Chromophoric DOM: Natural Tracer of Circulation and Diagenesis

Since 2003 the UCSB Global CDOM Project has studied the distribution of chromophoric (light absorbing) dissolved organic matter (CDOM) in the Atlantic and Pacific basins along the CLIVAR/Carbon Repeat Hydrography sections. Measurable amounts of CDOM are detectable in all ocean basins at all depths, and presumed CDOM sources and sinks in the ocean interior are very slow (as assessed using CFC-derived tracer ages). These properties make CDOM a potentially useful tracer of ocean circulation in intermediate water masses (such as subtropical mode water) and in the main thermocline, and possibly in the deep ocean as well. We here present a summary of the CDOM abundance (as light absorption coefficient) and spectral characteristics (exponential shape factor) in relation to oxygen, dissolved organic carbon and tracers in intermediate and deep water masses, with an eye toward discussing possible applications of CDOM as an ubiquitous tracer in the world ocean.