Global energy spectrum of the general ocean circulation

Sep. 16 () –

For the first time, researchers at the University of Rochester have quantified the energy of ocean currents of more than 1,000 kilometers.

In the process, they and their collaborators have discovered that the more energetic is the Antarctic Circumpolar Current, of about 9,000 kilometers in diameter, as can be seen in the image.

The team, led by Hussein Aluie, an associate professor of mechanical engineering, used the same coarse-grained technique developed by his lab to previously document energy transfer at the other end of the scale, during “swirl slaughter” occurs when wind interacts with temporary circular currents of water less than 260 kilometers in size.

These new results reported in Nature Communications, show how the coarse-grained technique can provide a new window to understand ocean circulation in all its multiscale complexity, says lead author Benjamin Storer, a research associate in Aluie’s Turbulence and Complex Flow Group. This gives researchers the opportunity to better understand how ocean currents function as a key moderator of the Earth’s climate system.

The team also includes researchers from the University of Roma Tor Vergata, the University of Liverpool and Princeton University.

Traditionally, researchers interested in climate and oceanography have chosen boxes in the ocean 500 to 1,000 square kilometers in size. These regions, which were supposed to represent the global ocean, they were then analyzed using a technique called Fourier analysissays Aluie.

“The problem is that when you choose a box, you are already limiting yourself to analyzing what is in that box,” says Aluie it’s a statement. “You miss everything on a larger scale. What we’re saying is we don’t need a box; we can think outside the box.”

When researchers use the coarse-grained technique to “smear” satellite images of global circulation patterns, for example, they find that “we gain more by settling for less,” says Aluie. “It allows us to tease out structures of different sizes from ocean currents in a systematic way.”

He draws an analogy to taking off your glasses and then looking at a very sharp and detailed image. It will appear to be blurry. But as he gazes through a succession of increasingly stronger glasses, you will often be able to spot multiple patterns at each step that are otherwise hidden in the details.

In essence, that’s what coarse graining allows researchers to do: quantify various structures in the ocean current and their energy “from the smallest and finest to the largest scales,” says Aluie.