical changes as documented in sediment cores collected from the sea floor.
"Productivity cycles of 200-300 years in the Antarctic Peninsula region: Understanding linkages among the sun, atmosphere, oceans, sea ice, and biota," appears in the December issue of the GSA Bulletin. The article was prepared by six Antarctic researchers.