Downslope Eulerian mean flow associated with high-frequency current fluctuations observed on the outer continental shelf and upper slope along the northeastern United States continental margin: implications for sediment transport

Eulerian current measurements made 5–7 m above bottom at six stations along the United States east coast continental margin show a net downslope flow of 1–5 cm s−1. Although the scalar current speed decreases with water depth and toward the bottom, fluctuations in the cross-isobath flow were stronger and increasingly asymmetric near the bottom. Maximum downslope flow exceeded maximum upslope flow by a factor of two to three. The strength of the low-passed downslope flow was proportional to the upslope Reynolds flux of density as well as to the amplitude of the current fluctuations that have periods shorter than 30 h. These flow characteristics may be caused by differential vertical mixing in the bottom boundary layer where a stratified fluid flows upslope (unstable) and downslope (stable). The asymmetry in current strength clearly favors net downslope transport of sediments that move as bedload.