[Note added after the meeting: Mike Kosro's report on the wind and stratification. Phil Barbour also made some useful wind plots. More discussion and investigation is needed on this option, and we must move quickly to make a decision about the viability of this option given that ship schedules are getting more and more firm.]
[Note added after the meeting: Tim Cowles and Jack Barth will meet with Ginny Goblirsch at 10am on Thursday 7 November to begin negotiations with the fishermen. Pat Wheeler will attend a Revelle cruise planning meeting at Scripps on Monday 4 November.
Questions for fishermen:
The issue of doing the downwelling experiment in Nov '03 before the start of the crab fishing season (~ Thanksgiving) was raised. Tim Cowles was tasked with investigating the possibility of changing both the Wecoma's and Revelle's schedules. Mike Kosro volunteered to investigate the historic wind fields in order to compare downwelling in Nov versus Jan-Feb.]
General update on COAST (Barth)
-- Annual Report due by mid-November to keep $$ flowing for CY03 Would each component please provide a brief (1-2 paragraphs) progress report to Jack by 7 November. Please include any papers that acknowledge COAST support.
-- San Francisco AGU Meeting will feature many talks by COAST and OSU scientists. The CoOP-motiviated Wind-Driven Processes along the U.S. West Coast Continental Shelf session, co-chaired by Toby Garfield (SFSU) and Pat Wheeler (OSU), will hold an oral session on Saturday 7 Dec morning and a poster session Sat afternoon. Several talks on coastal upwelling will be given in a session entitled Quantitative Developments in Coastal Oceanography which will have its oral session on Friday morning and a poster session on Friday afternoon. Finally, a couple of OSU talks will be made in the Scientific Results from Coastal Ocean Observing Systems session on Sunday morning.
-- We thought one more group meeting before the SF AGU meeting would be worthwhile. A suggested time is 10am-noon on Wed 27 Nov. Jack will check on room availability.
Review of downwelling field experiment as proposed (Barth)
The timing and scientific goals of our proposed downwelling experiment were reviewed. Here are relevant extracts from the proposal:
H6: The reduced cross-shelf transport implied by the presence of a downwelling front and jet allows nutrients, trace metals and seed stocks of phytoplankton and zooplankton to accumulate in the mid- to inner shelf, thus priming the system for a strong biological response at the outset of upwelling and higher light levels in the Spring.
During downwelling, model results indicate that a mid-shelf front separates an offshore region with strong alongshore flow and vigorous cross-shelf circulation from a less active inshore region with reduced alongshore and cross-shelf transport. This front and its modulation by wind forcing will strongly influence the distribution of terrestrially derived macronutrients and trace metals during winter downwelling.
Our proposed examination of a downwelling event was motivated in great deal by the modeling results of Allen and Newberger (1996). More recently, the GLOBEC LTOP program has provided cross-shelf information about physics, biology and chemistry during both November and February.
We proposed to study downwelling in the northern, "simpler topography" region off Cascade Head. Four moorings (3 oceanographic and one meteorological) are slated for that line. The profiling vessel would work along that line with the hope to catch a few downwelling events. The survey vessel would provide 3D information around the Cascade Head line on a variety of scales, and hopefully repeated the "big box" survey from Cape Kiwanda (45 15'N) south to the Umpqua River (43 45'N). We wanted to work in Jan-Feb of '03.
John Allen reported on preliminary model runs that he and Jianping Gan have done on wintertime downwelling. They ran a model with wintertime stratification forced by Jan-Feb '00 winds. After 8 days the downwelling front and jet were centered over about the 100 m isobath. John pointed out that the northward flow interacts with bottom features (e.g., Heceta Bank) differently than during southward flow and that this was a motivation for obtaining 3D information. John and Gan plan to analyze the model runs further. They could put in freshwater from the coastal rivers.
Mike Kosro showed monthly averages of surface velocity from land-based radar. The northward flow is definitely present by November and seems to be intensified toward the coast and both north and south of Newport.
Tim Cowles reviewed the meeting he and Mike Kosro had with the fishermen in Newport. His report is contained in a recent email to the group. The bottom line is that at least 10-15 times the number of crab pots that we've experienced in the summer will be deployed in winter on the Oregon shelf. Over 100,000 pots are deployed from Newport alone. The season starts on Thanksgiving each year. Tim discussed how a cable-laying company negotiated with the fishermen to obtain a clear lane in order to lay a cable across the shelf. Tim will continue to interact with the fishermen and Ginny Goblirsch on COAST's behalf.
We then discussed our experimental plans for the Jan-Feb cruise. We agreed that a minimal plan to accomplish our scientific goals would be to negotiate with the fishermen to keep a single cross-shelf line clear at Cascade Head. The lane would need to be 1-mile wide to allow safe passage of the two vessels past each other and the moorings. A question arose about whether we could mark the lane and whether that would have any legal implications. The exact location of the lane could be moved given the pot clustering that is sure to evolve as the season progresses. A line somewhere between the NH line (44 39.1N) and 45 3'N would be acceptable. The northern limit is set by the available radar coverage.
The group agreed that an alternate site for our work might be over the muddy bottom (less crab fishing?) near the Umpqua River and south. For example on the historical FM line (43 13'N) which is being occupied as part of the GLOBEC LTOP surveys. As big disadvantage is that there is no short-range radar coverage in that region. There would only be the possibility of experimental long-range radar.
The survey vessel should be able to SeaSoar on the single cross-shelf lane. If SeaSoaring on other cross-shelf lines is precluded, then the ship will conduct a CTD/ADCP survey. The hope is to cover the 8-line "big box" region as sampled during spring-summer 2001.
The next level of desired spatial coverage would be two more cross-shelf lines so that the SeaSoar operation could provide some 3D information around the central line (e.g., Cascade Head). Jack and others will think more about what the N-S separation of those lines would be. An even more desirable solution would be to have a "big box" capability over 3-5 widely spaced lines (e.g., 15 km as during spring-summer 2001) and the ability to conduct a "small box" with about 7.5 km on either side of the central line.