The Gulf of Alaska is particularly vulnerable to the effects of events like marine heatwaves and El Niños, which can devastate its lucrative fisheries. But a new study has found El Niños can offer some benefits to the Gulf of Alaska.
Élise Beaudin is a physical oceanographer at a research facility called Ocean Networks Canada in British Columbia, and a lead author on the study, which was published in the Journal of Physical Oceanography on Sept. 10. Her research focused on what’s called the Alaska subpolar gyre, which is basically a giant counterclockwise swirl of water, thousands of miles wide, that goes around the Gulf of Alaska and into the waters around eastern Russia.
She said she was interested in studying the subpolar gyre for two reasons. The Gulf of Alaska provides critical habitat for Alaska’s fisheries. And she said it’s also interesting because of the way water circulates.
“The center of the subpolar gyre in Alaska, is extremely depleted in nutrients, especially macronutrients,” Beaudin said.
Those nutrients are essential for phytoplankton, which are the base of the food chain that feeds everything else in the ocean. Beaudin said the phytoplankton living in the nutrient-depleted areas survive because of eddies, which are smaller rotating swirls inside of the gyre.
“They will trap the coastal water that is nutrient rich," Beaudin said, "and they will move it offshore into this subpolar gyre, which is depleted in nutrients.”
Beaudin wanted to study how quickly these eddies form and how effective they are at transporting nutrients in the Gulf of Alaska during unusual weather events, like marine heatwaves and El Niño events. A marine heatwave known as the Blob caused fisheries disasters, including the collapse of the Pacific cod fishery, in the Gulf of Alaska roughly a decade ago.
But Beaudin’s research found that similar climate events can also come with a failsafe: a boost to ocean circulation that could help fisheries stay resilient to the effects of marine heatwaves.
To better understand this, Beaudin used a computer model that simulates the ocean’s currents. She released millions of fake nutrients into her model along the coast of Alaska. Beaudin said she based the experiment off of a real life disaster: in 1992, a cargo ship capsized and spilled around 28,000 plastic ducks into the ocean.
“And then for several years, a lot of people used to find these plastic ducks around several coasts around the whole world," she said. "So I wanted to recreate that somehow. ”
Beaudin tracked the fake nutrients as they moved from Alaska’s coast to the subpolar gyre using nearly 25 years of weather data. She found that marine heatwaves slowed down winds, which should have slowed down the eddies in the Gulf of Alaska. But Beaudin said that when El Niños came through, something else happened.
“This El Niño will keep boosting the generation of these large eddies and keep carrying the food offshore, despite all the other stresses happening,” Beaudin said.
Beaudin said this is because El Niño events reshape oceans around the world through a process called teleconnection: as water warms elsewhere in the globe, it causes a chain reaction of small shifts throughout the ocean.
Because of teleconnection, El Niño events strengthen an ocean system called the Aleutian low, which allows for the eddies in the Gulf of Alaska to keep delivering nutrients.
A super El Niño is forecast to arrive later this year, which means potentially even warmer waters and stronger storms than a normal El Niño causes. But Beaudin explained the effects of the El Niño on eddy transportation might not come for a while.
“When we talk about El Niño boosting the energy to create those eddies, it will take months for them to properly form, and then many more months, or if not years, to travel all the way [there]," she said.
And she said the ocean transport benefits don’t cancel out the negative effects of El Niño events either. Beaudin said the more immediate, and worrying, component of an El Niño is increased water temperatures, which are compounded by the effects of climate change. The warmer waters could hurt temperature-sensitive species like plankton and cause ocean-wide die offs.
Beaudin said they’re not sure exactly when this year’s El Niño might hit. But when it does, she and her team will be keeping an eye on the Gulf.
