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depleting the nutrients. Today, site MD95-2041 is more
strongly influenced by the filament often extending south-
ward from Lisbon than site MD95-2042 and during glacial
times, when due to the lower sea level, the coastline was
displaced farther offshore; also, the local upwelling along the
Sines coast (Figure 1b) would be in the vicinity of site
MD95-2041. High glacial productivity at this site outside of
the ice-rafting events of MIS 2 was also observed by Voelker
et al. [2009]. In consequence, these two closely spaced sites
reveal that a local phenomenon like upwelling can strongly
modify the paleodata and result in locally different signals
that are not related to the millennial-scale climate variability.
5.3. Comparison Between the Last and Previous Glacial
Cycles
To verify if the temperature gradients described in section
5.1 and the associated frontal positions also existed during
previous glacials, we are using the records of core MD95-
2040, the site located north of the front, and spliced records
from the offshore sites off the Sines coast (Figure 5). The
planktic and benthic stable isotope records indicate that both
sites reliably recorded the glacial/interglacial cycles and ex-
perienced millennial-scale variability in the surface and
deep-water hydrography.
Figure 5.
Latitudinal gradients in surface and deep-water properties between the Porto seamount (core MD95-2040) and
the Sines coast (MD95-2042 in gray, MD01-2444 in gray, and MD01-2443 in black) over the last 420 kyr. (a) The
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G. bulloides records of cores MD95-2040 [de Abreu et al., 2003; this study], MD95-2042 [Cayre et al., 1999; Shackleton
et al., 2000], and MD01-2443 [de Abreu et al., 2005; Martrat et al., 2007]. (b) Alkenone-based mean annual SST records
for cores MD95-2040 [Pailler and Bard, 2002], MD01-2444, and MD01-2443 [Martrat et al., 2007]. (c) Foraminifer
assemblage-based summer SST. (d) Percent N. pachyderma (s) records of cores MD95-2040 [de Abreu et al., 2003; this
study], MD95-2042 [Cayre et al., 1999; Salgueiro et al., 2010], and MD01-2443 [de Abreu et al., 2005; this study].
Benthic (e)
δ
13
C records of cores MD95-2040 [de Abreu et al., 2003; Schönfeld et al., 2003; this study],
MD95-2042 [Shackleton et al., 2000], and MD01-2443 [de Abreu et al., 2005; Martrat et al., 2007]. Numbers mark
marine isotope stages (MIS) and terminations (T) II, III, and IV. H11 indicates Heinrich event 11. Gray bars highlight
events discussed in the text.
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O and (f)
δ
δ
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