A Perfect Storm of Warm

Unusually warm surface waters in California have made it easier to interact with uncommon creatures, such as smooth hammerhead sharks.

Every California diver I know has a recent story about when they first noticed things were changing at our local dive sites. Some recall their local kelp bed looking thin, while others mention the presence of yellowfin tuna on every shore dive, the range extension of a Mexican nudibranch or the appearance of a skinny baby sea lion on the swim step of their dive boat. For me it was when a 9-foot-long smooth hammerhead shark curiously bumped my camera rig. It was August 2014, and it was no secret that the surface waters were a few degrees warmer than normal.

On that day the swell and wind were formidable, but we were determined to get offshore. We hoped to get a good look at the hammerhead sharks — typically a subtropical species — that had been spotted at the surface by one or two multiday dive boats over the past few weeks. We couldn't believe our luck when one showed up and interacted closely (at times, very closely) with us for three hours.

Among divers the rumored cause for the oddities of the summer of 2014 was El Niño (the warm phase of the El Niño Southern Oscillation), an ocean-atmosphere interaction in the east-central equatorial Pacific that strongly influences ocean conditions and weather patterns. However, the U.S. National Oceanic and Atmospheric Administration (NOAA) had not confirmed the presence of El Niño conditions. Meanwhile, Washington state climatologist Nick Bond had already come up with an alternate name for the odd patch of warmer-than-usual ocean off the coast of the Pacific Northwest: "The Blob." This phenomenon, thought to be the result of locally persistent high pressure that inhibited normal wind-driven oceanic upwelling and cooling, had spread along the West Coast and encompassed multiple stretches of ocean from Alaska to Mexico.

A diver pauses over an Australian spotted jellyfish near the coast of San Diego.
In some places the ocean's surface was 5°F warmer than usual. Although the Blob quickly replaced El Niño as the established cause, 2014 diving and fishing reports in Southern California confirmed the effects, each more bizarre than the last. Tuna fishermen came back from a day offshore east of Catalina Island with images of a whale shark. The lush, iconic kelp of Catalina and San Clemente islands dwindled, and in some places this enabled prolific growth of Sargassum horneri, an invasive alga that better tolerates warmer water. A GoPro video of a manta ray, gracefully flapping among sparse kelp stalks, created a fanatical rush on local dive charters.

By the time NOAA confirmed the arrival of El Niño conditions in March 2015, it was hard to believe that things could get any stranger, but they did. Sea bird and California sea lion populations began experiencing devastating die-offs. In April 2015, strong west-to-east surface winds blew masses of violet-blue Velella velella, open-ocean hydrozoans related to jellyfish, onto beaches in California, Oregon and Washington. And in June 2015 I watched in amazement as pelagic red tuna crabs (a squat lobster-like crustacean normally found near central Baja California) swarmed one of our few remaining local kelp beds and ultimately littered the coastline from San Diego to Los Angeles.

The peculiarities didn't stop there. In July and August 2015, smooth hammerhead sharks were bumping near-shore kayak fishermen so commonly and assertively that local beaches were closed on multiple occasions. On the docks, anglers posed proudly next to bluefin tuna, caught only 10 miles offshore, and local photographs of finescale triggerfish and Guadalupe cardinalfish became commonplace. In September 2015, I hovered in disbelief next to the barren propeller of the HMCS Yukon, a San Diego-area artificial reef that had been thickly encrusted with giant plumose anemones only 12 months prior. And only a month after that, a cluster of wahoo passed me at a Catalina Island dive site days before I photographed a pulsing Australian spotted jellyfish near the San Diego harbor. The world — at least, the underwater world I frequented on a regular basis — seemed to have gone stark raving mad.

The propeller of the HCMS Yukon wreck in San Diego’s Wreck Alley was thickly covered with giant plumose anemones in spring 2014. By the summer of 2015, the ocean had become warm enough to wipe them out, leaving nearly bare metal behind.

Ed Parnell, Ph.D., research oceanographer at the Scripps Institution of Oceanography, wasn't terribly surprised to hear it. "The Blob was an unprecedented warm-water event that wasn't related to common oceanic indices," he explained. "Last year we had warmer surface conditions, but at depth things remained cold and nutrient-rich, so some deeper species were less affected than you might think. However, the water became very stratified and more resistant to mixing. Typically, an El Niño pattern results in advection of pulses of warm equatorial water northward, so that upwelled water is warmer than normal and less able to deliver nutrients to shallower structures. But this year, with things prestressed by the Blob, the seasonal thermocline is already deeper than normal, so upwelled water would likely be even warmer than we've seen with prior El Niños — in fact, this year upwelling might not deliver much cold, nutrient-rich water at all."

Parnell's key concern is further overgrowth of invasive Sargassum horneri. "Two years ago, we were seeing isolated pockets of it, but now it's popping up everywhere," he said. "If we lose the kelp in an area completely, sargassum can easily take over because it will no longer be suppressed by giant kelp shading."

Pelagic red tuna crabs, a denizen of Baja, Mexico, swarmed a
California kelp bed in June 2015.
Previous El Niño events have delivered mighty topside changes to the West Coast as well. In the past, the position of the jet stream has shifted south and east from the Gulf of Alaska so that storms track closer to the Southern California shoreline. The strong El Nino in 1982-83 brought crippling storm fronts, complete with waves that broke over the roofs of popular beachside restaurants. And in 1997-98, repeated deluges washed away roads and caused catastrophic mudslides. With California in the midst of a drought, it feels a little ungrateful to admit that stories of the past combined with ever-more-ominous nicknames bestowed upon the present El Niño ("Bruce Lee" is my current favorite) are more than a little frightening.

Parnell, however, says this may be one of the biggest reasons to remain optimistic. "Strong storms can revamp the bottom structure, remove urchin barrens and clear out the understory kelps, providing renewed areas for giant kelp to grow," he said. "El Niño may bring a series of storms, but we need to remember that those large storms act as a reset button for kelp forests in Southern California."

© Alert Diver — Q1 Winter 2016