Features of the central Norwegian shelf circulation

The central Norwegian shelf between 62 and 68°N covers an area of about 150 000 km2. The bottom topography is complicated and consists of several shallow banks separated by deeper channels. The area plays an important site-specific role for the recruitment strategy of the Norwegian spring spawning herring. The aim of this contribution is to elucidate the general circulation pattern and the physical processes related to drift and spreading of herring larvae, primarily by the use of satellite-tracked drifting buoys. The results indicate two drift routes; the main inner one on the coastal side of the banks, and a secondary outer one which follows the shelf break. Both routes are highly governed by the bottom topography. The inner transport route is the proper Norwegian Coastal Current characterised by having the higher drift speeds, the lower mean residence time and the higher current directional stability. Several banks at the shelf may induce topographically trapped eddies. The herring seems to prefer to spawn in these eddies.