UC Santa Cruz

Marine particles are a main vector by which the biological carbon pumpin the ocean transfers carbon from the atmosphere to the deep ocean. Marineparticles exist in a continuous spectrum of sizes, but they can be functionallygrouped into a small, suspended class (which constitutes most of the total particlemass) and a large, sinking class (which contributes most of the particle flux). Thesetwo classes are connected by aggregation and disaggregation processes. Theinterplay of processes that create, aggregate, and destroy marine particles determinesthe strength and transfer efficiency of the biological pump. Measurements ofradiocarbon, barium, and organic biomarkers on suspended and sinking particleshave provided qualitative insights into particle dynamics, and measurements ofthorium isotopes have provided quantitative estimates of rates. Here, we reviewwhat has been learned so far about particle dynamics in the ocean from chemical2measurements on suspended and sinking particles. We then discuss future directionsfor this approach.