HR: 17:15h
AN: PP54A-06 INVITED     [Abstracts]
TI: Revisiting the Glacioeusatic Significance of Glacial Terminations Based on Deep-Water T-d18O Estimates
AU: * Skinner, L C
EM: luke00@esc.cam.ac.uk
AF: Godwin Laboratory University of Cambridge, New Museums Site Pembroke Street, Cambridge, CB2 3SA United Kingdom
AU: Shackleton, N J
EM: njs5@cam.ac.uk
AF: Godwin Laboratory University of Cambridge, New Museums Site Pembroke Street, Cambridge, CB2 3SA United Kingdom
AB: In principle, globally synchronous changes in glacioeustatic sea-level may provide a uniquely useful stratigraphic reference in the study of glacial-interglacial, and perhaps even of millennial climate change. Indeed, global sea-level change forms the basis of the Marine Isotope Stage (MIS) system, which posits the dominance of a glacioeustatic signal in benthic foraminferal d18O. However, benthic d18O strictly does not represent a pure sea-level record; it is also sensitive to changes in local water temperature and d18O. In today's ocean basins, the temperature and d18O of deep-water, both of which are controlled by the conditions of deep-water formation, very clearly reflect the distribution of various deep-water masses (indeed they are generally used for the definition of such water-masses). We propose that this must also have been the case in the past, and that in a dynamically variable ocean these lateral water-property gradients must have also resulted in regionally time-transgressive changes in benthic d18O. We have verified this hypothesis across the last glacial Termination by comparing well-dated benthic d18O records from the deep northeast Atlantic and equatorial Pacific. The comparison indicates a significant discrepancy (~4000 years) between the timing of benthic d18O change in each basin. We do not believe that this discrepancy is only due to a 'lagged' deep Pacific response to de-glacial Laurentide melting. Rather it appears that each record represents a different history of hydrographic change. In the deep northeast Atlantic, deep-water T-d18O reconstructions suggest that the benthic d18O record across Termination I has been significantly affected by repeated pulses of low temperature and negative-d18O deep-water, inferred based on d13C and D14C evidence to represent Antarctic sourced deep-water. It can be shown that a strikingly similar pattern of deep-water change also occurred across Termination II in the Northeast Atlantic, suggesting that both de-glaciations experienced the same type of hydrographic variability. As a result of these deep-water changes, the timing of each benthic d18O Termination cannot precisely reflect the timing of de-glacial sea-level change, as many palaeoceanographic interpretations (and controversies) are prone to assume.
DE: 1600 GLOBAL CHANGE
DE: 4283 Water masses
DE: 4900 PALEOCEANOGRAPHY (0473, 3344)
DE: 4940 Isotopic stage
SC: Paleoceanography and Paleoclimatology [PP]
MN: Fall Meeting 2005