Climatological Mean Features and Interannual to Decadal Variability of Ring Formations in the Kuroshio Extension Region

Abstract:

We examine the climatological mean features of oceanic rings shed from the Kuroshio Extension jet and their interannual to decadal variability using satellite altimeter observations from October 1992 to December 2010. To objectively capture a ring shedding from the Kuroshio Extension jet, a new method that consists of the detection of the jet length changes and the tracking of a ring is proposed. A spatial distribution of the ring formations in the Kuroshio Extension region indicates that cyclonic (cold-core) rings were most frequently formed in the upstream region between 143°–147°E around the steady meander of the Kuroshio Extension jet. In contrast, most of anticyclonic (warm-core) rings formed in the downstream region west of the Shatsky Rise. These pinched-off rings in both the upstream and downstream regions generally propagate westward, but about two-third of the rings is reabsorbed by the jet. Nevertheless, about one-fourth of the meridional eddy heat transport at the latitude of the Kuroshio Extension results from the rings that are not reabsorbed by the jet. The number of ring formations shows substantial interannual to decadal variability. In the upstream and downstream Kuroshio Extension region, decadal and interannual variability is dominant, respectively. These fluctuations of the ring formations are negatively correlated with the strength of the Kuroshio Extension jet. It is also revealed that the ring formation variations play an important role in sea surface temperature changes north of the Kuroshio Extension jet.