HR: 1330h
AN: PP23B-07    [Abstracts]
TI: Twentieth Century Warming in the California Current Decoupled from Typical Decadal Variations
AU: * Field, D B
EM: David.Field@noaa.gov
AF: Southwest Fisheries Science Center, 8604 La Jolla Shores Dr., La Jolla, CA 92038-0271
AU: * Field, D B
EM: David.Field@noaa.gov
AF: Scripps Institution of Oceanography, 9500 Gilman Dr., La Jolla, CA 92093
AU: Baumgartner, T
EM: tbaumgar@cicese.mx
AF: Centro de Investigaci˘n Cientˇfica y Educaci˘n Superior de Ensenada, CICESE, Depto. de Ecologˇa. Apdo. Postal. # 2732, , Ensenada, BC 22830 Mexico
AU: Charles, C
EM: ccharles@ucsd.edu
AF: Scripps Institution of Oceanography, 9500 Gilman Dr., La Jolla, CA 92093
AU: Ferriera-Bartrina, V
EM: paleoc@cicese.mx
AF: Centro de Investigaci˘n Cientˇfica y Educaci˘n Superior de Ensenada, CICESE, Depto. de Ecologˇa. Apdo. Postal. # 2732, , Ensenada, BC 22830 Mexico
AB: Microfossils of planktonic foraminifera in marine sediments offer one of the few means available to reconstruct changes in hydrographic structure and infer the mechanisms of change in ocean climate. Here, we present a >250-year record of variations in upper ocean structure of the California Current, inferred from the abundances of planktonic foraminifera in annually varved sediments of the Santa Barbara Basin. Temporal variability in foraminiferal abundance follows two main patterns that are reflected in a Principal Components Analysis. The first pattern (PC 1) involves a substantial 20th century increase in the abundance of mostly tropical and subtropical species, beginning around 1925, that indicate a warming of near-surface waters across the annual cycle of isothermal shoaling and deepening. The second pattern (PC 2) involves species with subpolar affinities that probably reflect decadal scale dynamics within the thermocline. There is a clear separation of the two PCs after 1975 that indicates a near surface warming and isothermal deepening that is distinct from all other time periods of the record. This change coincides with the well-known shift that occurred around 1977 in the North Pacific, where an intensification in the Aleutian Low caused a warming and depression of isotherms in the eastern North Pacific, particularly during winter. While hydrographic structure since the mid-1970s is particularly anomalous with respect to decadal changes in previous centuries, the entire CalCOFI program has taken place in a time period with unusually high abundances of tropical and subtropical species that began in the early 20th century. The patterns observed in the 20th century suggest a response of the California Current to atmospheric warming attributed in part to anthropogenic activity.
DE: 1620 Climate dynamics (3309)
DE: 1635 Oceans (4203)
DE: 3344 Paleoclimatology
DE: 4267 Paleoceanography
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2005 Joint Assembly