Changes in North Pacific Wave Climate Since the Mid-1990s

Abstract:

Ocean wave reanalysis and in-situ wave observations show marked downward trends in significant wave height exceeding -0.1 m per decade in the mid-latitude of the North Pacific since the mid-1990s. Mean wave period in the tropical Pacific also shows downward trends exceeding -0.4 s per decade during this period. These changes in wave climate in the North Pacific and tropical Pacific are found to be attributable to recent changes in tropical Pacific climate. The downward trends in significant wave height in the mid-latitude North Pacific are found to be due to frequent occurrence of the negative phase of the Pacific-North American (PNA) pattern. The downward trend in the mean wave period in the tropical Pacific is found to result from an increased (decreased) occurrence frequency of wind wave (swell) which is caused by strengthened near-surface easterly winds in the equatorial Pacific.