Sand transport in the northeastern Caribbean characterized by wind-wave-current data

Sand transport around the northeastern Caribbean Virgin Islands (VI) is studied using global data-assimilation products and satellite measurements; with a focus on seasonal and event characteristics in the period 2002–2019. A review of applied research and a local statistical analysis indicate that currents accompanied by waves and wind mixing are capable of scouring near-shore sand bars.VI area (18.4–18.6N, 65.5–64.5W) time series analysis offer insights on the processes underlying suspended sediment concentrations estimated by 5 km resolution MODIS and VIIRS satellite red-band radiance. The winter season peak in turbidity derives from trade wind-driven waves and currents that reach critical thresholds to mobilize and transport the coarse sands. Instead of wave height, wave steepness and mixed layer depth are applied as coefficients to HYCOM3 near-surface currents, to create a multi-variate sand transport index. Statistical regression shows that a strengthened North Atlantic anticyclone and associated winter trade winds in the VI archipelago results in surface cooling and a deep mixed layer, making steep waves and westward currents more effective in sand transport.The leading case of satellite red-band radiance followed many months after the passage of tropical cyclones in September 2017. A sustained spell of intense trade winds in February 2018 induced 3 m waves of 3% steepness and near-surface currents up to 0.5 m/s. Rapid sea level oscillations >0.05 m suggest that long-period waves joined local wind-waves to mobilize coarse sands within a mixed layer >50 m deep. The plume of sand exhibited composite VIIRS red-band radiance of 0.1 W m⁻² μm⁻¹ sr ⁻¹; supplying coarse light-colored sands to downstream Caribbean islands.This study has universal application to near-shore sand transport by demonstrating the use of a high-resolution multi-variate index from freely available global data-assimilation products. Given rising sea levels, beach erosion and limited field data, such an index is an essential tool in coastal management.