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North Pacific expedition gets underway aboard four ocean-going research ships

A North Pacific research expedition is underway, with projects said to be bigger, bolder and more scientifically sophisticated than cruises in 2019 and 2020.
Four research vessels carrying more than 60 scientists from various countries will span out across the Pacific Ocean to increase their understanding of salmon — including migration, environmental stresses, availability of prey and risks from predators. Researchers aboard a U.S. ship operated by the National Oceanic and Atmospheric Administration left from Port Angeles this morning.

The NOAA Ship Bell M. Shimada

There has never been a research cruise as involved as this expedition, scheduled from now into April, according to Laurie Weitkamp, chief U.S. scientist for the 2022 Pan-Pacific Winter High Seas Expedition. The geographic reach is much larger than during similar expeditions in 2019 and 2020, Laurie told me. Advanced research equipment will help to improve data-gathering, and the analyses are growing ever more sophisticated.
Many salmon populations in the North Pacific have been declining since the 1990s. An important goal of the expedition is to better understand how physical and biological conditions can affect marine survival, especially during this critical winter period. Understanding the causes of poor marine survival could lead to better management of the ocean resources, experts say.
It will be interesting to follow the movement of the four ships in real time, as displayed on the Live Vessel Tracking Map.
The Live Vessel Tracking Map shows the location of the NOAH Ship Bell M. Shimada after leaving Port Angeles this morning. // Map: International Year of the Salmon

In addition, anyone interested can learn about shipboard activities as they are reported on social media:

“It is incredibly exciting to be part of such an amazing scientific expedition,” said Weitkamp, a salmon biologist with NOAA’s Northwest Fisheries Science Center in Newport, Ore. “This is definitely a once-in-a-career opportunity, and I am really looking forward to all the discoveries we will collectively make. It’s been a long road putting it all together, but I am confident this cruise will change how we think about salmon in the ocean. It’s Darwin’s voyage of the Beagle of our time.”
“This is an exciting time for salmon science,” agreed Brian Riddell, science adviser for Canada’s Pacific Salmon Foundation. “For the first time in decades, international cooperation across the North Pacific will provide an invaluable snapshot of salmon distributions, their health, and their environmental conditions in these times of changing climate. I expect these results will be foundational as we also begin a much larger study under the United Nations Decade of Ocean Science.”
For these and other prepared statements, check out the news release about the expedition.
The research fleet for the 2022 expedition consists of the NOAAS Bell M. Shimada from the United States, the CCGR Sir John Franklin from Canada, the RV TINRO from Russia, and a Canadian commercial fishing vessel, the FV Raw Spirit. This year’s expedition was originally planned for last year but was delayed because of COVID-19.

The Canadian Coast Guard vessel Sir John Franklin

To cover a major section of the ocean, the ships will travel in strategic patterns within assigned zones, as shown on the map above.
The North Pacific expedition involves a variety of government, academic, industry and non-governmental groups. It is part of a five-year endeavor called the International Year of the Salmon, which strives to understand the role of salmon in a worldwide ecosystem affected by human activities. The hemispheric partnership is led by the North Pacific Anadromous Fish Commission and the North Atlantic Salmon Conservation Organization.
Some areas of study:
Distribution of various salmon species: A key question has been where the salmon can be found at various times and places in the ocean. After the 2019 expedition, researchers were raising questions about the location of pink salmon, because so few were caught in deep waters where more had been expected, as I reported in Our Water Ways, March 22, 2019. On the other hand, the researchers had expected to catch fewer coho than they did that year, because they thought coho would be closer to the coast.
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In 2020 (without U.S. scientists because of COVID), the research vessels found more pink and chum salmon early in the expedition than they did later in the same area, suggesting that the fish were schooling more than expected from previous Russian studies. See Our Water Ways, April 9, 2020.
Also, besides covering more area of the ocean at one time, the researchers will deploy gillnets as well as trawl equipment to see whether different types of fishing gear catch different fish in the open ocean. Varying environmental conditions during all three years of research could help to identify what causes the fish to move to particular places.
Expanding use of environmental DNA: The technique of identifying what species are present in a given area by testing for DNA in the water has undergone major advancements. Now, thanks to a more extensive genetic baseline, researchers are able to identify many different populations of salmon as related to their streams of origin. Studies in 2019 and 2020 showed that the presence of salmon observed by using eDNA techniques was quite similar to the actual fish caught in the nets.
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These eDNA techniques also can determine the presence of species that only come to the surface at night, such as squid, or species that tend to avoid the ships, such salmon sharks and Dall’s porpoises, noted Christoph Deeg, postdoctoral fellow at the University of British Columbia, explaining the preliminary results from the 2019 and 2020 expeditions during an online seminar. Using eDNA to locate species that eat salmon, compete with them for prey, or provide them nutrition can help define the dynamic interactions taking place in the oceanic food web. Check out the online seminar featuring Deeg and Kristi Miller-Saunders, head of molecular genetics at Canada’s Department of Fisheries and Oceans.
Health and condition of salmon: The health of the salmon can be judged in part by their size at a certain age. In 2019, chum salmon seemed skinny and their stomachs were often empty, compared to coho salmon which seemed in better shape. The question of where the coho were finding prey not consumed by chum remained an open question. Measuring salmon stomach contents and analyzing fatty acids will continue to provide clues about what different salmon are eating.

New genomic techniques are being used to screen for pathogens in salmon, including a variety of bacteria and viruses. Non-lethal sampling involves using a swab on salmon gills, not unlike testing for the COVID virus in humans, according to Kristi Miller-Saunders. Preliminary analyses from the 2019 expedition revealed 21 pathogens in coho, chum, pink, and sockeye salmon.
Genetic techniques also can be used to identify chemicals produced by salmon under stress, with specific biomarkers determining the type of stress: temperature, low oxygen, viral disease and so on. The expedition is expected to result in the most comprehensive study of salmon health ever conducted in the winter, leading to insights into ocean mortality among salmon.
Ocean conditions: Besides traditional equipment that can measure ocean temperature, salinity, oxygen levels and other measures, the 2022 expedition will deploy underwater gliders, shaped like torpedoes, which monitor conditions as they move along. Gliders can be equipped with active and passive acoustic sensors to help locate marine creatures with sonar and identify species by the sounds they make. (Read the article by Caroline Graham, including glider routes, on the Year of the Salmon website.) Expedition ships also will deploy Argo floats that will drift with the currents and record various water quality data, including oxygen levels.
Plankton production and distribution: Since phytoplankton form the base of the food web, it is important to understand what limits their growth. Measuring levels of different types of phytoplankton and the surrounding physical conditions — from temperature to trace metals to stratification — could help explain the factors that limit primary production and ultimately the food for salmon. Studies of what drives the growth and consumption of different types of zooplankton in the ocean is another important piece of the puzzle.
As for financing the expedition, multiple sources of funding came together, including contributions of ship time by the U.S. and Canada as well as additional financial resources from agencies of the two governments. In addition, donations came from the North Pacific Research Board, the Great Pacific Foundation, the Pacific Salmon Foundation, the Russian Federal Research Institute of Fisheries and Oceanography, Japan Fisheries Research and Education Agency, the North Pacific Anadromous Fish Commission, the North Pacific Fisheries Commission, the Alaska Department of Fish and Game, the Washington Department of Fish and Wildlife, the Tula Foundation, the University of Alaska Fairbanks, the University of British Columbia, Oregon State University, and the University of Washington.

Scientists look for answers in methane bubbles rising from bottom of Puget Sound

In 2011, sonar operators aboard the ocean-going Research Vessel Thomas G. Thompson inadvertently recorded a surprising natural phenomenon, as the 274-foot ship traversed through Puget Sound while returning to port at the University of Washington.
At the time, researchers on board were focused on a host of other projects. They might not have known that the ship’s multi-beam sonar was even turned on. They certainly didn’t realize that the sonar was picking up images that would later be interpreted as multiple plumes of methane bubbles rising from the bottom of Puget Sound.

Methane bubble plumes (yellow and white circles) are shown along the ship paths (purple). Black lines depict fault zones. Major sewer outfalls, shown as black squares, do not line up with the plumes so were ruled out as a source. (From article by Johnson et al, UW)

“Nobody looked at the data until about three years ago, when a former student of mine was working on a project looking at bubble plumes out on the Washington (Coast) margins,” said Paul Johnson, a UW professor of oceanography. “What she found was astonishing.”
The initial discovery of the methane plumes, by Susan Merle of Oregon State University, would lead to further discoveries of methane bubbles throughout most of Puget Sound. The findings have raised many interesting questions while providing implications related to the Puget Sound food web, studies of earthquake faults and even worldwide climate-change research. Johnson, Merle and other collaborators just published their first report on Puget Sound’s methane bubbles in the journal “Geochemistry, Geophysics, Geosystems.”
Nobody was even looking for plumes of bubbles in Puget Sound when Merle, a senior research assistant at OSU’s Cooperative Institute for Marine Resources Studies, began looking at eight-year-old archived sonar data from the RV Thompson. Following the ship’s tracklines, she observed the data as the sonar picked up images of methane bubble plumes along the coast. The sonar was still on when the ship entered Puget Sound. Merle kept following the data, not realizing that the surprising bubble plumes being revealed by the recorded sonar were all the way into Central Puget Sound, off Kingston on the Kitsap Peninsula.
“Nobody knew that there were methane bubble plumes there,” Johnson said after confirming her findings. “I said, ‘This is incredible. I wonder if there are other data out there to verify this.’”
The UW’s smaller 72-foot Research Vessel Rachel Carson operates with a less sophisticated single-beam sonar, but the ship travels all over Puget Sound, carrying student as well as professional researchers, generally on short trips. Like the RV Thompson, the RV Carson records sonar soundings wherever it goes, and those data records are kept on file.
Johnson retrieved the data from 35 cruises and found much more evidence of bubble plumes.
“There were these bubble plumes all over the place,” Johnson said, “so I said, ‘Let me have a day with the Carson,’ and we went up to Kingston in 2019.”
An instrument package was dropped to the bottom to pick up samples of water and gas around the plumes. “Sure enough, it was methane,” Johnson noted.
Thanks to a grant from the National Science Foundation for “speculative” research that might lead to breakthroughs, Johnson and his colleagues began to map bubble plumes throughout Puget Sound. They found bubbles from the Tacoma Narrows to Everett and also in Hood Canal, some 350 plumes in all.
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Besides Kingston, the deep water off Seattle’s Alki Point contained a surprising number of the plumes, which are described as clusters of holes in the sea bed through which the bubbles pass. Johnson said one can get a general idea of the effect by turning a kitchen colander upside down and submerging it in a sink full of water to see bubbles emerging through the holes.
By using remotely operated vehicles, the researchers can record video of the bubbles emerging out of sharp, well-defined holes, 3 to 5 inches in diameter and roughly 3 feet apart. More than a few holes appeared to be abandoned, not producing any bubbles. Others intermittently released a series of bubbles that rose to the surface.
“You can tell which are active because of bacteria mats,” Johnson said, explaining that the bubble plumes can be a rich feeding ground for methane-loving bacteria, which grow around the holes.
In mapping the bubble plumes, it became clear that large numbers were aligned along geologic fault zones, primarily the ones running east and west, known as the Seattle, Tacoma and South Whidbey faults. Others lined up with smaller north-south faults, but the greatest number of bubble plumes occurred where the faults intersected, such as off Alki Point in West Seattle.
Much of this phenomenon has yet to be explained, Johnson said. One idea is that the methane gas is largely confined beneath a layer of clay and compressed sediments laid down during the last glacial period. If so, the methane may be rising up through cracks in the confining layer, cracks created through tectonic activity.
Methane gas is produced naturally during the breakdown of organic compounds found in all living things. Biogenic methane is produced during digestion by certain types of bacteria. Thermogenic methane occurs at higher temperatures, especially under pressure. (See discussion in Science Direct.)
Because of the lower temperatures in Puget Sound, Johnson said he suspects that the methane is from biological processes. Off the Washington and Oregon coasts, both biogenic and thermogenic methane are being released from thousands of bubble plumes, with pronounced clusters in a north-south band some 30 miles off the coast. This region is along the tectonic boundary where the Juan de Fuca oceanic plate collides with the North American continental plate.
High temperatures and pressures in this subduction zone leads to the release of fluids and methane gas. The vast majority of plumes are seen on the seaward side of the continental shelf in waters about 500 feet deep. Faults in this region, created by powerful subduction earthquakes, appear to be the routes for methane gas and fluids to escape to the surface.
An early hypothesis suggested that the bubbles in Puget Sound might be coming up from this underlying subduction zone, but that has not panned out. The chemical signature of the methane in Puget Sound, as revealed through isotope analysis, does not match that from sources deep underground, where samples can be obtained from terrestrial hot springs and water wells.
Because the methane feeds bacteria at the base of the food web, bubble plumes off the coast have been found to flourish with biological activity, including large populations of krill and fish, Johnson said.
“Fishermen know where these areas are, because they are biological hotspots,” he said.
How this methane may affect the Puget Sound ecosystem is yet to be studied in detail, Johnson said. The answer may depend on the location and specific physical and chemical conditions. While the methane is likely to increase biological productivity, it may also play a role in the low-oxygen conditions that can affect sea life and create other problems.
Because the bubble plumes seem to be coming up through faults underlying Puget Sound, seismologists might be able to use them to locate unknown geological features, identify changes over time, or determine which faults are active.
These findings also are relevant to climate change, as scientists search to find other natural sources of methane. Since methane is a powerful greenhouse gas, climatologists are challenged to identify all natural as well as human-caused sources in order to predict the effects of reduced emissions. (See “Methane Budget,” Global Carbon Project.)
Globally, between 35 and 50 percent of methane emissions are believed to come from natural sources, including wetlands, according to the Environmental Protection Agency.
Methane’s lifetime in the atmosphere is much shorter than carbon dioxide, but methane is more efficient at trapping radiation. That’s why this gas raises major concerns. Pound for pound, the impact of methane is 25 times greater than carbon dioxide over a 100-year period, according to a report from the Intergovernmental Panel on Climate Change. In 2019, methane was said to account for about 10 percent of all U.S. greenhouse gas emissions from human activities.
The total amount of methane released from Puget Sound is relatively small when considering the total methane from many natural and human sources — including natural-gas leaks, raising livestock and garbage dumps. Still, Johnson hopes to launch a project that would estimate the total atmospheric emissions from the bubble plumes, while continuing to examine what is venting from all these holes. These new findings also point to ways to search for other natural methane sources around the world.
Related work by Shima Abadi, an associate professor at UW Bothell, involves analyzing the sound that the bubbles make and determining how that might relate to the amount of gas being released and other factors.
Other authors of the new paper are Tor Bjorklund, an engineer in UW oceanography; Chenyu (Fiona) Wang, a former UW undergraduate; Susan Hautala, a UW associate professor of oceanography; Jerry (Junzhe) Liu, a senior in oceanography; Tamara Baumberger, assistant professor at OSU; Nicholas D. Ward, affiliate assistant professor in UW Oceanography; and Sharon L. Walker of NOAA’s Pacific Marine Environmental Laboratory.

Understanding the cold-water needs of salmon and helping them to survive

Salmon need cold water. This general statement is something I’ve been hearing since I first began reporting on these amazing migrating fish years ago. Cold water is a fact of life for salmon, known for their long travels up and down streams, out to saltwater and back. But colder is not always better.
Questions about why salmon need cold water and how their habitat might grow too warm or too cold led me into an in-depth reporting project. I ended up talking to some of the leading experts on the subject of stream temperature. Thanks to their fascinating research, I learned that temperature and food supply go hand-in-hand to dictate salmon metabolism, growth and survival. You can read my report, “Taking the Temperature of Salmon,” in the Encyclopedia of Puget Sound.

Middle Fork of the Snoqualmie River, near Mount Si trailhead
Photo: Christopher Dunagan

Later in this blog post, I will touch on some new developments regarding temperature and stream conditions — including Gov. Jay Inslee’s latest initiative to help salmon by proposing new laws and regulations along with $187 million in next year’s budget request.
In the Northwest, we almost never need to worry that salmon streams will get too cold. Logging, farming and development have removed large amounts of streamside vegetation, allowing the sun to warm the waters, often to excessive degrees. While sunlight can increase the growth of tiny organisms and boost the food web, higher temperatures also accelerate metabolic rates, increase stress hormones and alter behavioral responses, as I described in my story.
When a section of a stream grows too warm, fish will seek out cooler water, often by swimming upstream to areas cooled by springs or snowmelt. As a change in temperature alters metabolism and behavior, the result can be problems with finding food and with increased threats of predation.
“Anybody who does stream work soon learns that fish are amazing,” Jonny Armstrong, a University of Oregon researcher, told me. “They don’t just accept the habitat they are given; they do all kinds of things to game the system.”
Jonny’s work in Alaska documented how a run of coho salmon moved into cool water to feed on sockeye salmon eggs. After getting their fill, the fish returned to warmer water to digest the food and grow faster.
I’m especially indebted to Aimee Fullerton, who helped me understand a multitude of biological processes related to temperature, as I searched for ways to explain the complex findings. Aimee is a research fishery biologist with NOAA’s Northwest Fisheries Science Center. She has been working in the Snoqualmie River, where temperatures grow warm enough at times to impair the growth and development of salmon and sometimes kill them if they cannot escape into cooler waters.
The prospects of climate change raise concerns about even higher temperatures in the future. Careful temperature measurements, combined with computer modeling, have helped researchers predict future temperature changes. Other experts are developing new strategies for maintaining cooler temperatures to protect salmon, as I outlined in the story.
Just last week, Washington Gov. Jay Inslee announced a new initiative that he will take to the Legislature next year. He hopes to boost salmon populations by improving stream habitat, replacing culverts and other impediments, and cleaning up polluted waters. Inslee also intends to address harvest, hatcheries and hydropower along with critical issues of predation and food availability.
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“There is no time to waste,” the governor said in a news release. “We have a choice between a future with salmon or a future without them. Salmon need immediate and urgent action to ensure their survival. That’s why, for the 2022 legislative session, salmon recovery is a top priority and have both policy and funding to help protect them.”
One of the key ideas that the governor mentioned during his news conference on Tuesday is to build and/or protect streamside corridors based on the height of trees, which provide shade to cool streams. (See video, embedded on this page, at 11:03-14:30.) The riparian corridor is also important in reducing toxic pollutants, bacteria and fine sediments that enter a stream.
The so-called Governor’s Salmon Strategy Update (PDF 1.4 mb) includes provisions for riparian buffers on agricultural lands, which has been a concern of Indian tribes throughout the region. Details have yet to be proposed, but a combination of regulations and financial support are likely.
The latest initiative grew out of the 2019 Centennial Accord meeting between state agencies and tribal salmon experts led by the Northwest Indian Fisheries Commission.
“This is the first time we have seen legislation that would require landowners to protect riparian habitat,” said Dave Herrera, NWIFC commissioner and Skokomish Tribe policy representative who was quoted in a news release. “It is also groundbreaking because it includes incentives for landowners to create and maintain riparian zones, as well as regulatory backstops when compliance isn’t voluntary.”

Next year’s salmon-recovery legislation will be called the Lorraine Loomis Act, named for the late chairwoman of the Northwest Indian Fisheries Commission who promoted cooperative efforts to save salmon. Budget details are included in a policy brief (PDF 1.4 mb) released by the Governor’s Office.
“We know the status quo isn’t working when it comes to salmon recovery,” Lorraine wrote in a column last year. “We know what the science says needs to be done, and we know that we must move forward together.”
On the regulatory front, the federal Clean Water Act calls for standards that protect aquatic life, such as salmon. Where temperatures are not maintained within an approved range, the waters are considered “impaired” — just as they are when bacteria become too numerous or oxygen levels drop too low for the aquatic species of concern.
Although I did not address regulatory issues in my story about temperature, it is worth noting that numerous federal and state clean-water regulations are undergoing changes. Some changes are the result of lawsuits; some follow statutory requirements; and some stem from the coming and going of the Trump administration’s efforts to reduce environmental rules.
For example, the Environmental Protection Agency recently withdrew its approval (PDF 402 kb) for how the Washington Department of Ecology handles high temperatures in certain stream segments that grow naturally warm. The basic idea is that regulatory agencies need not seek out mitigation measures to cool such waters — even in areas too warm for salmon — if it can be shown that high temperatures represent the natural condition of the streams and that humans are not to blame.
The group Northwest Environmental Advocates first brought a lawsuit over such “natural conditions criteria” in Oregon, where NWEA contended that the state was allowing streams to remain dangerously hot by discounting the effects of humans. In this way, the group argued, Oregon was establishing new and higher temperature standards than allowed by existing regulations without going through a public review process. The higher temperatures should be subject to public review and federal oversight, including effects on endangered species, the group said. Federal courts agreed with that reasoning.
Although the Washington Department of Ecology rarely invokes natural conditions criteria for temperature, it must now review its practices and undergo federal oversight where experts believe that the natural condition of a water body would exceed established water-quality standards. Besides temperature, the review will cover criteria for dissolved oxygen. In some areas of Puget Sound, Ecology has determined that numerical water-quality standards would not be met even if no humans were around.
The methods of determining what the water temperature or oxygen level would be in the absence of human activity can become an elaborate exercise involving computer modeling. But Nina Bell, executive director of NWEA, argues that the process is important and should be open to public scrutiny. After all, she said, the outcome can determine whether unhealthy temperatures or oxygen levels persist or are reduced through mitigation efforts.
Other ongoing water-quality matters:

Map showing a marine heat wave known as "the blob" which spread across the northeastern Pacific Ocean from 2014 to 2016. Image: Joshua Stevens/NASA Earth Observatory, Data: Coral Reef Watch

Modeling “the blob” in the Salish Sea

In late 2013, a marine heatwave that scientists dubbed “the blob” began warming the ocean throughout the Northeast Pacific, causing temperatures to rise almost 3°C above normal. The disruption severely depressed salmon returns. Whales, sea lions and seabirds starved, and warm water creatures were suddenly being spotted off the coast of Alaska. In Puget Sound, temperatures also jumped, but the effects of the blob here proved difficult to study because of the natural variability of the Salish Sea and the heavy influence of freshwater mixing and circulation in the waterbody. Recently, computer simulations from our partners at the Salish Sea Modeling Center have begun to help scientists understand some of the complexities.
A new paper in the journal Frontiers in Marine Science analyzes results of a five-year simulation of the Salish Sea Model to assess the blob’s effects. Among its more surprising findings, the model shows that increased inflow of freshwater and nutrients from rivers and creeks was “the primary driver of increased biological activity” such as algal blooms in Puget Sound during the heatwave. The authors say that is counter to earlier assumptions that river flows were unrelated and warmer water generated by the heatwave alone was responsible. They now hope the paper will prompt further studies. Were these higher-than-normal freshwater inflows merely a coincidence? Or do they indicate the influence of heatwave impact on hydrological processes? PSI affiliate and collaborator Tarang Khangaonkar is the paper’s lead author.
Khangaonkar, T., Nugraha, A., Yun, S. K., Premathilake, L., Keister, J. E., & Bos, J. (2021). Propagation of the 2014–2016 Northeast Pacific Marine Heatwave through the Salish Sea. Frontiers in Marine Science, 1836.

Map showing a marine heat wave known as "the blob" which spread across the northeastern Pacific Ocean from 2014 to 2016. Image: Joshua Stevens/NASA Earth Observatory, Data: Coral Reef Watch

Modeling “the blob” in the Salish Sea

In late 2013, a marine heatwave that scientists dubbed “the blob” began warming the ocean throughout the Northeast Pacific, causing temperatures to rise almost 3°C above normal. The disruption severely depressed salmon returns. Whales, sea lions and seabirds starved, and warm water creatures were suddenly being spotted off the coast of Alaska. In Puget Sound, temperatures also jumped, but the effects of the blob here proved difficult to study because of the natural variability of the Salish Sea and the heavy influence of freshwater mixing and circulation in the waterbody. Recently, computer simulations from our partners at the Salish Sea Modeling Center have begun to help scientists understand some of the complexities.
A new paper in the journal Frontiers in Marine Science analyzes results of a five-year simulation of the Salish Sea Model to assess the blob’s effects. Among its more surprising findings, the model shows that increased inflow of freshwater and nutrients from rivers and creeks was “the primary driver of increased biological activity” such as algal blooms in Puget Sound during the heatwave. The authors say that is counter to earlier assumptions that river flows were unrelated and warmer water generated by the heatwave alone was responsible. They now hope the paper will prompt further studies. Were these higher-than-normal freshwater inflows merely a coincidence? Or do they indicate the influence of heatwave impact on hydrological processes? PSI affiliate and collaborator Tarang Khangaonkar is the paper’s lead author.
Khangaonkar, T., Nugraha, A., Yun, S. K., Premathilake, L., Keister, J. E., & Bos, J. (2021). Propagation of the 2014–2016 Northeast Pacific Marine Heatwave through the Salish Sea. Frontiers in Marine Science, 1836.

Plunging into a jungle of weather statistics to find the footprints of climate change

“Augusts in Seattle are getting hotter, leading to a change of 3.5°F since 1970.”
This was the sentence that caught my eye while reading an email from Peter Gerard, director of communications for Climate Central, an organization that prides itself on helping news reporters tell an accurate story of climate change.

Average temperatures for August at Sea-Tac airport, as analyzed by NOAA’s Applied Climate Information System, with enhanced graphics by Climate Central

I wondered immediately: Is there something special about the month of August? It turns out that there is, at least for Seattle and most areas around Puget Sound, but I needed to see the evidence for myself.
Thus began my journey down a rabbit hole of climate statistics in the Puget Sound region and across the state. I eventually dragged two experts — Washington State Climatologist Nick Bond and Climate Central meteorologist Sean Sublette — down into the hole to guide me. I found myself in a flood of data. These two experts showed me some clever tools to corral the numbers. And I finally emerged with a greater understanding of the pitfalls that climatologists must overcome to make sense of recorded temperatures as they try to forecast the future of climate change at the local level.
As Nick Bond stressed to me, temperature increases in one locale make up just a small piece of the overall climate-change picture. Most of the heat trapped in the changing atmosphere is absorbed into the ocean, he noted. Those oceanic conditions drive major shifts in weather patterns across the globe. Still, the increasing air temperatures that we measure locally can have a profound effect on plants and animals — including humans.
The heat wave of late June in the Northwest was a prime factor in the confirmed deaths of 100 people in Washington state — far above normal, according to the Washington State Department of Health. Heat may have contributed to the deaths of many others. Historically, June is an unlikely month to break all-time heat records, but climate change is altering a multitude of conditions and increasing the risks of perfect storms at unexpected times.
Because extreme heat can have devastating effects on humans and the natural ecosystem, I wanted to know how big this problem was in the past and how the trends are changing. While historical records have some problems, I learned that anyone interested could use tools readily available online to plot temperature trends and get an idea of how things are changing. I’ve added some footnotes along the way for those who would like to follow what I’ve been doing.
Starting point is critical
The first step in my journey through the numbers was to check the ongoing change in the average temperature for the month of August. But where does one begin? I quickly learned that when looking at trends, it makes a difference whether you start during a warm or cool period.
The same data from Sea-Tac as in the above graph but starting at 1973. // Source: Applied Climate Information System

For example, looking at Sea-Tac temperatures with a data-analysis tool by NOAA’s Applied Climate Information System, the trend from 1970 to 2021 is an increase of 3.4 degrees along a trend line that incorporates every average for August through 51 years. (See first graph at right.) 1
A trend line does not usually begin or end on the same temperature as the first or last data point in the series, but the starting and ending points can strongly influence the trend. For example, if one starts at 1973 (second graph), the change along the trend line to 2021 is 3.9 degrees.2 That’s a full 0.5 degrees higher than if one starts just three years earlier. The trend line becomes tipped by starting at 61.6 degrees for August 1973 instead of 64.5 degrees for August 1970 (along with the removal of three data points — 64.5, 67.7 and 66.7 for August 1970, 1971 and 1972, respectively).
One could say that the average temperature in August has gone up at Sea-Tac about 3.4 degrees since 1970 or 3.9 degrees since 1973. I also plotted the average of the maximum daily temperatures for August and found they had gone up by 4 degrees since 1970 (88° to 92°) or 5 degrees since 1973 (87° to 92°).3
Because heat extremes have an effect on health, one can also choose a temperature and see how many consecutive days reach that level, as in the graph at the top of this page. For example, I picked 90 degrees and asked how many times we saw that temperature at least two days in a row. From 1940 to 1981, the answer is 21 times.4 But from 1980 to 2021 — the same number of years — the answer is 43 times, about twice as often.5
You can pick any temperature and any length of “streak” for that temperature. Looking for at least three days of 85-degree heat, I found an occurrence of 27 times from 1980 to 2000 and 68 times from 2001 to 2021.6
What about a streak of at least 80 degrees for four days? The occurrence was 26 times from 2000 to 2010 and 63 times from 2011 to 2021.7 Even the changes in the last 10 years are significant with no cooling trend in sight.
Some people have noticed that the nights seem to be growing warmer, too. Plotting the average of the minimums, I found that the lowest temperatures in August have gone up at Sea-Tac by 4 degrees (49° to 53°) since 1973, slightly less for 1970.8
August normally cooks
Why the focus on August? It turns out that for much of the Puget Sound region, August is not only the hottest month of the year on average, but it is also the month in which the temperatures have been rising faster, year to year, than any other month.
While these numbers and the resulting trends may be revealing and are a good place to start, their value is limited by the time scale, starting and end points, and choice of a single location (Sea-Tac).
“It gets complicated, and the potential for cherry-picking is really high,” Nick told me. “You have to really guard against that.”
The goal is to dig into the numbers to understand what is happening, he said, not to support anyone’s convictions. Climatologists have spent considerable time trying to confirm historical temperature records and clear out discrepancies.
Across the country, it is easier to obtain complete and consistent data since 1970, according to Sean Sublette, explaining why Climate Central often uses that time period as a reference. But, as Sean points out, one may get a better idea of a long-term trend by considering a longer time scale. Since Sea-Tac data go back to 1945, we can see that the change in average August temperature from 1945 to 2021 is 5.3 degrees along the trend line. 9
For the sake of comparison, that’s 0.70 degrees per decade if you start from 1945, 0.67 starting at 1970, and 0.81 starting at 1973. So if one wanted to cherry-pick the data for a more extreme temperature rise, the starting year would be 1973.
Despite these differences, it is clear that the temperature is going up at Sea-Tac in a very significant way, no matter when one starts the graph. While I’m just fumbling with local numbers in relatively recent history, climate experts have made a compelling case for climate change by looking back thousands of years. (NASA: “How do we know?”)
Taking a look around
With Sea-Tac findings in hand, I began to look at other locations, using a helpful trend-analysis tool on the webpage of the State Office of Climatology. This data set, which goes back to the 1800s, uses temperatures adjusted for observed biases and inconsistencies, with the most reliable data usually coming in recent years.
Trend analysis tool for temperature, precipitation and snow water equivalent found on the website of the Washington State Climatologist. (Click to access.)

By choosing a starting year and selecting a trend range, one can simply move the curser across the map from one location to another and compare the differences. For example, with 1970 as the starting year and a time frame of August, I found a fairly wide range of temperature increases — up to 4.85 degrees in Vancouver in Southwest Washington.
According to Nick, some of the differences may relate to changing conditions around the monitoring stations themselves. Since concrete and hard structures absorb more heat, urbanization can result in a more rapid rise in temperatures than in surrounding rural areas, particularly forested areas. This is known as the “heat island effect.”
Some observers speculate that construction of a third runway at Sea-Tac Airport along with growth in surrounding residential and commercial areas may be responsible for higher temperatures at the Sea-Tac weather station than would have been recorded without that growth.
In any case, by comparing average temperatures from June through September at various locations, it appears that August temperatures are going up the fastest in most areas across the state — although for some stations July is changing nearly as fast or even faster than August. In some areas of Eastern Washington, September temperatures appear to be going up faster than July or August, based on these single-location numbers.
Why August would be growing warmer faster than other months is not easy to explain. One idea is that the ground is becoming drier over time near the end of summer because of our increasing temperatures. Drier conditions mean less evaporation and less transpiration from the leaves of plants. Since the processes of evaporation and transpiration lead to cooling effects at the source, less moisture may mean less cooling to offset the warming of the sun. Still, the variation in weather conditions — including precipitation — makes any specific cause difficult to prove.
Changing the scale
I like the map on the state climatology website because of its simplicity, but Nick advises not to draw broad conclusions from individual locations. Another useful analytical tool, Climate at a Glance, offers a variety of temperature sources. One can look at data for a city, county, state or region or take national or global perspectives using this webpage from NOAA’s National Centers for Environmental Information.
In recent years, annual average temperatures nearly always exceed the long-term average since 1901. Graph: Climate at a Glance, NOAA National Centers for Environmental Education

For the Puget Sound lowlands, go to “divisional” and “time series,” and pull down Washington state to pick a region. Since 1945, the average temperature across the Sound for August has gone up 0.5 degrees per decade, as shown in the upper right corner.10 Since 1970, the trend is 0.6 degrees per decade, 11 but it reaches 0.7 degrees with a starting point of 1973.12 This average increase in August temperatures in the Puget Sound region appears to be higher than for most other regions of the state.13
Another interesting way to look at the rising temperatures around Puget Sound is to compare monthly temperatures to a long-term average. For example, the average August temperature from 1901 to 2021 was 63.1 degrees, as shown by the “base period” in Climate at a Glance. 14
From 1901 to 1940, 57 percent of the August averages fell below the long-term average, as shown in the “departure” table below the graph.15 From 1941 to 1980, 52 percent were below the long-term average.16 But from 1981 to 2021, a similar period of time, only 2.4 percent were below the long-term average.17 In fact, over the past 20 years, only one August (2007) fell below the long-term average, and it was just 0.1 degree lower at 63.0 degrees. This is just another way of saying that temperatures have gone up to a remarkable extent over the past 20 years.
When looking at averages for the entire year, not just the month of August, the result is similar but less dramatic. Only six times in the past 41 years did the average annual temperature for Puget Sound fall below the overall 1901-2021 average.18 And that happened only twice in the past 20 years, with the last time coming a full decade ago.19
Heating in waves
Fall weather seems to be setting in even more now, and memories of the summer heat wave in June may be fading, despite long-term damage to the ecosystem from drought, wildfires and over-heated beaches (Our Water Ways, July 13).
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For people living in the Northwest, June’s heat wave was like nothing ever seen before. Visits to hospital emergency departments because of heat-related illness were 69 times higher than the same period of June 25-30 in 2019, according to a report from the Centers for Disease Control and Prevention. More than 1,000 heat-related illnesses occurred in Washington, Oregon and Idaho on June 28, when Portland reached 116 degrees and records were shattered throughout the region.
Extreme heat events are predicted to occur more often and last longer, according to Dr. Scott Lindquist, Washington’s acting state health officer, stressing that climate change is a major public-health threat as well as an environmental challenge.
“This huge jump in mortality due to heat is tragic and something many people thought they’d never see in the Pacific Northwest with its mostly moderate climate,” Lindquist said in a news release from the Department of Health. “But climates are changing, and we see the evidence of that with dramatic weather events, major flooding, historic forest fires, and more.”
People over the age of 60 have been shown to be especially vulnerable to heat waves, according to a report in the Canadian Medical Association Journal. Increased illness and the use of more medications among seniors can increase the risk of serious problems, but older people also appear to have less ability to sense heat and respond appropriately, the report says.
For more on heat-related illness, read the CDC report (PDF 676 kb) on the subject.
I had plunged into this jungle of weather statistics to see if I could learn something about climate change at the local level. Did I really need to be convinced that we are living in a world that is growing dramatically warmer? Probably not, but now I have a wider perspective when reading the findings of the Intergovernmental Panel on Climate Change, including “Climate Change 2021 — The Physical Science Basis” as well as new reports scheduled to be released next year.
FOOTNOTES with details of the analytical tools
1 SC ACIS Product selection: Single-station products, Seasonal time series. Options section: Average temp, 1970-2021, month: Aug, ✔Include regression line. Station/area selection: Seattle; click search, click on map for Sea-Tac, GO.
2 Same as footnote 1, with 1973-2021.
3 Same as footnotes 1 and 2 with Options section: Max temp.
4 SC ACIS Product selection: Single-station products, Consecutive days. Options section: 1940-1981, Criteria: Max temp >= 90, All runs >= 2 days. ✔Include start date with results. Station/area selection: Seattle, click search, click on map for Sea-Tac, GO.(The results can be ordered by clicking on the column header.)
5 Same as footnote 4 with 1980-2021
6 Same as footnotes 4 and 5, with Max temp >= 85, All runs >= 3 days.
7 Same as footnotes 4 and 5, with Max temp >= 80, All runs >= 4 days.
8 Same as footnotes 1 and 2 with Options section: Min temp.
9 Same as footnote 1, with 1945-2021.
10 Climate at a Glance Click on divisional, time series: ✔display trend, per decade, Start 1945, End 2021. Average temperature, 1-month, August, Start year 1945, End year 2021. State: Washington, Climate Division: 3. Puget Sound lowlands. Plot.
11 Same as footnote 10 with Start year 1970 for trend and plot inputs.
12 Same as footnote 10 with Start year 1973 for trend and plot inputs.
13 Same as footnotes 10, 11 and 12 with change in Climate Division input to selected options.
14 Same as footnote 10 with ✔Display base period: Start 1901, End 2021.
15 Same as footnote 14 with Start 1901 and End 1940 for trend and plot inputs. Sort “Departure from Mean” by clicking on the column head. Negative numbers are below the average.
16 Same as footnote 15 with Start 1941 and End 1980 for trend and plot inputs.
17 Same as footnote 15 with Start 1981 and End 2021 for trend and plot inputs.
18 Same as footnote 15, with Time Scale: annual and Start 1981 and End 2021.
19 Same as footnote 15, with Time Scale: annual and Start 2001 and End 2021.