2014 Volume 23 Issue 6 Pages 197-216
Annual barotropic and baroclinic responses of sea level anomalies (ΔDBT and ΔDBC) in the western North Pacific to seasonally varying wind stress curl are extracted by combining the sea surface height anomaly (SSHA) observed by satellite altimeter with the dynamic height anomaly (ΔDjdbar; j is the reference depth) calculated by the density fields observed by Argo floats, i.e., ΔDBT＝SSHA -ΔD2000 and ΔDBC＝ΔD2000 -DML (ML is the surface Mixed Layer depth). The most conspicuous feature in the seasonal change in ΔDBT is the tongue of negative values at the region of subarctic gyre in late winter (February to March) extending southward to the Izu-Ogasawara Ridge (IOR) in subtropical gyre. For annual ΔDBC variation, one of the much larger positive amplitude is also found in areas surrounding IOR in spring (April to May), suggesting the generation of the baroclinic activity through the coupling of the barotropic and baroclinic modes of motion on the steep bottom slope, i.e., the impinging response. The next prominent ΔDBC variability seems to be the adjustment of the ocean in terms of the baroclinic first-mode annual Rossby Waves, which can theoretically exist south of about 40°N.
