In deep fjords, the flushing of layers above sill
level is often dominated by intermediary
circulation caused by coastal density field
fluctuations, rather than by estuarine
circulation and tidal exchanges. Intensive
observations of such a flushing event in
Gullmar fjord, Sweden, including 20
microstructure profiling transects through the
entrance during two 24 hour periods, show
that dissipation rates of turbulent kinetic
energy were enhanced in the inflowing layers
in a wedge extending six kilometers into the
fjord from the narrow entrance. The density
and dissipation rate fields reveal non-linear,
oblique internal wave beams with typical
horizontal length scales from 0.3 to 3 km
extending from the bottom and from the
halocline near the entrance towards the
center of the inflowing layer, bounding the
enhanced dissipation wedge. Various
generation mechanisms for these beams are
discussed and related to the total loss of
energy and diapycnal mixing in the inflowing
layers.