PHOSPHORUS GEOCHEMISTRY AND EXPORT PRODUCTION IN THE SUBANTARCTIC SOUTH PACIFIC OCEAN

Ice core records indicate that atmospheric CO₂ varied considerably on glacial/interglacial time scales; however, what drives this variability is unknown. One set of hypotheses suggest increased primary productivity during glacial intervals led to CO₂ drawdown. Productivity has varied considerably in the past, but the extent, timing, impacts, and the importance of specific geographic regions remain poorly understood. The Subantarctic South Pacific is an area that is crucial to the understanding of both glacial climate and paleoproductivity. Unfortunately, few studies have investigated large regions of the South Pacific because it is so remote. The results from the bulk geochemical analysis (phosphorus and metals) of two cores in the Subantarctic South Pacific, MV0502-04JC (50°S) and ODP Leg 189, Site 1171 (48°S) will be presented. P is an important nutrient that limits productivity in the oceans on geologic time scales. Records of P burial can be useful when trying to reconstruct paleo-export production. Average P concentrations for marine sediments are ~30µmol/g. Average P concentrations at 4JC are typically low at the top of the core and increase steadily with depth to a maximum value of 50µmol/g, while at Site 1171 P concentrations oscillate between ~10 and 40µmol/g with maxima of ~60µmol/g. Results from a sequential extraction (SEDEX) will also be presented for both sites. The results will ultimately help to evaluate the relative importance of Subantarctic sites in Pleistocene climate change.