Abstract
A review of paleoceanographic studies dealing with late Quaternary deep-water circulation in the oceans is presented. These studies, which are based on the analysis of deep-sea benthic foraminiferal faunal and geochemical data and sedimentological data, are discussed in light of physical oceanographic conditions in the modern ocean.
We include in this review a re-evaluation of benthic foraminiferal data from North Atlantic and Southern Ocean piston cores and suggest that the dominance of Uvigerina during glacial intervals reflects increased amounts of organic carbon at the sea floor compared to modern values. A number of geochemical studies have suggested that the production or characteristics of North Atlantic Deep Water (NADW) changed during glacial times. Although these changes have been thought to result from a cessation of overflow water from the Norwegian-Greenland Seas, it is suggested here that seasonal sea-ice cover was possible over southern portions of the Norwegian Sea during glacial intervals. The presence of seasonally open water would have allowed Norwegian Sea Overflow Water to have been produced, although perhaps at lower volumes and with different hydrographic properties than at present.
The record of Antarctic Bottom Water (AABW) circulation does not show a simple relationship with paleoclimatic oscillations, indicating that changes in oceanographic conditions in the Southern Ocean had little effect on AABW formation. The AABW record contrasts with the glacial-interglacial cycles of NADW, suggesting no direct link between AABW and NADW circulation.
A variety of data suggests that changes in Pacific Deep Water circulation occurred as a result of glacial production of North Pacific deep water or from an increased flux of Southern Ocean water.
