Author:

Keywords:

suspended barite, equatorial pacific, deep-water, sea ice, paleoproductivity, particles, transport, western, matter, tracer, 0402 Geochemistry, 0405 Oceanography, 0602 Ecology, Oceanography

Abstract:

Particulate barium was analysed in the upper 600 m of the Southern Ocean water column during repeated transects along the 6 degrees W meridian in October-November 1992. The transects extended between the northern edge of the Weddell Gyre (57 degrees 30'S) in the south to 47 degrees S within the Polar Front Zone (PFZ) in the north. From earlier studies, it is known that the largest fraction of Ba in oceanic suspended matter occurs as barite micro-crystals. In the PFZ, an increase in the particulate Ba content in surface waters and at mesopelagic depths can be significant over the investigation period (1 month) and follows the increase of primary production during bloom development. Using an inverse one-dimensional advection-diffusion-consumption model, O-2 consumption between the base of the mixed layer and 1000 m was estimated. The shapes of the vertical particulate Ba profiles are very similar to those of calculated O-2 consumption rates, emphasizing the close link between organic matter oxidation and Ba-barite release at a mesopelagic depth. For the southern Antarctic Circumpolar Current (ACC), depth-integrated rates of O-2 consumption correlate significantly with primary production and mesopelagic particulate Ba concentration. For the PFZ, these relationships are subject to more speculation since this is a region of intense mixing, and the appropriate value of the turbulent diffusion coefficient is uncertain. For the ACC, the observed relationship presents the possibility of defining a transfer function between export production to the mesopelagic depth zone and mesopelagic Ba accumulation. The observed regression between rate of O-2 consumption and primary production in the southern ACC suggests that about 10% of the synthesized organic carbon can be oxidized in the upper 1000 m of the water column. (C) 1997 Elsevier Science Ltd.