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Posted September 25, 2014

By Elizabeth Dobbins, Research Scientist, UAF

 

Mooring Recovery and Deployment
Long term ecosystem mooring

Ecosystem mooring being tested at the Seward Marine Center

 

Today marks the end of our mooring deployment and recovery cruise in the Chukchi Sea. Ten moorings were recovered around Hanna Shoals. Several moorings belonged to our collaborator, Robert Pickart at WHOI, while the others were supported by BOEM's COMIDA/Hanna Shoal program.

Additionally, two moorings were deployed. One was a physical oceanographic mooring called BC2 in Barrow Canyon. The other is an ecosystem mooring that was deployed for Seth Danielson, Peter Winsor, Claudine Hauri, Andrew McDonnell, and Russ Hopcroft. This mooring was funded by a consortium of NPRB's Longterm Monitoring Program, AOOS, UAF and industry (particularly, Shell-Conoco Phillips which provided the ship time for deployments/recoveries). A brief article about the ecosystem mooring was written by the University of Alaska Museum of the North for the R/V Sikuliaq blog.

In addition to the mooring work, Acrobat surveys were performed as the ship steamed along.

 

Convergence Zone
HFR showing convergence Sept. 15, 2014

Convergence in surface currents as shown by the HFR, Sept. 15, 2014

 

From September 13 through 17, the surface currents measured by the High Frequency Radar (HFR) showed a large area of convergence between Point Barrow and Cape Simpson that reached from the shore to the shelf break. Winds had been strong and persistently from the east, and the Alaskan Coastal Current has been relatively weak this year. This convergence zone moved offshore and to the north over several days, and since the 19th it has only been intermittently visable at the edge of the HFR field.

Drifters - More of the Same

 

Drifters, Sept. 25, 2014

Drifters from the Pt. Hope and Pt. Lay deployments, Sept. 25, 2014.

 

Two weeks ago, I described how the drifters that had been deployed off Pt. Lay were spread along the coast between Pt Lay and Barrow. I could use the same description today. Three drifters that had reached the mouth of Barrow canyon have been transported northward to ~73° N, but the rest have not gone far - perhaps moved slightly offshore by the easterly winds. Meanwhile, the drifters that were deployed off Pt Hope remain over Herald Valley and Herald Shoal.

Drifters, Sept. 25, 2014

Drifters from the Wainwright deployments, Sept. 25, 2014.

 

The drifters that are along the shelfbreak are still there, advecting to the northwest - slowly. Some have reached as far north as 77° N. But one benefit of the minimal largescale advection is the chance to observe some beautiful oscillatory motions, which appear episodically, in the drifter positions.

These oscillations are not caused by eddies. Instead the entire surface of the water over a broad area is rotating as a slab, and not rotating around a local "fixed" center. These oscillations occur when sudden changes in winds result in currents veering in response to the earth's rotation. Eventually, we will determine the frequency of these oscillations, their magnitudes, their horizontal scale, and the forcing mechanism.

 

Field Ops

 

News

 


Last modified: September 25 2014 10:49:18.