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Abstract In the surfzone, breaking‐wave generated eddies and vortices transport material along the coast and offshore to the continental shelf, providing a pathway from land to the ocean. Here, surfzone vorticity is investigated with unique field observations obtained during a wide range of wave and bathymetric conditions on an Atlantic Ocean beach. Small spatial‐scale [O(10 m)] vorticity estimated with a 5 m diameter ring of 14 current meters deployed in ∼2 m water depth increased as the directional spread of the wave field increased. Large spatial‐scale [O(100 m)] vorticity calculated from remote sensing estimates of currents across the surfzone along 200 m of the shoreline increased as alongshore bathymetric variability (channels, bars, bumps, holes) increased. For all bathymetric conditions, large‐scale vorticity in the inner surfzone was more energetic than in the outer surfzone. 

Abstract Currents transport sediment, larvae, pollutants, and people across and along the surfzone, creating a dynamic interface between the coastal ocean and shore. Previous field studies of nearshore flows primarily have relied on relatively low spatial resolution deployments of in situ sensors, but the development of remote sensing techniques using optical imagery and naturally occurring foam as a flow tracer has allowed for high spatial resolution observations (on the order of a few meters) across the surfzone. Here, algorithms optical current meter (OCM) and particle image velocimetry (PIV) are extended from previous surfzone applications and used to estimate both cross-shore and alongshore 2-, 10-, and 60-min mean surface currents in the nearshore using imagery from both oblique and nadir viewing angles. Results are compared with in situ current meters throughout the surfzone for a wide range of incident wave heights, directions, and directional spreads. Differences between remotely sensed flows and in situ current meters are smallest for nadir viewing angles, where georectification is simplified. Comparisons of 10-min mean flow estimates from a nadir viewing angle with in situ estimates of alongshore and cross-shore currents had correlationsr²= 0.94 and 0.51 with root-mean-square differences (RMSDs) = 0.07 and 0.16 m s⁻¹for PIV andr²= 0.88 and 0.44 with RMSDs = 0.08 and 0.22 m s⁻¹for OCM. Differences between remotely sensed and in situ cross-shore current estimates are at least partially owing to the difference between onshore-directed mass flux on the surface and offshore-directed undertow in the mid–water column. 

This archive contains 2-min mean remotely sensed surface currents generated using optical imagery and PIV (Dooley et al., 2024) from field experiments (2013, 2018, 2021, 2022) occurring at the U.S. Army Corps of Engineers Field Research Facility, in Duck, NC. The README.txt file contains information regarding variables found in the MATLAB (PVLAB_PIV_SurfaceFlows.mat) file, including estimate locations, units, and timestamps. Estimates were generated at times with appropriate conditions for remote sensing (e.g., sufficient foam tracer) that were within 1-day of measured bathymetry at the field site. Additional data for the field site (obtained by the USACE Field Research Facility or by NOAA) including the measured bathymetry and wave conditions can be found at: https://chlthredds.erdc.dren.mil/thredds/catalog/frf/catalog.html Remote sensing estimates are not perfect and errors in filtering out bad data are possible. Please reach out to Ciara Dooley at cdooley@whoi.edu, Steve Elgar at selgar@mac.com, and Britt Raubenheimer at braubenheimer@whoi.edu if you have any questions. Additionally, the optical imagery (large dataset, many TBs) used to generate flow estimates can be accessed by contacting the authors.