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vertical gradients existed along the Iberian margin, i.e., in a relatively restricted
area, but suf
cient paleodata now exist to validate regional climate models for
abrupt climate change events.
1. INTRODUCTION
The Heinrich and Greenland stadials left their imprints
also farther down in the water column related to changes in
the Atlantic meridional overturning circulation (AMOC)
strength. One well-documented change was the increased
in
The western Iberian margin is a focal location for studying
the impact and intensity of abrupt climate change variability.
Sediment cores retrieved there at a depth of more than 2200 m
showed that the
uence of lesser ventilated southern sourced waters, in
particular, the Antarctic Bottom Water (AABW), due to the
shoaling of the interface between Glacial North Atlantic
Intermediate Water (GNAIW) and AABW [Margari et al.,
2010; Shackleton et al., 2000; Skinner and Elder
18
O of planktic foraminifer exhibits changes
similar to those found in Greenland ice core records (e.g.,
δ
δ
18
O record of benthic foraminifer varies
in a manner more reminiscent of the Antarctic temperature
signal [Shackleton et al., 2000]. Thus, core sites retrieved at
this margin allow studying interhemispheric linkages in the
climate system. In addition, the southern edge of the North
Atlantic
'
s ice-rafted detritus (IRD) belt [Hemming,2004;
Ruddiman, 1977] intercepted with the margin, so that melting
icebergs reached the margin during Heinrich and Greenland
stadials of the last glacial cycle and during ice-rafting events
of preceding glacials [Baas et al.,1997;Bard et al., 2000; de
Abreu et al., 2003; Moreno et al., 2002; Naughton et al., 2007;
Sánchez-Goñi et al., 2008; Zahn et al., 1997]. Following the
work of Sánchez-Goñi and Harrison [2010] who documented
that on the Iberian margin, the duration of the related surface
water cooling and the Heinrich ice-rafting event per se can
differ, Greenland stadials associated with Heinrich events are
referred to as Heinrich stadials. Otherwise, the Greenland
stadial and Greenland interstadial nomenclature in this chapter
follows the Integration of Ice-core, Marine and Terrestrial
Records (INTIMATE) group [Lowe et al., 2001, 2008] and
the North Greenland Ice Core Project members [2004]. Only
during Heinrich stadials did the Polar Front reach the Iberian
margin [Eynaud et al., 2009] associated with abrupt and
intense cooling in the sea surface temperature (SST) [Bard et
al.,2000;Cayre et al., 1999; de Abreu et al.,2003;Martrat et
al., 2007; Naughton et al.,2009;Vautravers and Shackleton,
2006; Voelker et al., 2006]. Using the records of three core
sites, Salgueiro et al. [2010] were the
18
O
ice
), whereas the
δ
eld, 2007;
Skinner et al., 2003] when AMOC was reduced or shut off.
Along with this change, ventilation of the deeper water
column was reduced [Baas et al., 1998; Schönfeld et al.,
2003; Skinner and Shackleton, 2004], and nutrient levels
were raised [Willamowski and Zahn, 2000]. In the middepth
range, another water mass is also important on the Iberian
margin: the Mediterranean OutflowWater (MOW). Evidence
for MOW changes mainly come from core sites in the Gulf of
Cadiz, i.e., the southern margin. Voelker et al. [2006] showed
that the lower MOW core reacted to abrupt climatic changes
and was stronger during most parts of the Heinrich stadials
and during Greenland stadials in accordance with evidence
for deep convection in the Mediterranean Sea [Kuhnt et al.,
2008; Schmiedl et al., 2010; Sierro et al., 2005]. Similar
evidence also emerged for the upper MOW core [Llave et
al., 2006; Toucanne et al., 2007], and for MIS 2, it has been
shown that the MOW was not only strengthened, but settled
signi
cantly deeper, as deep as 2000 m, in the water column
[Rogerson et al., 2005; Schönfeld and Zahn, 2000]. Thus,
abrupt climatic changes affected all levels of the water col-
umn on the western Iberian margin.
During the last decades, many cores have been retrieved
from this region and studied in high-resolution, but the records
were seldom combined for a comprehensive regional recon-
struction. In this review, records from several cores are being
compiled to look at regional variability in the response to
abrupt climate change events and to trace latitudinal, longitu-
dinal, and vertical gradients during the last glacial cycle. All of
this is important information needed for model/
data comparisons to validate how well climate models repro-
duce past conditions [e.g., Kjellström et al., 2010] and which
local phenomena might have to be included in regional models
to correctly represent the past conditions. Thus, this study aims
to describe how hydrographic conditions changed along with
the abrupt climate events and to relate them to the potential
driving mechanisms. After having identi
first to show that while
cooling was recorded at all sites during Heinrich events, there
existed a clear boundary between 40°N and 38°N that affected
not only the SST but also productivity. They attributed this
boundary to a stronger in
uence of subtropical surface and
subsurface waters in the southern region, which is in accor-
dance with evidence from nannofossils [Colmenero-Hidalgo
et al.,2004;Incarbona et al., 2010] and planktic foraminifer
stable isotope data [Rogerson et al., 2004; Voelker et al.,
2009]. Vo e l k e r e t a l . [2009], furthermore, showed that upper
water column strati
cation was diminished during the Hein-
rich events of marine isotope stage (MIS) 2, especially along
the western margin.
ed gradients during
the last cycle, their existence at the same position and with the
same intensity during previous glacial cycles will be tested.
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