The night’s watch

Every night, when the others are savouring a well-deserved beer or retreating to their cabin for a good sleep, one team rises. For the next four hours, they will watch a cable go down in the water and back up again. They will then collect freezing water, slowly, so that when everyone else gets up for breakfast, they finally fall in their bed. This is the story of the night deep CTDs…

Three crew members required, maximum, to get the CTD to go. Picture: Sara Sahlin

On the paper, it makes sense. The fisheries team needs help from the crew. The crew needs to sleep at night. Which team can work at any time of the day or night with minimum crew? Us.

Officially, I’m happy because I care about deep waters, and we are currently measuring down to 4000 m! But in reality, I’m also happy because being the only person working in the middle of the night gives you some rare genuine alone-time. It is really hard to be alone on a ship: you share your cabin, you share your lab with colleagues, you all eat together at the same time, and overall space is so limited that you can hardly walk 5 minutes without meeting someone.

And this work is not really demanding anyway. Get up. Get dressed. Walk to the bridge to fetch a radio. Prepare the CTD on the working deck. Put the kettle on. Say guten morgen to the winchman. Pour the boiling water over the coffee in the press. Put the CTD out on deck. Press two buttons when she’s in the water. Enjoy a nice cup of coffee. Read or work for the next two hours while she’s going down.

View of the winch control room abord R/V Polarstern. Picture: Gerit Birnbaum, modified by Céline Heuzé.

There’s a bit of action as you approach the sea floor. You want to stop between five and ten meters above it: closer and you may damage your instrument; further and you are unnecessarily missing measurements. Then you check your science screen and decide where you want to sample water: where does it have interesting salinity, tempeature, oxygen and/or chlorophyll features? And then you start the way up, telling the winch operator at which depth you want to stop for the sampling.

Except that sometimes, the winch disagrees. There are two crew members keeping an eye on it, and you can see them on your winch screen. If suddenly they do a duck beak with their hand, that’s no good news: the winch needs to slow down for the cable to be observed more carefully. If they raise their closed fist in the air, that is very bad news: stop. On one occasion, stop for over an hour at 3729 m deep. Nothing you can do then apart from cracking up the music and headbanging (…and be observed from behind the door by your colleague who thought she’d come and keep you company).

The water sampling. Left, close up on the pipe-tapping team (by Marcel Nicolaus); right, with spectators (by Gerit Birnbaum).

Eventually, the CTD goes back on deck, full of water, and the sampling ballet can begin. Three teams need water:

  • the filtration team (team BGC = biogeochemistry), which fills all the white bottles and then stands for hours next to their filtration rack in order to get the chlorophyll on their filters;
  • the Tromsø / American team, which if I understood correctly also does some filtering but to study the microbiology;
  • and us, who fill some delicate glass samples, tapping on the pipes to get rid of all the air bubbles for we want to know how much dissolved gas is in the water.

Depending on the time at which we finish, we can also have some audience. Or chat with the LOKI team who often are next to deploy their instrument.

Sara setting fire to glass. Picture: Céline Heuzé

And that is when my watch ends. Sara, who has gotten up when the CTD was close to the surface, then takes over and seals the glass samples. To do so, she has to melt the glass and sculpt it so that it is not too brittle. That is, she spends two hours breathing the butan gas fumes among glass shards, with a fire extinguisher at her feet. Then she can prepare more bottles for the next night sampling. Unless we have an ice station, which will be the topic of next post if I remember to get Elin’s pictures…

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