Posted September 25, 2014
By Elizabeth Dobbins, Research Scientist, UAF
Mooring Recovery and Deployment
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.
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
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.
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.
- 84 of the original 104 drifters sponsored by the North Slope Borough-Shell Baseline Studies program and BOEM remain active. Only 2 have beached this year.
- 29 more drifters have been deployed as part of the ARCTREX program.
- All 4 HFR sites are operational.
- 2 MetBuoys are deployed in the Chukchi and returning real-time data. 1 more is deployed but not transmitting data.
- During last week's cruise, 10 moorings were recovered and 2 were deployed. Also, Acrobat surveys were conducted.
- All 3 gliders were recovered on Sept. 23, 2014
- Yet another blog from aboard an Arctic research vessel.
- Arctic sea ice annual minimum is 6th lowest on satellite record: The sea ice minimum occured around September 17, 2104. This year was relatively cool, without any big storms early in the year to break it up, but the ice is thin and melted more than the long-term average.