1994 Arctic Ocean Section
Our objective is to study the ostracodes in boxcore sections from the last
glacial maximum through Termination 1a and 1b to the present. Termination
1a marks the beginning of the last deglaciation, dated at 15.7 kyr ago (16,650
calendar years B.C.), and Termination 1b marks the end of the last glacial
deglacial transition, dated at 7.2 kyr ago (6,000 calendar years B.C.). Modern
surface and deep-sea circulation patterns and seasonal ice-free conditions are
believed to have been established in the northern North Atlantic and Arctic
Oceans following Termination 1b. These changes are in direct response to the
drawdown and final collapse of the great Northern Hemisphere ice sheets (the
Laurentide and the Fennoscandian). Quantitative analysis of the downcore
ostracode assemblages by the MAT will record upslope and downslope
migrations of ostracode assemblages in response to changing oceanographic
conditions due to changes in circulation following the decay and collapse of
these ice sheets.
To date, we have sampled five of the eighteen boxcores from sites on the
Mendeleyev Ridge and slope, the Lomonosov Ridge and slope, and the Pole
Abyssal Plain. All of these cores have well-preserved ostracodes, except for the
one from the Pole Abyssal Plain, which has poorly preserved ostracodes in the
top few centimeters downcore and no calcareous faunas of any type farther
downcore. The well-preserved downcore ostracodes will greatly aid in the paleo-
ceanographic history of the Mendeleyev and Lomonosov Ridges and other
ridge areas of the Arctic Ocean. High-resolution downcore AMS 14C and oxy-
gen isotope records, which will be made available by Glenn Jones and William
Curry of the Woods Hole Oceanographic Institution, will be indispensable to
the project. These records, when augmented by the ostracode biostratigraphy,
will allow us to pinpoint the timing of paleoceanographic events in the Arctic
Ocean over the last few centuries and millennia, and these data will help pre-
dict future change. We are separating out adult specimens of two species of
the deep-sea ostracode genus Krithe for use in downcore single-valve geochemi-
cal analyses by Paul Baker and Gary Dwyer of Duke University, who, in collab-
oration with Thomas M. Cronin, are developing geochemical proxy tools to
determine paleotemperatures and other physicochemical variables in the deep
ocean based on the shell chemistry of Krithe. New distribution records of the
ostracodes in coretop samples will allow us to fine tune the Arctic Ocean
Database, and these data will greatly enhance the resolution of the MAT. We
will also examine selected piston cores for much older paleoceanographic and
paleoclimatic records when samples from these cores become available.
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