whose depth position coincides, in general, with the maximum velocities in the core
of the current. This is well seen over the sections and on the profiles in Fig. 3.
Profiles of velocity and salinity are relatively well correlated.
Intervals of high gradient velocity below the velocity maximum are located in
the upper part of the main thermocline. The structure of the velocity profiles here is
similar to the corresponding upper sharp thermo-halocline.
According to the CTD data, high salinity of surface water exceeding 36.0–36.2
psu was observed at the equator (Fig. 3). These high salinities in the surface layer
were caused by the clearly seen shallow location of the EUC core and its exposure
to the surface. A high temperature mixed layer (∼28 °C) was observed near the
surface within the first 40 m at all CTD stations. It was almost homogeneous south
of the equator and less mixed at the equator and north of it.
In the same depth interval, a quasi-homogeneous layer with minimum salinity
was formed by a surface intrusion of fresher water, probably of the Amazonian
origin [28]. At the equatorial station 2699, this surface intrusion is characterized by
the salinity minimum at a depth of 40 m within the homogeneous mixed layer. It is
accompanied only with weak distortions of the temperature layer structure. Its
traces were seen at stations 2698 and 2700.
The upper high-gradient thermocline is located immediately below the small
transition zone under the quasi-homogeneous temperature layer (starting from 70 m
at station 2698, from 60 m at station 2699, and from 40 m at station 2700). It is
extended down to a depth of 140 m south of the equator and to a depth of 130 m at
the equator and north of it.
As seen in Fig. 3, the beginning of a high-gradient thermocline approximately
corresponds to the maxima of salinity and velocity at the equator. The beginning of
the sharp thermocline is displaced downwards approximately by 20 m from the
maximum of speed and salinity depth at the southern station and upwards from
these maxima by 20 m at the northern station.
Salinity increases down from a depth of 40 m to the maximum values at a depth
of 63–66 m that is approximately the same as the depth of the velocity maximum.
At the southern station, the depth interval of high salinity values just below its
maximum is complicated by a sharp local minimum 10–15 m thick at a depth of
∼76 m (Fig. 3). The traces of it are seen as intrusions at the equator and at the
northern station. This local decrease in salinity is probably caused by the local
reduction of speed in the current core. The temperature field is weakly influenced
by these structural inhomogeneities of the velocity and salinity fields: only small
steps in the sharp-gradient thermocline are noted at each of the three stations.
Owing to this local complication, the upper high-gradient halocline at the three
stations begins deeper than the levels of the salinity and speed maxima and much
deeper than the upper level of the high-gradient thermocline: approximately at a
depth of 95 m.
Thermohaline Structure and Salt Fingering …
435
of the current. This is well seen over the sections and on the profiles in Fig. 3.
Profiles of velocity and salinity are relatively well correlated.
Intervals of high gradient velocity below the velocity maximum are located in
the upper part of the main thermocline. The structure of the velocity profiles here is
similar to the corresponding upper sharp thermo-halocline.
According to the CTD data, high salinity of surface water exceeding 36.0–36.2
psu was observed at the equator (Fig. 3). These high salinities in the surface layer
were caused by the clearly seen shallow location of the EUC core and its exposure
to the surface. A high temperature mixed layer (∼28 °C) was observed near the
surface within the first 40 m at all CTD stations. It was almost homogeneous south
of the equator and less mixed at the equator and north of it.
In the same depth interval, a quasi-homogeneous layer with minimum salinity
was formed by a surface intrusion of fresher water, probably of the Amazonian
origin [28]. At the equatorial station 2699, this surface intrusion is characterized by
the salinity minimum at a depth of 40 m within the homogeneous mixed layer. It is
accompanied only with weak distortions of the temperature layer structure. Its
traces were seen at stations 2698 and 2700.
The upper high-gradient thermocline is located immediately below the small
transition zone under the quasi-homogeneous temperature layer (starting from 70 m
at station 2698, from 60 m at station 2699, and from 40 m at station 2700). It is
extended down to a depth of 140 m south of the equator and to a depth of 130 m at
the equator and north of it.
As seen in Fig. 3, the beginning of a high-gradient thermocline approximately
corresponds to the maxima of salinity and velocity at the equator. The beginning of
the sharp thermocline is displaced downwards approximately by 20 m from the
maximum of speed and salinity depth at the southern station and upwards from
these maxima by 20 m at the northern station.
Salinity increases down from a depth of 40 m to the maximum values at a depth
of 63–66 m that is approximately the same as the depth of the velocity maximum.
At the southern station, the depth interval of high salinity values just below its
maximum is complicated by a sharp local minimum 10–15 m thick at a depth of
∼76 m (Fig. 3). The traces of it are seen as intrusions at the equator and at the
northern station. This local decrease in salinity is probably caused by the local
reduction of speed in the current core. The temperature field is weakly influenced
by these structural inhomogeneities of the velocity and salinity fields: only small
steps in the sharp-gradient thermocline are noted at each of the three stations.
Owing to this local complication, the upper high-gradient halocline at the three
stations begins deeper than the levels of the salinity and speed maxima and much
deeper than the upper level of the high-gradient thermocline: approximately at a
depth of 95 m.
Thermohaline Structure and Salt Fingering …
435