Straightening Out The Gear And Heading Toward More Interesting Seafloor
Andy Armstrong, NOAA’s Office of Coast Survey, Co-chief scientist aboard USCGC Healy
Today began on the same northwestward track as yesterday, with Healy multibeam echo sounding in the lead and CCGS Louis S. St-Laurent towing their multichannel seismic reflection gear astern. Although we had expected ice conditions to remain about the same, the ice actually got a little more closely packed, with more ridges and thick areas. On a couple occasions we had to back up and ram the ice to break through and make a path for Louis S. St-Laurent. Without a clear path through the ice, the towed seismic equipment on the Louis S. St-Laurent would be destroyed in short order.
Our survey and mapping progress was also slowed a bit by some of the inevitable problems that arise in any major project like this. Louis S. St-Laurent was experiencing intermittent problems with their seismic gear and decided to haul the gear in for service. Louis S. St-Laurent’s helicopter was sent aloft to find open water where the sled and streamer could be safely retrieved, and the two ships steamed about seven miles east of our track to the opening. With Louis S. St-Laurent temporarily out of service, Healy took advantage of this time to do some equipment repair of our own. About a week ago during the first CTD cast of the cruise, the CTD winch level-wind malfunctioned and mis-wrapped some of the wire on the drum. The result of that mishap was that the wire was jammed at about 1300 meters out. The Coast Guard engineers and science technicians have spent the past few hours carefully paying out wire and clearing the jam.
We should be on our way back to the track in about an hour. Because we want continuous lines of seismically determined sediment thickness, we will return to where we left off on our original track before heading northwestward again.
We should complete this leg of the track sometime tomorrow morning, and turn eastward to cross some of the bathymetric features on the margin of the Alpha-Mendeleev Ridge complex. The multibeam will have a more interesting task there than it had just a few days ago. In a part of the Beaufort Sea we mapped on August 13, the multibeam data hardly varied from about 3800 meters of depth, either across the 5-nautical mile wide swath or along the day’s 75 nautical mile track. That part of the Beaufort Sea is one of the flattest seafloors in the entire world; sediment has been drifting down and settling evenly in this basin for millions of years.
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Andy Armstrong – It is interesting tracking the work of the HEALY from Oklahoma. I wish all the participants the best of luck and don’t let a few minor problems interfere with data collection.