A mooring for oceanography

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Seth Danielson is a physical oceanographer with the UAF School of Fisheries and Ocean Sciences. Seth’s proposal to use a mooring in the Northeast Chukchi Sea for ecosystem monitoring is featured in the Arctic Odyssey exhibit.

The mooring site was selected because of the biological “hotspot” located on the NE Chukchi Sea shelf, where a thriving benthic community supports a major walrus foraging site during summer and fall months. Also, the site is close to Barrow Canyon and well positioned to record the effects of shelf-canyon exchange. Such a fully instrumented mooring is rare on any continental shelf; this mooring will enable many stand-alone multi-disciplinary and multi-parameter studies and its data will complement numerous underway and planned Arctic physical, geochemical, ecological, and fisheries studies.

We wanted to learn more about the proposal and a recent trip to Seward to test out the mooring, so we asked him a few questions.

1) What kind of mooring is this? Is it unique? Does it represent next-gen technology? Yes, next-gen technology and unique for Alaska’s waters. In fact, finding such a fully instrumented mooring of this type is rare on any continental shelf anywhere.  This package that will be deployed this summer will measure water current speed and direction, ice draft, wave height, wave period, wave direction, size spectra of suspended sediment, temperature, salinity, conductivity, pressure, fluorescence, light, and water clarity.  Future deployments (when we can afford the instruments) will also measure nitrate, dissolved oxygen, partial pressure of CO2 and pH.

2) How did the test go? The test went well – we found that some of the instruments were working properly; we found one problem with one of the instruments, so we were able to send that back to the factory to be fixed before deploying it in the ocean this summer. Here is an instance of finding a problem still qualifies as being a success.  The reason we do a lot of careful testing is to try to expose problems before they have a chance to manifest during a real deployment. We were able to do a limited test for interference between two of the acoustic instruments and found no sign of unwanted crosstalk.

3) How do you explain a mooring to a non-oceanographer? It looks like rubber balls attached to oxygen tanks! What makes moorings such a popular tool for oceanographers? The mooring is a set of instruments that record autonomously underwater for a whole year, attached to an anchor via an acoustic release.  At the time of mooring recovery, we send a command to the release, which lets go of the anchor. The floatation (red balls) pull the whole mooring (except the anchor) back up to the surface where we pull it all back on board and then download the data. Oceanographers like these because they return a long time series of multiple data streams back to us at the end of the deployment. Our task (the fun part, to me) is then to examine the data and figure out what “story” the data is telling. Does it support or refute a hypothesis? Does it look as expected or are there surprises?

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SFOS graduate student Jessie Turner and professor Andrew McDonnell review results from a mooring test at the Seward Marine Center, a UAF facility based in Seward.

 

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Mooring technician David Leech works in the shop at the UAF School of Fisheries and Ocean Sciences Seward Marine Center facility.

 

From left: Mooring Technician David Leech, Claudine Hauri, SFOS carbon chemist, and Jessie Turner, SFOS graduate student. at the  Seward Marine Center.
From left: Mooring Technician David Leech, Claudine Hauri, SFOS carbon chemist, and Jessie Turner, SFOS graduate student. at the Seward Marine Center.

 

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Scientists and technicians test the mooring at the Seward Marine Center to try to expose problems before they have a chance to manifest during a real deployment.

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