Sept. 14, 2005
Jim Cowen

Alvin went down this morning for hydrogeology objectives. Wind and seas are up a bit today as a small front passes through. We are all hoping that weather does not worsen. Our UH team spent the day reevaluating our strategy for the remaining dives in light of progress so far, and preparing for tonight’s CTD operations. The lead PIs also met with the ship’s captain and department heads to discuss the cruise to date and the outlook for the remaining days. The night-time operations occupied the entire night. The main objective was to test the capabilities of an electrochemical analyzer to detect reduced sulfur species and other redox chemicals in buoyant and/or neutrally buoyant hydrothermal plumes. We were after particularly vigorous, young hydrothermal plumes—basically intense discharges of hydrothermal fluids that had been only recently discharged from the vents. The first CTD cast started down at around 2100 hrs and was brought back on board at around midnight. The CTD-rosette carried our electrochemical (voltammetry) analyzer. The instrument package descended to the about 5 m above the seafloor, passing through some very intense hydrothermal plumes with large temperature and particle anomalies. We will post some plots of the data later. Unfortunately, a programming error prevented the electrochemical analyzer from yielding usable data. So…we reprogrammed the analyzer and sent the whole package back down again. This time we found even more intense plumes near the seafloor and everything worked as it should have. The instruments were recovered at about 0330 hrs in the morning. We downloaded the electronic data and sampled the water that we collected with the 10 liter Niskin bottles (we electronically trip these bottles to close one at a time where we see something interesting in the temperature or particle signals). Our team finally drifted off to sleep for a few hours between 0430 hrs and 0600 hrs.