Remotely sensed sea surface thermal patterns in the Gulf of Cadiz and the Strait of Gibraltar: Variability, correlations, and relationships with the surface wind field

Abstract

Satellite image sequences (covering periods of a few days throughout the annual cycle) of the waters off southern Iberia have been analyzed in conjunction with concurrent surface wind speed data from coastal stations. Qualitative analysis reveals a large degree of temporal and spatial variability in the thermal signature of the sea surface over periods of both a few days and several months. During the summer, a cool seasurface temperature signature extends from the western Iberian coast around Cape St. Vincent and eastward as far as Faro. At the same time, a warm signature originating on the Iberian coast between Faro and Cadiz extends into the Strait of Gibraltar. These two features are shown to sometimes adopt more westerly positions, and the strait experiences regions of cool thermal signature originating at its southern side. During winter, the surface flow into the Mediterranean through the Strait of Gibraltar is anomalously warm and appears to come from the interior of the Gulf of Cadiz. Quantitative measurements show that temporal variability over timescales of a few days at individual sites is maximum in midsummer. Spatial thermal variability over the whole region is found to peak toward the end of the summer. Statistical analyses of the data reveal the coupling between the surface wind field in the Gulf of Cadiz and the surface thermal pattern (especially during the summer). Wind‐induced, across‐stream upwelling in the Strait of Gibraltar, although dynamically subordinate to tidal and density‐driven processes, is shown to occasionally dominate the surface thermal signature.

Seasonal evolution of cholorophyll-<i>a</i> and cyanobacteria (<i>Prochlorococcus</i> and <i>Synechococcus</i>) on the northeast continental shelf of the Gulf of Cádiz: relation to thermohaline and nutrients fields

“…During summer, the circulation in the region is mainly anticyclonic (García et al 2002, Criado-Aldeanueva et al 2006a, shifting to cyclonic during winter (García-Lafuente and Ruiz 2007). Some characteristic mesoscale structures have been identified during the summer period: the "Huelva Front", a warm-cold-warm area southeastward of Cape Santa María (Stevenson 1977), the "Portuguese upwelling zone" close to Cape San Vicente, and the "Tarifa eddy", a mixing zone at Cape Trafalgar (Fiuza et al 1982, Fiuza 1983, Folkard et al 1997. Different water masses have been described in the Gulf of Cádiz: Surface Atlantic Water (SAW) and Surface Water (SW), located in the central part of the basin and over the continental shelf respectively; North Atlantic Central Water (NACW), between 100 and 700 m depth (Folkard et al 1997); and Mediterranean Water (MW) below 700 m depth.…”

Variations in Mediterranean–Atlantic exchange across the late Pliocene climate transition

“…While seasonal changes in SSS are < 0.5, SST variability is more prominent and may result in brief temporary reversals of SST gradients (MEDATLAS, 2002;Rogerson et al, 2010). The Alboran Sea shows colder temperatures than the Gulf of Cádiz during all seasons due to upwelling, with occasional exceptions in summer under the influence of easterly winds (Bakun and Agostini, 2001;Folkard et al, 1997;Peeters et al, 2002;Rogerson et al, 2010;Sarhan et al, 2000;Shaltout and Omstedt, 2014). The δ 18 O composition of present-day seawater is thus considered to be largely determined by changes in SST (Rogerson et al, 2010).…”

“…At the surface (0-∼ 200 m), inflowing Atlantic water enters the Mediterranean basin (Millot, 1999). On its way, it mixes with upwelled MOW within the Strait of Gibraltar (Folkard et al, 1997) and with surface waters of the Alboran Sea, creating the Modified Atlantic Water with temperatures of 15-16 • C and a salinity of 36.5 (Millot, 1999), which follows two anticyclonic gyres, the Western Alboran Gyre (WAG) and the Eastern Alboran Gyre (EAG; Fig. 1) (Gascard and Richez, 1985;Vargas-Yáñez et al, 2002).…”

Variations of Mediterranean–Atlantic exchange across the late Pliocene climate transition

“…While seasonal changes of SSS are < 0.5, SST variability is more prominent and may result in brief temporary reversals of SST gradients (MEDATLAS, 2002;Rogerson et al, 2010). The Alboran Sea shows colder temperatures than the Gulf of Cadiz during 200 all seasons due to upwelling, with occasional exceptions in summer under the influence of easterly winds (Bakun and Agostini, 2001;Folkard et al, 1997;Peeters et al, 2002;Rogerson et al, 2010;Sarhan et al, 2000;Shaltout and Omstedt, 2014). The  18 O composition of present-day seawater is thus considered to be largely determined by changes of SST (Rogerson et al, 2010).…”

“…At the surface (0 -~200 m), inflowing Atlantic water enters the Mediterranean basin (Millot, 75 1999). On its way, it mixes with upwelled MOW within the Strait of Gibraltar (Folkard et al, 1997) and with surface waters of the Alboran Sea, creating the Modified Atlantic Water with temperatures of 15-16 °C and salinity of 36.5 (Millot, 1999), which follows two anticyclonic gyres, the Western Alboran Gyre (WAG) and the Eastern Alboran Gyre (EAG) (Gascard and Richez, 1985;Vargas-Yáñez et al, 2002). The northern Alboran Sea is affected by upwelling along the Spanish coast providing nutrients and enhanced 80 primary productivity (Minas et al, 1991;Peeters et al, 2002;Sarhan et al, 2000).…”