Interannual Sea Level Variability in the North Pacific Ocean and Its Mechanisms

• Published in: Chinese Journal of Geophysics
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 2010
• Subjects: Bering Sea; Pacific; Subarctic; Alaska
• Online Access: http://dx.doi.org/10.1002/cjg2.1472; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1002%2Fcjg2.1472; https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1002/cjg2.1472

Abstract We use the 15 years (1993~2007) data of monthly‐averaged sea surface height anomalies (SSHA) to analyze their interannual spatial and temporal variability and their thermodynamic and dynamic mechanisms. The result shows that the prominent interannual variability occurred in the Kuroshio Extension and the western Pacific warm pool. According to decomposition using the EOF method, the first mode of interannual SSHA is more likely zonal, while the second is much more meridional. The steric SSHA induced by the heat flux explains more than 40% of interannual SSHA in the middle‐latitudinal northeastern Pacific Ocean. The time‐varying barotropic Sverdrup balance can account for 20%~40% in the western subarctic gyre, whereas their interannual variations are indistinctive. Among the baroclinic mechanisms, the first baroclinic Rossby waves model forced by large‐scale wind stress could explain the interannual SSHA 20%~60% in the tropical Pacific, 20%~40% in the central middle‐latitudes, and 20%~60% in the eastern Alaska gyre and western subarctic gyre, respectively. The interannual SSHA induced by the local Ekman pumping has a local structure, which could explain more than 40% of the observed changes in the northeast Pacific Ocean, likewise in the Bering sea and central tropical Pacific Ocean. The westward propagating Rossby waves, derived from the difference between the Rossby waves model and Ekman pumping model simulating SSHA, could explain 20%–60% of the interannual SSH observations in the central and western subtropical gyre and east of the Hawaiian Islands.