Interannual variability of temperature inversions in the subarctic North Pacific

A newly developed ocean reanalysis dataset ( 1987 2004) has been used to study interannual variability in the temperature inversion that characterizes the upper layer of the subarctic North Pacific. A local minimum in temperature at the upper edge of the inversion exhibits a significant interannual variability. Conversely, fluctuations in the local temperature maximum (T-max) found at the lower edge are relatively small. In the T-max case, the variation in the depth of Tmax is significant and is closely related to ENSO variability. Our estimate of the adjoint solution shows that during periods when the T-max is located at shallower ( deeper) depths, the source water comes from both the Gulf of Alaska and the Kuroshio Extension region ( only from the Kuroshio Extension region). These facts suggest that the depth of Tmax is an important indication for diagnostics of the interannual variability of water-mass property in the subarctic Pacific.