This project seeks to improve our understanding of how conditions in the high latitude oceans of both hemispheres changed over the course of the Earth's last major climate revolution from 2-4 million years ago (Ma). During this period, the northern hemisphere became glaciated, and large amplitude climate cycles began that continue to the present. The PI's propose to reconstruct time series (average sampling resolution of 3 ka) of past ocean surface temperature and biological activity from a number of deep sea sites in the N and S hemispheres with continuous sediment coverage across the 2-4 Myr time interval. State-of-the-art organic geochemical analyses of alkenone biomolecules will be utilized together with stable isotope measurements on benthic foraminifera to provide accurate dating of the samples. This project will test hypotheses that 1) temperature variability at the high latitudes grew substantially from 4 to 3 Ma and that glaciation was a late response (rather than a primary driver) to earlier shifts in the climate system; 2) the pattern of high latitude ocean cooling was more or less symmetrical in the two hemispheres, suggesting that declining greenhouse gas levels played a major role in the onset of northern hemisphere glaciation and 3) biological productivity shifted at approximately the same time in both hemispheres, indicating a major change in the planetary wind fields at high latitudes, and a major reorganization of the ocean carbon "pump" as northern hemisphere ice ages intensified.
Broader impacts of the project will include educational/outreach activities and the dissemination of a large and unique data set to the paleoclimatic/climatology community. This project will support undergraduate participation and will contribute to graduate and post-doctoral training and development. Research data will be posted on the NGDC Paleoclimate web site.
