Atmospheric responses and feedback to the meridional ocean heat transport in the North Pacific

Abstract

tmospheric responses and feedback to meridional ocean heat transport (OHT) have been investigated using a global climate model that is interactively connected with a high-resolution regional ocean model embedded in the western North Pacific. Compared with a global climate model without the regional model, the net heat supply into the Kuroshio-Oyashio Extension (KOE) region is increased due to the increase of the mean northward ocean heat transport (OHT) by the western boundary currents and mesoscale eddies. Resultant sea surface temperature (SST) rise sharpens the meridional SST gradient and reinforces the cross-frontal difference of the surface heat flux and thereby enhances lower tropospheric baroclinity. These changes cause northward deflection and strengthening of the wintertime storm track over the North Pacific, which leads to the Pacific-North America pattern-like anticyclonic response of the mean westerly jet. The increase of the eddy northward atmospheric heat flux (AHF) associated with the enhanced storm track activity is compensated by the decrease of the mean northward AHF. The changes of the atmospheric circulations reduce the mean northward OHT in the eastern North Pacific that compensates the increase of the mean northward OHT in the KOE region. The atmospheric responses, which have once been excited by the SST fronts in the KOE region, stabilize the trans-North Pacific OHT. Our modeling result suggests that basin-wide Bjerknes-like compensation works in air-sea coupled processes for the formation of the climatic mean state in the North Pacific.