ABSTRACT
High resolution paleo-climatological data from IMAGES core
MD97-2141 (8.80° N, 121.31° E) located in the Sulu Sea
within the western tropical Pacific reveal the first evidence of
continuous millennial-scale variability in surface ocean
conditions over the last 150,000 years. The millennial-scale
planktonic foraminiferal oxygen isotope (d18O) oscillations of Globigerinoides
ruber (G. ruber) between 30,000-65,000 years (MIS3) are
apparently in-phase with the Greenland ice core record and have
amplitudes 1/3 to 2/3 the size of the Sulu Sea
glacial-interglacial d18O amplitude of 1.3 %o. In the same
interval variations in planktonic foraminiferal Mg/Ca suggest that
millennial-scale sea surface temperature (SST) variations were
small (0.6-1°C) and out-of-phase with d18O indicating that
d18O variability was mainly driven by changes in surface water
salinity. This result implies that the linked East Asian monsoon
and the western Pacific Intertropical Convergence Zones, both
influencing the Sulu Sea, have fluctuated on the same millennial
time scale as higher latitude climatic systems.
To further investigate the origin of the MIS3 d18OG.ruber
variations, the relative abundance of all planktonic foraminifer
species and the d18O values of four planktonic foraminifer species
was determined during MIS3. Combined, these data provide a
detailed reconstruction of changes in the western tropical Pacific
thermocline structure. The d18O composition of the mixed-layer
foraminifera (G. ruber and Globigerinoides sacculifer) and
upper thermocline species (Neogloboquadrina dutertrei)
displays poor similarity with the d18O of the sub-thermocline
dweller Globorotalia crassaformis. d18OG.crassaformis
shows larger d18O variations (~1 %o) than the surface dwellers
indicating past fluctuations in the influence of high salinity
North Pacific Tropical Waters that currently enter the Sulu Sea
across the Mindoro Strait during the months of the winter monsoon.
The faunal and isotopic data suggest a switch from winter to
summer monsoon predominance after 55 kyr. However this
predominance is interrupted by at least three episodes of
increased winter monsoon between 42-46 kyr.
Comparison of the proxy SST and planktonic foraminiferal d18O
profiles for the last glacial/interglacial sequence from fourteen
cores in tropical and subtropical oceanic settings indicates that
termination I in d18O coincides with SST change at some sites,
while d18O lags SST by 3,000 years at other locations. A
comparison of SST and d18O shows a linear increase in SST from
glacial to interglacial conditions. Sites where SST is leading the
d18O record indicate fresher conditions during the LGM, and these
sites are all located in areas influenced by increased atmospheric
water vapor during times of todays La Nina.
Dannenmann, S., 2001. A multi-proxy study of planktonic
foraminifera to identify past millennial-scale climate variability
in the East Asian Monsoon and the Western Pacific Warm Pool.
Unpublished PhD dissertation, State University of New York at
Albany. 165pp., +xii
University at Albany Science Library call number: SCIENCE
MIC Film QE 40 Z899 2001 D36
Copies of this PhD dissertation can be ordered
from Proquest UMI
Front matter (title,
table of contents, abstract, acknowledgements) - 0.3MB pdf
file
Figure pages in dissertation
(colour
and greyscale figures, with captions): - 9.4MB pdf file
Appendices 1-7 (digital
pdf data tables; ocr from page scan images) - 1.1MB pdf file
(scan
pages pdf - Ax1
- Ax2
- Ax3
- Ax4
- Ax5
- Ax6
- Ax7)
- (0.1 to 1.3MB pdf files)
Return to PhD dissertations completed
in the Geological Sciences Program, University at Albany