Diurnal Baroclinic Shelf Waves in the Area of the South Kuril Islands Observed in TOPEX/Poseidon Satellite Altimetry Data

Abstract

The existence zones of diurnal shelf waves near the South Kuril Islands were determined based on the analysis of small-scale amplitude and phase variations of diurnal O1 and K1 tidal waves estimated from along-track TOPEX/Poseidon altimetry data. The amplitudes and phases of the these waves were revealed not only along the original tracks (1992)(1993)(1994)(1995)(1996)(1997)(1998)(1999)(2000)(2001)(2002), but also along those shifted by half the intertrack distance (2002)(2003)(2004)(2005). This made it possible to more accurately determine the zone of existence of diurnal shelf waves. It was found that these waves, existing in the form of baroclinic coastal trapped modes, strongly in uence tidal motions on the oceanic shelf of Urup and Iturup islands. Two wavelengths t in this section of the shelf (one pair of quasi-stationary eddies is localized on the shelf of Urup Island and the second one on the shelf of Iturup Island). This is an unexpected and interesting result; barotropic shelf modes usually form one pair of eddies (for example, on the northeaster shelf of Sakhalin Island, on the northern shelf of Hokkaido Island and on the oceanic shelf of the North Kuril Islands). We found that the zone of in uence of both K1 and O1 tidal waves starting from Chirpoi Island, which means that shelf waves are generated as a result of the diffraction of a large-scale Kelvin tidal wave on the deep Bussol Strait. The existence of lower frequency O1 tidal shelf wave was found not only on the shelf of Urup and Iturup islands, but also on the shelf of Shikotan Island, which is consistent with the earlier results of Ye mov and Rabinovich (1980). Diurnal shelf waves cause signi cant increase of O1 and K1 amplitudes on the coast of Iturup Island (especially in its southern part) and Urup Island in comparison with the open ocean and produce strong diurnal tidal currents in these regions, as it follows from the direct instrumental. Baroclinic diurnal shelf (coastal trapped) waves are also the reason of vertical movements, forcing water temperature variations at su ciently great depths, which can have a signi cant impact on the living conditions of benthic communities.