Dispatch 18: Recovery of Mooring A: a View from the Bridge!     Print

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Mengnan Zhao

October 5, 2015

This morning we arrived at 75N, 150W for the recovery of Mooring A in the southwestern basin. Now surrounded by open water, we expected the recovery to be much easier with no ice cover to break in preparation for the surfacing of the mooring’s top floatation sphere.

Rick kindly suggested to me that I take the view from the bridge – it is the cooperation between the bridge and the fore deck that makes for a successful recovery or deployment of a mooring. I had experienced and documented mooring recovery on the fore deck twice, so this would be an opportunity for me to learn how the other side functioned, as well as to have a great tour of the bridge. The bridge is located on the top deck of the Louis, where the navigation and transit of the ship is carried out with a breathtaking view of our Arctic surroundings as well as the rest of the ship. Each one of our scientific missions (buoy recovery, mooring recovery/deployment, rosette casts, sea-ice measurements and plankton tows and other sampling activities) all require essential assistance from the bridge to break ice, turn on bubblers to keep the ice away from the side of the ship, and control the distance between the ship and the equipment over the side.

In previous recoveries, from my perspective on the fore deck, the recovery always seemed to begin with the appearance of the floatation sphere over the side. Here on the bridge, the recovery process begins way before the top sphere appears at the surface. As soon as the mooring position is confirmed by Rick, our captain Anthony Potts (with his 35 years of coast guard experience) combines all of the information including winds and ocean currents and positions the Louis to ensure the floatation sphere comes up on the starboard of the Louis where the winches operate. After the releases are triggered to let go of their anchor, the 50 floatation glass balls (at more than 3000 m depth on the other end of the mooring to the surface sphere) slowly rise from the bottom, which takes around half an hour by the captain’s estimates. And here comes another tricky part – we require the glass balls to appear on the same side of the ship as the top floatation sphere; this relies on the rich experience of the officers on the bridge to control the position of the Louis with the changing weather conditions. About half an hour after the surface sphere appeared, the glass balls at the other end of Mooring A, just as planned, appeared on the surface on the starboard side – impressive! The long mooring wire also adds complexity compared to a buoy recovery. As more than 3 km of wire and instruments are brought on board, the distance between the ship and the glass balls must be maintained just right to prevent any tangles of the wire in between.

It is intense work and the captain, second officer Mark Gould, third officer Adam Manning and others keep close contact via radio with fore deck scientists and crew during the entire recovery. It is exciting to see the whole skillful team at work.