Click here for a detailed diagram. Moorings A mooring is an instrument, or series of instruments, attached along a cable that extends over a portion of the water column. In this experiment we are using sub-surface moorings, which will extend to 40 meters beneath the surface. Any shallower than this and the instruments would be subject to damage from ridging due to the ice pack. A flotation buoy at the top of the mooring keeps the cable taught, and a heavy anchor at the bottom keeps the mooring from moving around. A variety of instruments can be attached to the mooring line; for instance, current meters and temperature/salinity sensors. These instruments collect data at specific time intervals and store the data until the mooring is recovered at a later date. The primary mission of our cruise is to deploy a variety of moorings at key locations in the Chukchi and Beaufort Seas. How do scientists retrieve moorings? We use a device called an acoustic release. At the time of recovery we steam to the mooring site and lower a transponder into the water which sends out a unique sequence of acoustic pulses. When the release “hears” this sequence, it releases the cable near the bottom, and the flotation distributed along the mooring carries it to the surface. We then bring the mooring on deck and retrieve the data from the instruments. In the Arctic this task can be especially challenging due to the presence of ice. If the mooring is under the ice pack at the time of recovery, the icebreaker attempts to clear a “pond” with its propellers, then try to bring the mooring up within the pond. If this fails, then avalanche beacons attached to the moorings will help the scientists locate exactly where the mooring surfaced under the ice. Since ours is a two-year experiment, we will re-furbish and re-deploy the moorings after the first year, with final recovery after the second year.