Steven Wynne, age 10, of Santa Maria, California, for his question:

Why is the Japanese Current Warm?

Majestic currents within the oceans sweep in eddying circles from the equator al¬most to the polar regions. They ignore the boundaries between tropical and temperate zones. Like the weather, they treat the globe as a single unit, a world wide playing field for their stupendous activities.

Sailors and marine experts call it the Japan Current. The people of Japan call it Kuroshio, the Black Current. This sweeping wide stream within the ocean does indeed wash the shores of the islands of Japan, plus many other shores of the Pacific. But black is not the best word for it, though its waters are darker than the Pacific waters around it. Actually its color is a beautiful rich indigo blue, a deeper color than the top of the midsummer sky plus a tinge of violet.
The Japan Current is merely one section of a vast eddy of circling currents that swirl around and around through the North Pacific. Off Japan, it is warmer than the ocean around it because its streaming waters are swept along from warmer regions of the globe. So let's trace it back to its beginnings. This takes us southward to the equator, the wide waist of the world where the globe spins fastest and the tropical sun shines bright and warm all through the year.
Somewhat north of the equator, a mighty ocean current is driven westward by the prevailing trade winds that circle the globe. This North Equatorial Current of warm tropical water is the longest of any current in the world oceans. It sweeps from off the shores of Panama 9,000 miles due west across the Pacific to the Philippines. Here the island barrier forces most of the streaming warm water to turn northward. It brushes along the coastline of Asia, passing east of Formosa and onward to Japan. Its water from the tropics is still warmer than the sea around it. This warms the air above and brings a milder climate to the shores it brushes.
From north of the Japanese islands, cold Arctic waters creep down into the northern Pacific. They merge in the chilly Oyashio Current. This section of the circling eddy is the Northeast Drift that reaches our Pacific coast and bends southward along shores of California. At this stage it has lost its tropical warmth and it tends to make our Pacific coast weather cooler than it should be. Off lower California, the eddying current links up again with the North Equatorial Current. Here it is swept westward on that 9,000 mile journey where it soaks up tropical warmth for its next majestic swirl through the Pacific.

The North Atlantic has a similar cycle of currents on a smaller scale. The Gulf Stream compares with the Japan Current, but it is warmer, perhaps because the Atlantic cycle is smaller. The Gulf Stream is turned eastward by the cold Labrador Current. Off Newfoundland, where the warm and cold currents clash, we get a region of dense fogs and wild winds. The same wild weather occurs in the northern Pacific where the warm Japan Current clashes with the cold Oyashio Current.