Spatiotemporal current variation of coastal-trapped waves west of the Noto Peninsula measured by using fishing boats

Abstract Spatiotemporal current variations of coastal-trapped waves (CTWs) were investigated by using a current dataset obtained from daily fishing operations west of the Noto Peninsula (NTP), Japan. Cross-shore lines located in southern, middle, and northern parts of the west coast of the NTP were designed to detect characteristics of CTWs with a time interval of a few days and about 5-km resolution in the cross-shore direction. Accuracy validation by using moored current meter data and sea level data demonstrated that the established dataset expresses accurate variations with periods of several days. The generation and propagation of a CTW event associated with a low-pressure zone passing north of the study area in late May 2010 were analyzed. Along-shore currents with the coast on the right strengthened in every line simultaneously with the domination of the southerly wind, and then weakened in order from south to north simultaneously with weakening of the southerly wind. Although the along-shore currents of the CTWs linearly decreased heading offshore along the south and middle lines, these currents broadened within about 50 km from the coast along the north line, with small variations in the cross-shelf direction, with an increase in shelf width. These generation, propagation and current structure characteristics are clarified and interpreted by the characteristics of the estimated possible CTWs west of the NTP and numerical experiments, which reproduce wind-induced freely propagating CTWs. A change in the propagation characteristics and the structure of the CTWs associated with bottom topography indicates the possibility that adjustments can occur on the order of a few dozen kilometers.