Seasonal Two-way Relationships among the Sea Surface Net Heat Flux in the Kuroshio Extension Region and the North Pacific Climate Indices during 1989 – 2006

Seasonal variations of oceanic and atmospheric variables are dominant in mid- and high-latitude regions and are thought to play important roles in the mechanisms underlying the interannual and seasonal Pacific climate variability. The sea surface net heat flux is one of the key components of oceanic and atmospheric variables. In this study, to better understand the role of seasonal atmosphere-ocean interactions in the mechanism underlying the North Pacific climate variability, the seasonal correlations among the satellite-derived net heat flux (HFN) in the Kuroshio Extension region, the North Pacific index (NPI), the NINO3.4 index representing the El Nino-Southern Oscillation events and the Pacific Decadal Oscillation (PDO) index from January, 1989 to December, 2006 are examined. According to the specified criteria, 8 dominant relations with rapid responses shorter than 6 months are identified together with 6 dominant relations with slow responses longer than 12 months. The two-way relationships in the different seasons except between PDO and NINO3.4, are detected, i.e., the HFN and NPI respond to PDO and NINO3.4, respectively, but the PDO and NINO3.4 respond to HFN and NPI, respectively, in different seasons. Among the 14 relations, the February PDO response to the December NPI before 2 months has the highest correlation, the April NINO3.4 response to the December HFN before 4 months has the second highest correlation, and the September PDO response to the June NINO3.4 before 3 months has the third highest correlation. The spring NINO3.4 is found to delay the NPI by 3 years, while the fall NINO3.4 leads the NPI by 2 years. These two-way relationships with slow responses provide a new basis for the long-term prediction of ENSO events.