| The long-term upper-ocean (0–400 m) temperature trends between 1955 and 1994 are studied using the observations of expendable bathythermograph (XBT) and the simulation of an ocean general circulation model.; The observations show that the Pacific Ocean has a warming trend near the surface above 50 m and a cooling trend below 50 m. These temperature trends are not zonally uniform. In the tropical Pacific, the thermocline has a warming trend in the east but a cooling trend in the west. The warming in the east and cooling in the west are also manifested in the North Pacific mid-latitudes. These salient features of ocean temperature trends are well simulated.; The analysis of ocean heat budget shows that the temperature trends are dynamically controlled by ocean currents in the Pacific Ocean. The downward net surface heat flux, on the other hand, tends to damp the temperature trends near the surface. In the western tropical Pacific, the warming near the surface seems to be caused by the reduction of the South Equatorial Current, while the thermocline cooling is caused by the reduction of the equatorward convergent flow. In the central tropical Pacific, the warming near the surface is caused by the reduction of the off-equatorial Ekman flow, while the cooling in the thermocline is caused by the reduction of the equatorward convergent flow. In the eastern tropical Pacific, the warming appears to be caused by the reduction of the upwelling current. The change of these currents is caused by the decrease of the trade winds. |
