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> July 21, 2006 - Location 71 33 north, 155 22 W
post Jul 26 2006, 01:54 AM
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Group: TREC Team
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Since 6:47 pm July 20, the engines have been shut down and the ship has been moving with the ice to the east. The wind and current have been moving this huge mess of dirty compressed ice and the ship at about 0.3 knots. The ship is very quite, without the noise from the engines or from colliding ice.

Dirty Ice
IPB Image

Fortunately, the path that the ship has been moving is over areas of the seafloor that have not been surveyed with the multibeam sonar. Since the ship is moving so slowly, and there is no ice striking the ship, the map of the seafloor produced from this multibeam data is very good.

Everyone, science party and Coast Guard Support, are working to get all of the equipment ready when the ship gets to workable ice. Helicopter recon located some open water and less compacted single year ice in which it would be possible to do our science, but that was about 30 miles away. At this time it doesn't make sense to break the ice to get where we want to be. The ice is so compacted, and the current strong enough that we were breaking ice at about the same speed of 0.3 knots, but the ship was burning fuel at a higher rate than was reasonable.

On the Healy's transit to Barrow, a large block of ice was flipped onto the aft deck area where the cradle for the sediment corer is located. The frame for the cradle was seriously bent, and the Coast Guard fabricated a new one. The marine techs and the coring group from Oregon State were working on the repairs most of the day yesterday. Their repairs included not only some heavy lifting and welding, but also a number of well-placed hits from a heavy sledgehammer.

Much of the seismic prep is going on at all hours. Cabling for controllers and computers is being run to operate the air guns. There are a few more guns that need to be assembled. Some of the parts needed for finishing the gun array are on their way and may be in Barrow by Monday. There are a hundred little things that have to be done to make sure that the whole system works once we get to the good ice.

There are two types of seismic data acquisition that will be done during the cruise. The first type is called seismic reflection and makes use of a long series of connected hydrophones that are towed behind the ship. These hydrophones are called a streamer. The hydrophones detect sound reflected from the seafloor. The sound that the hydrophone detects is produced by high pressure pneumatic air sources that are also towed behind the ship.

The scientists will also be collecting seismic refraction data. To do this they will deploy hydrophones on the ice that will radio the detected sound data to the ship. These detectors can relay data back to the ship from distances as much as 100 km or more. Both techniques profile the seafloor crust and allow the scientists to interpret different information about the structure of the seafloor crust.

Helicopters will be used to deploy these seismic refractor units. Both science party and Coast Guard personnel were required to participate in a helicopter training session at 2:00 if there were any chance that they would be involved in deployment, recovery or a future ice recon aboard the helicopter. Dave, our flight manager for the cruise spoke and presented a PowerPoint covering the basic safety procedures and concerns for operating the helicopters aboard the ship and on the ice.

Safety is the first concern for everyone. To ride on the helicopter you must wear a mustang suit, which provided floatation in the event of a water landing or crash and helmet to protect you from the noise and materials that can be blown by the rotors.

I started the second day of watch with Russell and Chase at 4:00 local time, 00:00 GMT. Our shift marks the day change, because all of our data is correlated to Greenwich Mean Time rather than local time. We continued to move with the ice at about 0.3 knots.

Change of watch was uneventful. Looking forward to tomorrow.
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