Abstract

Ocean circulation is thought to play a key role in the Earth’s climate system because surface ocean currents transport heat from the equator to the poles and deep ocean water sequesters carbon dioxide from the atmosphere. Geochemical proxies measured on the biogenic components of marine sediments have been widely-utilized to reconstruct past ocean changes. However, because these proxies are controlled by biology and chemistry in addition to physical circulation it is difficult to use them to quantitatively reconstruct physical oceanographic parameters such as deep water advection speed. I will present new data of coupled sediment grainsize and source measurements, from highly resolved grain-size separates across the clay and silt fraction, allowing reconstruction of the dispersion of fine detrital sediment by ocean currents. We have initially worked in the North Atlantic because it hosts a strong deep current that transports sediment from geological sources with distinct and well-constrained geochemistry (i.e. Iceland and the Canadian Shield). Our core-top data shows that grainsize separation in the 0-63 m range allows “unmixing” of North Atlantic marine sediment samples into at least three different sources; the finest grain-sizes are derived from Scandinavia and Iceland and have been transported great distances by deep current flow, while the coarser fractions are locally derived. Time slice reconstruction during the last deglaciation place new constraints on glacial-interglacial changes in sediment sources, input, and ocean circulation pathways.

Quaternary Discussion Group seminar