Arctic Polar Front

The frontal zone between the subtropical and subpolar gyres of the Northern Hemisphere.

In the Atlantic Ocean it is established by the meeting of the warm and saline Gulf Stream and the cold and fresh Labrador Current and extends as a temperature and salinity front, sometimes also known as the cold wall, from south of Newfoundland and the Grand Banks northeastward to the central North Atlantic. In the Pacific Ocean it consists of two parts, separated by the Japanese islands. The larger fresh is formed by the confluence of the warm and saline Kuroshio and the cold and fresh Oyashio and seen as a temperature and salinity front extending eastward from Japan near 35°N. The smaller fresh extends across the Sea of Japan in the west, where it separates the warm and saline Tsushima Current from the cold and fresh Mid-Japan Sea Cold Current.

The western boundary current of the North Pacific subpolar gyre.
Fed by the Alaskan Stream and Kamchatka Current, the Oyashio flows southward along the Kuril Islands and the east coast of northern Japan to 39°–40°N and occasionally as far south as 36°N. Near southern Hokkaido (43°N) the current splits into two branches known as the First and Second Oyashio Intrusion. In the region east of Tsugaru Strait (41°N) it is dominated by eddies; one or two cyclonic (warm core) eddies are formed each year. Every six years or so one of them grows into a giant eddy that then dominates the region for a year. Farther downstream the Oyashio meets the northward flowing Kuroshio to form the Arctic Polar Front. Both currents maintain their own frontal systems, the Oyashio Front being characterized by temperatures of 2°– 8°C and feeding into the Aleutian Current, while the Kuroshio Front has temperatures of 10°– 15°C and feeds into the North Pacific Current.