Internal waves and short‐scale distribution patterns of chlorophyll in the Strait of Gibraltar and Alborán Sea

Abstract

A selection of ASAR images have been analyzed, together with instantaneous images of surface chlorophyll recorded with MERIS and MODIS, in order to study the relationship between the physical and biological processes associated with internal waves in the Strait of Gibraltar and Alborán Sea. The images show peak levels of chlorophyll at the coastal edges to the north and south of the Camarinal Sill (CS) during the generation of internal waves, and peak levels of chlorophyll associated with the wave fronts as they travel into the Alborán Sea. The images have been compared with in‐situ data. The results seem to indicate that, during the generation of the internal waves, a suction process takes place by which coastal waters rich in chlorophyll are drawn towards the center of the channel and then accompany the internal waves as they move towards the Alborán Sea.

Submesoscale, tidally-induced biogeochemical patterns in the Strait of Gibraltar

“…This suggests that surface divergences and coastal suction are associated with these smaller topographic internal arrested waves typical of neap tides . These tongue-shaped structures were also found in satellite data by Vázquez et al (2009) during spring tides, but we present here the first evidence of this process during neap tides (Figures 5 C,F,I and 7 C).…”

“…This hypothesis was recently confirmed by Vázquez et al (2009), who used in-situ data and satellite images showing how the generation of internal waves induced transport of chlorophyll-enriched coastal waters to the channel and their advection towards the Alboran Sea. Bartual et al (2011) found evidence of a change in the plankton primary production pattern concomitant with the presence of an internal bore in the main channel of the strait, which was consistent with the arrival of active coastal plankton communities.…”

“…This zone has specific dynamics within the Gulf of Cadiz with an intense bloom in September due to a highly localized input of nutrients in the surface layer from mixing and tide-topography interactions (Vargas-Yáñez et al, 2002). At the same time, the dominant mesoscale circulation seems to increase the water residence time in this region, protecting this area from the intense hydrodynamics of the main channel (Vázquez et al, 2009) and, hence, increasing biological productivity. Consequently, there was a considerable reduction in chlorophyll and other biological variables in the sampled region (Table II and Figure 5 C,F,I ).…”

“…The generation of internal waves over the Camarinal Sill during spring tides Vázquez et al, 2008) has been observed to coincide with the suction of coastal waters (e.g., Vázquez et al, 2009), which introduce high-chlorophyll patches within the main along-strait circulation (Macías et al, 2006;2008b;Bartual et al, 2011). In our data, a high chlorophyll patch was observed at the eastern entrance of the strait during HW-2 at spring tides (Figure 4 C), which could originate from the suction of coastal waters in the previous outflowing event (see details of the mechanics and timing in Macías et al, 2006).…”

Generation sites of internal solitary waves in the southern Taiwan Strait revealed by MODIS true-colour image observations

“…Based on sea surface roughness in sunglint area, these waves can also be imaged on high-resolution optical imagery (Apel et al 1985), such as Satellite Pour l'Observation de la Terre (SPOT) (Mitnik et al 2000). In addition, the chlorophyll images derived from ocean colour measurements of the Seaviewing Wide Field-of-view Sensor (SeaWiFS) and Moderate Resolution Imaging Spectroradiometer (MODIS) have also been successfully employed in the study of ISWs (da Silva et al 2002;Vázquez et al 2009;Pan et al 2012;Muacho et al 2013). However, the application of ocean colour images in studying ISWs is severely limited by their relatively low resolution (1.1 km) and, in some cases, by the interference of upwelling signatures at the ocean surface.…”