8. Holocene Climate Variability from Gulf of Mexico Marine Sediment
Proxy climate records for the current interglacial interval, or Holocene, contain clear evidence for significant variability and abrupt change. For example, multidecadal droughts during the 13th and 16th centuries were more severe and widespread than the "dust bowl" event of the 1930s and at least four severe, century-scale "megadroughts" affected the Great Plains and western United States between AD 1 and AD 1200. Continuous multiproxy records from marine cores in the subpolar and subtropical North Atlantic indicate that the current interglacial was punctuated by a series of quasi-periodic cold events that occurred about every 1500 years. The most recent cold event, the Little Ice Age (LIA), was preceded by a period of warmer climate, the Medieval Warm Period (MWP).
Although proxy records provide clear evidence that the climate of the Holocene is highly variable, the details of the variability and regional patterns of change are poorly known. In addition the causes of high-frequency variability are uncertain. Better characterization of Holocene climate variability and the affects of the variability on specific regions are needed to establish the likely forcing and help discriminate between natural climate variability and any human-related climate changes.
Recent studies on Holocene sediments from the Gulf of Mexico show evidence for pervasive decadal to century climate variability throughout much of the Holocene and suggest that the variability is related to changes in solar insolation. The Gulf of Mexico studies also indicate that variations in foraminifer assemblages in marine sediments from the Gulf of Mexico can be used as a proxy for the intensity of the southwestern monsoon and that isotopic and chemical variations in surface dwelling foraminifers record large flood events in the Mississippi Basin.
The Mendenhall Fellow will need to be able to use marine sediments to determine proxies for climate change in the geologic record. She/he will conduct faunal, isotopic and chronologic studies on previously collected marine cores from the Gulf of Mexico to develop decadal- to century-scale records of environmental variability and link marine records to changes on adjacent land areas for the last few thousand years.
The Mendenhall Fellow will be closely linked to the researchers at the University of South Florida who have access to state-of-the-art stable isotopic, elemental and molecular composition instrumentation with which to study paleoclimate variability in selected cores. As such, the close interaction between USF and USGS advisors will allow the Mendenhall Fellow to be closely integrated with ongoing multidisciplinary studies involving a team of researchers from the USGS and the University of South Florida.
Proposed Duty Station: St. Petersburg, FL
Areas of Ph.D.: Geology, oceanography, geochemistry
Qualifications: Applicants must meet one of the following qualifications: Research Geologist, Research Chemist, Research Oceanographer
(This type of research is performed by those who have backgrounds for the
occupations stated above. However, other titles may be applicable depending
on the applicant's background, education, and research proposal. The final
classification of the position will be made by the Personnel specialist.)
Research Advisor(s): Richard Z. Poore (727) 803-8747, rpoore@usgs.gov; Terry Quinn (University of South Florida, College of Marine Science) (727) 553- 1658, tquinn@marine.usf.edu
Personnel Office contact: Rosetta Alexander, (703) 648-7468, ralexand@usgs.gov
U.S. Department of the Interior, U.S. Geological Survey
URL: http://geology.usgs.gov/postdoc/2006/opps/opp8.html
Direct inquiries to Rama K. Kotra at rkotra@usgs.gov
Maintained by Mendenhall Postdoctoral Fellowship Program Web Team
Last modified: 12:05:09 Tue 24 Aug 2004
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