HR: 0800h
AN: PP51D-0631    [Abstracts]
TI: Isotopic Records of Planktonic Foraminifera indicate a distinct response of the California Current to 20th century warming
AU: * Field, F B
EM: David.Field@noaa.gov
AF: Southwest Fisheries Science Center, La Jolla, 8604 La Jolla Shores Drive , La Jolla, CA 92037-0271 United States
AU: * Field, F B
EM: David.Field@noaa.gov
AF: Scripps Institution of Oceanography, 9500 Gilman Dr. , La Jolla, CA 92093 United States
AU: Baumgartner, T
EM: tbaumgar@cicese.mx
AF: Centro de Investigaci¢n Cient¡fica y Educaci¢n Superior de Ensenada (CICESE, Km 107 Carretera Tijuana-Ensenada, Ensenada, Mexic, B.C 22860 Mexico
AU: Charles, C
EM: ccharles@ucsd.edu
AF: Scripps Institution of Oceanography, 9500 Gilman Dr. , La Jolla, CA 92093 United States
AU: Ferriera- Bartrina, V
EM: paleoc@cicese.mx
AF: Centro de Investigaci¢n Cient¡fica y Educaci¢n Superior de Ensenada (CICESE, Km 107 Carretera Tijuana-Ensenada, Ensenada, Mexic, B.C 22860 Mexico
AB: Isotopic records from planktonic foraminifera are developed from Santa Barbara Basin sediments to understand the nature of upwelling and hydrographic variability beyond the multiannual time scale in the California Current and determine whether the 20th century warming is different from other warm periods. δ¹⁸O measurements from multiple species of planktonic foraminifera are examined from two (five) year sampling intervals from 1737-2001 (255-1955 AD). There is shared variability between species that reflects variations throughout the water column, while the differences between species reflects changes in hydrographic structure and species' preferred habitats. The δ¹⁸O of G. bulloides, is generally believed to reflects variations in SST during upwelling while the δ¹⁸O of G. ruber reflects variability during summer and fall. There is a negative relationship between near surface temperatures of the California Current, inferred from the δ¹⁸O of G. bulloides, and northern hemisphere temperatures for nearly 1700 years prior to the 20th century but a positive relationship in the 20th century. The negative relationship is apparent on multidecadal to centennial time scales, particularly during the peak warming (cooling) of the Medieval Warm Period (Little Ice Age) and indicates greater upwelling in the California Current during times of northern hemisphere warming. Comparison of δ¹⁸O of G. bulloides with δ¹⁸O of G. ruber and abundances of several species of foraminifera that show a good relationship with SST indicates that the 20th century warming in the California Current is associated with different vertical ocean structure then previous warm periods. There is a greater thermal gradient in the near surface due primarily to increased ocean-atmosphere heat exchange as well as an underlying shoaling of isotherms from greater alongshore winds. The 20th century changes in hydrographic structure and positive relationship with northern hemisphere temperatures are consistent with models and hypotheses of a greenhouse gas-induced warming.
DE: 0473 Paleoclimatology and paleoceanography (3344, 4900)
SC: Paleoceanography and Paleoclimatology [PP]
MN: Fall Meeting 2005