Selected aspects of the physical oceanography and particle fluxes in fjords of northern Norway

Results regarding the physical oceanography and the dynamics of particulate fluxes in fjords of northern Norway are presented. The phytoplankton spring bloom takes usually place in April in almost homogeneous water and comes to an end before the estuarine circulation starts in late May/early June when snow and ice melting gives rise to usually one pronounced pulse of freshwater run-off. During late summer and autumn river run-off is usually small and of limited significance for the particulate dynamics. Much of the spring bloom material is apt to sink to the bottom, but overwintering herbivores give rise to decreased vertical losses from the upper layers as well as a tendency towards a decreased seasonal variability compared to more enclosed coastal systems in boreal fjords of southern Norway. While destruction and mineralisation of sedimenting matter is of significance below the euphotic zone, giving rise to a decrease in vertical flux, resuspension is of importance in the lower water column and close to the rivers. Coastal currents strongly influence the north Norwegian fjords and particulate signals from rivers are small and do not penetrate extensively into the fjords. Advection of particulate matter, phytoplankton and zooplankton along with various water masses in and out of the fjords seems to play an important role for the ecology and particulate fluxes in this area. The rapid exchange of water masses between the coastal currents and even the innermost fjords as well as the comparatively small discharge of freshwater gives rise to scenarios where particulate fluxes inside the coastal zone are to a large extent determined by external, oceanic forcing. North Norwegian fjords are, therefore, not independent entities, but in various degrees part of the Norwegian Coastal Current.