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Fontan, A, Cornuelle B.  2015.  Anisotropic response of surface circulation to wind forcing, as inferred from high-frequency radar currents in the southeastern Bay of Biscay. Journal of Geophysical Research-Oceans. 120:2945-2957.   10.1002/2014jc010671   AbstractWebsite

The short-term (less than 20 days) response of surface circulation to wind has been determined in waters of the southeastern Bay of Biscay, using wind impulse response (time domain) and transfer (frequency domain) functions relating high-frequency radar currents and reanalysis winds. The response of surface currents is amplified at the near-inertial frequency and the low-frequency and it varies spatially. The analysis indicates that the response of the ocean to the wind is slightly anisotropic, likely due to pressure gradients and friction induced by the bottom and coastline boundaries in this region. Thus, the transfer function at the near-inertial frequency decreases onshore due to the coastline inhibition of circularly polarized near-inertial motion. In contrast, the low-frequency transfer function is enhanced toward the coast as a result of the geostrophic balance between the cross-shore pressure gradient and the Coriolis forces. The transfer functions also vary with season. In summer, the current response to wind is expected to be stronger but shallower due to stratification; in winter, the larger mixed layer depth results in a weaker but deeper response. The results obtained are consistent with the theoretical description of wind-driven circulation and can be used to develop a statistical model with a broad range of applications including accurate oceanic forecasting and understanding of the coupled atmosphere-ocean influence on marine ecosystems.

Kim, SY, Cornuelle BD, Terrill EJ, Jones B, Washburn L, Moline MA, Paduan JD, Garfield N, Largier JL, Crawford G, Kosro PM.  2013.  Poleward propagating subinertial alongshore surface currents off the US West Coast. Journal of Geophysical Research-Oceans. 118:6791-6806.   10.1002/jgrc.20400   AbstractWebsite

The network comprising 61 high-frequency radar systems along the U.S. West Coast (USWC) provides a unique, high resolution, and broad scale view of ocean surface circulation. Subinertial alongshore surface currents show poleward propagating signals with phase speeds of O(10) and O(100-300) kmd-1 that are consistent with historical in situ observations off the USWC and that can be possibly interpreted as coastally trapped waves (CTWs). The propagating signals in the slow mode are partly observed in southern California, which may result from scattering and reflection of higher-mode CTWs due to curvature of shoreline and bathymetry near Point Conception, California. On the other hand, considering the order of the phase speed in the slow mode, the poleward propagating signals may be attributed to alongshore advection or pressure-driven flows. A statistical regression of coastal winds at National Data Buoy Center buoys on the observed surface currents partitions locally and remotely wind-forced components, isolates footprints of the equatorward propagating storm events in winter off the USWC, and shows the poleward propagating signals year round.