Multidecadal variability of the upper ocean heat content anomaly field in the North Pacific and its relationship to the Aleutian low and the Kuroshio transport

The upper ocean heat content (OHC) anomaly field in the North Pacific is analyzed to explore its relationship with the Aleutian Low (AL), Kuroshio transport (KT), core-layer temperature of the North Pacific subtropical mode water (CLT), sea-surface temperature (SST), and sea-level pressure (SLP) on a multidecadal timescale. It is found that the OHC anomaly circulates clockwise around the North Pacific subtropical gyre and that the clockwise propagation is closely linked to AL, KT and CLT after 1980. It was pointed out that five years after the intensification of AL, the volume transport associated with KT started to increase, and several years later, the magnitudes of the CLT and the OHC anomalies in the region southeast of Japan also began to increase. Such a relationship is similar to that on an interdecadal scale pointed out in previous studies. It is also shown that the OHC, SST and SLP anomalies are in phase to the southeast of Japan and also in the mid-latitudes of the central Pacific to the east of the Kuroshio Extension. In these regions, the clockwise propagation of OHC is found to have been enhanced. The results of this study provide new information on the spatio-temporal variability of the OHC anomalies and their relationship to the related atmospheric and oceanic anomaly fields on a multidecadal scale.