Bering Sea 2019 heatwave produced extreme change

The Bering Sea region is front and center for federal fisheries researchers after the 2019 heatwave produced extreme change in the marine ecosystem. That’s according to Bob Foy, the Juneau-based science and research director of the Alaska Fisheries Science Center, or AFSC for short.
“This region has experienced extreme change in the ocean environment, so our need to get to Nome and other communities in northwest Alaska has been really important,” Foy said in an interview last week with the Nugget.
“Sea ice dominates the ecosystem in this part of the world—the marine mammals, the fish that are available, the subsistence that can occur,” Foy said. “With that heat affecting sea ice, it’s making the changes that we’re seeing in this region from 2019 to the present some of the greatest changes that we see in the world. And we know they’re caused by climate change. So this region is really front and center. When you add the fact this is a region of small communities, where infrastructure is limited to deal with some of these changes, it makes it all that much more important.”
Foy was visiting Nome last week with several of his colleagues to share details about their upcoming projects and reconnect with various stakeholders that they had not been able to see due to the pandemic. AFSC is part of the National Oceanic and Atmospheric Administration, or NOAA, and its researchers study the health and sustainability of fish, marine mammals and marine habitats.
Michale Cameron, the polar ecosystems program manager at the AFSC’s Marine Mammal Laboratory who was visiting Nome with Foy, added that the northern Bering Sea region is especially important because it is experiencing some of the greatest changes in sea ice quality and extent.
“The difference between liquid ice and solid ice is one degree,” Cameron said. “A difference of location in that one degree means the location of the sea ice is going to change. With these rapid warming events, that location has changed. We’re obviously going to be seeing some of the greatest impacts at the interface of where the ice is and isn’t. For that reason this area is impacted more because you have such a dramatic change on the physical side of the environment.”
Changes in sea ice don’t just produce changes in habitats for marine mammals that depend on the ice. Sea ice is also creates a layer of extra cold water at the seafloor during summertime. Known as the cold pool, this layer prevents some species like Pacific cod and pollock from crossing into the eastern Bering Sea shelf and northward toward the Bering Strait.
Researchers have long been worried about how ecosystems could be permanently altered by the slow creep of rising temperatures. But they’ve also started to recognize how extreme events like marine heatwaves could have long-term impacts that are sometimes event greater than the ones caused by gradual warming. One recent study from AFSC researchers found that the eastern Pacific marine heatwave, which affected waters from California to Alaska from 2014 to 2016, created clear winners and losers in the ocean environment. For example, in the Gulf of Alaska, sockeye salmon suffered while pollock populations grew. Warm water temperatures lingered years after the event in some areas. And while some species returned to pre-heatwave levels soon after, others did not. The authors of the study argued that the Gulf of Alaska ecosystem passed a tipping point because of the heatwave that it could not easily bounce back from.
Upcoming AFSC projects should help researchers study the changes occurring post-heatwave in the Bering Sea. For example, the Bering Sea bottom trawl survey will occur in the eastern Bering Sea in June and July and then, in August, arrive in the northern Bering Sea, including the Norton Sound. While the annual trawl surveys of the eastern Bering Sea began in 1982, a first bottom trawl survey of the northern Bering Sea was initiated in 2010, followed by another in 2017.
It’s only in the last few years that the survey has become annual because the ecosystem of the fisheries resources is moving northward. The fisheries resource was limited to the south, Foy said, and the ecosystem in the northern Bering Sea had been fairly stable until the recent heatwave.
“In a matter of months—I wish I was exaggerating—that stability eroded,” Foy said. “That stability continues to be a problem. If you have a stable ecosystem, that makes things much more predictable, and understandable. And I think that those that rely on the marine environment would say the same thing. When it becomes unstable, we need to put all our resources, or as many as we can, into understanding the system, and that’s what we’re doing.”
During the bottom trawl surveys, a net will sample species and take temperature readings in the bottom six to 10 feet of the water column. The intent is to track changes in the food web and species distribution, and to monitor environmental conditions. The results should help answer whether the ecosystem can continue to support the fish, like pollock, that came up from the south chasing warmer temperatures. Daily updates with preliminary results and temperature readings will be available during this year’s cruise.
There’s been another recent challenge in understanding changes in the northern Bering Sea: Russia’s conflict with Ukraine has made official partnerships and data sharing with Russian colleagues on the other side of the waterway impossible for more than a year now.
“Especially at a time of such change, the gap in information is incredible,” Foy said. “We have 30 percent of our pollock stock that goes back and forth across the dateline. It means that we have to estimate what’s moving back and forth, and we err on the side of caution. Moving toward the north, we still are seeing the effects of that 2019 heatwave, and not knowing what’s happening on the western side of the Chukchi is inhibiting our continued understanding of the ecosystem.”
AFSC’s Marine Mammal Lab also used to conduct surveys of ice seals with Russian colleagues. “We’re hopeful that at some point, we might be able to work with them again,” said Cameron. The last survey was about a decade ago and Cameron is now planning an April 2024 aerial survey of the four species of ice seals. His visit to Nome was largely to communicate with and get feedback from tribes and other members of the community about the details of this work before it begins. Mabel Baldwin Schaffer, the tribal research coordinator with AFSC, was also visiting Nome. She heard from communities that they would like to see a protocol that ensures there’s communication before, during and after any projects.
“We want to make sure that the data that we’re collecting is of use to the folks in the area,” Cameron said. The surveys will capture high-resolution imagery from aircraft. Cameron said that, in addition to data on the ice seals, community members have expressed interest in imagery of river mouths to see the progress of breakup at certain locations next spring. Cameron added that he hopes to find individuals from various communities to go fly with his team during the surveys. “As they see something interesting or different or unique out the window, we can break off survey and take images and investigate things that those participants might find very useful and helpful.”