Red crabs swarm Southern California, linked to ‘warm blob’ in Pacific

La Jolla, California, June 11, 2015. (Scripps Institution of Oceanography, UC San Diego)

Red crabs, by the thousands, have invaded Southern California beaches, washing ashore from San Diego to Newport Beach.

Sea surface temperatures some 4-7 degrees warmer than normal, possibly connected to a radical change in a Pacific ocean weather pattern, are likely driving the crabs northward away from their typical habitat.

“Experts said the crabs … haven’t been seen in the area for decades,” reported the Orange County Register.

The crabs, resembling miniature lobsters too small to eat, are known as tuna crabs or pelagic red crabs.

“Typically such strandings of these species in large numbers are due to warm water intrusions,” said Linsey Sala of Scripps Institution of Oceanography, UC San Diego.

The crustaceans usually inhabit the west coast of Baja California, the Gulf of California, and the California Current (spanning from offshore the U.S. West coast down to southern Baja California), a Scripps news release said.

In addition to the crabs, the warm Pacific coastal waters have drawn northward a number of other creatures seldom or never previously seen, which last fall included: a live ocean sunfish and warm-water blue shark in the Gulf of Alaska, mahi mahi off the coast of Oregon, a Pacific sea turtle common in the Galapagos near San Francisco, and marlin in the waters off Southern California.

“In recent weeks, blue, jellyfish-like creatures known as ‘by-the-wind sailors’ have been spotted, and tropical fish like yellowtail and bluefin tuna are showing up earlier than normal this year,” the Orange County Register said.

The warm plume of water developed in the spring of 2014.

Sea surface temperature difference from normal June 15, 2015 (NOAA)

Nick Bond, a climatologist at the University of Washington, dubbed it “the blob” and published a study exploring its origins. “[The study] finds that it relates to a persistent high-pressure ridge that caused a calmer ocean during the past two winters, so less heat was lost to cold air above,” explained a University of Washington news release. “The warmer temperatures we see now aren’t due to more heating, but less winter cooling.”

The blob has been linked to the weather pattern that has led to drought in California, and much colder than normal conditions during winter in the eastern U.S. the past two years.

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