OOI Regional Cabled Array Sampling Guidelines

RCA includes 3 Shallow Profiler Moorings, 3 Deep Profiler Moorings, 2 Benthic Experiment Packages (BEP) and a host of seafloor instruments, along with primary nodes and junction boxes along the 900 km of high-power, high-bandwidth backbone fiber optic cables. Niskin bottles attached to the Remotely Operated Vehicle (ROV) capture water samples near seafloor instruments. In general, water samples are collected for analysis at depths that correspond to instrumentation making in situ measurements at platforms and profilers. A 24-bottle CTD rosette is allowed to equilibrate at target depths for at least 1 minute or more (depending on conditions) and a minimum of 30 seconds between duplicates.

Sampling at the RCA mooring locations entails the full suite of measurements (O2, Salts, Carbon, Nutrients, Chlorophyll). Sampling near the seafloor instruments vary depending on which sensors are present at the location.

Carbon System Measurements

Carbon system measurements were provided by the laboratory of Burke Hales at Oregon State University. All carbon parameters were reported at in situ temperatures. Calculated carbon parameters were generated by Hales using custom software routines and published values for the relevant carbon chemistry constants. The carbonic acid dissociation constants were from Millero (2010), with full-resolution constants provided by Millero via private communication and equal to Lueker’s constants at salinities greater than 25. Additional constants used in the calculations were Kw from Millero (1995), Kb from Dickson (1990), Ksp for calcite and aragonite from Mucci (1980), and Kh from Weiss (1973). Alkalinity was modeled as HCO3⁻ + 2CO3²⁻ + B(OH)4⁻ + OH⁻ − H⁺.