2016) show that the pycnocline
is mostly decoupled from the low-salinity surface layer, with low turbulence in the deeper layer.
Along seven selected longitudinal transects, vertical profiles of temperature and density were obtained to detect the thermocline and pycnocline
depth, and confirm where the coastal upwelling likely occurred using further evidence from Aqua MODIS SST and chlorophyll satellite images (https://coastwatch.noaa.
Differently from the open ocean, the main pycnocline
is located relatively close to the sea surface in winter (normally at a depth of 30-50 m) and much deeper (at a depth of about 100 m) in summer.
The Brazil Current flows southward along the continental slope of the SBB (Silveira et al., 2000) transporting warm and saline Tropical Water in the upper mixed layer and cold South Atlantic Central Water (SACW) at the pycnocline
. An additional water mass exists in the neritic zone, the warm Coastal Water, with lower salinity than the Tropical Water (Castro Filho and Miranda, 1998).
These neutrally buoyant gelatinous egg masses are thought to maintain their location in the water column by floating at the interface between water layers of slightly different densities (above the pycnocline
The presence of a stronger and shallower OMZ off Peru could be due to: 1) a high rate of remineralization influenced by high primary productivity, 2) a lack of ventilation due to the presence of a strong pycnocline
that keeps subsurface waters isolated from the atmosphere, plus deoxygenation of equatorial currents that are the main source of oxygen in this zone (Stramma et al 2010.) and; 3) the long residence time of the waters with a cumulative reduction of oxygen (Czeschel et al.
The step height Ah we called here is the height difference of the pycnocline
. The whole two-layer system keeps quiescent at the initial time.
As water masses of this gulf are often strongly stratified, motions above the main pycnocline
are only weakly connected with the motions in the lower layer.
However, the stratified model takes into account the formation of the pycnocline
in the sea.
These waves occur in the ocean's interior and propagate horizontally, concentrating their energy around the oceanic pycnocline
(Small & Martin, 2002).
They also derived a more complex functional density model in order to account for a large seawater density gradient within the pycnocline
, caused mainly by a combination of decreasing water temperature and increasing salinity with the increasing ocean depth.