Chukchi Borderland Project

Daily Updates from

our Teacher at Sea


August 23

Mooring Deployment

Underwater Instrument Mooring Diagram (courtesy Jim Johnson)


Mooring Anchors.

Anchor being moved by crane.

Acoustic Releases.

The University of Washington, Polar Science Center, is deploying three underwater instrument arrays.  These three instrument moorings will be deployed in the Chukchi Sea for a period of one month.  Each mooring consists of four primary instruments.  Starting near the bottom of the mooring at the floor of the ocean, are the anchors, holding the mooring under the water. 

Luckily, we have a crane on the Polar Star to move the mooring anchors as they each weigh about 1400 lbs.

Immediately above the anchor will be two Acoustic Releases. 
The function of an Acoustic Release is during the recovery of the mooring.  An Acoustic Release will let go of the mooring anchor via commands sent through the water from a surface ship, by way of a hand held hydrophone.  Each release is tuned to a specific series of acoustic frequencies.  By sending these specific sound commands from the ship, we are able to control the releases and have them do certain things, most importantly the releasing of the anchor, causing the instrumentation to float to the surface.

The next instrument above the releases is the Seabird SBE-16.  Essentially, this is a stationary CTD.  It will sample the temperature and salinity of the surrounding water once every hour and store the data internally.

The third instrument is a current meter.  This device uses a paddle wheel rotor to measure current speed, a small compass for current direction, a temperature sensor, and a conductivity sensor which gives values of salinity.

SBE-16 on bottom (white instrument).
Current meter on top (green instrument).

Glass floats placed periodically along the kevlar line between instruments of the mooring, allow it to float vertically when deployed at the bottom of the ocean.


Acoustic mooring location device.
The last instrument on the mooring is mounted at the top just below the top float.  This instrument is another acoustic device that allows us to accurately find the location of the mooring when it is covered by ice.  By sending out one acoustic pulse at a unique frequency, we will get back a reply pulse that the electronics will convert to a slant range in meters.  How do you think it does that?


Top float on mooring.


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