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Figure 1. Taylor Dome record of atmospheric CO
2
over the most recent glacial termination [Smith et al., 1999] and the
INTCAL [Reimer et al., 2004] reconstruction of atmospheric
14
C excursion record from the Baja margin by
Marchittoet al. [2007] occurs during the rise in deglacial atmospheric CO
2
and the decline in atmospheric
14
C. The
Δ
Δ
14
C.
Δ
[Toggweiler et al., 2006]. Depending on the ratio of upwelling
to downward carbon export, this could reduce the
may have increased over some parts of the Southern Ocean
[Abelmann et al., 2006]. Instead, biogenic opal accumulation
rates, a proxy for export production, was highest during the
last deglaciation when atmospheric CO
2
was rising [Ander-
son et al., 2009]. Ice core records of NH
4
+
and SO
4
+2
further
indicate there was no substantial change in marine produc-
tivity within the Southern Ocean during glacials [Wolff et al.,
2006]. In fact, ice core records show that dustiness and
transport of iron to the Southern Ocean began to decrease
~4
flux of
metabolic CO
2
to the glacial atmosphere. However, recent
estimates suggest that ventilation of CO
2
through the Southern
Ocean today is roughly balanced by the uptake of CO
2
by
marine primary productivity and export of carbon to the deep
ocean [Gruber et al., 2009]. For the Southern Ocean to have
played a primary role in regulating atmospheric CO
2
changes
on glacial/interglacial time scales, its biological system must
have worked in tandem with dynamical changes in ocean
ventilation to reduce the net
8 kyr before the beginning of the rise in atmospheric CO
2
during the last glacial termination [Wolff et al., 2006]. Con-
sequently, the available records do not provide clear evi-
dence that there was major changes in the biological
sequestration of metabolic carbon in the Southern Ocean
during the last glacial. The extent to which iron affected
carbon export in the Southern Ocean and in
-
flux of metabolic CO
2
to the
atmosphere [Gruber et al., 2009; Sigman et al., 2010].
If Southern Ocean biological and physical processes were
responsible for glacial/interglacial CO
2
variations, there
should be evidence to support this idea in proxy records
collected from the Southern Ocean. Martin [1990]
rst sug-
gested atmospheric CO
2
would decrease during glacials due
to increased biological export production in the Southern
Ocean that would result from increased wind-blown iron.
The
uenced atmo-
spheric CO
2
is therefore highly uncertain [Archer et al.,
2000; Boyd and Trull, 2007; Boyd et al., 2000].
Carbon cycle models that attempt to simulate a drawdown
of atmospheric CO
2
via a Southern Ocean mechanism depend
signi
flux of soluble iron to the Southern Ocean did increase
during glacials [Gaspari et al., 2006; Martínez-Garcia et al.,
2009; Wolff et al., 2006]. However, proxy data indicating
marine carbon export south of the Polar Front was not
substantially higher during the last glacial maxima when
atmospheric CO
2
was at a minimum [Downes et al., 1999;
Masson-Delmotte et al., 2005], although export production
cantly on various parameterizations employed, particu-
larly a biological response to Fe availability. Recent modeling
results suggest that Fe fertilization would have a smaller
overall in
uence on CO
2
sequestration than early estimates
indicated [Fischer et al., 2010]. Furthermore, in experiments
using a dynamical atmosphere-ocean model coupled to an
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