Suspended particulate matter (SPM) in the North Sea-Baltic Sea transition: Distributions, inventories, and the autumn 2002 inflows

Abstract

Geografisk Tidsskrift, Danish Journal of Geography 108(2):37–47, 2008 The present study describes the spatial distribution of suspended particulate matter (SPM) in the North Sea—Baltic Sea transition in autumn 2002 based on cruises in August, September, and October. The cruises comprised CTD and optical backscatter measurements supplemented with water sampling and determination of SPM concentrations. Each cruise covered 4 days whereby a close to synoptic SPM distribution was obtained in each of the 3 months. Supplementary cruises were carried out in February 2002 and November 2004. Results showed that surface water SPM concentrations varied around 2–4 g m−3 in the transition with no temporal variation during the autumn. In comparison, bottom water SPM concentrations varied around 4–6 g m−3 except at the Skagerrak/Kattegat boundary where concentrations reached up to 20–22 g m−3. Total SPM inventory, which comprises the Kattegat, the Belt Sea, and the western Baltic Sea, is in the range 2.06* 106- 3.53* 106 tons SPM of which 14 is organic material. Data from the Arkona Basin in the southwest Baltic Sea showed no indications of an enhanced SPM transport into the basin during the autumn 2002 inflows. It was estimated that about 0.18–0.36* 106 tons SPM were transported towards the Baltic Sea with the autumn 2002 inflows. Inflows to the Baltic Sea from the Kattegat are infrequent but it was estimated that a mass between 0.77–1.16* 106 tons of SPM was transported into the Baltic Sea at an average inflow.