HR: 16:15h
AN: PP44A-02    [Abstracts]
TI: A 14,000 Year Foraminiferal Trace Metal Record of ENSO-Influenced Upwelling Near Southern Baja California
AU: * Marchitto, T M
EM: tom.marchitto@colorado.edu
AF: INSTAAR and Dept. of Geological Sciences, University of Colorado, 450 UCB, Boulder, CO 80309 United States
AU: Ortiz, J
EM: jortiz@kent.edu
AF: Kent State University, P.O. Box 5190, Kent, OH 44242 United States
AU: Carriquiry, J
EM: jose_carriquiry@uabc.mx
AF: Universidad Aut¢noma de Baja California, A.P. 453, Ensenada, BC 22,800 Mexico
AU: Levi, C
EM: clevi@ldeo.columbia.edu
AF: Lamont-Doherty Earth Observatory of Columbia University, 61 Rt. 9W, Palisades, NY 10964 United States
AU: van Geen, A
EM: avangeen@ldeo.columbia.edu
AF: Lamont-Doherty Earth Observatory of Columbia University, 61 Rt. 9W, Palisades, NY 10964 United States
AB: A number of numerical modeling studies predict that the early to mid Holocene tropical Pacific should have been characterized by more La Niña-like conditions than today, with generally more vigorous trade winds and a steeper zonal tilt of the thermocline. The primary driver of this change is orbital, but various models differ in the exact mechanisms and hence timing of the change. Existing paleoclimate records offer a sometimes contradictory picture of the Holocene development of the tropical Pacific. Additional high quality records could help to resolve the true pattern of change, including its timing, and thus constrain the important climate mechanisms at work. Here we present new data from a sediment core collected in Soledad Basin, which is located off of southern Baja California (25°N) and has an effective sill depth of 290 m. Sedimentation rates are relatively constant at about 1 m/kyr, bioturbation is negligible, and foraminiferal preservation is excellent. Today the primary productivity in this region is strongly impacted by ENSO: during springs following El Niño events, upwelled waters are anomalously warm and poor in nutrients because of the deepened thermocline and nutricline. The actual intensity of upwelling, controlled by local winds, is of much less importance. Hence records of planktonic foraminiferal paleotemperatures (Mg/Ca) and paleonutrients (Cd/Ca and Zn/Ca) should mainly reflect the depth of the regional thermocline and nutricline. Preliminary Globigerina bulloides measurements appear to follow an orbital pattern and suggest that conditions were most La Niña-like (cool temperatures and high nutrients) around 6 ka. We suggest that measurements on individual tests of G. bulloides and Globigerinoides ruber may help to constrain changes in interannual ENSO variability. We will also present data spanning the Younger Dryas oscillation to determine if millennial scale climate change is reflected in the depth of the thermocline and nutricline.
DE: 4900 PALEOCEANOGRAPHY (0473, 3344)
DE: 4922 El Nino (4522)
DE: 4924 Geochemical tracers
DE: 4954 Sea surface temperature
SC: Paleoceanography and Paleoclimatology [PP]
MN: Fall Meeting 2005