The surface temperatures of the Pacific Ocean. Blue is the coldest, while white is the warmest.

Currents regulate the temperature of the North Pacific Ocean. Warm waters enter the Northern basin along the Canadian west coast via the Kuroshio (Japan) current, which originates in the Sea of Japan. This current is, in turn, warmed by the easterly North Equatorial Current, which runs in a westward direction from about 5ºN latitude. Meanwhile, the California Current runs along the North American west coast, and carries cold water away from the North Pacific into the South Pacific Basin.

Generally, ocean waters are layered, with each layer having a different temperature. The bottom layers of the ocean are considerably colder - near freezing - than the surface layers. The surface layer of the Pacific Ocean waters ranges from about 300 to 900 metres thick. This warm layer is shallower along the coasts of North America than in the central and western regions of the Pacific. Along Canada’s west coast, the surface temperatures of the Pacific Ocean rarely get warmer than 15ºC.

The ocean temperatures in the North Pacific tend to be warmer than those in the South Pacific. This seems strange because the surface waters in the South Pacific are definitely warmer. However, because the ratio of land to sea area is greater in the North Pacific, the cumulative amount of cold deep water is less. In other words, the average temperature of waters in the North Pacific is warmer because there are more coastal areas. Also, the deep currents coming up from Antarctica into the South Pacific bring intensely cold waters with them. By contrast, most of the cold outflow from the Arctic Ocean enters the Atlantic Ocean via a strong current known as the Transpolar Drift.