HR: 14:25h
AN: PP53A-04 INVITED     [Abstracts]
TI: Fossil Coral Snapshots of ENSO and Tropical Pacific Climate Over the Late Holocene
AU: * Cobb, K M
EM: kcobb@eas.gatech.edu
AF: Georgia Inst. of Technology Dept. of Earth and Atmospheric Sciences, 311 Ferst Dr., MC 0340, Atlanta, GA 30332 United States
AU: Charles, C D
EM: ccharles@ucsd.edu
AF: Scripps Inst. of Technology Univ. of California, San Diego, 9500 Gilman Dr., La Jolla, CA 92093 United States
AU: Cheng, H
EM: cheng021@umn.edu
AF: Minnesota Isotope Laboratory Dept. of Geology & Geophysics, 310 Pillsbury Dr. SE, Minneapolis, MN 55455 United States
AU: Edwards, R L
EM: edwar001@umn.edu
AF: Minnesota Isotope Laboratory Dept. of Geology & Geophysics, 310 Pillsbury Dr. SE, Minneapolis, MN 55455 United States
AB: Following on previous work, we present new 30 to 150-yr long reconstructions of ENSO activity and mean climate in the central tropical Pacific over the last several millennia based on the oxygen isotopic composition of fossil corals from the Line Island chain. Three recent field trips to Palmyra (2N, 162W), Fanning (4N, 160W), and Christmas (2N, 157W) islands yielded over 130 new fossil coral cores. The cores range in size from 30cm to 200cm in length (roughly 15 to 150 years of continuous record) and date from 6kybp to present, as determined by high-precision U/Th dating. Of the cores that we have processed for high-resolution oxygen isotopic analysis, some supplement our previously published results from the last millennium, filling in critical gaps from the Medieval Warm Period (MWP) and the Little Ice Age and allowing for more stringent tests of regional-scale reproducibility across the Line Island chain. These data confirm the existence of cooler and/or drier conditions early in the millennium, a centuries-long anomaly whose amplitude is not captured by a model of tropical Pacific ocean-atmosphere interactions forced by solar and volcanic forcing (Mann et al., 2005). Cooler, drier conditions in the central tropical Pacific are consistent with an increase in the mean zonal SST gradient across the tropical Pacific, which may have been responsible for significant climate anomalies observed in circum-Pacific paleoclimate records during the MWP. A new decades-long sequence from 6kybp extends our reconstruction back in time, and exhibits markedly different characteristics than the last millennium sequences previously published from Palmyra. While it is tempting to interpret such differences as climatic variability (possibly related to changing orbital configuration), accurate climatic interpretations of this older record, which comes from Fanning Island, await a more thorough analysis of additional Fanning island fossil sequences, including a decades-long sequence from 3kybp that is currently underway.
DE: 1041 Stable isotope geochemistry (0454, 4870)
DE: 1616 Climate variability (1635, 3305, 3309, 4215, 4513)
DE: 1635 Oceans (1616, 3305, 4215, 4513)
DE: 4916 Corals (4220)
DE: 4922 El Nino (4522)
SC: Paleoceanography and Paleoclimatology [PP]
MN: Fall Meeting 2005