340-ky-long d18Oplk and SSTMg/Ca records from core MD97-2120
compared to the Vostok dD record (A) G. bulloides d18O was measured
at a sampling interval of 2 cm, equivalent to a time step of 192 ± 83 years.
(B) SSTMg/Ca record (time step, 931 ± 405 years). The Mg/Ca scale
is also given. Mg/Ca ratios were converted to SST using the equation of Mashiotta et al.
[Mg/Ca = 0.4740.107T (T, temperature)].
(C) dD record (time step, 126 ± 100 years) of the Antarctic Vostok ice core on the
orbitally tuned age scale of Shackleton. Beyond ~230 ky, the resolution of
d18Oplk is equal to or exceeds that of the Vostok record.
dD documents air temperature changes that are indicated along the dD axis as deviations from
the modern value (DT) Vostok DT and our SSTMg/Ca are scaled to the
same temperature range to facilitate comparison of both records.
(D) Residual d18Oplk [variability above 5 ky was removed from
d18Oplk in (A)]. Amplitudes of the residual d18Oplk
are systematically increased during glacials, indicating increased climate variability during
periods of enhanced global ice volumes. Steep d18Oplk gradients
labeled TI through TIV are glacial Terminations I through IV. Blue vertical bars mark
the Antarctic Cold Reversal (ACR) [14 to 12.4 ky, and a prominent d18Oplk
reversal in midTermination III. Gray vertical bars denote d18Oplk
and SSTMg/Ca excursions not seen in the Vostok dD record. In contrast to the ACR,
the d18Oplk reversal in TIII does not coincide with a drop in
SSTMg/Ca, suggesting a local seawater d18Ow anomaly at this time.
The mid-TIII reversal is not as clearly developed in the Vostok dD record but exists
as a distinct anomaly in the Vostok Ar record. Age control points used to construct
the age model are shown along the bottom axis as follows: 14C AMS dates (gray),
Kawakawa tephra (red), tie points for correlating the benthic d18O section to
that of northeast Atlantic core MD95-2042 (blue), and tie points for correlating
SSTMg/Ca to the Vostok dD record (black).