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EOS, Transactions, AGU, 1997 Fall Meeting, Vol. 78, No.46, November 18, 1997, page 29
Glacial to interglacial changes of ocean thermohaline conveyor during late Quaternary
Dan Seidov1 and Bernd J. Haupt2
1Earth
System Science Center, Pennsylvania State University, University Park, PA 16802-2711
2Sonderforschungsbereich 313, Universität Kiel, Heinrich-Hecht-Platz
10, 24118 Kiel, Germany
The global ocean conveyor at present, at the last glacial maximum, and at a subsequent meltwater event (MWE) is simulated using an ocean circulation model and a Lagrangian trajectory tracing technique. The major changes of the deep ocean conveyor occurred at the MWE. These changes include a reversal of the Indian-Atlantic branch of the deep conveyor caused by capping of convection by a localized meltwater impact in the North Atlantic (NA). This result supports the idea of a global response of the world ocean to the Heinrich-type events. However, the model challenges the idea that an ultimate global conveyor now or ever directly connected the high-latitudinal NA and North Pacific. The two oceans are only weakly connected by a series of basin-scale horizontal gyres. The trajectories indicate strong vertical displacement of water parcels traveling within these gyres, which allows inter-basin communications via circulation of both deep and intermediate waters. This interpretation contradicts a view of these remote basins being directly connected by a global-scale deep-water flow. Counter-intuively, the Antarctic Circumpolar Current (ACC) plays a disconnecting role, trapping the Atlantic deep water in the circumpolar transport. The trajectories indicate that the deep water escapes from the ACC does not penetrate as far northward as might be thought on the basis of the global conveyor paradigm. The primary mechanism for the transocean water conveying is deep convection, allowing water to be tunneled upward or downward and thereby escape circumpolar motion. Hence, changes in the production of NADW might still have had a major impact over the entire deep-to- intermediate depths ocean circulation, in spite of the inability of the deep ocean conveyor alone to connect the most remote parts of the world ocean.