CTD profiles at the Hydrostation S site have been collected since station cruise #60643 in October 1988 and although there have been some changes during the past thirty-two years as a result of new instrumentation or methodologies, the the general sampling procedures have been consistent with those detailed in the BATS method manual version #4 (Knap et al., 1997).

In summary, the CTD is operated as per SeaBird's suggested methods with data collection at the full scan rate of 24 Hz. The CTD is powered up and allowed to stabilize at 12 m prior to profiling and once stable (typically 4 minutes) the CTD is brought back to the surface from which point the profile begins with typical descent rates of 0.7-1.0 m/s, depending on weather conditions. Water samples are collected on the upcast and prior to triggering bottles the CTD is kept at the desired depth for a minimum of 60 seconds to ensure that entrainment from the following wake has subsided. Once the water sample is taken the CTD immediately continues with the upcast at an ascent rate of 0.7-1.0 m/s.

The basic system used to acquire CTD data is a Sea-Bird SBE 9plus CTD, with an internal Digiquartz pressure sensor, a Sea-Bird SBE-3F temperature sensor, a Sea-Bird SBE-4 conductivity cell and a Sea-Bird SBE-5 pump. Additional sensors include the Sea-Brid SBE-43 dissolved oxygen sensor, the WET Labs C-Star or Chelsea/Seatech
Transmissometer, the Chelsea Aqua 3 Fluorometer, and the Biospherical/Licor PAR/Irradiance sensor. Present configuration also includes a secondary temperature sensor, a Sea-Bird SBE-35 temperature sensor, a secondary conductivity sensor and pump, which are connected independently from the primary units. The temperature and conductivity sensors are connected by a standard Sea-Bird TC-duct (clear, low viscous type), which ensures that the same parcel of water is sampled by both sensors, improving the accuracy of the computed salinity. The dissolved oxygen sensor is connected downstream from the conductivity cell and the flow rate through this sensor configuration is maintained at a steady rate by the inertia balanced SBE-5 pump.

Ship information:

R/V Weatherbird I (Jan 1983 - September 1989)
R/V Weatherbird II (October 1989 - February 2005)
R/V Atlantic Explorer (May 2006 - Present)
R/V Endeavor (December 2024)