To Clarify: Of the Less Erroneous Pictures of Gyres

In news stories about the bath toys lost at sea, or about the so-called garbage patch, one occasionally encounters some confusion about oceanic gyres--altogether understandable confusion because the ocean is a strange place and its currents are complicated, chaotic even. The general as opposed to oceanographic sense of "gyre" is the sense in which Yeats famously used it in "The Second Coming"--

Turning and turning in the widening gyre
The falcon cannot hear the falconer;
Things fall apart; the centre cannot hold...

--a circular or spiraling motion or form. The oceanographic sense of the word "gyre" is narrower. In oceanography, a gyre is a circuit of major currents. Or to be a bit eye-crossingly precise about it, you'd say a gyre is a circuit of major wind-driven surface currents that orbit the ocean basins. The Gulf Stream, for instance, is a major surface current and it describes one arc of a gyre--the North Atlantic Subtropical Gyre, which, simplified by cartographers at NASA, looks like this:

A gyre is not a "garbage patch." Nor is a gyre by definition a current that collects floating debris. That said, there are currents in the five largest gyres--the subtropical gyres, which include the North Atlantic one pictured above--that do have the tendency to collect floating debris. Such currents create what oceanographers call "convergence zones." Convergence zones lie within gyres, but they are not the same thing as gyres. The most famous one is--take a breath--the North Pacific Subtropical Convergence Zone. You can see why people tend to prefer the somewhat misleading yet far catchier term "garbage patch." Here, on the map that appears at the front of Moby-Duck, is the North Pacific Subtropical Convergence Zone:

And here it is on a map created by the US National Oceanographic and Atmospheric Administration (NOAA):

Even within convergence zones there is no one uniform "garbage patch." As the folks at NOAA explain:

While a gyre may aggregate debris on a very large scale, debris patches, as seen by those sailing the North Pacific, are actually the result of various smaller-scale oceanographic features such as oceanic eddies and frontal meanders...

Those arrows on the above maps only show the big scale tendencies. Let's zoom in. Up where the castaway bath toys first made landfall, in the Gulf of Alaska, which is orbited by the North Pacific Subpolar Gyre, there are currents that diverge, expelling rather than collecting floating debris. Here, again from NOAA, is a map:

Zoom in even further and you start to get a sense of just how chaotically complicated the currents are. But you don't just have to zoom in. You also have to stop time. Because the currents change. Here is what the coast of the Gulf of Alaska looked like back in 1995, as seen through a physical oceanographer's  eyes.



Those little black marks? Arrows.