HR: 0830h
AN: PP21C-1189    [PDF]
TI: Links Between the Eastern Equatorial and Mid-Latitude Regions of the Eastern Pacific Ocean During the Pliocene-Pleistocene Transition
AU: * Dekens, P S
EM: dekens@cats.ucsc.edu
AF: University of California at Santa Cruz, Ocean Sciences Department Earth and Marine Science building, A316, Santa Cruz, Ca 95064 United States
AU: Ravelo, A C
EM: acr@cats.ucsc.edu
AF: University of California at Santa Cruz, Ocean Sciences Department Earth and Marine Science building, A316, Santa Cruz, Ca 95064 United States
AU: Wara, M W
EM: mwara@emerald.ucsc.edu
AF: University of California at Santa Cruz, Ocean Sciences Department Earth and Marine Science building, A316, Santa Cruz, Ca 95064 United States
AU: McCarthy, M D
EM: mdmccar@cats.ucsc.edu
AF: University of California at Santa Cruz, Ocean Sciences Department Earth and Marine Science building, A316, Santa Cruz, Ca 95064 United States
AB: The sustained warm period of the early Pliocene (4.6Ma to 3.1Ma) was the most recent period in the Earth's history when long-term equilibrium temperatures exceeded those of today. The subsequent continuation of the Earth's general cooling trend after 3.1Ma has been well documented, predominantly with records from the high latitudes of the Northern Hemisphere. The Pliocene - Pleistocene provides an excellent opportunity to better understand the importance of the connection between high latitudes and the tropical Pacific via the California and the Peru-Chile subtropical systems, during a major climate transition. We present the first comprehensive investigation of the role of the eastern Pacific Ocean in the Pliocene-Pleistocene transition using U$^{k'}$$_{37}$ records of SST. ODP site 847 ($0\deg$12'N, $95\deg$19'W, 3346m water depth) is located within the equatorial upwelling zone in the Eastern Equatorial Pacific (EEP) and serves as an excellent recorder of tropical Pacific climate dynamics. ODP site 1014 ($32\deg$50'N, $119\deg$59'W, 1165m water depth) is located within the California Current (CC), and ODP site 1237 ($16\deg$0.4'S, $76\deg$22.7'W, 3212m water depth) is located within the Peru-Chile current (PCC). These sites record both the strength of the eastern boundary currents in which they are located, which serve as a direct link between high and low latitudes via the advection of cold water, as well as changes in SST related to offshore upwelling. Sites 1014 and 1237 are also indicative of conditions within the ventilated thermocline, an additional connection between the subtropical and tropical Pacific. Temperature records in both the tropic and subtropical Pacific show a gradual cooling trend, rather than a stepwise change at 2.75Ma often seen in northern hemisphere and ice volume records. Initial results indicate that the temperatures in the CC decreased by $8\deg$C from 3 to 2Ma, and that modern conditions along the California margin were established by 2Ma. Temperatures in the EEP decreased by $3\deg$C from 4Ma to the present, with increased variability in the last 1Ma. These results imply that reorganization in the tropical and subtropical Pacific was occurring before, during, and after the onset of major Northern Hemisphere glaciation, therefore making a tropical mechanism for increased northern hemisphere ice volume shift unlikely.
DE: 4267 Paleoceanography
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2003 Fall Meeting