Sunday, March 13, 2016

A day in the life of a CTD watch - part 2/3

At the end of the first part of this post, I started to describe how we recover the rosette from the water after a cast is complete. Just to recap, a CTD watch stander helps to get the rosette into and out of the water as safely and as efficiently as possible. We do a bit of everything. You will find us in the lab and out on the deck, doing whatever it takes to ensure that each station goes by smoothly.

Hannah getting ready to recover the rosette. Her pole has a hook at the end, which will slip off as soon as she latches onto the rosette. Photo credit: Cara Nissen.
I have already talked about how we prep and launch the rosette. Now I will describe how we get it back onto the ship. I should mention here that every crew has their own way of doing things. Even on our cruise, the day and night shift crew did things a bit differently. It all depends on who is running the show and the circumstances that they are up against. The method I describe here is the method the night shift crew used for most of the cruise.

As with the rosette launch, our job is provide stability as the winch raises the rosette into the air. The winch does all the upward lifting while we provide lateral support. Strong winds and large swells can cause the rosette to swing uncontrollably once its in the air, which is a very dangerous situation that everyone wants to avoid. It is our job to prevent that from happening.

First person perspective of a rosette recovery. Here, Dave and I make first contact with the rosette after it breaches the surface. Once we are latched in, we try to keep our ropes taut as the winch lifts the package into the air.
For recoveries, we typically use three lines of stability. We establish the first two by hooking onto the rosette as soon it breaks the surface. We do this by using long poles with hooks attached to one end; the hooks are tied off to the ship by a long rope. After we hook into the rosette, we slip our poles and wrap our ropes around a metal cleat to gain leverage. Once we are in position, we try to keep our ropes to tight as the winch hoists the rosette out of the water.

Hannah and Seth providing support during a recovery. Josh (the res-tech) directs operations. Photo credit: Cara Nissen.
As the winch lifts the rosette into the air, we (the tag-liners) try to keep the rosette stable. Above, Dave is about to latch the third hook onto rosette; Natalie and I have already established the first two lines of stability.
After the rosette clears the deck, we establish a third line of stability with another hook and rope. The first two lines can only control for swings parallel to the ship. The third line helps to damp the swings that are perpendicular to the ship. This is probably superfluous in most parts of the ocean, but in the Southern Ocean, where the currents are strong and the winds are violent, this final line of support is absolutely necessary.

Yet another recovery. Here, Natalie is the third line of support. John (white helmet) is the on duty res-tech who directs operations from the ground. This is one of the many night recoveries we did on this cruise.
With all three lines of support providing lateral stability, the winch operator slowly lowers the rosette onto its landing pad. This usually takes a couple tries and requires a fair bit of coordination between the res-tech and the winch operator. After the rosette is safely on the ground, we strap it in and haul it into the hangar for sampling.

Day shift crew leading the rosette into the hangar where the samplers await. This is not as hard as it looks. The rosette sits on a moving track that is powered by a motor. We sometimes need to give it an extra push to get over small bumps. Photo credit: Cara Nissen.
In the next installment of this series, I will describe how we collect water samples from the rosette. That's all for now!

Dave and Maverick collecting samples from the last cast. 

-EW

9 comments:

  1. Replies
    1. The cruise was fantastic and I will definitely miss the friends I made onboard. That said, I think I'm ready to go home.

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  2. The rosette looks small at first then really big. must have been heavy.

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  3. Why do some of the boat people where the bright colored vests and some not. I understand why you where them. But I don't understand why only some people wear them.

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    Replies
    1. We only wear life vests when were working outside on the deck. If we are inside, the risk of fall over-board is pretty much zero, so no life vests are not necessary.

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  4. What do you think is the best insulator out of these materials and why:Denim,fleece,nylon,wool,gortex,or cordoroy

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  5. Are you happy that the trip is almost over?

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  6. What do you think is the best insulator out of these materials and why:Denim,fleece,nylon,wool,gortex,or cordoroy

    ReplyDelete