Antarctic Intermediate Water – Pacific sector variations over the past 150ka

A variety of ice core and marine records have demonstrated regular climatic shifts in atmospheric and ocean temperature and nutrient content between glacial and interglacial periods. Reconstructions of Antarctic Intermediate Water (AAIW) have primarily focused upon the changes in the Atlantic, yet AAIW flows northward throughout the world’s oceans after forming in subantarctic waters in the Southern Ocean. The trace metal content of benthic foraminifera is commonly used to reconstruct changes in the nutrient content and temperature of waters. Trace metal incorporation into foraminiferal tests is usually controlled by environmental parameters. This proves not to be the case in the aragonitic foraminifera Hoeglundina elegans. Multi-element analysis demonstrates the covariance of unrelated proxies, suggesting there is an internal control upon trace metal incorporation. Calculating changes in the nutrient content and temperature of AAIW was accomplished by measuring calcitic foraminifera from core MD97-2120 located on Chatham Rise, East of New Zealand. AAIW is warmer and more nutrient rich during interglacial periods. Combining the nutrient data with previously published stable isotopic data from the same core allows estimation of changes in salinity and the average windspeed in the region of AAIW formation. During glacial times temperature decreased and salinity increased as a result of the incorporation of freshwater into continental ice caps. Nutrient levels decreased, as did the average wind speed. These changes were a result of the motion of the Westerlies away from the subantarctic and an increase in levels of export production in the region of AAIW formation. This reduced the preformed nutrient content of AAIW. AAIW also displays Heinrich Event signatures, which are resolvable as shifts related to the motion of the glacial Westerlies causing a change in the measured carbon isotopic signature.EThOS - Electronic Theses Online ServiceGBUnited Kingdo