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Hereby, one focus will be on the glacial upper water column
structure as this will allow identifying boundaries between
subpolar- and subtropical-dominated waters with implications
for the position of hydrographic fronts.
persistent feature, however, is an eastward extension of
the filament along the southern Portuguese shelf break and
slope [Relvas and Barton, 2002] where, when westerly
winds prevail, the waters merge with locally upwelled waters
(Figure 1b).
The Portugal Current (PC), which branches of the North
Atlantic Drift off Ireland, consists of the PC per se in the
open ocean and the PCC along the slope during the upwell-
ing season. The PC advects surface and subsurface waters
slowly equatorward [Perez et al., 2001; van Aken, 2001] and
is centered west of 10°W in winter (Figure 1a) [Peliz et al.,
2005]. The PC
2. MODERN HYDROGRAPHIC SETTING
The western Iberian margin represents the northern part of
the Canary/northwest African eastern boundary upwelling
system, and its upper water column hydrography is marked
by seasonally variable currents and countercurrents (Figure 1a).
Upwelling and its associated features (Figure 1b) dominate
the hydrography generally from late May/early June to
late September/early October [Haynes et al., 1993] and is
driven by the northward displacement of the Azores high-
pressure cell and the resulting northerly winds. Intense up-
welling on the western margin is linked to topographic
features like Cape Finisterre, Cape Roca, and Cape São
Vicente (Figure 1b) or submarine canyons [Sousa and Bri-
caud, 1992]. The Lisbon plume, linked to Cape Roca, can
either extend westward as in Figure 1b or southward toward
Cape Sines. During intense upwelling events, the filament
off Cape São Vicente extends southward and is fed by the
Portugal Coastal Current (PCC) [Fiúza, 1984]). The more
is subsurface component is the Eastern North
Atlantic Central Water (ENACW) of subpolar (sp) origin,
whichisformedbywintercoolingintheeasternNorth
Atlantic Ocean [Brambilla et al., 2008; McCartney and
Talley, 1982]. The PCC, on the other hand, is a jet-like upper
slope current transporting the upwelled waters southward
[Alvarez-Salgado et al., 2003; Fiúza, 1984]. At Cape São
Vicente, a part of this jet turns eastward and enters the Gulf
of Cadiz [Sanchez and Relvas, 2003]. In the Gulf of Cadiz, it
'
flows along the upper slope toward the Strait of Gibraltar
[Garcia-Lafuente et al., 2006], then called the Gulf of Cadiz
Slope Current [Peliz et al., 2007]. This current either forms
an anticyclonic meander in the eastern Gulf of Cadiz or
Figure 1. (a) Map of the western Iberian margin with core sites and surface water circulation in winter as summarized by
Peliz et al. [2005]. The location of core MD95-2039 (white circle), which is mentioned in the text but for which no data are
shown, is also indicated. (b) NASA Aqua MODIS satellite-derived chlorophyll a picture (http://oceancolor.gsfc.nasa.gov/
FEATURE/gallery.html) for 13 September 2005 showing the regions most affected by upwelling along the Iberian margin
(lighter shades) and the extensive
filaments off capes Finisterre, Roca, and São Vicente. Dots mark the same core locations
as in Figure 1a (except for MD95-2039).
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