Salmon are one of the species most threatened by rises in water temperature, both at sea and in their spawning streams. Credit: Flickr user hey_skinny
Scientists nicknamed it “the blob” last summer. Since then the mass of water penetrating the North Pacific has become persistent in waters from Alaska to Baja, showing up as red and orange when scientists map it. A new report by NOAA Fisheries’ Northwest Fisheries Science Center and Southwest Fisheries Science Center notes record-high sea surface temperatures characterized by as much as 5.4 degrees F higher than average.
“We are seeing unprecedented changes in the environment,” says Toby Garfield, director of the Environmental Research Division at the Southwest center.
Climate and ecological indicators point to reverberations throughout the marine food web.
Waters in the Gulf of Alaska began warming in the winter of 2013/2014 because the area wasn’t getting the kinds of winter storms needed to extract heat from the surface of the ocean and cool it, explains Garfield. A separate report issued by the National Snow and Ice Data Center last week notes that Arctic sea ice was at its lowest level ever recorded . Numerous studies confirm that 2014 was also the warmest year ever recorded.
United Nations experts, many scientists and federal authorities link the dramatic thinning and disappearance of Arctic ice to climate change. “This is the latest in a series of warm years, in a series of warm decades,” says Gavin Schmidt, director of NASA’s Goddard Institute of Space Studies in New York. “While the ranking of individual years can be affected by chaotic weather patterns, the long-term trends are attributable to drivers of climate change that right now are dominated by human emissions of greenhouse gases.”
Warm waters have been occurring with more frequency in the North Pacific, but what makes the current warming atypical is that it’s coming ahead of the appearance of any El Niño, the name given to the phenomenon of regular and sometimes large annual variations in sea surface temperatures, air pressure and rainfall. An El Niño usually develops around the equatorial region and tropics and migrates northward. This time the warming is emerging from three North Pacific hot spots, the Bering Sea, the Gulf of Alaska and Southern California/Baja.
Among scientists that NOAA’s Toby Garfield works with, there’s debate of whether the unusually warm waters are due to natural variability or climate change. “I wish I had enough certainty to say ‘a’ or ‘b,’ when in fact, the jury is still out.” What he can confirm is that warm temperatures dominate the three hot spots mentioned earlier. When the hot spots converge with normally cold waters prevalent in the California current, a Pacific ocean cold water current that moves south from British Columbia to Baja, the warm waters will dominate. Heavier cold water tends to slide beneath warm water and return to the depths, taking with it cold-water nutrients.
Shifts are also happening with the source of waters coming into the Pacific, along with weaker upwelling of deep, cold waters. Upwelling occurs when wind patterns push surface water away from the coast. Generally these waters have higher nutrients than the water that is replaced. Combined with record-high sea temperatures, the shifts appear to be contributing to a serious decline in nutritious food along the entire coast. Leaner subtropical copepods, tiny shrimp like creatures, are dominating offshore waters. Normally energy-rich copepods from cold waters support the base of the West Coast food chain. The leaner varieties, often associated with low productivity and poor nutrition, are not a winning recipe for fish, birds or mammals.
Salmon face a potential “double jeopardy,” says Chris Harvey, a biologist with the Northwest Fisheries Science Center. In addition to warm seawater, which is as high as anything in the historical record, the winter of 2014/2015 has seen one of the lowest years in recorded history for mountain snow pack and volume of snow water. The low volume means stream conditions later in the year will be shallow and warm. “None of which is good for tiny salmon that are going to be emerging from the gravel around this time of year,” says Harvey. As for grown salmon who will be swimming out to sea, not only will they have poor river conditions to contend with, “but once they hit the ocean, the copepods they’ll find will be of very low nutritional value.”
Warm waters can be productive for some species, such as albacore tuna, which normally swim all over looking for little patches of food to exploit, Harvey says. But northern waters are generally too cold for tuna to live in year around. Fisheries biologists are also concerned about how the Pacific’s subtropical waters will impact forage fish, such as herring, sardines and anchovies. Some stocks of herring have seen comebacks, but most forage fish are already impacted by coastal development, overfishing and the natural variability of ocean waters.
Biologists also look at what record high sea surface temperatures mean for the lifespan of any given fish. For those that have a relatively short life history, like salmon or forage fish; one peculiar year can constitute between 10 and 50 percent of the fish’s entire lifespan, says Harvey. “How will it affect their growth, how many eggs a female will produce, and how many fish will survive into maturity?” Fish that can live up to 100 years old, like rock fish, may be able to survive “whacky years” like those being recorded. But for others, biologists are watching closely.
“The blob” has also caught the attention of birdwatchers and West Coast Marine Mammal Stranding Network. Large numbers of seabirds called Cassin’s auklets have been found dead or emaciated from California to Alaska since last winter. A University of Washington seabird expert, Julia Parrish, told an Audubon magazine writer that volunteers reported seeing 10 to 100 times the normal number of Cassin’s bodies along coasts from central California north to British Columbia. “That doesn’t actually translate into knee-deep in bodies,” according to Parrish, “but in the stretches with the highest number of birds 350 per kilometer, probably the highest wreck value we’ve seen in the Lower 48 you’re going a few steps before you see the next one.” Most of the dead birds were juveniles.
California sea lion pups have also been found dying and emaciated in large numbers in recent months, which may reflect the loss of energy-rich copepods and corresponding repercussions through the marine food chain. A February report from NOAA notes that high numbers of pups on California’s Channel Islands, a primary breeding colony for this species, appear to be suffering from starvation.