Various turbulent heat flux data indicate remarkable increase in heat loss by latent and sensible heat fluxes over Kuroshio and Kuroshio/Oyashio Extension regions during the 1990's. This increase is found in net heat flux, and the heat flux reached its maximum during last 50 years. The slope is about 5.8 W m−2 year−1 on average and is found over the most part of Kuroshio, Kuroshio/Oyashio Extension regions and Japan Sea. The increase in latent heat flux dominantly contributes to the increase in turbulent heat flux mainly due to the increase in SST. Although the increase in wind speed also contributes to the increase in turbulent heat flux, the contribution is smaller than that of SST. In contrast, the increase of specific humidity which contributes the decrease in latent heat flux is also found.