The baby sea lions started washing ashore in high numbers in 2013. But the Pacific along the U.S. West Coast really got weird in 2014, when fishermen started catching ocean sunfish and warm-water thresher sharks—off Alaska.
Since then, hungry young Cassin’s auklets have died by the thousands and Central American birds like brown boobies began showing up in California’s Farallon Islands. This week the number of starving sea lion pups stranded on southern California beaches hit 2,460 —roughly 20 times higher than the average over the last 10 years.
Scientists now believe these changes are all loosely connected to a giant swath of warm water sitting in the eastern Pacific. The northern portion of that blob, in turn, has the same cause as the drought that continues to ravage California: a persistent ridge of high-pressure in the atmosphere that has blocked storms and kept them from reaching the West Coast.
And the flip side of that ridge is a low-pressure trough over central and eastern North America—aka the polar vortex—that accounts for the crazy snows of last winter.
In other words: A lot of weirdness is connected. But is it connected to global warming? Probably not, many experts believe, but it’s not clear.
The dramatic shifts underway in the eastern Pacific Ocean’s food web, however, are baffling researchers and fisheries managers as they scramble to predict what might come next.
“It’s the oddest thing – it’s just completely outside our experience,” says Bill Peterson, an oceanographer with National Oceanic and Atmospheric Administration’s Northwest Fisheries Science Center in Newport, Ore. “When the present is nothing we’ve ever seen before, it’s hard to know what the future will bring.”
Birth of a Blob
The strange warming of the eastern North Pacific appears to have been kicked off in the winter of 2013-14 by the persistent high-pressure ridge, according to a new study by climate scientist Nick Bond of the University of Washington and his colleagues. The high pressure suppressed the storms and winds that normally cool the Gulf of Alaska.
“The winds usually extract heat and evaporate water off the surface and mix and cool the upper ocean,” says co-author Nate Mantua, with NOAA’s Southwest Fisheries Science Center.
That just didn’t happen, which kept heat from escaping the sea and allowed water temperatures to rise 5 degrees Fahrenheit or more above normal. Meanwhile the lack of winter storms caused western snowpacks to dwindle.
That warm offshore blob in the Northeast Pacific since has merged with another patch of warm water, further south and closer to shore, caused by persistently weak winds off California. Upwelling driven by stronger winds usually brings cold water and nutrients from the deep ocean to the sea surface.
The upshot is that most of the offshore eastern Pacific Ocean is warmer than it has ever been.
“What we’re seeing now is just not in the playbook,” says Toby Garfield, director of environmental research at NOAA’s Southwest center. “This is a pattern we’re not familiar with. We’ve never seen anything like it.”
According to one theory, the drought in California and the extreme cold in the East in the past two winters are linked to climate change through the melting of the Arctic, which has supposedly caused the polar jet stream to become weaker and wavier and allowed extreme weather patterns to become more persistent.
But a recent study by Dennis Hartmann of the University of Washington instead traces both the weird weather over North America and the warm blob in the Northeast Pacific to anomalously warm water in the western tropical Pacific—and to an El Nino-like ocean-atmosphere oscillation called the North Pacific Mode. “We do not know for sure whether this is just part of the natural variability of climate, or whether climate change is favoring” the weirdness, Hartmann writes. Mantua and other researchers think the weirdness of the West Coast is most likely just an extreme example of natural variability.
The Food Web Is Shaking
Whatever their ultimate cause, the changes in the Pacific ocean and atmosphere have helped reduce the production of primary sources of food in waters off the West Coast. Changes in wind appear to have reduced tiny ocean plant life called phytoplankton along much of the West Coast to levels not seen in 18 years.
Meanwhile Peterson, who has surveyed animal plankton off Oregon for decades, says the volume of larger, fattier, cold-water copepods, a dietary staple for many birds and fish, has plummeted. Yet Peterson has spotted 17 species of tinier, less nutritious tropical copepod that he’s never seen before in these waters.
“The problem is the northern copepods are the ones that make you fat and happy,” Garfield says, empathizing with the fish. “The southern ones are like chewing on a stalk of celery.”
The unusually warm water and the type of food it brings has helped create bizarre conditions. Last year a mostly tropical skipjack tuna was caught off Alaska’s Copper River, 200 miles north of the previous northernmost sighting.
Last month, a Tristram’s storm-petrel, a species native to Japan and Hawaii, was found dead in California’s Farallon Islands—only the third sighting of this bird along the continental United States. A dozen brown boobies also have been seen in the Farallons this spring, four times more than in any other year.
There have been more deadly consequences, too. Some scientists believe the precipitous drop in Pacific krill and other hearty plankton species is what led to the largest seabird die-off in recent history. Thousands of juvenile Cassin’s auklets from California to British Columbia washed up dead on Western beaches between October and February. (Read about the die-off.)
Peterson also fears the lack of primary food will be catastrophic to West Coast salmon and steelhead, a possibility that won’t be known for several months. The high temperatures and low water in West Coast rivers from a lack of winter snow will only make things worse.
Sardines Like It Hot, But...
The sardine fishery is already on the ropes. Sardine populations have dropped so steeply that federal regulators are expected to eliminate the commercial fishing season that begins in July. That would be a first since sardine fishing roared back after the decades-long bust in the 1950s made famous by John Steinbeck’s novel Cannery Row.
Warm waters didn’t cause sardine numbers to drop; they actually favor warmth. Their mammoth decline began five years ago when waters were cold. But their loss is coming as the jolt of high temperatures may reduce other fishing options.
“I keep telling my guys, ‘I hope you’ve been saving your money,’ “ says Diane Pleschner-Steele, director of the California Wetfish Producers Association, which represents owners of 63 boats.
Sea lions are also suffering from the loss of sardines. Southern California’s sea lion numbers had risen greatly in recent decades, causing fierce competition for food. But sardine numbers fell to new lows just as nutrient-poor waters began reducing food for other fish. And because of those warm waters, a lot of the food that remains for sea lions—squid, mackerel, anchovies and the few remaining sardines—has been pushed hundreds of miles north. That’s making it harder for moms to feed their pups.
“The sardine stock may rebuild, but it’s going to take multiple generations to get back to the numbers we had, and the sea lions don’t really have the luxury of waiting,” says Mantua. “There’s a lot of hungry mouths to feed.”
Follow Craig Welch on Twitter: @craigawelch