HR: 08:15h
AN: PP51E-02 INVITED    [Abstracts]
TI: Zonal and Meridional Sea Surface Temperature Gradients and Orbital Variability During the Plio-Pleistocene Transition
AU: * Lawrence, K T
EM: lawrenck@lafayette.edu
AF: Lafayette College Department of Geology and Environmental Geosciences, 102 Van Wickle Hall, Easton, PA 18042, United States
AU: Cleaveland, L C
EM: Laura_Cleaveland@brown.edu
AF: Brown University Department of Geological Sciences, Box 1846, Providence, RI 02912, United States
AU: Mulligan, A B
EM: anna_mulligan@brown.alumni.edu
AF: Brown University Department of Geological Sciences, Box 1846, Providence, RI 02912, United States
AU: Herbert, T D
EM: Timothy_Herbert@brown.edu
AF: Brown University Department of Geological Sciences, Box 1846, Providence, RI 02912, United States
AB: As the most recent interval of sustained warmth in Earth's history the Pliocene represents a potential analog for future climate scenarios. Yet, the ultimate causes of both early Pliocene warmth and the subsequent major climatic transition, which resulted in the development of large ice sheets in the Northern Hemisphere, remain unclear. Here, we compare and contrast three orbital-resolution, alkenone-derived sea surface temperature (SST) records for the interval from 4 to 1.4 Ma, shedding new light on the evolution of the ocean surface temperature field during the Plio-Pleistocene Transition. We examine the trends and orbital scale variability as well as the zonal and meridional temperature gradients elucidated by SST data from Ocean Drilling Program Site 846 (3°S, 91°W) in the eastern equatorial Pacific (EEP), Site 982 (58°N, 16°W) in the North Atlantic, and Site 662 (1°S, 12°W) in the Eastern Equatorial Atlantic (EE ATL). Our data indicate that although the rate of cooling in the EEP (1°C/Myr) was nearly twice that in the EE ATL (0.6°C/Myr), the overall structure of the data from these two sites is remarkably similar. This marked similarity in structure suggests the operation of a large-scale forcing mechanism, such as a change in atmospheric CO₂ concentrations. The zonal temperature gradient between our two tropical sites grew steadily from <1°C at 4 Ma to ~2°C at 1.4 Ma, perhaps as a result of strengthening Walker circulation in the equatorial Pacific. The North Atlantic meridional temperature gradient was ~8°C between 4 and 3.5 Ma and grew steadily to ~12°C at 2.5 Ma when it plateaued until the end of the record at 1.4 Ma. Not surprisingly, the variance at our high latitude site is much greater than that at our tropical sites. However, the presence of significant variance at Site 982 prior to the intensification of Northern Hemisphere Glaciation (~2.75 Ma) is anomalous given the very small amplitude of variations in all other climatic time series from this time period. Obliquity variations are notable in all three records. Significant obliquity variability exists throughout the Site 982 time series while the obliquity response at both tropical sites increases markedly at ~2.7 Ma. In contrast to the minor role of precessional variations at Site 846 and Site 982, precession played very prominent role at Site 662, likely related to variations in the strength of the African monsoon system.
DE: 1616 Climate variability (1635, 3305, 3309, 4215, 4513)
DE: 4900 PALEOCEANOGRAPHY (0473, 3344)
DE: 4946 Milankovitch theory
DE: 4954 Sea surface temperature
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2007 Fall Meeting