We arrived at our first sampling station at about 6 a.m. and started our first CTD cast of the trip. CTD stands for “conductivity, temperature and depth,” and is the name commonly used by the scientific community to refer to the instrument that measures these characteristics in the ocean. Although we were greeted by heavy rain, we didn’t let it stop us.
A rosette, which is the CTD attached to a round frame along with water sampling containers called Niskin bottles, is attached to an electronic cable and lowered to the desired depth.
Also attached to the rosette are two instruments called fluorometers – one calibrated to detect plant matter in the water, and another calibrated to detect hydrocarbons, such as oil. All of this is controlled from the ship to collect water samples and data at the desired depth and various depths along the way.
The CTD data is used to create a profile that graphically shows how characteristics such as temperature and salinity (which is inferred through conductivity) vary with depth.
By the time the sun set that evening, we had completed our fifth CTD. Everyone on the sampling team mastered their role quickly, allowing us to get slightly ahead of schedule.
Check back frequently during our mission to learn more about the methods our science team uses to analyze these water samples.