We are developing and deploying an in situ cavity ring-down laser absorption spectrometer capable of measuring carbon stable isotopic composition (δ13C) of both methane and carbon dioxide in the deep ocean. Leveraging several technical advances developed with our in situ mass spectrometer (ISMS), this new instrument allows measurement of stable isotopes in real-time, improving our ability to biogeochemically map “hotspots” of processes such as anaerobic methane oxidation (AOM) in environments such as hydrocarbon-rich cold seeps and brine pools. To date, this instrument has surveyed a number of cold seeps in Monterey Bay at depths of ~1000m, proving itself by facilitating the isotopic detection of subsurface AOM.
Figure 1. The “laser spectrometer” is really an integrated cavity optical spectrometer that is designed to measure the proportion of gases — and their isotopes — in its sample chamber. Working with engineers at Los Gatos Research Inc, we have created an instrument capable of working in the deep ocean.
Figure 2. Many of our deep sea expeditions use remotely operated vehicles (or ROVs) to deploy our instruments and collect samples. Shown here is the control room for the ROV Ventana, a workhorse sub hosted on the RV Point Lobos. Sampling by the laser spec can be seen in the overhead monitors.