On the bounding main, ocean currents are driven by wind, tides, density gradients, and planetary motion. The world turns to the East. Because of this rotation, currents will bend to the right, an ocean motion known as the Coriolis Effect.
When a land mass is encountered in the Northern Hemisphere, the waters will veer to the right (left in the Southern Hemisphere). The Equatorial Drift, winds, and water westward across the Atlantic set up the clockwise gyre of waters in the upper 100 meters, with the Gulf Stream flowing north and the Azores Current flowing south.
Another phenomenon set up by the Earth’s rotation is Kelvin waves. Stir a cup of coffee, and the swirling liquid does not stay flat; it wobbles or waves up and down. These are very fast-moving waves of low amplitude. Kelvin waves are contrarian; at the equator, they propagate to the east against the trade winds. Kelvin waves go counterclockwise in the northern hemisphere, using the coastline as a waveguide. As a result, coasts on the east side of the ocean receive more energy and wave action. West-facing harbors will often see more dramatic tides than harbors on the opposite shore.
Most of the ocean moves in the thermohaline circulation, which flows to different water densities. The pump house for the world’s ocean is located near the bottom, the Antarctic, where water is coldest and densest. In the ice-forming process, salt is extruded to increase the density of the surrounding waters. Surface waters become dramatically denser in the flash of a freeze and sink into Antarctic Bottom Water. Freezing seawater at the surface drives the deep ocean waters below.
The most dramatic impact of Climate Change is found at the North Pole. Once, the summer Arctic Ocean stayed mostly icebound, with 2.7 million square miles of ice. Since 1979, the summer ice extent has declined 13.4 percent per decade on average. Where once about a third of the Arctic Ocean was open, now it is about two-thirds ice-free.
The percent open Arctic Ocean in August varies yearly, with changes in summer rainfall on warmed adjacent lands, including the MacKenzie River watershed and the Yukon River delta. The more rainfall and river input, the more sea ice melts.
But, there’s more. With twice the open water in the Arctic Ocean during summers, there is a much greater volume of surface water freezing when winter arrives. This cold, extra-salty water is the densest in the world.
[Follow us over to my Substack blog to see where Part 4 of our Narwhals' Tale takes us.(https://robmoir469011.substack.com/p/stronger-atlantic-ocean-currents)
See you over there,
Rob
