Time Series of Oxygen Concentration, Methane Concentration and Methane Oxidation Rate Change of Deep Santa Barbara Basin Water Column

Qianhui Qin, University of California Santa Barbara, IGPMS, Santa Barbara, CA, United States, Frank Kinnaman, University of California Santa Barbara, Earth Science, Santa Barbara, CA, United States and Kelsey Gosselin, University of California Santa Barbara, Interdepartmental Graduate Program in Marine Science, Santa Barbara, United States
Abstract:
The Santa Barbara Basin (SBB) is a physically-constrained region experiencing seasonal deoxygenation. The maximum water depth is about 589m at the depocenter and the basin is fully enclosed >475m. Because of the depth difference between sill and depocenter, SBB bottom waters are poorly circulated and are regularly deoxygenated (to <1 μmolO2/L) following periods of increased surface productivity. Oxygen is replenished to the deep SBB around springtime, when upwelling events occur, then gradually return to the normal deoxygenated status, typically in the Fall. We are interested in building a time series to track the impact of seasonal deoxygenation on methane biogeochemical processes. Starting in late June 2019, we sampled the SBB every other week to track oxygen concentration, methane concentration, methane oxidation rate, and methane turnover time changes. Preliminary data show decreases in oxygen concentration and commensurate increases in methane concentration and methane oxidation rate through the summertime period of oxygen decline. The results of continued observations will also be presented.
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