When telling people you’re headed out to sea, the response you often get is, “that’s so cool!”, which it is of course, but it’s also a lot of mundane work. Days go by in a blur, each day running into the next without much to distinguish one from the next. There are no weekends (well, they don’t mean anything to us anyway) and days are distinguished by weather changes and pirate or fire drills (every Tuesday!) and the slow but steady increase in our station numbers. Today we reached station 162 and officially entered the Bay of Bengal. We have been seeing signatures of bay water for the last couple days, but now the surface waters are quite fresh (lower salinity values than you would find in the open ocean thanks to runoff from rivers on the continent). We also expect to see some important changes (increases) in iron and nutrient levels as we move north.
But what is life like for a scientist on a research vessel out at sea? Here is a quick glimpse into what days are like for me, as a CTD watch-stander. My shift begins at 11:50pm and lasts until 11:50am. I get up around 10pm to enjoy some downtime and get ready for the day. I’ll often do some yoga and go outside for some stargazing. Around 11:30pm I’m up in the galley, scrounging for breakfast, scoping out the leftovers from dinner the night before, and making some coffee (iced coffee specifically- hot coffee tastes strange on the ship. Something about our desalinized water I think.) Then I head down to the computer room to see where we are. Science happens 24 hours on the ship so at midnight we could be transiting between stations, sending the rosette down to the bottom, or sampling the water we retrieved. Each station lasts about 6 to 7 hours total so you have an idea of the schedule for the next day, but lots can happen in the 12 hours you are off shift so you never really know. |
Today, when I started my shift, the rosette had just gone in and was heading down to the bottom. During the descent, we watch the data being sent back in real-time as it descends at 60 meters per minute. The values we are watching include temperature, salinity, oxygen, and fluorescence. We monitor these values to ensure that the sensors are all working well and also to determine which depths samples should be taken from including the oxygen minimum zone, the mixed layer depth, and the deep chlorophyll maximum. After an hour or so (depending on how deep the ocean is below us), we slow the descend, and using the altimeter data being sent back from the rosette, we lower it to 10 meters above the bottom. This is the most stressful part as it is very important that we not hit the bottom, causing damage to many of the instruments on the package. On my previous cruise, the altimeter would kick in and report readings when we were about 100m off the bottom. On this rosette, the altimeter kicks in at 30m above the bottom if we are lucky. A bit more stressful in this case! I am happy to report that we have not hit the bottom though. |
At the deepest depth, we ‘fire’ a bottle, capturing water in an air-tight container from the deepest depth of the ocean, and begin the slow return to the surface. Along the way, we fire our remaining 34 bottles (we are now working with a 35 bottle rosette as one of the bottles was continuing to misfire due to a faulty magnetic mechanism that releases the hold on the bottle’s caps). There are standardized schemes of sampling depths that we use, rotating between 3 schemes, in order to capture a complete picture of the ocean with the best resolution possible. These schemes, and our observations during the descent, determine the depths of the water that will be brought up in the bottles. After an hour or two (again, depending on the depth), the rosette returns to the surface and is brought on board by our trusty winch operators. Immediately sampling begins. First up are the gases: CFCs, Oxygen, pH, DIC (dissolved inorganic carbon), and sometimes N2. |
It is important for the gases to go first, and sample quickly, because once each bottle is opened it is in contact with the atmosphere and contaminating the water collected at depth. Each bottle from the deep ocean contains a glimpse into what the atmosphere was like the last time that parcel of water was at the surface of the ocean- for the deep waters, that would be thousands of years ago. Check out the collaborative cruise blog to learn more about using CFCs to trace the age of water (http://goship-i09n-2016.blogspot.com/)!
While we all recognize the importance of quick and efficient sampling, the mood around the rosette is typically joyful. We usually have music playing which is punctuated by the sporadic shouting of bottle numbers and temperatures. There is a strong sense of camaraderie with everyone pitching in to help however they can to make things go quickly and smoothly. During sampling, my job is either to act as “sample cop” making sure that samplers are matching the correct bottle number to the right Niskin of water, calling our what bottle number goes with which Niskin. Additionally, we make sure that the samplers are going at a similar pace so the CFCs (who sample first) aren’t getting too far ahead of DIC. Temperature measurements for the water coming out of each bottle are also recorded, as this value is important for oxygen titration. Often I will help with taking alkalinity samples and salinity samples. |
Once the gases have collected their samples and rushed back to the lab to begin analysis, the other parameters including chlorophyll, CDOM, POC, and nutrients (nitrate, phosphate, etc) can sample. After everyone is done, we empty the Niskin bottles (this is where the boots become important!) and wash down the entire rosette with fresh water to help prevent corrosion from the salt. Typically sampling takes anywhere from 1- 2 hours. After sampling is done, I have some free time until we arrive on the next station.
Prepping the rosette is probably the most tedious and least-popular task we have. When we are about 30 minutes from reaching the station, the CTD watchstanders (and sometime some helpers) go out and prepare the rosette for deployment. This involves cocking open 36 Niskin bottles by hooking fishing line lanyards around hooks, which are magnetically controlled to release when commanded by the computer. After hooking open the top of each bottle, we go around and open the bottoms, using lots of arm strength to stretch the metal coil inside the Niskin and clip the landyard of the top and bottom together. The close proximity of the bottles makes this an arduous task. Between cocking the tops open and clipping the bottoms I have developed an array of cuts and scrapes on my hands as well as a mapwork of dotted bruises on the backs of my arms from reaching over the top of the rosette and bracing myself as I and reach to clip the lanyards, all while balancing on the frame 2 feet above the ground. |
Lastly, we go around and make sure the top vent cap is screwed in tight and the nozzles are snapped out to ensure no leakage will happen during the ascent back to the surface. Then it’s time to go back inside and get ready for another deployment. This happens over and over again, over a hundred times by the end of the cruise. While the work does get monotonous at times, there is variability with each cast and we find ways to remain engaged and interested. You will often find us googling maps and reading reports from previous cruises in the area in order to help us identify an interesting feature we see in the water during descent. As we passed the equator we saw signatures of water coming through the Indonesian through-way from the Pacific Ocean and as we approach the Bay of Bengal we are seeing a strong salinity cap at the surface. |