Advection and mixing of deep water masses in the tropical and western North Atlantic Ocean from thorium and protactinium isotopes
Final Report Abstract
Ventilation - How do 230Th and 231Pa in NADW evolve on its way south? The deep ventilation is the main driving force for the distribution of Pa and Th in the North Atlantic ocean. The application of Pa/Th as a proxy for ventilation is possible, but scavenging regimes need to be better understood. Particle Composition - Does the fractionation of Pa from Th depend on the particles? Yes, two different scavenging regimes (subarctic vs. N-Atlantic) are clearly visible. Within the N-Atlantic regime the fractionation is homogeneous and the particle effect does not obscure the ventilation effect. Bottom Nepheloid Layer - How does the Pa/Th signal change at the sea floor? The total Pa/Th is shifted to lower values due to bottom scavenging, however, the data from sediment and water column agree well. Future perspecitve. The data will be used for modeling the Atlantic circulation. Pa/Th as circulation tracer will be further developed. The oceanic Nd- and Pa/Th distribution pattern as a result of circulation will be better understood. The results on plutonium in particulate fractions are expected soon from Tim Kenna, Lamont (LDEO).
