Changes in biogenic and detrital fluxes across the last two glacial terminations at the Shatsky Rise

The Shatsky Rise is located within strong gradients in SST and biological productivity between the subtropical and subarctic Pacific gyres. The region is highly sensitive to changes in atmospheric and oceanic circulation on glacial-interglacial timescales, which affect the delivery of Fe-bearing dust and other major nutrients, respectively. Here we use a range of proxies in an attempt to determine the effects of changes in westerly winds and gyre boundaries on dust delivery and biological productivity. We present 230Th-normalized fluxes of opal, Corg, CaCO3, and detrital material at ODP Site 1208 over the last two glacial terminations, extending to 145ka. Opal, Corg, and carbonate are products of surface biological productivity, while most detrital material at this site arrives in the form of windborne East Asian dust. In addition, we calculate the concentration of authigenic U as an indicator of relative oxygenation of the sediment water interface. We observe elevated opal and dust fluxes during the last two glacial maxima, and a decrease in both components during deglaciations. Authigenic U shows distinct peaks at the onset of both terminations. The peak at the penultimate deglaciation is also associated with a large peak in opal flux, while the peak in authigenic U during the last termination does not appear to be associated with any large changes in biogenic fluxes. We compare our records with other data from the subtropical-subarctic transition zone, and suggest that our data are consistent with northward shift of the mean position of the westerly jet and subarctic front during deglaciations.