Prospects For a Carbon ARGO [ II ]

Understanding the dynamics and sedimentation of biologically fixed particulate organic and inorganic carbon (POC and PIC) is fundamental to the prediction of future levels of atmospheric carbon dioxide. Over the last four years LBNL has been working to bridge a major 'space-time' gap in upper ocean carbon cycle observations. We have launched twelve robotic Carbon Explorers built on SIO's Orbcomm/GPS enhanced Sounding Oceanographic Lagrangian Observer (SOLO). These 'souped up' versions of ocean-profiling ARGO floats, operating in remote and stormy seas, have returned in real-time year-long high-frequency records of POC variability and recently have explored the systematics of carbon sedimentation to kilometer depths. We briefly recap the success of a new fast profiling optical sensor for PIC (sensitivity better than 0.1 μ M) which was deployed during routine CTD/rosette casts during the R/V Ron Brown June - July 2003 reoccupation of WOCE A16N (Iceland to Madiera) in the N Atlantic Ocean. Our primary aim is to report on the development of paired autonomous imaging sediment traps designed to optically record hourly variations of POC and PIC flux at depth for weeks to months. Preliminary analysis of 22 days of observations achieved this year near Hawaii indicate a major contribution of zooplankton parts to carbon flux at station ALOHA. We further recorded multiple events of simultaneous arrival of fecal material and associated zooplankton feeders. This supports the importance of such animals in determining the attenuation of carbon flux to the deep sea. The success of the Carbon Explorers, the new PIC sensor, and the developing capability for season to year-long high frequency records of POC and PIC carbon sedimentation in the very observation-poor but biologically-active upper kilometers of the ocean suggest excellent prospects for a 'Carbon-ARGO'.