Strange Visitors Appear in Warming Pacific

A green sea turtle like this one, usually found in warm waters to the south, recently was discovered near San Francisco.

U.S. Fish and Wildlife Service

In September, a man fishing for salmon off the northern California coast near San Francisco was shocked when he hooked a different sort of catch — a Pacific green sea turtle, a creature that usually is found in the warm waters near Mexico and further south. Fortunately, the captain of his chartered fishing boat had the presence of mind to catch the endangered species in a net, and then release it back into the ocean unharmed, according to San Francisco TV station KGO.

But that turtle was far from the only unusual visitor from a far-off locale who’s shown up in the waters off the U.S. West Coast lately.  An odd assortment of warm-water species — from Hawaiian ono to tripletail, a fish species normally found between Costa Rica and Peru — are being attracted by a mysterious sudden rise in water temperatures.

Temperatures off the California coast are 5 to 6 degrees Fahrenheit warmer than the average, and among the warmest fall conditions of any time in the past several decades, the San Jose Mercury News reports.

Some scientists believe the ocean warming is being caused by changes in wind patterns rather than climate change. According to that explanation, winds that normally blow from the north, trapping warm water closer to the equator, have waned since the summer. That’s allowed the warm water to move north. Additionally, there’s been little upwelling, a process in which the winds churn up colder waters from below to cool temperatures closer to surface.

“If the wind doesn’t blow, there’s no cooling of the water,” Nate Mantua, a research scientist with the National Marine Fisheries Service in Santa Cruz, explained to the Mercury News . “It’s like the refrigerator fails. The local water warms up from the sun, and is not cooling off.”

Other scientists, though, don’t seem completely sold on that explanation. “The North Pacific hasn’t been this warm ever, as far as anyone knows. It’s really strange,” Bill Peterson, oceanographer with the National Oceanic and Atmospheric Administration’s Northwest Fisheries Science Center in Newport, Ore., told the Seattle Times . “It looks like an El Niño, but it really isn’t. We don’t really know what it is.”

The phenomenon has been seen up and down the North American coast. Off the coast of Alaska, for example, a fisherman was hauling in a net filled with salmon when he spied an unusual addition to the catch. It turned out to be a skipjack tuna, a species customarily found off the waters of southern California and Hawaii.

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