OOI Global Array Sampling Guidelines

Global Arrays are comprised of 2 sub-surface Flanking Moorings, 1 sub-surface Hybrid Profiler Mooring, and at the Irminger Sea Array 1 Surface Mooring. Open Ocean Gliders and Global Profiling Gliders are also present at the Arrays. Subsections below define the strategy for sampling in the vicinity of each type of platform. Given the number of depths required to be sampled at Global Arrays, a 24-bottle CTD rosette is required.

There are a few general guidelines which also inform the strategies defined below:

Nutrient data are useful when validating the Carbon system data.
Samples should span the full water depth at one site at least (typically HYPM).
Only sample Chlorophyll in the euphotic zone where there is a fluorescence signal detected on the CTD casts. Collect at least one sample per Array where the fluorescence signal is negligible to confirm lack of Chlorophyll.

Sampling at the Global Surface Mooring Location

Sample the full suite (O2, Salts, Carbon, Nutrients, Chlorophyll) at the surface, 12, 40, 80, 130 m.
Sample Carbon at additional depths where pH sensors are mounted (at 20, 100 m).
Also sample O2 and Salts at intervals below 130 where there are CTD sensors.

Sampling at Global Flanking Mooring Locations

Sample the full suite (O2, Salts, Carbon, Nutrients, Chlorophyll) at 30 m.
Sample Chlorophyll additionally at surface and the chlorophyll max.
Sample Nutrients additionally at 130 m.
Also sample O2 and Salts at 60, 90, 130, 250, 500, 1000, 1500 m

Sampling at the Global Hybrid Profiler Mooring Location

Sample the full suite (O2, Salts, Carbon, Nutrients, Chlorophyll) at 30 m.
Sample Chlorophyll additionally at surface and the chlorophyll max, and also at 150 m if there is fluorescence signal.
Sample O2 and Salts at 150 m, and ~4-6 places along the profiler path(s)

Sampling at Global Profiling Glider Deployment and Recovery Locations

Sample O2, Salts and Nutrients at the surface, 30, 50, 100 and 200 m.
Sample Chlorophyll at the surface, 30, 50, 100, and 200 m (if there is a fluorescence signal).

Sampling at Open Ocean Glider Deployment and Recovery Locations

Sample O2 and Salts at the surface, 30, 50, and every 100 m from 100-1000 m.
Sample Chlorophyll at the surface, 30, 50, 100, and 200 m (if there is a fluorescence signal).

Methodology

Salinity

Salinity measurements are performed following the methodology outlined in the WHOI Hydrography Blue Book, Automated Oxygen Titration and Salinity Determination (Knapp et al. 1990). Measurements are performed using a Guildline Autosal model 8400B salinometer (Guildline Instruments of Canada). Manufacturer stated accuracy and precision at 35 psu is +/- 0.003 psu and 0.0002 psu. IAPSO standard seawater is used to standardize the Autosal daily before runs.

Oxygen

Dissolved oxygen measurements are performed following the methodology outlined in the WHOI Hydrography Blue Book Automated Oxygen Titration and Salinity Determination (Knapp et al. 1990). Measurements are performed using a Metrohm Model 888 Titrando dosing device, with the titration endpoint determined amperometrically. Stated accuracy is 0.02 ml/l, with a precision of 0.001 ml/l.

Nutrients

All nutrient values are reported as the average of triplicate analysis on a single collected sample.

Carbon System

Carbon system measurements are performed by the Wang lab (Woods Hole Oceanographic Institution). DIC and TA measurements follow the methodology of Wang and Cai (2004) with uncertainties of 2 umol/kg. DIC measurements are performed with an Apollo Sci-Tech AS-C3. TA measurements are performed with an Apollo Sci-Tech AS-ALK2 and ROSS electrode. pH measurements follow the methodology of Clayton and Byrne (1993) with an uncertainty of 0.002 pH units using an Agilent 8453.

Chlorophyll and Phaeo

Analysis was completed using a Turner Designs Aquafluor Handheld 800446.