The vertical structure of North Pacific temperature anomalies

Abstract

The existence of large‐scale thermal anomalies in the North Pacific motivates a study of the reflection of a wind‐driven anomaly at the eastern boundary. A continuously stratified, linear model is used to calculate the vertical and horizontal structure of large‐scale waves forced by fluctuating wind stress patterns. Thermal anomalies caused by eastward, westward, and standing wind wave patterns are investigated. Although exact comparison with data is not possible, the model can predict downward phase propagation as observed at OWS station N without invoking friction or vertical mixing of heat. In the same solution, upward propagation is predicted at other locations. An eastward moving, forced anomaly in the thermocline transports energy toward the eastern boundary. In the model the anomaly is reflected at the wall in the form of westward moving, internal Rossby waves which have a much lower group velocity. A small amount of friction will attenuate the outgoing waves much more than the incoming waves, providing a mechanism for eastward intensification.