Fronts in fjords

Abstract

Severa1 types of fronts have been observed in the surface waters of Norwegian fjords: shear fronts along river jets, tidal/wind induced river fronts, river-river fronts and wind-driven foam fronts. A river jet spreading over a layered fjord mixes predominantly with the surface water. Farther seaward, wind and tide drive the river plume. In most Norwegian fjords wind mixing causes an entrainment of deeper water to the river plume. In the absence of wind and tide, a geostrophic balance in the top brackish water layer controls the velocity of a river plume in wide fjords. For narrow fjords, topography plays a significant role for the residence time of river water in the basin. River fronts are permanent features of the surface waters. Foam fronts, related to slicks, are observed during the spring and summer months at wind speeds less than those for the better-known windrows.