TITLE: GLOBEC Collaborative Research: Mesoscale and finescale mapping of physical and biological fields in the northern California Current system
T. Cowles, J. Barth, S. Pierce [Al l at Oregon State University], W. Peterson [Northwest Fisheries Science Center and Oregon State Univ.]

This collaborative proposal will address the mesoscale physical and biological oceanographic distributions and processes that influence juvenile salmonid habitat characteristics along the Oregon/California coast. We prop ose to characterize, across a range of spatial scales, the circulation patterns associated with upwelling fronts and coastal jets, particularly in response to coastal promontories such as Cape Blanco. These patterns will be evaluated in the context of the retention and/or loss of phytoplankton and zooplankton bio mass and species within the coastal system in both spring and late summer. We will use an instrumented, towed, undulating vehicle to map physical and biological distributions over spatial scales of 5-30 km along the Oregon/California coast. The SeaSoar ve hicle will be equipped with appropriate sensors/instrumentation to measure physical fields (conductivity, temperature, depth), phytoplankton and bio-optical parameters (multi-wavelength fluorometers and multi-wavelength absorption meters), copepod and sma ll euphausiid mesozooplankton (Optical Plankton Counter), and large euphausiids and fish (HTI Acoustics system) for the mesoscale region extending from Newport, OR to Eureka, CA. In addition there will be continuous underway surface sampling and alongtrac k Acoustic Doppler Current Profiling (ADCP) of water transports. Primary responsibility for data collection and analysis is tasked as follows: physics (Barth), phytoplankton (Cowles), mesozooplankton (Peterson), juvenile and adult euphausiids, (Peterson and Pierce), and ADCP (Barth and Pierce). Additional in situ sampling and processing of phytoplankton (Cowles) and mesozooplanton and euphausiids (Peterson) will be done to calibrate the remotely sensed observations. The onshore-offshore t ransects will extend 150 km offshore in order to capture the offshore meandering currents and eddy structure prevalent in the region. Mesoscale surveys will be conducted twice (May and September) during years 1 and 3 of the project (2000 and 2002), and wi ll require approximately 8-10 days to complete, including associated in situ sampling directed at specific target features. Immediately following each mesoscale survey will be a sequence of interconnected finescale mapping surveys of a region ca. 50 km of fshore extent by 80 km alongshore, with 5 km spacing between onshore-offshore transects (requiring about 2 days), followed by process-oriented field studies (requiring 2 days). This combined 4-day survey-process activity will be repeated at least twice du ring each cruise at each of two locations (north of Cape Blanco, south of Cape Blanco). We expect these locations to display contrasting juvenile salmonid habitat properties due to the offshore transition of the main jet of the California Current at Cape Blanco which results in distinctly different physical and biological regimes north and south of the Cape. We propose 25 days of shiptime for each of these cruises (including transit time), for a total of 50 days at sea in each of the field years. We anti cipate close collaboration with funded GLOBEC investigators and new proposers, including physical/biological modeling (McWilliams), salmon surveys (Brodeur et al), euphausiid swarming (Miller), primary productivity (Abbott and Letelier), satellite remote sensing (Strub), coastal radar studies (Kosro and Paduan), and marine mammals and seabirds (Tynan and Ainley).

STATEMENT OF WORK FOR YEAR ONE

The first year of work will include equipment calibration and testing, followed by two 25-day ocea n surveys, one in late April/early May and the second in late August/early September. We propose to coordinate our field work with the on-going Long-Term Observational Program (Huyer et al.) that is conducting transects normal to the Oregon and Californi a coasts from Newport OR to Eureka CA five times per year. Immediately following the LTOP cruise from Newport to Eureka in April and August 2000, we will conduct a mesoscale mapping survey of the physics, phytoplankton, and zooplankton between Eureka and Newport, towing a SeaSoar vehicle instrumented with CTD, bio-optics, and an Optical Plankton Counter and a new towed bioacoustics system for the detection of large zooplankton and juvenile fish. (see Figure 1 for a map of the study area). The onshore-offs hore transects will provide 1m vertical resolution to within 10m of the bottom over the continental shelf, or to a depth of 350m off the shelf.

May and September:

Coarse mesoscale (30 km spacing between offshore lines) between Eureka and Newport ( once per cruise). The SeaSoar undulations along the 15 lines will be equivalent to approximately 100 CTD casts per line, or an ocean volume defined by approximately 1500 CTD casts. This portion of the cruise will require 7-8 days of shiptime.

Finescal e (5 km spacing between offshore lines) within survey box 1 and 2 (north and south of Cape Blanco, Figure 1) twice per cruise. These smaller grid surveys will have an offshore and alongshore extent of approximately 50 km and 80 km, respectively.

Durin g the coarse and finescale surveys we will measure

Temperature, salinity, sigma-t,

Currents from shipboard ADCP, Bio-optics: PAR, multi-wavelength fluorescence, multi-wavelength particulate absorption and attenuation,

Optical plankton counting: biomass and size distribution of mesozooplankton,

Bio-acoustics: biomass and size discrimination,

Surface nutrients, particulate carbon, nitrogen, phytoplankton pigments from the underway flow system.

Ea ch finescale survey will be followed by a process study within that survey box that will consist of

Vertical profiling with CTD and bio-optical instruments (with discrete sample collection of nutrients, particulate C & N, phytoplankton pigments) to de fine the vertical structure of physical, biological and chemical properties while tracking a specific water mass,

Zooplankton tows (MOCNESS) along fronts and boundaries of coastal jet.

These finescale surveys and process studies will requ ire approximately 16 days of shiptime.

At the end of each cruise, we will process the SeaSoar CTD and bio-optical datasets, create maps of physical properties, calculate circulation and transport of biological properties, and evaluate the habitat char acteristics of the coastal zone north and south of Cape Blanco. We will collaborate with other investigators within GLOBEC for the most effective interpretation of the mesoscale patterns and processes. These collaborations include Abbott and Letelier (pri mary production), Kosro (coastal radar), Brodeur et al. (salmon surveys), Huyer et al. (LTOP), McWilliams (modeling), Strub and Abbott (satellite remote sensing), Miller (euphausiid swarming), and Tynan and Ainley (marine mammal and seabird distributions).

This page was last updated on March 15, 2007.

Maintained by:
Hal Batchelder
College of Oceanic and Atmospheric Sciences
Oregon State University
Corvallis, OR 97331-5503
phone: 541-737-4500; FAX 541-737-2064