A Review of Abrupt Climate Change Events in the Northeastern Atlantic Ocean (Iberian Margin): Latitudinal, Longitudinal, and Vertical Gradients - Abrupt Climate Change: Mechanisms, Patterns, and Impacts - page 18

Figure 2. Salinity profile of World Ocean Circulation Experiment (WOCE) transect A3 [Schlitzer, 2000] (http://www.
ewoce.org/) with dots marking from top to bottom depths of core sites MD99-2336, MD99-2339 (both not on correct
longitude), MD01-2444, MD95-2042/MD99-2334K, and MD03-2698. Water mass abbreviations are ENACW, Eastern
North Atlantic Central Water; MOW, Mediterranean Outflow Water; NADW, North Atlantic Deep Water; NEADW,
Northeastern Atlantic Deep Water; AABW, Antarctic Bottom Water; LDW, Lower Deep Water.

enters the Mediterranean Sea as Atlantic inflow [Garcia-
Lafuente et al., 2006; Sanchez and Relvas, 2003].
The Azores Current (AzC), another current branching of
the Gulf Stream/North Atlantic Drift, and the associated
Subtropical Front reveal large meanders between 35°N and
37°N in the eastern North Atlantic. While most of the AzC
recirculates southward, its eastern branch flows into the Gulf
of Cadiz [Johnson and Stevens, 2000; Peliz et al., 2005;
Vargas et al., 2003], where it feeds the offshore flow (Figure
1a). Ocean models indicate that the AzC flow into the Gulf is
quite significant [Penduff et al., 2001], and they link the
existence of the current itself to the entrainment of surface
to subsurface waters into the MOW [Jia, 2000; Oezgoekmen
et al., 2001]. Between October and March, when the Iberian
Poleward Current (IPC) (Figure 1a), also a branch of the
AzC, becomes a prominent feature off western Iberia, the
thermal Subtropical Front (at ~17°C) is shifted northward
and reaches the SW Iberian margin [Pingree et al., 1999].
Along with this shift, AzC waters tend to recirculate from the
Gulf of Cadiz into the region off Sines (Figure 1a). Peliz et
al. [2005] observe a recurrent frontal system, the Western
Iberia Winter Front, which follows the thermal Subtropical
Front in the south but then meanders northward and separates
the IPC from the PC (Figure 1a). The IPC, extending down to
400 m, transports warm and salt-rich waters of subtropical
origin [Frouin et al., 1990; Haynes and Barton, 1990] and
can be traced into the Bay of Biscay. The IPC ' s subsurface or
undercurrent part conveys ENACWof subtropical (st) origin

poleward year round. ENACW st , which is formed by strong
evaporation and winter cooling along the Azores Front
[Fiúza, 1984; Rios et al., 1992], is poorly ventilated, warmer,
and saltier than its subpolar counterpart. ENACW is the
source for the water upwelled from May to September,
and in general, ENACW st is upwelled south of 40°N and
ENACW sp north of 45°N. In between, either water mass can
be upwelled depending on the strength of the wind forcing.
Between 500 and 1500 m, the water column along the
western Iberian margin is dominated by the warm, salty
MOW (Figure 2) that is formed in the Gulf of Cadiz by
mixing of Mediterranean Sea with Atlantic water, the above
mentioned entrainment. Owing to the mixing, the MOW
splits into two cores centered at about 800 and 1200 m
[Ambar and Howe, 1979], which flow as undercurrents
northward along the western Iberian margin. Facilitated by
the margin ' s topography (e.g., canyons, capes, and sea-
mounts), the MOW cores shed many eddies [Richardson et
al., 2000; Serra and Ambar, 2002], called meddies, which
greatly contribute to the MOW ' s admixing into the wider
North Atlantic Basin. Below the MOW at a depth around
1600 m, Labrador Sea Water (LSW), the uppermost compo-
nent of the North Atlantic Deep Water (NADW), can be
found on the margin north of 40.5°N [Alvarez et al., 2004;
Fiuza et al., 1998]. Deeper down in the water column,
Northeastern Atlantic Deep Water (NEADW) and Lower
Deep Water (LDW) are found. LDW (>4000 m) is warmed
AABW that enters the eastern Atlantic Basin through the