Annual and Intra-annual Sea Level Variability in the Region of the Kuroshio Extension from TOPEX/POSEIDON and Geosat Altimetry

Abstract

Using 4.2 years of sea surface height data collected by the TOPEX/POSEIDON altimeter and 2.3 years of data collected by the Geosat altimeter, the authors study the annual, intra-annual, and linear-trend sea level height variability in the region of the Kuroshio Extension. Both the annual and intra-annual variabilities are separated spatially into large (≥2000 km), intermediate (?1500 km), and short scales (?800 km). The intermediate and short-scale annual and intra-annual sea level height fluctuations in both periods have large components with two-dimensional phase propagation. Close correspondence between the characteristic spatial structure of both the intermediate and short-scale annual and intra-annual sea level height fluctuations and major bottom topographic features suggests that bottom topography plays a critical role in the generation of those low-frequency variabilities. On the other hand, large-scale annual variability is primarily a standing oscillation, and bottom topography does not appear to be involved in its generation. The linear trend of the sea level change in the 4.2-yr TOPEX/POSEIDON period suggests that both the northern and the southern recirculations have been weakening considerably in the last 4.2 years, and that there exists a strong intradecadal to decadal sea level height change.