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DWT already implied: the deeper
flowing MOW was ad-
mixed into the GNAIW and led sometimes to a better venti-
lation of the intermediate-depth water column along the
western Iberian margin. Extremely low benthic
Because the western Iberian margin is an upwelling area,
upwelling can always affect the climate records. A clear indi-
cation for upwelling events, modifying climate records and
thus leading to different paleodata for the same events in
close vicinity, is given by the differences observed between
cores MD95-2041 and MD95-2042 on the Sines coast. Core
MD95-2041, located closer to the coast, experienced much
more variability in its G. bulloides stable isotope records that
can only be explained by upwelling. Upwelling also seems to
be driving some of the variations observed in the planktic
stable isotope records of core MD95-2040 during MIS 6.
A second
13
C values,
on the other hand, were recorded at 4602 m during MIS 2 and
4 (Figure 9h). This record is from core MD03-2698 [Leb-
reiro et al., 2009] located in the Tagus Abyssal Plain and
shows that bottom waters in this deep basin were hardly
renewed during the glacial maxima. Even today, the deep
abyssal plains off Iberia can only be ventilated by
δ
ows
through a few deep gaps [Saunders, 1987]. However, addi-
tional modi
13
C signal due to remi-
neralization of organic matter transported down the canyons
by the frequent turbidites [Lebreiro et al., 2009] could also
have played a role.
cation of the benthic
δ
hydrographic phenomenon affecting the
water column in the eastern North Atlantic is the MOW.
During glacial times and especially the Heinrich events and
Greenland stadials, the MOW settled deeper in the water
column allowing it to be admixed into the intermediate-depth
water masses. Thus, records from 2465 m water depth indi-
cate imprints of MOW by warming events, so far con
“
local
”
8. CONCLUSIONS
rmed
for Heinrich events 4 and 5, and by a better ventilation of
these water depths relative to the western basin. Owing to the
admixing, the boundary between GNAIW and AABW was
located between 2465 and 3100 m on the Iberian margin. As
a consequence, Greenland-type climate oscillations can be
traced down to this level, while the deeper sites follow the
Antarctic-type of climate change. The deepest basins on the
Iberian margin apparently experienced periods of reduced
water mass renewal during MIS 2 and 4.
For the last glacial cycle, we now have a comprehensive
picture regarding latitudinal and vertical gradients in the
water column along the Iberian margin, and it is hoped that
the existing data can serve as grounds for regional climate
models of abrupt climate change events.
The combination of various high-resolution records al-
lowed studying how events of abrupt climate change affected
the water column along the western Iberian margin and
which latitudinal and vertical boundaries existed. The abun-
dance of records from the Sines region on the southwestern
margin, furthermore, permitted assessing signal modi
cation
due to upwelling.
The surface water records from the Iberian margin clearly
reveal that two fronts intercepted with the margin during the
Heinrich stadials of the last glacial cycle and during extreme
cold events of previous glacial periods. During the last glacial
cycle, the Polar Front was located near 41°N, leading to the
harshest climate conditions in the northern regions. The Arc-
tic Front was located about 2° farther to the south, near 39°N,
and might have coincided with the Azores Front. The latitu-
dinal positioning of these fronts led to steep temperature
gradients along the margin with SST
su
increasing by 1°C per
degree of latitude, i.e., from 4°C at 42°N to 10°C at 36°N. The
foraminifer data, furthermore, showed that Heinrich events
became more frequent and had stronger hydrographic impacts
during the last glacial cycle. Similar events were recorded
only with Heinrich event 11 during termination II and along
with the Heinrich-type events during early MIS 8 and termi-
nation IV. MIS 6 was overall a warm glacial with subtropical
waters dominating the hydrography along the southern Iberian
margin and penetrating at least as far north as 40.6°N during
much of the period. Hydrographic conditions north and south
of the 39°N boundary were, in general, similar during MIS 2
and 4, but MIS 4 like MIS 6 seems to have more strongly been
affected by subtropical subsurface waters. MIS 6, however,
differed from its younger counterparts in regard to the in-
creased seasonality and the extreme variations in the nutrient
level of the subtropical surface waters.
Acknowledgments. We are indebted to Yvon Balut, IPEV, and
the crew of R/V Marion Dufresne as well as the IMAGES project
for the recovery of excellent core material. The EU Access to
Research Infrastructure PALEOSTUDIES program is acknowl-
edged for the
financial support that allowed the multispecies stable
isotope analyses. Monika Segl and the Geosciences Department
(FB 5) of the University of Bremen are thanked for hosting A. V.
and L. A. during their respective PALEOSTUDIES stays. Addition-
al thanks for excellent stable isotope results go to Helmut Erlen-
keuser (Leibniz Labor, University Kiel) and Mike Hall and James
Rolfe (Godwin Laboratory, University of Cambridge). A. Rebotim
is thanked for her help in completing the benthic isotope records of
core MD95-2040. The Fundação de Ciência e Tecnologia (FCT)
supported this research through the MOWFADRI, SEDPORT and
INTER-TRACE projects and postdoctoral fellowships to A. V. and
L. A. A. V. furthermore acknowledges her Ciência 2007 grant.
Finally, L. A. would like to remember all the dedication, incentive,
and enthusiasm of the late Nick Shackleton and his guidance and
collaboration throughout many of the studies involving these par-
ticular Iberian margin cores.
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