The interdecadal variation characteristics of arctic sea ice cover - ENSO-East Asian monsoon and their interrelationship at quasi-four years time scale

Interdecadal and quasi-four years variation characterstics of Arctic sea ic e cover, ENSO and East Asian monsoon index (EAMI) are analyzed based on Sin gular Spectrum Analys. (SSA), lead-lag correlation and EOF for the past fou r decades. Results show that the Arctic sea ice cover decreased in the earl y 1970s, several years earlier than that of global SSTA increase in the mid 1970s, which indicates that recent warming over the Northern Hemisphere fi rstly begins in the Arctic region in the 1970s. Great change of the East As ian monsoon intensity from stronger to weaker in summer (from weaker to str onger in winter) took place in the mid 1970s response to the abrupt modulat ion of SSTA particularly in the tropical eastern Pacific. Focus on the quas i-four years oscillation, close relationship is found among the sea ice cov er, ENSO and EAMI based on lead-lag correlation. In which, the correlation coefficient reaches its maximum when the index of NINO3 SSTA variation take s 6 and 9 months lead of the western Pacific subtropical high and sea ice c over index in Section-III. Their interaction can be explained in the framew ork of asymmetric Walker circulation anomaly and Western Pacific Northern P ole (WPN) teleconnection pattern in the context of quasi-four years oscilla tion.