The Cooperative Institute for Climate, Ocean, and Ecosystem Studies

By Theo Stein, NOAA Research

For decades, firefighting crews counted on falling temperatures and rising humidity at night to dampen wildfire activity, allowing them to rest, regroup and prepare for the next day.

Over the last 20 years though, satellite measurements have confirmed a change reported in the western US by firefighters on the ground: a dramatic increase in nighttime fire activity by larger fires. Previous studies attributed the increase to warmer, drier nights, conditions that help to maintain the flammability of fuels.

New research from NOAA, the University of Washington and the U.S. Forest Service has investigated other weather conditions that influence fire behavior, the extent to which these factors have been changing over recent decades and how they may have contributed to changes in nighttime fire behavior.

“We looked for simultaneous changes in winds, atmospheric mixing and fuel moisture that might enhance nocturnal fire activity,” said lead author Andy Chiodi, a University of Washington scientist working with NOAA’s Pacific Marine Environmental Laboratory. “Our results show that, indeed, all the atmospheric measures that influence wildfires have changed towards supporting more intense nocturnal fire behavior.”

The findings were published in the Journal of Climate.

The implication of these findings, said Chiodi, is that researchers need to better understand the interplay of each of these factors in driving increases in nocturnal fire activity, which not only complicate firefighters’ jobs, but also could jeopardize public safety.

In 2022, a study led by the US Forest Service confirmed that the amount of fire radiative power, or the amount of heat generated by burning, detected at night over the contiguous U.S. by two NASA satellites (VIIRS and MODIS) increased by approximately 50 percent during the 2003-2020 study period. That study found the change was most pronounced for the larger fires burning in drier heavy fuels that experienced more active nighttime burning.

The current study expands on Chiodi’s previous work that examined changes in night time vapor pressure deficit, which determines the rate at which woody fuels lose moisture to the air, over the western U.S. during the last 40 years. As fuels dry they become more susceptible to burning. The study found over that period that the number of dry-air nights had indeed increased.

The new paper explored not only the frequency of dry nights but also how often they were accompanied by other weather factors conducive to burning. “It’s important to know how each of these has changed to accurately interpret changes in nighttime fire behavior,” Chiodi said.

Chiodi explained that typically, when the sun sets, reduced solar heating cools the surface, calms winds and turbulence, and allows for the formation of a stable layer at the surface, called the planetary boundary layer, which acts as a kind of cap. Reduced wind speeds tend to moderate fire activity. Cooler air below a lower, stable boundary layer traps humidity and smoke, which can further subdue fire behavior.

The new study found that in the 2010s, dry-fuel nights were not only more than 10 times more frequent compared to the 1980s and 1990s in some locations, fire risk was compounded by simultaneously windier and deeper boundary layers, over 81% of the Western U.S.

“So the problem is that it’s not just drying out, it’s that places that are getting drier are seeing a double or triple whammy: drier nights, more wind and a deeper atmospheric boundary layer.”

The study found southern California, especially the western slopes of the Sierra Nevada, are hot spots for this trend. This region was already quite dry in terms of fuel moisture in the 1980s and 1990s. More recently, it has experienced some of the greatest increases in frequencies of dry and windy nights.

These insights not only have value for operational firefighting decisions, Chiodi said they can also help inform decisions about when conditions are appropriate for prescribed burns, which are critical for mitigating wildfire risk, especially near developed areas.

Chiodi is presently working with Forest Service colleagues to build user-friendly tools that can quickly identify safe weather windows for effective prescribed burns.

By NOAA Alaska Fisheries Science Center

To locate endangered North Pacific right whales, scientists listen for their calls in Alaskan waters believed to be a part of their historical feeding grounds. To do this, scientists use underwater microphones, known as hydrophones. The NOAA Fisheries/University of Washington scientific team documented sounds from these rare right whales at all six acoustic mooring sites in the Aleutian Island passes and northern Gulf of Alaska. This is remarkable because it is believed that fewer than 50 animals remain in the eastern population. The findings also support the idea that the whales use this area as a migratory corridor.

“We detected these whales in both the eastern Aleutian Island passes and northern Gulf of Alaska habitats,” said lead author Dana Wright, conservation biologist for the University of Washington Cooperative Institute for Climate, Ocean, & Ecosystem Studies. “We observed peaks in calling between June and August at most sites, which supports the belief that these areas are currently being used as feeding grounds.” 

The scientists were listening for the two most common sounds that these rare whales produce: the upcall and the gunshot call. North Pacific right whale upcalls follow an upsweep pattern and occur in irregular spaced clusters of calls, called bouts. In contrast, their gunshot calls are very short (less than 1 second) broadband signals. They’re made up of a wide range of sound frequencies—like the snap of your finger or a clap. These calls can occur in a pattern to create songs. 

The greatest number of detections occurred in the whale’s designated critical habitat off Kodiak, Alaska between September and November. Right whales have been acoustically detected at mooring sites further north, in the whale’s Bering Sea critical habitat, at the same time of year.

In addition to summer and fall, right whales were also detected for at least 1 day at each of the mooring sites between December and April. This is when scientists believe the species migrates between its northern feeding grounds to lower latitudes.

“One of the great mysteries about this species is that we still don’t know where they go once they leave the feeding grounds,” says Wright. “One hypothesis is that these whales swim along the coastline of the northern Gulf of Alaska, between Kodiak Island and the Aleutian Islands, as part of their migratory route. The winter detections in our dataset are helping to piece together the puzzle.”

The timing of overwinter (roughly December–May) detections at the Aleutian Islands Pass sites relative to the Bering Sea detections supports their use as a migratory corridor. This study area includes Unimak Pass, a major vessel traffic corridor where right whales have been acoustically detected in prior years.

The Importance of Identifying Habitat for Eastern North Pacific Right Whale Population Recovery 

The genetically distinct eastern population of the North Pacific right whale is one of the most endangered large whales in the world. This is largely due to targeted, extensive legal and illegal commercial hunting in the 19th and 20th centuries. 

Historically, North Pacific right whales’ range included the Gulf of Alaska, eastern Aleutian Islands, and eastern Bering Sea. Stomach content data from harvested whales suggest that these areas were feeding grounds. However, the contemporary distribution of the eastern  population, including possible migratory routes, is poorly known.

Data from this study and other recent research led by Wright using ratios of amino acids in the skin tissue are helping to uncover a record of migration and foraging. 

“Given their remote and elusive nature, opportunistic photographs taken by the public can also be really helpful,” said co-author Jessica Crance, marine mammal biologist, Alaska Fisheries Science Center. “In fact, the first visual evidence of a North Pacific right whale feeding in the Bering Sea during winter months was provided by a fisherman.”

If you are ever fortunate enough to spot a North Pacific right whale, your photos could provide another valuable clue about their movements. 

Remember to keep a safe distance (500 yards at minimum). Take photos or video of the sides of the whale’s head if you can. Please send the photos or videos along with your name, and the location where you made your sighting, to np.rw@noaa.gov.

By Theo Stein, NOAA

The global ocean covers 71% of the planet. Across these vast spaces, interactions between the ocean and atmosphere are primary drivers of Earth’s weather, climate and marine productivity.

Satellites, instrumented moorings, and infrequent ship-borne research missions have revealed much about these interactions, but large areas of the ocean are significantly undersampled.

To fill in the gaps, scientists have increasingly turned to an array of Uncrewed Surface Vehicles (USV), some of which can navigate tens of thousands of kilometres to capture key observations autonomously. Most rely upon renewable energy from wind, waves, and the Sun for propulsion and to power their sensors and telemetry systems.

“This technology is currently booming,,” said Ruth Patterson, an oceanographer with Charles Darwin University in Australia. “We urgently need to establish a global network to agree on standards and best practices so that USV data can be used to enhance our understanding of the oceans and climate.”

To rectify that, Patterson and an international team of researchers including scientists from NOAA’s Pacific Marine Environmental Laboratory (PMEL), the University of Washington, and the Cooperative Institute for Climate, Ocean, and Ecosystem Studies (CICOES), conducted a review of the global use of USVs and how well the recommended attributes of a global observing network are met.

The Observations Coordination Group (OCG), which oversees the Global Ocean Observing System (GOOS), has identified ten important attributes of an in-situ GOOS network, about half of which were well-met or progressing. In particular, the review cited 200 USV datasets, published in 96 peer reviewed studies, capturing observations of 33 physical, biogeochemical, biological and ecological processes spanning the air-sea transition zone across the global ocean.

“An endorsed USV GOOS network needs to have or be working towards a data management infrastructure that includes defined standards and recommended practices,” said Kevin O’Brien, a CICOES scientist and vice chair of the OCG. “This is the next step for an emerging network of GOOS.”

The review was carried out under the auspices of the Observing Air-Sea Interactions Strategy (OASIS), a program of the United Nations Decade of Ocean Sciences for Sustainable Development, and was published in the journal Frontiers of Marine Science.

Patterson will present a proposal to establish a permanent global USV network within the Global Ocean Observing System to the Observations Coordination Group during its April meeting in France.

PMEL scientist Meghan Cronin, co-chair of the OASIS program, said “this offers a roadmap for building this international network that offers a key to new frontiers in ocean sciences.”

Scientist(s): Dr. Meghan F. Cronin, Dr. Calvin W. Mordy, Dr. Adrienne J. Sutton, Eugene F. Burger, Dr. Dongxiao Zhang, Dr. Chidong Zhang, Kevin O’Brien, Catherine Kohlman, Dr. Elizabeth McGeorge

Watch CICOES Director John Horne on the International Council for the Exploration of the Sea’s web series Hidden Gems. He discusses a solar-powered acoustic monitoring system that delivers near-real-time data to support sustainable fishing.

By Hannah Hickey, UW News

As we burn fossil fuels, the amount of carbon dioxide in Earth’s atmosphere is gradually rising, and with it, the planet’s average temperature. How fast the level of atmospheric carbon dioxide — and with it, the temperature — goes up matters for the ability of humans and ecosystems to adjust. A slower increase gives humans time to move away from low-lying areas and animals time to move to new habitats.

It turns out the rate of that increase matters for non-living systems, too. A recent University of Washington study looked at how a major current in the Atlantic Ocean that includes the Gulf Stream will respond to a doubling of carbon dioxide from preindustrial levels. The study, published in the Proceedings of the National Academy of Sciences, found that when carbon dioxide levels rise more gradually, they have less impact on the ocean circulation.

UW News sat down with author Camille Hankel, a UW postdoctoral researcher in the Cooperative Institute for Climate, Ocean and Ecosystem Studies, to learn more about her study.

Why did you choose to study how the rate of rising CO2 affects the climate system?

Camille Hankel: In my PhD, some of my work was on “climate tipping points,” which emerge from the hypothesis that there might be some sort of critical thresholds of warming or CO2 change that can lead to very abrupt and irreversible change in some parts of the climate system. Through that work, I got exposed to some literature on “rate-induced tipping points,” which is the idea that instead of crossing a critical level, that there could be some critical rates of CO2 change that are important for the climate system.

Specifically, I read this study that was looking at this idea in the context of the AMOC, the Atlantic Meridional Overturning Circulation, which is this large-scale ocean circulation. That study was using what we call a box model — a simplified, mathematical representation of the ocean circulation. And I thought, hey, I can run these global models, which are much more realistic representations of the Earth’s climate, including ocean, atmosphere, land and sea ice, and test whether the rate of CO2 change really is that important.

What is the Atlantic Meridional Overturning Circulation, which includes the Gulf Stream ocean current, and why is it so important for Earth’s climate?

CH: It’s one of the large-scale, key features of the climate system. In particular, it transports a lot of heat from the low latitudes in the South Atlantic to the higher latitudes closer to the North Pole.

So it delivers a lot of heat, primarily to Northern Europe. It also distributes nutrients around through this sort of sinking motion that characterizes the circulation — it draws the surface waters down into the deep ocean, and recirculates deep water up to the surface. It’s a big feature of the climate system, particularly in the North Atlantic, but also globally.

We’ve heard about a potential slowdown of the Gulf Stream current that could affect European weather. This was dramatized (perhaps not accurately) in the 2004 disaster movie ‘The Day After Tomorrow.’ Are we actually seeing a slowdown in Atlantic Ocean circulation?

CH: We have a pretty short observational record of the AMOC current, and it’s sparse. You have to imagine, this is a 3D circulation in the entire Atlantic basin, and we have a couple little slices of data in particular parts of the Atlantic. We are seeing a modest slowdown so far, but it’s a pretty noisy and uncertain observational record, so it’s hard to tell.

I would say, however, that slowdown seen in current observations would match the model predictions of future slowdowns. And we also see a pattern in temperature changes where, while the rest of the globe is warming right now as we increase CO2, there’s what people call a “warming hole” over the North Atlantic: We’re not seeing as much warming in that North Atlantic region compared to the rest of the globe. And it’s hard to conclusively attribute what’s causing it in the Earth’s climate, but the idea is that the modest slowdown of the AMOC that we’ve seen so far could be one contributing factor to that lack of warming we’re seeing in the North Atlantic.

So the observations suggest some slowdown, though much less dramatic than what was depicted in that movie.

Why is the AMOC expected to slow down under climate change?

CH: One way of thinking about what drives this major ocean current is differences in ocean density. You have this really important zone in the North Atlantic where the waters sink because the surface waters are heavier than the waters below. When you change CO2 levels, you do two things. You start to warm the ocean’s surface, and by melting glaciers as well as changing sea ice, you add freshwater to the surface of the otherwise salty ocean. Both warming and freshening reduce the density of that upper ocean water and potentially inhibit or disrupt that critical sinking motion.

There are other ways of looking at it, but the one I look at in the study is understanding how those density perturbations happen in a higher-CO2 climate and how they modulate the sensitivity to the rate of CO2 change that I find in the AMOC’s response to CO2.

Your study finds that if atmospheric carbon dioxide doubles from pre-industrial levels more slowly, there’s less slowdown in the Atlantic Ocean compared to if CO2 doubles more quickly. Is that because everything is happening more slowly?

CH: Yes, that’s part of it. The different parts of the climate system — the ocean, atmosphere, and ice — all have different response timescales to CO2 changes, meaning they respond to perturbations with different lag times. Then how these components of the climate interact with each other under slower or faster CO2 changes can look very different, and in this case influence the ocean circulation.

Specifically, I found what’s known as a positive feedback — a sort of self-amplifying cycle — that helps explain why the level of AMOC weakening depends on the rate of CO2 change. In this feedback cycle, the initial modest amount of AMOC slowdown leads to a reduction of heat transport into the Arctic, which in turn cools the region and leads to a temporary period of Arctic sea ice expansion. This sea ice expansion causes more ice to be exported to the North Atlantic, where it melts and adds freshwater to the ocean, causing the AMOC to slow down even more: hence the self-amplifying cycle. It turns out that this feedback cycle is more effective at amplifying AMOC weakening under more rapid CO2 changes than under gradual CO2 changes.

What is the importance of this work?

CH: We know about AMOC slowdowns — there’s a ton of work on that, and the mechanisms that drive such an AMOC slowdown. But what’s new is this sensitivity of circulation changes to the rate of CO2 increase, independent of the total change in concentration of CO2.

When we think about policy and basic science, we tend to focus a lot on how the level of global warming can impact the climate system. I’m trying to bring a new perspective by thinking about the rate of increase as a driver itself, that could have a lot of impacts.

You can imagine that if multiple different climates are possible for the same level of warming, then limiting us to 1.5 C or 2 C could have different meanings, right? I do think the most important thing for the climate system is always how much CO2 have you put into the atmosphere, but how quickly you got to that point clearly matters as well.

By Theo Stein, NOAA

New research on the Arctic confirms that even as the Arctic is warming faster than the rest of the world, cold-air outbreaks from the polar region will continue across the Northern Hemisphere in the coming decades.

The big challenge now is to better understand what triggers these cold-air outbreak events and how to improve their predictability. 

Much of the previous research has shown how a weakening of the stratospheric polar vortex can allow pockets of frigid air to plunge much farther south than normal. The new study, conducted by an international team including Arctic researchers from NOAA, provides additional insights as to how other influences — stalled weather systems, stretching of the stratospheric polar vortex and even events in the distant midlatitudes — can influence these polar patterns.

“A better understanding of these Arctic-midlatitude linkages would improve forecasts covering periods of weeks to months, which would give communities more time to plan for adverse winter weather conditions,” said co-author Muyin Wang, a scientist from the Cooperative Institute for Climate, Ocean, and Ecosystem Studies who works at NOAA’s Pacific Marine Environmental Laboratory (PMEL). “The impacts can be more significant as societies conditioned to global warming become increasingly less used to them.”

The study was published in Environmental Research: Climate. 

The stratospheric polar vortex is a mass of cold whirling air bounded by the jet stream that forms 10 to 30 miles above the Arctic surface in response to the large north-south temperature difference that develops during winter. Generally, the stronger the winds, the more the air inside is isolated from lower latitudes, and the colder it gets. But sometimes it can be shifted or stretched off the pole toward the United States, Europe or Asia.

“It seems really counterintuitive, but there will be plenty of ice, snow, and frigid air in the Arctic winter for decades to come, and that cold can be displaced southward into heavily populated regions by Arctic heat waves,” said co-author Jennifer Francis with the Woodwell Climate Research Center.

The study, which resulted from an international workshop held in 2023 in Great Britain, provides a new analysis of recent research that offers a pathway to improved forecasts. 

The authors said the stratospheric polar vortex has been relatively under-studied in previous reviews of Arctic-midlatitude climate linkages that focus predominantly on the role of changes in the tropospheric polar jet stream. They suggest that future research should focus on the complicated interactions between Arctic, midlatitude and tropical influences. 

While many analyses focus on warm Arctic and cold midlatitude events, connections have also been found between unusually cold Arctic temperatures and warm winter events in midlatitudes, especially in Europe. 

“Such a range of results confounds those who would like the science to offer a simple way to anticipate seasonal outlooks,” said James Overland, a research oceanographer at PMEL. 

One of the complicating factors occurs when a weather system stalls, creating an atmospheric block: a quasi-stationary modification of the jet-stream flow that occurs at middle and high latitudes and typically last for one to a few weeks. Blocking events are associated with persistent weather conditions in the vicinity of the block and frequently lead to extreme weather events in midlatitudes, including winter cold air outbreaks.

Tropical climatic drivers, such as the El Niño-Southern Oscillation and the Madden-Julian Oscillation, can create the conditions that lead to the establishment of these atmospheric blocks thousands of miles away. 

The study authors underscored the need for research to better understand how to predict cold outbreaks in lower latitudes, which will help communities adapt to the consequences of extreme cold weather.

“The Arctic may seem irrelevant and far away to most folks, but our findings show that the profound changes there affect billions of people around the Northern Hemisphere,” said lead author Edward Hanna with the University of Lincoln.

The international research team was composed of scientists from the United States, United Kingdom, Germany, Finland, South Korea, China and Japan.

“The most interesting part of the research is that the polar vortex stretching events could be an important driver of North American cold air outbreaks,” said Amy Butler, a climate researcher with the Chemical Sciences Laboratory who was not involved in the study. “It’s a novel way of looking at how the stratosphere might influence the surface climate. It’s certainly worth understanding better to improve predictability.”

(Material from University of Lincoln and Woodwell Institute press releases were included in this story. See related reporting at the Associated Press.)