Slope‐induced tidal straining: Analysis of rotational effects. Issue 3 (16th March 2017)

• Record Type: Journal Article
• Authors: Schulz, Kirstin; Endoh, Takahiro; Umlauf, Lars
• Is Part Of: Journal of geophysical research. Volume 122:Issue 3(2017)
• Page Start: 2069
• Page End: 2089
• Publication Date: 2017-03-16
• Subjects: tidal straining -- bottom boundary layer -- turbulence -- sediment transport; Oceanography -- Periodicals; 551.4605
• DOI: 10.1002/2016JC012448
• Languages: English
• ISSNs: 2169-9275

Abstract

Abstract: Tidal straining is known to be an important factor for the generation of residual currents and transports of suspended matter in the coastal ocean. Recent modeling studies and field experiments have revealed a new type of "slope‐induced" tidal straining, in which the horizontal density gradient required for this process is induced by the presence of a slope rather than by river runoff (as in classical tidal straining). Slope‐induced tidal straining is investigated here with the help of an idealized numerical model, and results are compared to a recent data set from the East China Sea providing first direct observational evidence. The focus of this study is on the effect of rotation that was ignored in previous investigations. The model is shown to reproduce the key features of the observations, in particular the strain‐induced generation of unstable stratification in the bottom boundary layer during periods of upslope flow. Rotation effects are found to significantly reduce the upslope tidal pumping of suspended material and also give rise to a newly identified pumping mechanism that results in a vigorous transport of suspended material along the slope. It is shown that slope‐induced tidal straining is likely to be relevant for a wide range of oceanic slopes exposed to tidal motions. Key Points: Observational evidence of slope‐induced straining could be reproduced with a one‐dimensional numerical model Earth rotation induces a significant along‐slope flux of suspended sediment When the main current is orientated along‐slope, the tidal pumping contribution to the cross‐slope flux is reduced or inverted