Spatiotemporal characteristics of the sea level anomaly in the Kuroshio Extension using a self-organizing map

Abstract

AbstractSatellite altimeter SSH data in the Kuroshio Extension (KE) region gathered during the period January 1993 to December 2014 are analyzed using self-organizing map (SOM) analysis. Four spatial patterns (SOM1, SOM2, SOM3, and SOM4) are extracted, and the corresponding time series are used to characterize the variation of the sea level anomaly. Except in some individual months, SOM1 and SOM2 with single-branch jet structures appear alternately during the periods 1993–1998 and 2002–2011. However, during 1999–2001 and 2012–2014, SOM3 and SOM4 with double-branch jet structures are dominant. The sea level anomalies exhibit interannual variations, while the KE stream demonstrates decadal variation. For SOM1, the change in the KE path is less evident, although the KE jet is strong and narrow. For SOM2, the KE jet is weakened and widened and its jet axis moves towards the southwest. Compared with the SOM3, for SOM4 the trough and ridge in the upstream KE region are deeper in the northeast–southwest directio...