Particulate concentrations and vertical fluxes of sedimentary material and chemical elements, composition of particulate and sinking material in the water column of the Bear Island Trough, Norwegian Sea, July 1995

CTD and nephelometric sounding data are considered along with parameters of the near-bottom currents and particulate fluxes measured by a subsurface mooring station in the northern part of the Bear Island Trough. It is shown that the near-bottom current is characterized by highly variable parameters, while distribution of suspended particulate matter demonstrates surface and bottom maxima. Horizontal and vertical fluxes of sedimentary material in the nepheloid layer are studied.

Particle flux at mooring sites in the Pacific Ocean (Table 1)

In order to understand the vertical transport of particulate matter, suspended and settling particles were collected along a meridional transect between 46°N and 35°S and an equatorial longitudinal transect between 135°E and 175°E in the Pacific. The low COrganic/N atomic ratios (<8.2) of suspended particulate organic matter (OM) and good correlation between particulate organic carbon (OC) and chlorophyll-a confirmed that the suspended particulate OM in the surface water was mainly produced by phytoplankton. Only 0.1-3.2% of primary production was transported to 1.3 km water depth in the boreal central Pacific. All data on settling particles (excluding deep trap data) showed strongly positive correlation between total mass and OM fluxes with high correlation factor of 0.93. Biogenic opal-producing plankton, mainly diatoms were responsible for most of the vertical transport of particulate OM in association with higher COrganic/CCarbonate ratios in the subarctic and equatorial hemipelagic regions in the Pacific. This vertical transport of settling particles potentially works as a sink of CO2. In the transition zone during the May 1993, large difference between PCO2 (<300 µatm) in the surface water and pCO2 (340 µatm) in the atmosphere was actually due to enhanced particulate OM flux. Since the deep water of the Pacific is enriched in CO2 and nutrients, upwelled seawater may tend to release CO2 to the atmosphere. However, higher production of particulate matter could reduce the partial pressure of CO2 in the surface water. Also terrestrial nutrients' inputs in the western equatorial Pacific have potential for the reduction of CO2 in the surface water.