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Coastal Ocean Advances in Shelf Transport (COAST) Project Leaders (Oregon State University): Jack Barth, Patricia Wheeler and John Allen Co-Principal Investigators (all OSU unless indicated otherwise): Mark Abbott, John Bane (UNC), Tim Boyd, Doug Caldwell, Tim Cowles, Jianping Gan, Burke Hales, Mike Kosro, Ricardo Letelier, Murray Levine, Jim Moum, Bill Peterson (also NMFS), Roger Samelson, Yvette Spitz and Alexander van Geen (LDEO) A collaboration between scientists at Oregon State University, the University of North Carolina and the Lamont-Doherty Earth Observatory has been funded by CoOP to address a specific set of scientific hypotheses related to cross-shelf transport processes in a wind-driven system by conducting field experiments off the Oregon coast together with coordinated ocean circulation/ecosystem and atmospheric modeling. The hypotheses, motivated below, are: (H1) the presence of upwelling and downwelling jets and fronts locally alters cross-shelf circulation in the surface and bottom boundary layers and in the interior; (H2) alongshore topographic variations dictate the relative importance of two-dimensional versus three-dimensional cross-shelf transport processes; (H3) patterns of turbulence on the shelf during upwelling and downwelling are influenced by fronts and jets, and the levels of turbulence can reach sufficient intensity to influence the mesoscale circulation; (H4) the magnitude and distribution of primary production on the shelf and its subsequent transport offshore is controlled solely by the geometry of upwelling as described in H1 and H2; (H5) (a hypothesis competing with H4) alongshore variations in turbulent mixing control the magnitude and distribution of primary production, e.g. via enhanced nutrient and/or trace chemical supply from the bottom boundary layer; (H6) the reduced cross-shelf transport implied by the presence of a downwelling front 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. The Oregon coastal ocean exhibits a strong wind-driven response, both physically and biologically and in both upwelling favorable (summer) and downwelling favorable (winter) seasons. Off northern Oregon, the region of active upwelling is narrow and the bottom topography is relatively uniform alongshore. Here, three-dimensional effects should be minimized and the presence of a strong baroclinic upwelling jet and front will locally alter cross-shelf circulation in the surface and bottom boundary layers (BBL) and in the interior. Off central Oregon, the continental shelf broadens and alongshore uniformity is broken by Heceta Bank. The distribution of cold water and surface chlorophyll from satellite imagery mimics the width of the continental shelf, suggesting the control of bottom topography on shelf circulation and upwelling. An exception to this general pattern is associated with Heceta Bank, where cold, chlorophyll-rich upwelled water is found well seaward of the continental shelf break, representing an important cross-shelf transport process. Far less is known about the shelf flow and thermohaline fields during the downwelling season. Recent two-dimensional modeling results predict the formation of a strong downwelling front and jet near the mid-shelf. Offshore of the mid-shelf density front there is onshore transport in a surface Ekman layer, which turns downward at the mid-shelf front, and returns offshore in a thick BBL. Inshore of the downwelling front, the water column is well mixed, the alongshore flow is considerably reduced compared with that in the mid-shelf jet, and cross- shelf flow is nearly zero. Thus, the inner shelf is a region of relatively quiescent flow. To address the above hypotheses we will make intensive observations in two regions off the Oregon coast during the upwelling season: one north of Newport in a region of relatively simple topography and one south of Newport centered on Heceta Bank. High-resolution sampling will be conducted using two ships simultaneously. One ship will conduct rapid, high-resolution surveys of the three-dimensional thermohaline, bio-optical, zooplankton and velocity fields using SeaSoar, shipboard ADCP and a towed, multi-frequency acoustics system (Barth, Cowles, Peterson). A second ship, operating within the same region, will conduct high-vertical resolution profiling of water properties: T, S, turbulence (Moum, Caldwell), nutrients and carbonate species (Hales), phytoplankton photosynthesis parameters via Fast Repetition Rate fluorometry (Letelier, Abbott), particulate and dissolved organic material (Wheeler, Cowles) and the important trace metal iron (van Geen). We will conduct two three-week cruises during the upwelling season (June and August) 2001 and sampling will take place in both the northern and southern regions during each cruise in order to directly compare results. A downwelling experiment will be conducted during Jan-Feb 2003 during one three-week cruise and measurements will be concentrated in the northern study region where the bottom topography is simpler. An instrumented aircraft will be used to make measurements of the lower atmosphere (wind, temperature, humidity, pressure) and the upper ocean (SST, ocean color, subsurface temperature via AXBTs) (Bane). A set of moorings, spanning the continental shelf in each study region and equipped with instruments to measure velocity, T, C, spectral irradiance, phytoplankton fluorescence and particulate light scattering, will be deployed during both upwelling and downwelling experiments (Levine, Boyd, Kosro, Abbott, Cowles, Letelier) . Land-based coastal radar will be used to make high-spatial resolution surface current maps (Kosro). A high-resolution, three-dimensional shelf circulation and coupled ecosystem ocean model will be used in direct support of the field experiments by contributing to the dynamical synthesis of the observations and for relevant process studies (Allen, Gan, Spitz). A mesoscale atmospheric modeling effort will provide estimates of surface forcing, continuous in space and time, for the ocean model and for interpretation of the oceanic observations (Samelson). The COAST project will obtain satellite remote sensing information through existing projects at OSU: ocean color (Mark Abbott) and SST (Ted Strub). Other collaborations include the regular sampling being done off Newport through GLOBEC (Jane Huyer, Bob Smith, et al.) and the nearshore (15-m isobath) observations being made as part of the PISCO project to study oceanographic influences on marine communities in the rocky intertidal (Jane Lubchenko and Bruce Menge, OSU Zoology).