SPATIAL VARIATION OF WINTER SEA SURFACE TEMPERATURE IN NORTH PACIFIC AND ITS RELATION TO ATMOSPHERIC OSCILLATION MODES

The spatial variation of sea surface temperature anomalies (SSTA) in the North Pacific Ocean during winter is investigated using the EOF decomposition method. The first two main modes of SSTA are associated with Pacific Decadal Oscillation (PDO) mode and North Pacific Gyre Oscillation (NPGO) mode, respectively. Moreover, the first mode (PDO) is switched to the second mode (NPGO), a dominant mode after mid-1980. The mechanism of the modes’ transition is analyzed. As the two oceanic modes are forced by the Aleutian Low (AL) and North Pacific Oscillation (NPO) modes, the AR-1 model is further used to examine the possible effect and mechanism of AL and NPO in generating the PDO and NPGO. The results show that compared to the NPO, the AL plays a more important role in generating the NPGO mode since the 1970s. Likewise, both the AL and NPO affect the PDO mode since the 1980s.