Edge of the Arctic Shelf

Send in the Cavalry
I'm pretty proud of myself - I didn't get lost today. I can successfully navigate from my room to the mess deck (where I can find sustenance) and to the main laboratory (where I can find my computer). Ask me about any other location in the ship, and you'll get a blank stare. This ship is huge. At 420' long, it's longer than a football field. The interior is a maze of passageways (hallways), ladders (stairs), and compartments (rooms). Healy is the newest Coast Guard icebreaker, and the most technologically advanced. Due to the many modernizations, only 70 crew members are required to keep the ship running -- roughly half the crew size of the other US Coast Guard icebreakers Polar Star and Polar Sea. Instead of a noisy and inefficient loudspeaker information system, everyone carries a pager. For more information on the Healy, visit our ship page or the Healy homepage.

The science party continued setting up equipment today. On the bridge (where the crew drives the ship), I found Lisa Munger setting up a complicated array of tape drives, cables, and other computer equipment. She has the best view from her "office". That's because Lisa has to be able to spot whales with her binoculars, and also listen to the noises those whales are making. To do this she uses a passive (meaning it doesn't emit any sounds itself) listening device called a sonobuoy. The buoy is simply a big floating microphone (called a hydrophone since it listens underwater) that collects all of the noises it can "hear" and sends them to Lisa as a radio broadcast. She then records all of these noises on digital tapes for future analysis. While Lisa was busy on the bridge, David Leech, a mooring technician from the University of Alaska, Fairbanks was busy getting ready to recover the first mooring.

This mooring is in Barrow Canyon (it's the star near Wainwright on this map). The instruments on the mooring have been collecting data since the mooring was initially deployed last summer. Last year this proved to be a difficult task -- our first attempt to put in the mooring was aborted due to a high concentration of ice (read 2002 Dispatch 10 for details). We had no such problems this year -- Barrow Canyon, like most of the Chukchi Sea, is usually ice-free in September. The previous winter's ice has melted away, and the temperatures are not yet cold enough to form new first-year ice. These conditions make David Leech smile, because he doesn't have to battle the ice to get his priceless data back. The first step in retrieving a mooring is to tell the mooring to drop its anchor. We do that with an acoustic release system. When we're ready to pull out the mooring, we put a sound source in the water and send a complex series of "chirps" into the water. When the mooring hears these chirps, it drops the anchor and floats to the surface. It took a few tries to get the mooring to hear our chirps today, but eventually the mooring floated right up to the surface, amid many cheers, within sight of the ship.

Next, we have to get this equipment back on deck so that David can retrieve the data that is stored in the instruments. Since the top float is relatively small, it's too difficult to try to pick it up directly with the ship's crane. Instead David set out with a Coast Guard team in a small boat called a zodiac. They shot off through the waves, sending spray flying. After hooking the mooring floats, they towed the entire mooring back to the Healy. Once the zodiac pulled alongside, the team attached the crane hook to the mooring, and let the crane lift the delicate instruments out of the water and onto the deck. Mission accomplished! Now David must extract the data and get the instruments ready to be redeployed.

Tomorrow the instruments will go back into Barrow Canyon to collect data for one more year.