Coherent Signals in Northern Hemisphere Proxy Records Over the Past Two Millennia: Shared Variability and Support for a Warm Tropical Pacific During the Little Ice Age.

HR: 10:50h
AN: PP51D-03 [PDF]
TI: Coherent Signals in Northern Hemisphere Proxy Records Over the Past Two Millennia: Shared Variability and Support for a Warm Tropical Pacific During the Little Ice Age.
AU: * Graham, N E
AF: Scripps Institution of Oceanography, Climate Research Div., La Jolla, CA 92093-0024 United States
AU: * Graham, N E
AF: Hydrologic Research Center, 12780 High Bluff Dr., Suite 250, San Diego, CA 92130 United States
AU: Hughes, M K
EM: mhughes@ltrr.arizona.edu
AF: Labratory for Tree-Ring Research, University of Arizona, Tuscon, CA 85721 United States
AU: Cobb, K
EM: kcobb@gps.caltech.edu
AF: Dept. of Geological and Plantary Sciences, California Institute of Technology, Pasadena, CA 91125 United States
AB: Proxy tree ring, ocean core, and pollen records show a coherent pattern of increased precipitation in California and into the Great Basin, decreased temperatures in the Sierra Nevada and increased sea surface temperatures (SSTs) off Southern California consistent with the recent suggestion of warm tropical Pacific SSTs during the Little Ice Age (LIA)and cool SSTs during antecedent centuries. Low frequency signals coherent with these changes appear in lacustrine records from the central and eastern US, a recent reconstruction of the strength Iceland Low, the Quelccaya Ice Cap d18O record, and SST records from the subtropical Atlantic. We suggest scenarios consistent with this suite of changes in terms of altered circulation patterns. Comparisons between the proxy records and results from a recently completed 1150-year simulation with the NCAR CCSM reveal points of agreement and disagreement. These points support an important role for radiative forcing as a driving force behind low frequency variability during much of the last two millennia, and at the same time suggest that the responses of the actual climate system to such forcing may be larger and more discontinuous than those seen in the model climate.
DE: 3344 Paleoclimatology
DE: 4267 Paleoceanography
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2003 Fall Meeting