The fine details of overmarsh circulation remain largely unexplored and yet they are typically assumed to control many attributes of salt marsh material cycling, transport, and accretion. We characterized the spatial and temporal variability in overmarsh circulation at a 2 km2 Georgia, USA, salt marsh using field observations, dye tracer, and numerical simulations. The marsh bathymetry was created with a high‐precision Global Positioning System survey that details the geomorphic structure of intertidal creeks and salt marsh platform features greater than about 1 m in width. We assessed flow path dynamics at four spatial scales ranging from 1 m to 1000 m. Results show the development and decay of simultaneous flow divergence and convergence, concentrated flow and large‐scale rotational flow, and strong differences between flood and ebb pathways. This current complexity is set by submergence and emergence of subtle salt marsh platform geomorphic structure, and it highlights the role of topography in system‐wide flow processes.
Data collected during winter from a set of offshore buoys and coastal meteorological stations on the continental shelf of the southeastern United States were analyzed as part of a meteorological and oceanographic study of the genesis of winter cyclones (Project GALE). The analyses were designed to describe the temporal and spatial variability of wind stress and heat flux over the shelf. While there were some episodes of strong spatial variations in wind stress, the wind field, on the whole, was remarkably uniform. Largest gradients were associated with times immediately preceding outbreaks of cold continental air over the shelf. Maximum heat fluxes occurred during these cold air outbreaks and reached as high as 1400 W/m2 on the outer shelf near the Gulf Stream. The largest wind stress values occurred in the cross‐shelf component and reached 0.7 Pa. The cross‐shelf wind was highly correlated with the geostrophic wind, but there were significant ageostrophic deviations in the alongshelf component. These deviations were correlated with fluctuations in sea‐air temperature differences. The fluctuations in heat flux are thought to modulate the alongshelf component by inducing added vorticity in the planetary boundary layer over the scale width of the continental shelf.
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