Dataset: CTD - Profiles

Sampling and Analytical Methodology:
A single SBE9plus CTD (S/N 831) was used for all casts and was deployed with all sensors and pumps as recommended by SBE. In situ salinity and dissolved oxygen check samples were collected to calibrate conductivity and dissolved oxygen sensors (see MV1310 Preliminary Cruise Report).

The primary conductivity and temperature sensors failed on the up-casts of stations 19, 21-27 and on the down-cast of stations 28 and 29. The secondary sensors were chosen for consistent reporting.

In addition to the 0.0073 second temperature and conductivity standard alignment factor an offset of 0.08 seconds was applied for each station and sensor configuration.

On casts 1/1, 2/1, 3/1, 3/2, 10/1, 12/2, 13/1, 14/1, 15/1, 17/2, 17/3, 17/4, 21/1, 33/1 the temperature, conductivity or oxygen sensors had not stabilized before casts had started. A delayed start was applied to the cast pressure sequence to reduce spiking and smooth fits from surface. No more than 10 m of surface data was interpolated from any of the aforementioned casts.

CTD Pressure: Paroscientific Digiquartz pressure transducer (S/N 831-99677) last calibrated in November 2012 at the SIO/STS Calibration Facility. Residual pressure offsets indicated that an offset of -0.84350 dbar be applied to pressure sensor calibration.

CTD Temperature: A SBE35RT Digital Reversing Thermometer sensor was not used, therefore only standard laboratory calibrations were used for T1 and T2 sensors. The secondary sensors were chosen for consistency. An offset observed in cast 12/3 was adjusted based on data from adjacent casts at the same station. Sensors used: The SBE3plus secondary (T2/03-2309) was swapped for (T2/03-4307) after cast 12/1. The SBE3plus secondary (T2/03-4307) was swapped for (T2/03-2309) after cast 12/3. The SBE3plus secondary (T2/03-2309) was swapped for (T2/03-2322) after cast 28/1.

The 95% confidence limits for the MV1310 data mean low-gradient differences are ± 0.00137°C for T1-T2 .The 95% confidence limit for deep temperature residuals (where pressure > 1800 dbars) is ± 0.00105°C for T1-T2 .

CTD Conductivity: Pre-cruise calibration coefficients were applied to convert raw frequencies to conductivity. Secondary sensors were compared to conductivity calculated from check sample salinities using CTD pressure and temperature. Sensors used: The SBE4C secondary (C2/04-2819) was swapped for (C2/04-2765) after cast 28/1. The 95% confidence limits are ± 0.00445 relative to bottle salinities for all salinities, where T1-T2 is within ± 0.01°C; and ± 0.000781 relative to bottle salinities for deep salinities, where pressure is more than 1800 decibars. Within the context of having only a small number of salinity check samples, when questionable check samples were ignored, the final CTD salinities (and temperatures) appear to meet a reasonable standard, though less reliable than the reference cruises (P16N (2009) and P17N (2001)).

CTD Dissolved Oxygen: SBE43 dissolved oxygen sensor (DO/43-0275) was calibrated to dissolved oxygen bottle samples taken at bottle stops. At the end of the cruise, standard and blank values for bottle oxygen data were smoothed, and the bottle oxygen values were recalculated (changes were less than 0.01 ml/l for most stations). Standard deviations were 3.142 µmol/kg for all oxygen and 1.365 µmol/kg for deep oxygen. CTD dissolved oxygen ml/l data are converted to µmol/kg units.