Edge of the Arctic Shelf

Weather Day
Our calm weather ended late last night as a fierce polar low slammed the Beaufort Sea. My alarm jarred me awake at 4AM - time to photograph a night net tow. My sleep-addled brain was blasted awake as I stepped out onto the weather deck. Whoah, that's refreshing! I made my way back to the fantail where the net tow crew was standing ready. As the ship maneuvered into position, the wind raked across the deck. The snow wasn't accumulating much since it was blowing horizontally. This was going to be an interesting net tow.

Carin Ashjian describes the evolution: "It was blowing about 20 knots so we had to be careful that the net didn't get away from us. It was great to have four of us out there, since there were plenty of hands to hang on! For some reason, it always snows during the net tows. We didn't raise the net too high, so that the wind couldn't catch it. Everything went really well, from the ship handling to the winch driving to the deck work and it was a very successful tow."

The wind continued to build today, gusting to 40 knots at times. The winds whipped up the waves, and the ship started rocking for the first time since our first day out from Barrow. Although we aborted our mooring recovery plans, we managed to get some other important tasks done. John Kemp confirmed the location of the Acoustic Recording Package (ARP) that we deployed last year. Lisa Munger also got two ARPs ready for deployment, installing the lithium batteries. Sarah Zimmermann, Dan Torres, and Ryan Schrawder continued to extract data from the mooring instruments. Ryan even got a haircut!

Mrs. Werner's 6th grade class at the Morse Pond School has two excellent questions.

Question: What is the thickest ices the cutter has cut through?
Answer: The Operations Officer, Lieutenant Commander Daryl Peloquin, helped me out with the answer to this question. He showed me some summary documents from the Healy's ice trials in Spring 2000. This is when Healy first tested her strength against the Arctic icepack.

The tests were a success. It was confirmed that Healy could break flat ice 6 feet thick continuously under full power (30,000 horsepower) at a speed of 5 knots. The ship's icebreaking power was then tested against a pressure ridge. A pressure ridge results when two slabs of ice collide, forming a thick layer where the plates meet. The portion of a ridge extending above the water is called a sail, and the portion below the water is called a keel. It this case the ridge they selected was 46 feet thick from sail to keel - as tall as a two-storey house! This quote from the ice trials summary document describes the operation: "After making sure that the data from all transducers were being recorded, we moved the ship ahead in thin ice towards the middle of the ridge under full power (29,500-30,000 HP)... During the first ram, the ship stopped in the ridge after the bow went over the sail and depressed it down. We backed the ship and rammed forward again at a speed of 7.5 kt to advance a distance of 44 m. After another similar operation, the aft of the ship cleared the ridge completely, as is evident from the increasing ship speed at the end of the test." Backing and ramming is a technique icebreakers use against very thick ice. The trials determined that the ship can advance about a quarter mile per hour through 11 foot thick multi-year ice.

Question: How different is this trip from last year?
Answer: This trip is different from last year in many ways. The most important difference is that our objectives are different. Last year our mission was to deploy the moorings and conduct a CTD survey. This year we are recovering the moorings, then redeploying all of them. We are also conducting CTD surveys, collecting shipboard bathymetry and current data, and performing net tows and Video Plankton Recorder casts! As opposed to last year's small (11 people) science party, this year there are 20 of us. We have a much broader spectrum of oceanographers, including biologists and acousticians. Finally, the most striking difference to me is the environment. What a difference a few months makes! The ice we fought last year in July and August is all but absent here in September. We may also get to see sea-ice forming in late October as the winter chill sets in.

Our plans for tomorrow are the same as they were for today... assuming the weather improves! We are all hoping that the storm passes quickly and leaves us calm seas so we can finish the mooring recoveries.