Factors controlling CaCO 3 dissolution in the Weddell Sea from foraminiferal distribution patterns

Abstract

Surface samples of sediment cores from the Weddell Sea contain foraminiferal assemblages which are distinctly divided into calcareous or arenaceous populations and reflect CaCO 3 dissolution in some regions. Water depth apparently is only partly responsible for this CaCO 3 dissolution, the present CCD varying from 250 m to greater than 3700 m. Other factors such as water-mass properties, biological producitivity and sedimentation, all of which are controlled by the glacial regime of a region, are of major importance. Perennial sea-ice formation over the southwestern continental shelf causes a deficiency in surface productivity, limits air—sea interaction and produces cold, Saline Shelf Water which is apparently undersaturated with respect to CaCO 3. In the eastern Weddell Sea, less severe glacial conditions appear to favor CaCO 3 preservation on the continental shelf. In this area the CCD coincides approximately with major water-mass boundaries varying from over 700 m to approximately 500 m. The deepest and most widespread occurrence of calcareous foraminiferal assemblages coincides with the present region of Antarctic Bottom Water production in the Weddell Sea. Here the CCD is depressed from approximately 1500 m to over 3700 m from east to west along the outer edge of the slope and reflects intensification of mixing and subsequent increased biological productivity in that direction.