HR: 0800h
AN: PP21A-1373    [Abstracts]
TI: A High-Resolution Mid- to Late-Holocene Sea-Surface Temperature Record from the Subtropics, Baja California, Mexico
AU: * Coombs, M
EM: coombs@umail.ucsb.edu
AF: University of California, Santa Barbara, Department of Geological Sciences, Building 526, Santa Barbara, CA 93106-9310 United States
AU: Herguera, J C
EM: herguera@cicese.mx
AF: CICESE, PO Box 430340, San Diego, CA 92143-0340 United States
AU: Lea, D W
EM: lea@geol.ucsb.edu
AF: University of California, Santa Barbara, Department of Geological Sciences, Building 526, Santa Barbara, CA 93106-9310 United States
AB: San Lazaro basin provides a unique environment in which to study paleoclimate because it lies at the intersection of the cooler California Current that originates to the north and the warmer Pacific tropical current that originates to the south. Studies in this basin will provide insight into the varying strength of these currents at decadal and centennial resolutions. In addition, the present-day basin is suboxic ($<$3 uM/kg), and laminations throughout the top $\sim$6 m of ocean floor sediments indicate that it may have been suboxic for the past $\sim$6.5 ky. Suboxia is advantageous in the study of high-resolution paleoclimate records, as lower levels of oxygen inhibit the activity of sediment-disturbing organisms that might smooth climate records. We will present parts of a new decadal-resolution sea-surface temperature (SST) record from San Lazaro (AKA Soledad) basin, Baja California, Mexico. We estimate SST using Mg/Ca and d18O data measured on surface-dwelling planktonic foraminifera Globigerinoides ruber and Globigerina bulloides from ocean-sediment giant box core MD02-2506C2. This 4.6-m core exhibits an $\sim$0.8 mm/yr sedimentation rate (van Geen et al., 2003) and represents the period $\sim$5,000 to $\sim$500 years BP. We sampled the core at 1-cm continuous (i.e., approximately decadal) resolution. Preliminary results indicate that Mg/Ca values for G. ruber range between 2.3 and 3.3 mmol/mol ($\sim$20 and $\sim$24 deg C), with higher values characteristic of the mid-Holocene. Annual sea-surface temperatures for the period 1950 to 1990 ranged between $\sim$19 and $\sim$23 deg C (CalCOFI, COADS), suggesting that mid- to late-Holocene SST values were $\sim$1 deg C higher than the those of the last half century. We will compare our SST proxy results with d18O records from Santa Barbara basin (e.g., Kennett and Kennett, 2000); tree-ring records from Baja California (Bullock, 2003) and Southern California (De Nava et al., 1999); and pluvial (Davis, 2003) and packrat midden (Clark and Sankey, 1999) records from Baja California.
DE: 4267 Paleoceanography
DE: 4512 Currents
DE: 1620 Climate dynamics (3309)
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2004 AGU Fall Meeting