Author: Leah Chomiak
Meet Jay & Andy – Jandy, as they are collectively known. As the most beautifully orchestrated scientific tag-team out there, these guys are responsible for the heartbeat and blood flow of our scientific endeavor out here on the Gulf: maintaining and running the CTD. The two have worked together for the past 6 years, clearly demonstrated in their friendship and mutual enthusiasm onboard. The two work at NOAA’s AOML laboratory in Miami, FL; Andy in the engineering department, and Jay in the physical oceanography department. The two love being out at sea, seeing the world from a different point of view, but most importantly “escaping Miami traffic”, as Jay puts it.
The two are CTD geniuses, knowing the ins and outs of each sensor, wire, and software program pertaining to data collection. The CTD, which stands for Conductivity, Temperature, and Depth, is the most highly regarded oceanographic instrument used to assess a water column, from the surface to the ocean floor. Lowered by a conductive wire off the starboard side of the ship, this mighty instrument serves the needs of 20 of the 24 scientists on board through means of water samples and profile data. Although the instrument is collectively termed a CTD, the actual CTD probe is merely a small part of the totality of the instrument. Within the steel cylindrical frame lie 24 Niskin bottles for sampling water at different depths, two ADCPs (Acoustic Doppler Current Profiler) for measuring the speed and direction of water currents, a transmissometer for detecting the chlorophyll maximum, and a series of sensors for measuring oxygen, temperature, and depth within the water. Prior to arriving on station, our CTD techs ensure all sensors are clean, functioning, and talking to the main computer. Sensors must be kept moist in between stations when the instrument is onboard the ship, this is done by connecting tubing filled with water to the probes. Before the CTD is deployed the techs remove the tubes and turn the sensors on. On deck, there is one CTD tech and one Survey tech suited up to deploy and successfully recover the instrument. The techs are outfitted with hard hats, steel-toed boots, a life jacket, and a tether to the ship when handling the instrument, to ensure safety as a 3000lb instrument dangles on a wire above their heads. Sitting in the main lab of the ship, the Chief and Co-Chief scientists stand by a series of computer monitors that show the output of the instrument sensors, and as the CTD is lowered through the water column, profiles of temperature, salinity, oxygen, and density appear, giving the scientists a first-hand look at the structure of the water column. The scientists use radios to communicate to the deck techs and wire operator, directing them when to lower and raise the CTD in the water. The scientists at the computer look for interesting features in the profiles shown to them on the screen. Are there any unusual temperature spikes or oxygen minimums? Based on these features and common features of a water column (thermocline, mixed layer, oxygen minimum zone, chlorophyll maximum) the scientists tell the wire operator where to stop the CTD, and then a signal is sent through the wire to close a Niskin bottle at that depth. As the CTD works its way back up the surface, Niskin bottles are triggered to close at other specified depths. The techs then recover the CTD and bring it back on board safely, the sensors are cleaned and tubes replaced, and a plethora of data is now ready for scientists to use in their analysis. As mentioned in previous blogs, once the CTD is back on board, a sampling frenzy ensues.
Jay and Andy make sure the sensors are calibrated by comparing the sensor values to that manually determined through salinity and oxygen analysis, the job I do here on board. Jay and Andy are certainly the silent heroes of scientific data collection here on the Brown, keep up the good work boys!