Mooring recovery and deployment
This article is part of the series “2024-08: Fram Strait cruise KPH”.
For science it is important to get measurements, preferably a lot of measurements. That’s not so easy if you have to take the icebreaker, you have only one and very limited ship time. One thing to go round this is to have sets of instruments that are moored at different locations in the sea. A weight and a buoy keep the communication cable with the instruments vertically and make the mooring stationary
On this cruise we had to recover seven moorings between 78° und 79° N and between 2° and 10° W. To communicate with the mooring a so-called hydrophone is used which can transmit and receive acoustical signals. The hydrophone is used to find the mooring and also to release it. Then the mooring will detach from the weight at the bottom and the upper buoys will slowly drift to the surface.
Then you have to find the mooring . Visually. That’s not an easy task because you will release the mooring in a certain distance to the ship to avoid crashing it into the hull. Beside of that it was pretty foggy this day when a team of NPI engineers and the ship’s crew tried to recover the first mooring with the id F10-19.
But look: There it is! It was found a while ago and our ship Kronprins Haakon is already in position for the recovery.
Now it takes a while to get everything on board without to destroy the scientific instruments. A lot of winch work is involved in the process.
This recovery at 2° W took approximately took one and a half hours. I think that’s quite fast if you consider, that the depth of the sea is round 2650 m at this place. That’s a lot of cable to pull up.
In the afternoon the second mooring recovery took place, this time at 3° W. I’ll show some more photos because this was one of the rare occasions when we actually had sun.
When the mooring was on board the collected data had to be fetched from the instruments and checked while other research was going on in parallel. And so the work continued until the last mooring was recovered three days later.
Of course you want to proceed with the continuous measurements. So on our way back the same amount of moorings had been deployed at the same places. Sometimes a mooring could be re-used, sometimes instruments had to be calibrated on mainland and a replacement was deployed. Each deployment started with the heaviest part, the iron weight that moors the cable to the ground following by the cable, the instruments and some buoys. And then again – a lot of winch work, setting carbines and so on.
Today we got the message: “All moorings are deployed! 🎈” – Great news!
P.S.: One instrument was lost but already in November. The data anyhow is saved elsewhere in the mooring and could be recovered.
Disclaimer: This is a private blog. I try to stick to the facts as good as I can. However this article has not proofread by any other people. Therefore some facts can be slightly inaccurate or even plainly wrong. If you find a mistake, please let me know and I will correct it. Thank you!