Instances of strong oxygen variations are described for two shallow wa
ter stations in the Kattegat, situated at the fluctuating frontal zone
between outflowing surface water from the Baltic and inflowing bottom
water from the Skagerrak/North Sea. The events consist of both a rapi
d emergence and a rapid disappearance of oxygen-depletion. Changes in
oxygen concentration amounted to more than 20 g m-2 d-1 for the total
water columns. Such high rates of change can not be explained by net l
ocal bottom oxygen consumption (0.6 g M-2 d-1) or net local water oxyg
en consumption (1.6 g M-2 d-1). The oxygen variations were influenced
by the local and regional meteorological conditions. The observed inst
ance of shallow water oxygen-depletion was connected to upward movemen
t of the pycnocline and associated advective transport of oxygen-deple
ted Kattegat bottom waters to a shallow water area. Similarly, rapid d
isappearance of the bottom water oxygen deficit in a shallow water are
a was found to depend more on pycnocline lowering in connection with a
dvective transport, than on the effect of local wind driven mixing.