Heat wave across expanse of Pacific Ocean surface stokes concerns for sea life
An expanse of warm surface water similar to “The Blob,” which caused widespread disruption in ocean conditions in 2014 and 2015, has appeared off the West Coast in recent months, prompting concerns about a potential repeat of disastrous effects for marine life and fisheries in California.
Federal scientists sounded the alarm Thursday about what they’re calling the Northeast Pacific Marine Heatwave of 2019, saying the phenomenon already is nearly as large and as intense as the earlier warm water mass.
The situation, signs of which were evident as early as last fall, is sustained by a persistent ridge of low pressure that could shift at any time, National Oceanographic and Atmospheric Administration experts told reporters during a conference call Thursday. But the heat wave began forming in mid-June off the Gulf of Alaska and has developed much the same way The Blob did, they said.
It now occupies about 2.5 million square miles — forming a wedge from Hawaii to southern Alaska and down the length of California — aided by weaker-than-usual winds that would otherwise mix and cool the ocean’s surface water, said Nate Mantua, a research scientist with NOAA’s La Jolla-based Southwest Fisheries Center.
As a result, surface temperatures are 5 to 6 degrees Fahrenheit above normal in the warmest areas, though only about 50 meters deep — shallow enough to dissipate “fairly quickly,” if conditions change, said Toby Garfield, director of the center’s Environmental Research Division.
“At this point, it’s really only time that will tell if this feature is going to persist and then also rival this past event in terms of its duration and impacts,” said Andrew Leising, research oceanographer with the Southwest Fisheries Science Center.
The Blob was associated with a host of devastating effects that included an unprecedented harmful algae bloom that shut down the California Dungeness crab fishery for a large portion of the 2015-2016 season and poisoned numerous marine mammals.
Elevated temperatures also correlated with suppressed circulation of the cold, nutrient-rich upwelling that forms the base of the coastal food web, reducing food supply and disrupting wildlife migrations near the coast with unforeseen consequences in some cases. One of the them was a record number of whales getting entangled in fishing gear once they started feeding closer to shore.
In some instances, shifting of wildlife distributions also meant increased concentrations of predators near shore, Mantua said. During The Blob, for example, juvenile salmon leaving freshwater rivers to mature in the ocean were confronted with too little food and higher than usual predation rates, slowing their growth rates and increasing death rates, with a direct effect on several years of salmon harvests, he said.
Warm, nutrient-poor water also was considered a contributing factor to the collapse of the North Coast’s iconic bull kelp forest, largely decimated by voracious sea urchins. Thousands of California sea lions, mostly pups, also starved, stranded and died. Some suffered from domoic acid poisoning, the result of eating fish that had accumulated the same algae-related neurotoxins that delayed the Dungeness crab season by 4.5 months.
Stephanie Moore, an oceanographer with the Seattle-based Northwest Fisheries Science Center, said concerns about another algae bloom of that magnitude would not be raised until next spring, assuming the heat wave still persisted and begun to hug the coastline.
“We’re going to be watching what happens very closely here in the next six months or so,” she said.
Mantua said that long-term warming of the northern Pacific Ocean as a consequence of climate change is a separate factor from the more abrupt temperature elevation marked by the heat wave at issue, though it may help strengthen it.
In California, the warm water expanse has not yet reached the coastline, because of the cold water upwelling that has kept it offshore. The upwelling typically diminishes each fall, so if the heat wave persists it could soon hug the shoreline. It’s already doing that in Washington and parts of Oregon, more directly affecting the critical food web, experts said.
“It’s on a trajectory to be as strong as the prior event,” Leising said. “Already, on its own, it is one of the most significant events that we’ve seen.”
You can reach Staff Writer Mary Callahan at 707-521-5249 or firstname.lastname@example.org.