Unusually warm waters in the Pacific Ocean — now pushing up against the Washington coast — are keeping oceanographers on alert for changes that could reverberate through the food web, potentially affecting fish, birds and marine mammals in coastal waters and in Puget Sound.

Rising ocean temperatures may be related to recent sightings of warm-water fish not usually seen in the Northwest, including a bluefin tuna that washed up on Orcas Island and large schools of mackeral observed in the Strait of Juan de Fuca. Worrisome levels of domoic acid, a dangerous toxin produced by a type of plankton, have been reported off the Oregon coast.

While it is too early to know how severe conditions may get, strengthening El Niño climate patterns suggest that regional ocean warming may grow even stronger next spring. Nobody has forgotten the years 2013-2016, when a huge patch of warm water, dubbed “the blob,” arrived on the coast during a strong El Niño and proceeded into Puget Sound. In some places, temperatures rose as much as 7 degrees Fahrenheit with catastrophic effects on the ecosystem.

Before the end of the warm period, toxic algae blooms forced the closure of a multi-million-dollar Dungeness crab fishery. Fish populations were dislocated, some pushing up from the south and competing with more local species. Food shortages, particularly along the coast, took the lives of thousands of sea birds and marine mammals.

So far this year, a band of cold, upwelling water along the coast has kept the warm ocean waters from creeping into Puget Sound, according to Christopher Krembs, lead oceanographer with the Washington Department of Ecology. That cold upwelling — a function of winds and coastal currents — is normal during the summer months but typically declines during the fall. As today’s stormy weather hit the West Coast, there were signs that the upwelling had stopped. That could allow warm water to make its way more swiftly into Puget Sound with stronger effects for the inland waterway.

During the blob, coastal upwelling relaxed in September 2014. The warmer, heavier sea water was able to flow into the Strait of Juan de Fuca. Weak tidal forces at the time allowed the water to spill over the Admiralty Inlet sill — a distinct mound that rises from the bottom and forms an impediment to seawater coming into Puget Sound. The warmer water arrived quickly. Within two weeks, waters throughout most of the Sound had gone up by 1 to 2 degrees Celsius, Krembs said, and that was only the beginning.

Although the warmest waters in the North Pacific are now well offshore, much of the region’s sea surface temperatures have remained unusually warm long enough to be recognized as a “marine heat wave,” joining a growing number of heat waves reported across the globe.

 Krembs has been watching closely for changes in temperature and upwelling, based on data from satellites and monitoring buoys. Like dozens of scientists studying the Puget Sound region, he would like to mark the arrival of these warm waters as well as their effects in Puget Sound. While nobody can change the conditions, experts hope that early warnings can help people be better prepared as warming conditions disrupt normal ecological functions.

Formation of marine heat waves

Against a backdrop of rising ocean temperatures caused by global warming, experts can observe patches of water growing ever warmer, gaining in size and moving with the currents. Basically, this excess of warm water occurs when the forces of heating exceed the forces of cooling. For example, direct sunlight heats the water in the absence of clouds. To avoid net heating over time, this must be counterbalanced by winds and storms that bring cold water up from the deep ocean.

Leading up to the blob in 2013, weather conditions, including a record high-pressure area over the North Pacific, created an imbalance in favor of heating, according to Washington State Climatologist Nick Bond, who coined the term “blob” in a June 2014. Such conditions included a diminished force of the winds, which reduced the mixing of seawater while suppressing evaporation and other cooling forces.

Contributing to today’s warm conditions in the Pacific Ocean was a sunny summer just ending. Warmer conditions starting last May in the eastern Pacific was accompanied by lower wind velocities, resulting in less mixing and less cooling, Bond said. The surface of the ocean grew warmer, but not uniformly so, as both atmospheric and ocean conditions caused heat to concentrate in various locations.

The presence of El Niño, which is related to the heat buildup in the tropics, is predicted to remain strong well into next year. This could help to maintain warm water off the Northwest coast, with uncertain effects on Puget Sound. If similar sunny weather patterns are repeated next summer, we could see patches of warm water continue grow in depth as well as in surface area in the Pacific Ocean.

Thanks to satellites and advanced imagery, researchers now have a pretty good understanding of sea surface temperatures and their movements across the wide ocean, Bond said. But to understand the full scale of ocean warming, it is also important to understand the depth of the warm layers, which can go down hundreds of feet. Recent technology, including autonomous buoys, gliders and other instruments, can move up and down and through the ocean, measuring temperatures and other physical conditions and biological indicators at various depths.

“I think it is really remarkable that the technology allows us to use autonomous platforms instead of huge ships burning god-awful amounts of fuel each day,” Nick said. “That used to be the only way to get it done.”

By analyzing different types of data together, oceanographers are getting better at describing the three-dimensional heat signatures of these massive bodies of warm water, he noted, and that helps in predicting how long they might last. Using refined computer models to pull together climate, weather and ocean conditions, researchers hope to eventually predict marine heat waves before their arrival, he added.

Even with increasing deployments of new instruments, the result is often a patchwork of data without sufficient coverage of the entire ocean, Bond said.

“A lot of work is being done to produce better models that can take patchy and incomplete information and fill in the blanks,” he said, “and there has been progress on that front.”

Puget Sound conditions

While ocean temperatures and biological conditions exert a strong influence, Puget Sound maintains an independent streak that greatly determines the fate of the animals living in and around the waterway. Currently, one of the Sound’s unusual characteristics for this time of year is a lack of layering — known as stratification — which is typically the result of freshwater flowing in from the rivers and lying on top of the heavier seawater.

The issue this year, according to Christopher Krembs, is that nearly all of Puget Sound’s rivers have been flowing at very low levels. While the winter snowpack in the mountains was somewhat above average last winter, warm temperatures in May and June left little water to feed the system for the remainder of the year. The Fraser River in Canada, which delivers large quantities of water into northern Puget Sound, dropped down to near record-low levels this past summer.

As in the ocean, Puget Sound waters were warmed by long days of sunny weather during the summer, even as the warm waters from the Pacific Ocean made their way into the Strait of Juan de Fuca. With reduced freshwater flows, winds and tides of normal strength produced an unexpected uniformity of slightly warmer water in the Sound. Smaller bays and inlets grew higher in temperature.

With little or no stratification, experts have been less concerned this year about the effects of low oxygen, which are known to occur during late summer or fall in Southern Hood Canal and in South Puget Sound.

Now, with fall rains arriving, the rather stagnant conditions of summer could be in for a change driven by higher streamflows. Without the cold upwelling to hold back warm waters on the coast, temperatures inside Puget Sound could stay warmer than usual this winter.

Although Puget Sound has not yet experienced a significant rise in water temperature, observers are reporting the arrival of warm-water fish — which has captured much attention, especially considering similar observations during the blob years. Besides a rare bluefin tuna in the San Juan Islands, a sport fisherman captured a video of a mola mola, or ocean sunfish, in South Sound between McNeil and Anderson islands.

Mola mola, which generally average 5 feet long, are most commonly seen in tropical waters, but they were also seen in Puget Sound during the blob years. They are one of a few species that can feast on jellyfish, which are known to become more prevalent in Puget Sound during warm-water periods.

Other unusual fish seen this year include a salmon shark in Elliott Bay. The only other salmon shark reported in Puget Sound was in Bellingham Bay in 2013 at the beginning of the blob years, according to a list of uncommon fish maintained by the Washington Department of Fish and Wildlife.

Northern anchovies, a small species of fish, seem to thrive in South Puget Sound during warm-water conditions — and that has a variety of implications for the food web, experts say.

During the blob years, when anchovies were in large numbers, researchers with NOAA’s Northwest Fisheries Science Center discovered that hungry harbor seals were more likely to eat the anchovies than going after juvenile steelhead. This “buffering effect” might also reduce seal predation on threatened Chinook and other salmon species.

Young anchovies, like herring, also can help to increase food supplies for salmon during a critical time in their development. This can be especially important under warm-water conditions, which tends to boost a fish’s metabolism and overall demand for calories. If food is not available at the right time, the fish cannot survive.

A possible downside of anchovies as a forage fish is the recent discovery that they contain an enzyme that breaks down thiamine, a vitamin essential to proper nerve, muscle and heart function. In California, Chinook salmon that consumed a diet high in anchovies were shown to produce deformed offspring that rolled over while swimming, creating an inefficient “corkscrew” effect. Studies are ongoing into the effects of thiamine deficiency and possible remedies, such as feeding the vitamin to hatchery fish. Wild salmon are harder to study.

Questions about the metabolic effects of warm water on sea life are being asked at every level of the food web, from plankton to whales. For example, near the bottom of the food web, one group of tiny crustaceans, called copepods, provide a major source of nutrition for all sorts of small fish and other marine creatures. Researchers looking at different species of copepods are reporting that warm waters tend to shift the dominant species from one that is nutrient-rich in fat content to one that is nutrient poor. The effects on animals that depend on copepods is still under study.

Jellyfish, which seem to become more prevalent during warm-water periods, can eat copepods and other food in competition with salmon and other fish. If that’s not bad enough, few Puget Sound fish consume jellyfish — so the gelatinous creatures become a kind of dead end in the food web.

Heat waves severe enough to affect multiple populations of marine animals were rare in historical times, experts say, but now warming events are occurring much more often. The question is whether the various species affected have time enough to recover before they sustain another heat wave. While some species are expected to do better with warmer water, the need for recovery time generally applies to every ecosystem on Earth — from coral reefs to arctic seas to estuaries like Puget Sound.

Since the blob years, monitoring programs in Puget Sound have been expanded to better understand all the species living in the waterway, as biologists try to determine which creatures do better under various conditions. I hope to write more about these studies in the coming weeks.

Following the blob, which ended in 2016, dozens of scientific articles were published in journals, covering the cause and effects of the warm waters inside Puget Sound as well as along the coast. As often happens with science, these studies have raised more questions about species interactions and survival under extreme conditions. If something positive can be said about the threats of warming water, it could be that climate change will be better understood as researchers study these intermittent heat waves.