INVESTIGATION OF SMALLSCALE
VERTICAL MIXING IN RELATION TO THE
TEMPERATURE STRUCTURE IN
STABLY STRATIFIED WATERS
GUNNAR KULLENBERG
Institute of Physical Oceonogrophy, University 4 Copenhogen
Copnhagn. Denmark
INTRODUCTION
The present experiments were designed to yield information on the rate of
mixing in an internal layer of the sea with a view to investigating the dependence of the mixing on environmental conditions. A density-adjusted solution of rhodamine B was injected over an interval of 2-5 min in a subsurface
layer at depths below the surface ranging from 20 to 50 m. The density of the
solution was measured with hydrometers and adjusted within k0.2q-unit of
the in situ density, The dye concentration distributions, both vertical and
horizontal, were continuously recorded with an in situ fluorometer (Fig. 1)
towed behind the ship and cycling in.a certain depth w g e . The signal from
a rapid response thermistor mounted on the fluorometer was simultaneously
recorded, so that the dye and temperature distributions were observed with
the same vertical resolution. The fluorometer and the tracing technique have
been described by Kullenberg (1969).
The environmental observations were made with conventional equipment : water samples, in situ temperature-conductivity probes, moored and
shipboard current meters, and in Lake Ontario electronic bathythermographs. The vertical resolution of these observations was 1-2 m. Profiles of
salinity, temperature, and current were observed before and during the tracing period. In most cases one ship has been employed with the environmental observations and another with the tracing. The current measurements
were made from a single anchored ship. Care has been taken to avoid the use
of observations which apparently have been strongly infiuenced by the ship
motion. The data have also been compared with data from the moored
current meters,
From the profiles, average values of the mean vertical gradient of the
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VERTICAL MIXING IN RELATION TO THE
TEMPERATURE STRUCTURE IN
STABLY STRATIFIED WATERS
GUNNAR KULLENBERG
Institute of Physical Oceonogrophy, University 4 Copenhogen
Copnhagn. Denmark
INTRODUCTION
The present experiments were designed to yield information on the rate of
mixing in an internal layer of the sea with a view to investigating the dependence of the mixing on environmental conditions. A density-adjusted solution of rhodamine B was injected over an interval of 2-5 min in a subsurface
layer at depths below the surface ranging from 20 to 50 m. The density of the
solution was measured with hydrometers and adjusted within k0.2q-unit of
the in situ density, The dye concentration distributions, both vertical and
horizontal, were continuously recorded with an in situ fluorometer (Fig. 1)
towed behind the ship and cycling in.a certain depth w g e . The signal from
a rapid response thermistor mounted on the fluorometer was simultaneously
recorded, so that the dye and temperature distributions were observed with
the same vertical resolution. The fluorometer and the tracing technique have
been described by Kullenberg (1969).
The environmental observations were made with conventional equipment : water samples, in situ temperature-conductivity probes, moored and
shipboard current meters, and in Lake Ontario electronic bathythermographs. The vertical resolution of these observations was 1-2 m. Profiles of
salinity, temperature, and current were observed before and during the tracing period. In most cases one ship has been employed with the environmental observations and another with the tracing. The current measurements
were made from a single anchored ship. Care has been taken to avoid the use
of observations which apparently have been strongly infiuenced by the ship
motion. The data have also been compared with data from the moored
current meters,
From the profiles, average values of the mean vertical gradient of the
3 39