The measurement site over the Mascarene Ridge was in the region that
encompasses the southern part of the Saya de Malya bank and the northern part of
the Nazareth bank (Fig. 1). In this region, there is a strong alternating current,
which consists of two main components: a quasi-constant mean flow directed from
the east to the west and an alternating tidal current. The velocity of the
quasi-constant flow reached 1 m/s, and the amplitude of the current of the semidiurnal tide was 0.5 m/s. In the course of the work, a region with intense internal
waves above the underwater sill was discovered.
The observations of internal waves were carried out using line temperature
sensors by means of towing of the line sensor in the upper thermocline. During the
ship drift, a series of rapid vertical soundings (“yo-yo”) of the CTD profiler were
also conducted.
The measurement cycle over the bank included continuous measurements over
several runs oriented across the underwater sill (Fig. 1). The towing was carried out
at a ship speed of 7.5–8.5 knots; the lower end of the line sensor was located at a
depth of 100–106 m. The sensor then covered the interval of the well-pronounced
subsurface thermocline. A record of the line sensor during the passage above the sill
is shown in Fig. 2.
Fig. 1 Bottom topography in
the measurement site and the
track of the vessel during
towing. Letters C and B
denote the locations of
internal waves of large
amplitudes (C is related to the
solitary wave mode 2, B is
related to the train of
soliton-like waves)
212
A. N. Serebryany
encompasses the southern part of the Saya de Malya bank and the northern part of
the Nazareth bank (Fig. 1). In this region, there is a strong alternating current,
which consists of two main components: a quasi-constant mean flow directed from
the east to the west and an alternating tidal current. The velocity of the
quasi-constant flow reached 1 m/s, and the amplitude of the current of the semidiurnal tide was 0.5 m/s. In the course of the work, a region with intense internal
waves above the underwater sill was discovered.
The observations of internal waves were carried out using line temperature
sensors by means of towing of the line sensor in the upper thermocline. During the
ship drift, a series of rapid vertical soundings (“yo-yo”) of the CTD profiler were
also conducted.
The measurement cycle over the bank included continuous measurements over
several runs oriented across the underwater sill (Fig. 1). The towing was carried out
at a ship speed of 7.5–8.5 knots; the lower end of the line sensor was located at a
depth of 100–106 m. The sensor then covered the interval of the well-pronounced
subsurface thermocline. A record of the line sensor during the passage above the sill
is shown in Fig. 2.
Fig. 1 Bottom topography in
the measurement site and the
track of the vessel during
towing. Letters C and B
denote the locations of
internal waves of large
amplitudes (C is related to the
solitary wave mode 2, B is
related to the train of
soliton-like waves)
212
A. N. Serebryany