HR: 1340h
AN: PP33A-1554    [Abstracts]
TI: Multiple Modes of Orbital-Scale Change in Thermohaline Circulation
AU: * Lisiecki, L E
EM: lisiecki@bu.edu
AF: Boston University, 685 Commonwealth Ave, Boston, MA 02215
AU: Raymo, M E
EM: raymo@bu.edu
AF: Boston University, 685 Commonwealth Ave, Boston, MA 02215
AB: Principal component analysis of Late Pleistocene δ¹³C and δ¹⁸O time series from approximately 30 globally distributed marine sites reveals two independent modes of thermohaline circulation change associated with different orbital frequencies. Most paleoclimate studies of deep ocean circulation have either reconstructed only a few points in time (e.g., comparing the Last Glacial Maximum and the Holocene) or have examined the temporal evolution of relatively few (3-6) paleoceanographic records. These techniques have produced a simple model of circulation change in which North Atlantic Deep Water (NADW) shoals during glacial conditions and is replaced at depth by water from the Southern Ocean. Our analysis is consistent with NADW shoaling proportional to ice volume change over the last four glacial cycles. However, our analysis also reveals a second, independent mode of circulation change with more precessional power. Spatial gradients in δ¹⁸O also indicate orbital-scale changes in the physical properties of deep water masses.
DE: 4870 Stable isotopes (0454, 1041)
DE: 4900 PALEOCEANOGRAPHY (0473, 3344)
DE: 4910 Astronomical forcing
DE: 4924 Geochemical tracers
DE: 4962 Thermohaline
SC: Paleoceanography and Paleoclimatology [PP]
MN: Fall Meeting 2005