20,000 leagues under the sea

We are reaching the end of week 2 of our six-week Atlantic passage on the RRS James Cook, and what does this mean? Well, the whirlwind of the first few days are behind us, the night shift are slowly getting used to curry for breakfast and we’ve run out of marmite.

Our food-related issues aside however, we have now completed over 50 CTD (conductivity, temperature and depth) profiles throughout the Florida straights and off into the deeper waters of Atlantic Western Basin. As we steam on, we are now sending the CTD to greater and greater depths and can only marvel at what’s down below. The last few profiles have been approximately 5,500m and we’re getting deeper.

For every metre you descend in the ocean the pressure increases by approximately 1 decibar. So, by the time you have reached 6,000m this is equivalent to having around 16 Boeing 747s sitting on top of you. As a way to gauge just how much pressure this is, and what our equipment has to withstand, we have been conducting our own little experiment with the help of Ludlow Junior School. Every student from Willow class in Year 3 created a design on a polystyrene cup which were brought onboard. We then stuffed the cups with tissue paper, put them in one of Brian’s socks, attached the sock securely to the CTD and sent it down to the depths of the Atlantic. This is what they looked like when they came back up.

For every depth at each station we are aiming to achieve measurements of carbon and oxygen to an accuracy of 1 to 2 micromoles and temperature to 2 millidegrees. Sometimes the sensors that read the profile as they descend are affected by the pressure. This is why we take bottle samples; to calibrate our measurements and ensure we are achieving the accuracy we know our equipment is capable of. Therefore, to make sure we are sampling correctly, the night shift now have a very strict routine. The music goes on, the dance move of the day gets decided and we have our daily dose of bad jokes from our resident Irishman, Dan. Some of my favourites include: “My sister had baby girl there, she named her Denise. I wonder if she has a son will she call him Denephew?”; “Where do creatures of the Atlantic Ocean store their beers?” – “Mid-Atlantic Fridge”. To top it off, there’s been some pretty epic sunrises.