NOAA/WDS Paleoclimatology - South China Sea ODP1144 260KYr Mg/Ca SST

High-resolution sea surface temperatures (SST) derived from Mg/Ca
ratios of Globeriginoides sacculifer at ODP Site 1144 were reported
to reveal the SST changes during the last 260 ka in the northern
South China Sea (SCS). The results indicate an average Holocene SST
of about 26.7°C, about 3.6°C increase from LGM to the Holocene,
and higher temperature during MIS 5.5 than the Holocene. These agree
well with other foraminifer Mg/Ca and Uk37 SST records in this region.
The Mg/Ca records suggest warmer SSTs during MIS 3 in the northern SCS,
compared with those in the eastern Pacific. Strong East Asian summer
monsoon during MIS 3 indicated by paleoclimate records from nearby
continents may account for it. Step-wise increases during terminations
are shown in our SST record, and the beginning of deglacial warming
occurs at about 19 ka, which precedes the change of oxygen isotopes,
suggesting a tropical driven forcing for the SST change in the northern
SCS. This is further supported by a robust semiprecessional cycle
centering at ~9.1 ka in the spectra of the SST record, which is absent
in that of the oxygen isotopes. However, tropical driven forcing seems
not to be indicated in another Mg/Ca SST record in the northern SCS
[Oppo, D.W. and Sun, Y.B., 2005. Amplitude and timing of sea-surface
temperature change in the northern South China Sea: Dynamic link to
the East Asian monsoon. Geology, 33 (10): 785–788.]. The discrepancy
may be caused by different post-deposition dissolutions of foraminifer
tests at these two sites. Details about the modification of foraminifer
Mg/Ca ratios after burial, however, are not well known in this region,
and further studies are needed.