The Portugal Current System
The Portugal Current itself is poorly defined spatially because of the intricate interactions between coastal and offshore currents, bottom topography, and water masses. The system is comprised of the following main currents:
1) The Portugal Current, which is a broad, slow, generally southward-flowing current that extends from about 10°W to about 24°W longitude;
2) The Portugal Coastal Countercurrent (PCCC), a southward flowing surface current along the coast during downwelling season, mainly over the narrow continental shelf to about 10-11°W longitude and flow from about 41-44°N; and
3) the Portugal Coastal Current (PCC), a generally poleward current that dominates over the PCCC during times of upwelling and like the PCCC, extends to about 10-11°W from shore, also present mainly from 41-44°N, where flow is 13.5 ± 5.7 cm s-1 (Perez et al., 2001; Martins et al., 2002).
The Portugal Current system is supplied mainly by the intergyre zone in the Atlantic, a region of weak circulation bounded to the north by the North Atlantic Current and to the south by the Azores Current (Perez et al., 2001). This current system should be envisaged within a very broad perspective of the dynamics of eastern oceanic boundary layers as outflow from the Mediterranean Sea has a significant influence on the underlying water masses that are part of the PC system (Ambar & Fuiza, 1994). The PC system is also influenced by the more dominant neighboring Canary and Azores Currents (Perez et al., 2001). The literature cites several inconsistencies in the seasonal patterns of this current system. As noted by Maze and others (1997), "these apparently contradictory views reveal the need for a better definition of the Portugal Current in terms of lateral extent and possible temporal variability and should be addressed by repeated surveys in the periods of well-established winter and summer regimes."
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Analysis of CTD measurements, drifter data, and satellite images from the past several decades taken from the Portugal Current system itself has revealed the hydrology of the region and proven its geostrophic circulation to include a complex and not completely understood interaction between underlying water masses as well as meteorological conditions. Other significant influences on the Portugal Current System are seasonal winds, freshwater runoff from the Iberian Peninsula, the bottom topography found along the continental shelf break and slope, and the three main underlying water masses that are found below the seasonally variable surface layer. (Perez et al., 2001; Ambar & Fuiza, 1994; Huthnance et al., 2002; Martins et al., 2002). Meddies (eddies comprised of Mediterranean water) are also present, particularly in the region of the Tagus Abyssal Plain (about 11-13°W; 37-39°N) and along the shelf break, which are thought to be controlled mainly by the topography of the seafloor (Bower et al., 2002; Cuelho et al., 2002; Cherubin, 2000; Huthnance et al., 2002).
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http://oceancurrents.rsmas.miami.edu/atlantic/portugal.html
http://oceancurrents.rsmas.miami.edu/atlantic/portugal_2.html
http://oceancurrents.rsmas.miami.edu/atlantic/portugal_3.html