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Title : NSF 93-58 NSF FACILITY USING FOSSIL MOLLUSCS TO DATE "CLIMATIC OPTIMUM" Type : Press Release NSF Org: OD / LPA Date : August 3, 1993 File : pr9358 Cheryl Dybas August 3, 1992 (202) 357-9498 NSF PR 93-58 NSF FACILITY USING FOSSIL MOLLUSCS TO DATE "CLIMATIC OPTIMUM" WITH ACCELERATOR MASS SPECTROMETRY Most of Greenland, the world's largest island, is covered by a 3,000 meter-thick ice cap; only 16 percent of this arctic island -- its coastal perimeter -- is exposed. In summer, countless lakes and melt water rivers drain into glacier-scoured fjords. Hardly a place one would expect to find evidence of the warm period of Earth's history known as the Climatic Optimum. However, during the past two summers, director Glenn Jones of the National Ocean Sciences Accelerator Mass Spectrometry (AMS) facility in Woods Hole, Massachusetts, has done just that: by combing the weather-beaten coast and fjords of this region to locate and collect fossil molluscs from a time warmer than today. The AMS facility is used to date seawater, marine sediments and other material containing carbon, and is funded by the National Science Foundation (NSF)'s division of ocean sciences. Many tales are told of Viking exploration during Greenland's "Medieval Warm Period." Eric the Red, a rebellious warrior, made his famous voyage of discovery to southwestern Greenland after being forced to leave Iceland in 981 CE. Archaeological remains of two earlier Inuit cultures are preserved in the Sisimiut district where the AMS fieldwork was carried out. Jones' fieldwork involved recovering fossil shells of seven thermophilous, or "warm-loving," molluscs that extended their range northward during the Climatic Optimum, 4,000 to 8,000 years ago - a time considerably warmer than today. Beginning about 8,500 years ago, these mollusc populations formed in isolated pockets along the coast of southwest Greenland and in the shelter of smaller fjords. By 4,000 years ago, when colder conditions returned, the molluscs had died out. They have remained extinct into the present. Although evidence associated with the Climatic Optimum is relatively common in high latitudes, records of the rate at which these events occurred are not. Although thermophilous molluscs were identified from collections made by Danish geologists as early as the 1890's, the recent technological innovation of AMS radiocarbon dating has allowed the most detailed study yet of these animals. The logistics of the Greenland fieldwork involved covering rugged terrain by foot and portaging necessary gear -- and frequently a 12-foot inflatable "boat." "We learned to sleep without darkness, to be comfortable in headnets, to cook and dry clothes with a Primus stove, and reluctantly, to forego a shower or fresh food for weeks on end," says Kathryn Elder, a research assistant at the AMS facility. A team of scientists excavated three mollusc species (Panopaea norvegica, Arctica islandica, and Zirphaea crispata), and shells of two other mollusc species. By correlating the dates of first and last appearance of each species with its known temperature tolerance, researchers can produce a time history of the evolution of marine temperatures during a period warmer than today. This record can in turn be used to better understand the response of high latitudes to projected "greenhouse warming." The mollusc Zirphaea crispata currently lives in regions with water temperatures greater than 9o C. Using AMS radiocarbon dates of Z. crispata from southwest Greenland, scientists can ascertain that as early as 5,500 years ago the water at that locality was near 9o C. Panopaea norvegica can tolerate colder conditions, around 3 1/2o C, and was the first of these species to inhabit southwestern Greenland about 8,500 years ago. This data implies as much as a 6o C increase in water temperature in approximately 3,000 years. This 6o C difference compares in magnitude to the difference observed today in summer ocean temperatures between Woods Hole, Massachusetts, and Bermuda. AMS researchers hope to establish whether Z. crispata was the first and P. norvegica the last of the thermophilous molluscs to die out from Greenland waters at the close of the Climatic Optimum. Says Elder, "This dataset might provide modelers with a tool for comparing computer-predicted rates of greenhouse warming with actual rates of past change in an attempt to answer questions like how quickly we might re-enter a human-induced `Climatic Optimum,' and what the biological response to that change might be." AMS radiocarbon dating of molluscs from southwest Greenland may supply one more piece to the global climate change puzzle. -end- The National Science Foundation is an independent agency of the federal government established in 1950 to promote and advance scientific progress in the United States. NSF accomplishes its mission primarily by competitively awarding grants to educational institutions for research and education in the sciences, mathematics, and engineering. This and other information is available electronically on STIS, NSF's Science and Technology Information System. For more information about STIS contact the Publications Section at (202) 357-7861 and request the "STIS Flyer," NSF Publication #91-10, or send an E-mail message to stisinfo@nsf.gov (INTERNET) or stisinfo@NSF (BITNET).


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