Explanation of the ocean current map

Explanation of "Kuroshio axis"

“Kuroshio path” is shown in the area between Yonaguni Island and off Boso Peninsula. And “Kuroshio extension” is also indicated.

1. The width of Kuroshio is 40 nautical mile (nm) from the northern edge of the Kuroshio Current.
2. The Kuroshio axis has the maximum surface current. It exists at about 13 nm from the northern edge of the Kuroshio Current.
3. Northern edge of the Kuroshio Current is determined from synthetically analyzing each area as below.
   • The area where the current velocity is faster than about 2 knot. Those current data is observed by ships, HF radars and drifting / mooring buoys.
   • The area where the contours for sea surface temperature (SST) are thick. This SST data is derived from ships and satellites.
   • The area where the sea surface gradient derived from satellite altimeter increases sharply.
   • The area where the contours for the temperature at the layer of 200m are thick around 15-16℃.
   • The area where the current becomes faster suddenly south of a cold eddy on the Enshu Sea.