HR: 17:15h
AN: PP34B-06    [Abstracts]
TI: Plio-Pleistocene Ocean Productivity: A Story of Interbasin Symmetry
AU: * Lawrence, K T
EM: Kira_Lawrence@Brown.edu
AF: Department of Geological Sciences, Brown University, Box 1846, Providence, RI 02912 United States
AU: Cleaveland, L C
EM: Laura_Cleaveland@Brown.edu
AF: Department of Geological Sciences, Brown University, Box 1846, Providence, RI 02912 United States
AU: Mulligan, A B
EM: Anna_Mulligan@Brown.edu
AF: Department of Geological Sciences, Brown University, Box 1846, Providence, RI 02912 United States
AU: Herbert, T D
EM: Timothy_Herbert@Brown.edu
AF: Department of Geological Sciences, Brown University, Box 1846, Providence, RI 02912 United States
AB: The precipitous decline of biological productivity in the high latitude oceans of both the north Pacific and Antarctic synchronous with the intensification of northern hemisphere glaciation (NHG) (2.75 Ma), has previously been attributed to the abrupt onset of ocean stratification in both of these regions. Using the concentration of alkenones, organic compounds exclusively produced by a few species of haptophyte algae, in ocean sediments from the north Atlantic (ODP Site 982), eastern equatorial Pacific (ODP Site 846) and eastern equatorial Atlantic (ODP Site 662) we document the continuous evolution of high latitude and tropical ocean productivity over the past 3.5 Myr. We find that biological productivity in the north Atlantic behaved similarly to that in the high latitude regions of the north Pacific and Antarctic, declining precipitously just after the intensification of NHG. These data suggest that high latitude stratification may have extended into the north Atlantic Ocean, implying that overturning in the north Atlantic after the intensification of NHG may have been significantly weaker than previously proposed. In contrast, productivity in the eastern equatorial Pacific and Atlantic, both low latitude upwelling zones, rose sharply approximately synchronous with the intensification of NHG. We hypothesize that nutrients that were inhibited by the onset of water column stratification from upwelling at high latitudes were instead entrained into the source waters for low latitude upwelling zones feeding the dramatic rise in productivity that occurred in these regions. Our high-resolution (3 kyr) records indicate that on orbital timescales, ocean productivity was anti-correlated to sea surface temperature changes at all sites. In the north Atlantic productivity variations beat at precessional and obliquity periods, while those in the upwelling zones of both the eastern Pacific and Atlantic Oceans beat primarily at obliquity periods. The symmetric behavior of both high latitude and low latitude productivity on both orbital and longer timescales, suggests that nutrient bearing mode waters communicated changes from the high to low latitude ocean in both the Atlantic and Pacific basins.
DE: 4900 PALEOCEANOGRAPHY (0473, 3344)
DE: 4964 Upwelling (4279)
SC: Paleoceanography and Paleoclimatology [PP]
MN: Fall Meeting 2005