Identification of tidal mixing fronts from high-resolution along-track altimetry data

Abstract

Coastal fronts can significantly impact the cross-shelf material exchange and the marine ecosystem. Therefore, it is important to detect their locations and intensities as well as temporal evolutions. In this article, we show that coastal tidal mixing front (TMF) signals can be extracted from both 20-Hz and 1-Hz along-track sea surface height anomalies (SSHA) measured by satellite altimetry. The physical mechanism for the existence of the TMF in the SSHA data is explained. Then the Hilbert-Huang Transform is applied to selected along-track Jason-2 data over Georges Bank. The extracted fronts have a cross-front sea surface height difference of 13–21 cm over distance of 20–27.5 km. The surface geostrophic current anomalies associated with these fronts are estimated to be 0.38–0.45 m s−1, consistent generally with previous studies from in situ observations. The present study clearly demonstrates the potential of satellite altimetry for monitoring TMFs. It is also shown that tidal fronts can be better extracted from the 20-Hz than 1-Hz data.