Water from the Depths

Water from the Depths

By Patrick Mears

A few days into the IO9N line everyone is settled into their roles onboard the RV Revelle.   Most people work 12-hour shifts that start at either noon or midnight. Three to four times a day we send down a CTD rosette that measures conductivity, temperature and pressure as well as 36 niskin bottles to collect water from various depths. 

From these bottles, groups onboard measure a large range of water parameters including dissolved gases, carbon, nitrogen, nutrients and various others.

It is the job of the CTD watch standers to prepare the rosette for deployment, monitoring its decent, and to coordinate with the winch operator to collect water samples at specific pressures. 

[CTD Watch Standers and interested parties beginning their training for a practice cast. Photo credit Leticia Barbero]

[CTD watch standers, Amanda Fay, Net Charoenpong, and Patrick Mears leading the consoles. Photo credit Carmen

Once the CTD is onboard, the CTD watch standers assist in sampling where needed, and direct the sampling by ensuring different parameters are measured in the order of most to least time-sensitive. For instance, once a niskin bottle is opened, air will slowly diffuse into the water and this can alter the concentration of gases (and temperature) in the sample. So the dissolved gases, like CFCs and oxygen, should be sampled first, and ensuring this order is the responsibility of the CTD “Bottle Cop.”

Once the sampling is complete the CTD is prepped for the next deployment.   The whole process from deployment, recovery, sampling, and preparing the CTD for the next deployment takes five to six hours.

As we go along in the cruise we will be focusing on different lab groups and what they are specifically measuring. 

[Sampling on station 88, onboard the R/V Revelle. Photo credit Carmen Rodriguez]