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Dispatch 9: Mooring Redeployment

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September 14th Photos
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Hugo Sindelar

September 14, 2018

Location: 74° 0′ N 140° 0′ W

Weather: -5°C (23°F), Mostly sunny, seas calm, Northeast winds at 6 knots, seawater temperature 0.5°C (33°F)

Sea Ice: None

Mooring redeployments, in other words doing what you did yesterday in reverse.  We spent the day putting Mooring D for the Beaufort Gyre Observing System back into the water.  As I mentioned yesterday, this redeployment is for two years; so the next time these instruments will be seen is in 2020.  Talk about needing a bit of patience.  Because of the length of this deployment, the WHOI mooring team took great care to make sure everything was set up properly.

Arctic mooring deployments start with setting up the 3,800 lb. anchor.  These huge metal disks are linked to two acoustic releases using chain.  The acoustic releases are designed to unhook from the anchor when signaled from the surface (using sound, of course).  It’s amazing that a sound wave from a boat 3,500 meters above them can trigger their release.  They are critical components because they allow the recovery of the whole mooring deployment except for the anchor.  Because of their weight and depth, you just don’t recover anchors.  After the anchors and releases it is time for forty-six yellow balls.  These balls help provide flotation if the primary buoy fails during recovery.

Following the yellow balls, it’s all about spooling out over 3,000 meters of cable that has already been proportioned into carefully measured sections.  Connecting the different sections of cable resembles trying to tie two pieces of spaghetti end to end.  While the winch sure makes it easier, it still takes some finesse to get all linkages put together.  Jim Ryder and Nico Llanos have clearly done a few moorings in their day, and it was fun to watch their carefully orchestrated work with the deck crew of the CCGS Louis S. St-Laurent.  They make sticking spaghetti together look easy!

Two McLane Mooring Profilers (MMPs) were installed on different 1,000 meter sections of the cable.  Due to the length of this deployment, two MMPs had to be used to patrol 1,000 meters of depth each.  The battery on one profiler would not last long enough to patrol 2,000 meters for two years.  DispatOnce the MMPs were installed, it was time for the finishing touches.  An array of sensors sits just below the buoy.   They include – dissolved CO2, pH, and a MicroCat (to measure conductivity, temperature and depth near the buoy).  Finally, the main buoy is added to the top and lowered over the side.  Piece by piece, a 3,500 meters line of sensors, linkages, and cables has slowly been assembled and placed into the ocean.

The WHOI team attaches the main buoy to a quick release system and the crane on deck is used to lower it to the side.  Then it is time to say farewell for a long time.  Once Rick gave the final okay, the quick release was pulled, and the buoy plunged into the ocean, not to be seen again until the WHOI team returns in two years’ time.

Last updated: October 7, 2019

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