Ocean Acidification is Exacerbated by Natural Cycles in the Gulf of Alaska

The Gulf of Alaska is a North Pacific Ocean extension that runs along the southern coasts of the United States state of Alaska. From Kodiak Island and the Alaska Peninsula in the west to the Alexander Archipelago in the east, the gulf stretches. The Alaska Peninsula separates it from Bristol Bay.

The variations of major wind and ocean circulation systems can briefly accelerate or reverse the pace of ocean acidification in the Gulf of Alaska, according to new study from the University of Alaska Fairbanks. The Malaspina Glacier and the Bering Glacier, Alaska’s biggest glaciers, flow down into the Gulf of Alaska’s coastline line. Cook Inlet and Prince William Sound, the two biggest linked bodies of water, are severely indented along the coast.

“We typically think of ocean acidification as this slow press onto the environment that gradually changes the carbon chemistry in the ocean,” explained Claudine Hauri, a researcher at the UAF International Arctic Research Center.

Gulf of Alaska

Instead, the research demonstrates that the chemical circumstances that marine creatures face can fluctuate on a daily and seasonal basis, according to Hauri. Despite a long-term trend of ocean acidification linked to continuous increases in atmospheric carbon dioxide concentrations, this variation occurs. Massive cycles that occur every five to ten years are also documented in the latest study.

According to SeaWiFS data, the Gulf of Alaska is a Class I, productive ecosystem with more than 300 grams of carbon per square meter per year. The Gulf of Mexico is 1,533,000 km2 in size. Mountains, woods, and many tidewater glaciers make up the rough Gulf of Alaska shoreline.

Chemical processes occur when carbon dioxide (CO2) is absorbed by saltwater, lowering the pH, carbonate ion concentration, and saturation states of biologically essential calcium carbonate minerals. “Ocean acidification,” or “OA” for short, is the name given to these chemical processes.

“Chemical conditions will deteriorate for several years in a row in offshore areas, before stabilizing or even slightly improving again,” said co-author Andrew McDonnell from the UAF College of Fisheries and Ocean Sciences. “We don’t know exactly how organisms respond to that, but in general some organisms are sensitive to these types of changes in environmental conditions.”

Many ocean species, particularly creatures like oysters and corals that form hard shells and skeletons by combining calcium and carbonate from seawater, are already suffering from acidification. Continued ocean acidification, on the other hand, is leading many regions of the ocean to become undersaturated with these minerals, potentially affecting certain species’ capacity to create and maintain shells.

Hauri and her colleagues looked at ocean acidification using a model that included physical, biogeochemical, and hydrological ocean models to recreate conditions in the Gulf of Alaska from 1980 to 2013. Natural decadal variations in chemical conditions are governed by the intensity of the North Pacific subpolar gyre, according to the study.

The Gulf of Alaska is affected by this gyre, which is a huge wind-driven system of cycling ocean currents. When the gyre is powerful, it delivers more carbon dioxide-rich deep water to the surface of the ocean. This can hasten ocean acidification, resulting in severe occurrences that put delicate species under stress. When the gyre is weak, less carbon is transported to the surface, which can reduce or even reverse ocean acidification.

A powerful phase of the gyre resulted in a severe ocean acidification event in the middle of the Gulf of Alaska from 2011 to 2013, according to the model. This occurrence occurred before the 2014-2016 “blob” of unusually warm water in the same area.

“The blob followed right after this very strong ocean acidification event,” Hauri explained. “First, some organisms were probably stressed because of ocean acidification, and then they were hit right after with heat.”

The Gulf of Alaska is home to a number of economically significant fish. Pacific cod, mackerel, Alaska pollock, Alaska salmon, pink salmon, halibut, and sockeye salmon are among them. Shrimp, king crab, and tanner crab are among the crustacean species found here. The whole ocean, including coastal estuaries and rivers, is currently affected by ocean acidification. Ocean food is the major source of protein for billions of people across the world.

More study is needed, according to Hauri, to understand the effects of numerous simultaneous stresses on marine ecosystems, as well as to determine how ocean acidification and climate change interact.

Another conclusion of this research is that many decades of observational data are required to distinguish the long-term trend of ocean acidification from natural fluctuation caused by the subpolar gyre’s intensity. For the Gulf of Alaska, this type of data is presently unavailable.

Hauri and her colleagues believe that this research, as well as the activities it inspires, will give critical knowledge to those involved in subsistence and commercial fishing as they plan and adapt for the future.