Event-Scale to Interannual Variations in Shelf Water Properties and Dynamics

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A glider-based observational study of shelf-slope dynamics designed to examine the relative roles of wind-forcing and bathymetry (simple and complex geometries) over a broad range of timescales is proposed. Initially, gliders will be employed to occupy a single cross-shelf section in a region of relatively simple bathymetry (north of Heceta Bank, along a regularly-occupied hydrographic line). This effort will involve two Webb Research Corporation 200-m gliders (already owned by the PIs) operating serially to provide continuous time series. During the second year, the PIs request support for a third, 1000-m capable glider to be added to the rotation which will then include a second line, south of Heceta Bank, to measure wind-driven response over complex bathymetry. Gliders require roughly 5 days to traverse each section, yielding four crossings per 20-day mission. The three-year record of sections will be combined with remote sensing data, moored time series and numerical simulations to examine weather-band to interannual variability in water mass properties, stratification and along-shelf transport, evaluate how wind-forcing and bathymetry govern coastal jet separation and to test two-dimensional upwelling and downwelling front models. The study addresses a suite of important issues in coastal dynamics using a technology that permits year-round sampling. With three years of sections repeated at 5-day intervals, sampling will capture multiple realizations of target processes. Frequent section occupations under a range of forcing conditions will provide an exceptional data set for examining how variable wind and buoyancy forcing interact with differing underlying bathymetry to govern evolution of the coastal jet. The combination of long time series and weather-band temporal resolution will lend a statistical confidence to the results beyond that normally available.