HR: 0800h
AN: PP31A-0176    [Abstracts]
TI: Geochemical Proxy Records From a Bahamian Sclerosponge: Reconstructing Temperature and Salinity Over the Last 500 Years
AU: * Waite, A J
EM: awaite@rsmas.miami.edu
AF: University of Miami, Rosenstiel School of Marine and Atmospheric Science, 4600 Rickenbacker Cswy, Miami, FL 33149, United States
AU: Rosenheim, B E
EM: brosenheim@whoi.edu
AF: Woods Hole Oceanographic Institution, Department of Geology and Geophysics, Woods Hole, MA 02543, United States
AU: Swart, P K
EM: pswart@rsmas.miami.edu
AF: University of Miami, Rosenstiel School of Marine and Atmospheric Science, 4600 Rickenbacker Cswy, Miami, FL 33149, United States
AB: Sclerosponges have a demonstrated potential as recorders of environmental and climate conditions in the oceans over a range of depths, and periods of tens to thousands of years. Their slow growth rates, and consequent long records, coupled with the fact that their skeletons calcify in apparent C and O isotopic equilibrium with their surrounding environment, give sclerosponges a clear advantage over corals for paleoenvironmental studies. In this investigation, stable C and O isotopes and minor element ratios (Sr/Ca and Mg/Ca) are presented from a 550+ year old specimen of Ceratoporella nicholsoni, collected from 122m water depth off of Lee Stocking Island in the Bahamas. The record is generated from sub-sampling at 100 micrometer intervals over an 11 cm length of the specimen, yielding 1100 sub-samples at a resolution of ~2 samples per year back to 1405. Using previously established relationships between Sr/Ca, δ¹⁸O, temperature, and salinity for this species, it is possible to reconstruct salinity variations in the tropical Atlantic Ocean over this extended time period. As such, this is the first sclerosponge from Exuma Sound to yield a multi-century salinity reconstruction. Between 1400 and 1996, the salinity shows a gradual long term increase of ~.5 psu. Superimposed on this long term trend are larger variations with periodicities between 25 and 66 years. Around 1740, a notable salinity minimum (<36 psu) is attained coincident with one of the coldest intervals of the Little Ice Age (based on constant growth rates calculated from U/Th age estimates and verified by the δ¹³C Suess effect). Over the last 100 years of the record, the salinity reconstruction from this sclerosponge is similar to previously published data and can be linked to forcing associated with the North Atlantic Oscillation.
DE: 1041 Stable isotope geochemistry (0454, 4870)
DE: 1050 Marine geochemistry (4835, 4845, 4850)
DE: 1065 Major and trace element geochemistry
DE: 1616 Climate variability (1635, 3305, 3309, 4215, 4513)
DE: 4924 Geochemical tracers
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2007 Fall Meeting