THE NEAR-SURFACE LAYER OF THE OCEAN
The front sometimes splits into a group of frontal interfaces. In mid- and
high-latitudes, the Coriolis effect winds these lines up into spirals (Figure
5-5), but they may still be very narrow.
Although oceanic fronts are observed over a wide range of horizontal
scales, turbulent mixing events in the ocean tend to occur on relatively small
scales. The small-scale structure of oceanic fronts therefore potentially
contains information about horizontal and vertical exchange processes in the
upper ocean.
In situ measurements sometimes reveal sharp frontal interfaces in the
upper ocean (Zenk and Katz, 1975; Soloviev and Zatsepin, 1992; Yoder et
al., 1994; Soloviev and Lukas, 1997b). Many sharp frontal interfaces are
found in the temperature, salinity, and density records made during TOGA
COARE, using bow-mounted sensors (Soloviev and Lukas, 1997b;
5.4.1 Observations of sharp frontal interfaces in the western Pacific
warm pool
The western equatorial Pacific warm pool region – the TOGA COARE
domain – is characterized by heavy precipitation and generally light winds.
As a result, both heat and freshwater fluxes contribute substantially to the
buoyancy influx to the top of the surface mixed layer, and both temperature
and salinity stratification is found in the upper ocean (Lukas and Lindstrom,
1991). The thermohaline fields in the warm pool area are heterogeneous and
non-stationary to a surprising degree (Huyer et al., 1997); there are
numerous instances of sharp fronts in the surface layer of the ocean
(Soloviev and Lukas, 1997b).
Figure 5-17 shows a sharp front in a photograph taken from the bridge
of the R/V Kaiyo in the western equatorial Pacific warm pool during a
TOCS cruise (This is believed to be the same type of front as in the image
from space shown in Figure 5-16.) A description of the upper ocean
currents, thermohaline structure, and atmospheric forcing during TOCS can
be found in Matsuura et al. (2002).
The sharp frontal line in Figure 5-17 is roughly aligned in the east-west
direction and extended from one horizon to the other. The front is clearly
seen in the photograph because the wind waves to the north of the front
break much more intensively than those to the south of the front. There is
also some difference in ocean color across the front.
CTD stations made along 156
o E from 8
o N to 3
o S (prior to crossing the
front) reveal a surface salinity minimum at about 5
o N and the related
meridional salinity gradient at the equator (Figure 5-18). A CTD station
taken just north of the front (see map in Figure 5-19) reveals a nearly
314
Wijesekera et al., 1999a; Soloviev et al., 2002).
The front sometimes splits into a group of frontal interfaces. In mid- and
high-latitudes, the Coriolis effect winds these lines up into spirals (Figure
5-5), but they may still be very narrow.
Although oceanic fronts are observed over a wide range of horizontal
scales, turbulent mixing events in the ocean tend to occur on relatively small
scales. The small-scale structure of oceanic fronts therefore potentially
contains information about horizontal and vertical exchange processes in the
upper ocean.
In situ measurements sometimes reveal sharp frontal interfaces in the
upper ocean (Zenk and Katz, 1975; Soloviev and Zatsepin, 1992; Yoder et
al., 1994; Soloviev and Lukas, 1997b). Many sharp frontal interfaces are
found in the temperature, salinity, and density records made during TOGA
COARE, using bow-mounted sensors (Soloviev and Lukas, 1997b;
5.4.1 Observations of sharp frontal interfaces in the western Pacific
warm pool
The western equatorial Pacific warm pool region – the TOGA COARE
domain – is characterized by heavy precipitation and generally light winds.
As a result, both heat and freshwater fluxes contribute substantially to the
buoyancy influx to the top of the surface mixed layer, and both temperature
and salinity stratification is found in the upper ocean (Lukas and Lindstrom,
1991). The thermohaline fields in the warm pool area are heterogeneous and
non-stationary to a surprising degree (Huyer et al., 1997); there are
numerous instances of sharp fronts in the surface layer of the ocean
(Soloviev and Lukas, 1997b).
Figure 5-17 shows a sharp front in a photograph taken from the bridge
of the R/V Kaiyo in the western equatorial Pacific warm pool during a
TOCS cruise (This is believed to be the same type of front as in the image
from space shown in Figure 5-16.) A description of the upper ocean
currents, thermohaline structure, and atmospheric forcing during TOCS can
be found in Matsuura et al. (2002).
The sharp frontal line in Figure 5-17 is roughly aligned in the east-west
direction and extended from one horizon to the other. The front is clearly
seen in the photograph because the wind waves to the north of the front
break much more intensively than those to the south of the front. There is
also some difference in ocean color across the front.
CTD stations made along 156
o E from 8
o N to 3
o S (prior to crossing the
front) reveal a surface salinity minimum at about 5
o N and the related
meridional salinity gradient at the equator (Figure 5-18). A CTD station
taken just north of the front (see map in Figure 5-19) reveals a nearly
314
Wijesekera et al., 1999a; Soloviev et al., 2002).