Robinson et al., Supplementary Material
Age Control
Dating Southern Ocean sediments is, and always has been, exceptionally difficult due to
the lack of CaCO3 and the effects of sediment remobilization. Our goal in this study was
to understand the spatial variability in nutrient dynamics during the last glacial period and
the deglaciation. Each core studied has an independently determined published age
model, that when plotted together, showed widely variable timing for some of the key
markers of the LGM and deglaciation (Figure S1; [Anderson et al., 2009; Charles et al.,
1991; Chase et al., 2003; Kanfoush et al., 2000]. We re-examined the published
stratigraphies using three proxy records 1. opal concentration, 2. abundance of the marker
diatom species, E. antarctica, and 3. oxygen isotopes (Figures S1 and S2). Core TN05713PC04 was used as the pointer record because it is well dated, high resolution, and all
three stratigraphic marker datasets are available from it [Anderson et al., 2009]. Because
all cores had an available opal profile, we tuned each AZ opal record to the TN05713PC04 opal record by assigned the TN057-13PC04 ages for three tie points: 1. The mid
point of the early Holocene opal peak, 2. the mid point of the deglacial increase in opal
concentrations and, 3. the opal minimum during the LGM were selected. The E.
antarctica and 18O records were used to evaluate the adjusted ages and verify that the
opal based adjustment improved the timing agreement of the other chronological markers
(Figure S2). No changes were made to the age models of SAZ cores NBP9802-09PC
[Chase et al., 2003] and E11-2 [Ninnemann and Charles, 1997]. In the case of ages
beyond the 30 ka and the published ages of TN057-13PC4, we either used the published
age control (NBP9802-09PC, E11-2) or, in the case of RC13-259, we correlated the opal
record to nearby ODP 1094 for consistency (Figure 5).
Figure S1. Opal content versus published age (ka) for each of the sediment cores used in
this study. The cores are grouped into Subantarctic (top panel) and Antarctic (lower
panel) Zones to display the characteristic glacial-interglacial patterns, which run opposite
one another for the two regions. In the Antarctic, opal content tends to be low during the
LGM with an increase upon deglaciation. In the Subantarctic, opal is high in the glacial
and low in the Holocene.
Figure S2. Opal (A.-SAZ; B.-AZ), 18O (C), and E. Antarctica relative abundance (D)
records versus revised age. Again, the opal records are displayed by zone, with
Subantarctic records shown in the top panel and Antarctic records in the second panel.
The LR04 benthic oxygen isotope stack is shown in (C) for comparison [Lisiecki and
Raymo, 2005]. The revised ages present a more coherent timing of the LGM from each of
the stratigraphic markers than the original published ages did.
Species variation
Our understanding of the role of species specific isotope effects on the diatom 15N and
30Si records presented in this paper is far from complete. Moreover, the data were
collected prior to our preliminary understanding of the species effects and the assemblage
data were not compiled. There are, however, some data available to assess the potential
impact of species variations, as we currently understand them, in the literature. We have
compiled these data to show that the changes inferred for ODP 1094 based on its
proximity to TN057-13PC4 are likely valid. Two, 2-point (Holocene and LGM) records
from the SAZ (E11-2 and RC13-254 ) suggest that species related variations may be
minor to insignificant in these sites.
Figure S3. Downcore percent relative abundances of Fragilariopsis kerguelensis in cores
TN57-13PC4 [Nielsen, 2004], E11-2, and RC13-254 [Shemesh et al., 1989] (left axis)
and qualitative relative abundance in ODP 1094 (right axis) [Shipboard Scientific Party,
1999] plotted against age.
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