Deep Sea CTDs and Shrunken Heads ... I Mean Cups

Yay we are shrinking cups again! Somebody tried to shrink a skull but it didn't go so well. How does this happen? Well it all starts with an instrument called a CTD. A CTD is a collection of bottles on a rosette that is lowered into the water. The operators on the ship have the option of collecting water at different depths by “firing” the bottles. This is the same instrument we used last year but this year its sampling is being directed by a Physical Oceanographer from NOAA’s Atlantic Oceanographic and Meteorological Laboratory (AOML).

Since we are collecting fish from these areas it is also good to get an idea of the physical attributes of where they are located. We could just take the latitude and the longitude of the location but what is the water like? The CTD gives us information on salinity (conductivity), temperature and depth at each location and all depths that it reaches.

It also gives us information on chlorophyll levels aka primary production aka the amount of plant matter in the ocean. They collect water and measure the chlorophyll to help validate/reinforce some of the information we get from satellites which measure chlorophyll from space. Scientist also collect water samples to track how much oxygen is in the water. They can use chemicals to preserve the oxygen in the water until they get back to land to analyze it.

The CTD also has this awesome piece of equipment on it known as the ADCP (Acoustic Doppler Current Profiler). They use this to measure how fast the water is moving at different depths. Current speeds change at different depths so this information is important.

Since we can sample water at any depth with the CTD the scientists decide to investigate the deep water movement of the Atlantic into the Caribbean Sea. Deep water most likely moves in and out of the Atlantic through deep passages such as Winward and Anedada. These are about 1500 – 2000 meters deep. Other passages barely hit 1000 meters deep.

While in these deep passages we can use the water pressure to push the air out of Styrofoam cups and shrink them to at least a third of their original size. So we put the cups into a mesh bag, attach them to a spot on the CTD and kind of let them ride the wave (not literally). The scientist do what they need to do with the CTD and voila, the cups come back up to the surface shrunken.

It’s a pretty cool souvenir, I did some cups last time too. Any who, I hope you learned something new from this post or even got a refresher, I know I did.

#researchcruise #equipment