Interpretation of interbasin exchange in an isopycnal ocean model

Abstract

This paper reports an analysis of interbasin and interlayer exchanges in the component ocean part of the coupled ECHAM4/OPYC3 general circulation model, aimed at documenting the simulation of North Atlantic deep water (NADW) and related thermohaline circulations in the Indian and Pacific Oceans. The modeled NADW is formed mainly in the Greenland-Iceland-Norwegian Seas through a composite effect of deep convection and downward cross-isopycnal transport. The modeled deep-layer outflow of NADW can reach 16 Sv near 30 S in the South Atlantic, with the corresponding upper-layer return flow mainly coming from the ''cold water path'' through Drake Passage. Less than 4 Sv of the Agulhas ''leakage'' water contribute to the replacement of NADW along the ''warm water path''. In the South Atlantic Ocean, the model shows that some intermediate isopycnal layers with potential densities ranging between 27.0 and 27.5 are the major water source for compensating the NADW return flow and for enhancing the circumpolar deep water (CDW) flowing from the Atlantic into Indian Ocean. The modeled thermohaline circulations in the Indian and Pacific Oceans indicate that the Indian Ocean may play the major role in converting deep water into intermediate waterAvailable from FIZ Karlsruhe / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman