Dispatch #2

Thanks to a combination of skill, good judgment, and luck, the final Southern Ocean GLOBEC mooring recovery cruise of the Laurence M. Gould (LMG03-02) is back on track.  We reached the SIO acoustic mooring S2A just off the edge of the continental shelf, 100 miles from Palmer Station, early Tuesday morning, February 18.  John contacted it by an acoustic signal, and the instrument replied that it was fine. However, Captain Robert said the seas were too rough and winds too high to attempt to recover it, so we immediately set off for S7A, which is back in shallower water on the inner shelf 94 miles away, arriving there at 1600. The acoustic mooring seemed to be okay, but we waited for the Captain to decide if it was safe to proceed.  He got into position a little bit downwind and essentially stopped the ship headed into the wind.  The seas weren't too bad, and conditions on the main deck were acceptable. The flock of cape petrels that had been circling the ship dropped down and sat in the water in a funny little flotilla. After testing conditions he gave permission to go for it.  John sent a signal to the mooring to tell it to come up.  This causes a current to be sent through the wires holding the two weights.  After a 20-minute burn the wires are supposed to break, and then it would take only ten minutes to come up from 470 m.  There were people on the bridge with binoculars to spot it, and a large crew dressed and ready to work on the deck.  It didn't seem to respond to the first burn, so another was ordered, and Zan and I ran down to get a quick lunch.  We got back up to the bridge and things looked bad; they had ordered a third and fourth burn but no clear indication that it had released.  Then John called Bob on the bridge and said he should look right now because it might have released without their knowing it.  Bob stepped outside with binoculars and there it was, really close. No binoculars needed. Three yellow objects, the two glass floats and the crate with the instrument, held together by the tether for the hydrophone. It's really lucky that he looked when he did.

The barometer was high, so we immediately set off back to the SIO mooring S2A, arriving well before 0600 on Wednesday.  When I got up to the bridge, John and team had already spoken to the mooring and sent the signal to come up some time earlier. There were lots of eyes on the ocean, the weather was very smooth and indeed sunny, and the barometer was high.  We didn't see it in that spot, and using the ship's sonar transducer to range to the instrument wasn't giving clear signals. We sailed back and forth and up and down, but we had to stop and declutch in order to probe for the distance because of interference from the ship's noise. Finally John and team put Scott's transducer over the side, and it picked up a much better signal indicating the range. With no directional information, it is a little like finding someone buried in an avalanche, however with drift of position due to wind and currents.  There was concern that it might not be on the surface, that we might have been going over it. Meanwhile some whales were sighted blowing.  Bob and I were looking at the whales, when he suddenly saw the yellow floats quite close again. He has now spotted both recoveries. It had taken four hours to locate the instrument.

With the instrument on board, two sonobuoys were launched and excellent recordings of Sei whales were made at the same time that they were being observed visually. This is the first time such a simultaneous set of visual and acoustic observations of Sei whales has ever been made, so this was a very significant event, and the whale observers are actually glad that it took so long to find the instrument.

We proceeded 163 miles southwest during the night. The seas have been quite rough ever since we moved to the edge of the shelf.  Thursday morning I got up to the bridge shortly after 0600. The mate had just stopped the ship and was holding position near but not on top of the position of the SIO mooring S4A.  Captain Robert gave the word that it was okay to proceed, and John concurred, so they sent the burn signal. Then everyone waited for the instrument to come up from 2900 m just downwind from where they put it over last year. This time they made a cleaner transfer from the ship's sonar transducer, which is a cone of sensors focused on the bottom, and the omnidirectional WHOI transducer, which they lower over the side of the ship, but for which the ship has to declutch each time. They were able to track its ascent, and when it popped up it was right in front of the ship. The retrieval went smoothly, in spite of a 15-20'swell.  Each of these acoustic moorings has a year of data on it.

Next we headed for the SIO mooring S5A, 54 more miles to the southwest. We waited awhile for the weather to improve.  The barometer was rising and eventually the seas were calmer and the sun came out. Mike the mate had us positioned perfectly, even predicting what side of the ship it would come up on. This time Captain Robert spotted the yellow floats first. Two albatrosses were sitting in the water next to them. The deck gang got it on board with no trouble.  There is one more out here just off the shelf, after that, then we can head in to
Marguerite Bay, where whale watching should be easier, and the WHOI group can start worrying about their own instruments.

Irene Beardsley