The study was published recently in the journal Estuarine, Coastal and Shelf Science, and was authored by scientists from the University of Alaska Fairbanks School of Fisheries and Ocean Sciences and the University of California Santa Cruz Long Marine Lab.
The study has implications for the future health and management of the region, which is home to some of the world's most productive salmon fisheries and other economically and culturally important marine organisms.
"This is a pretty important piece of oceanographic information for understanding how this ecosystem is going to respond to climate change," said lead author Sam Laney, an assistant professor of fisheries oceanography at UAF. "The circulation of carbon is one of the fundamental ways in which ecosystems transfer energy."
For the study, the researchers deployed six moorings in the Clarence Strait, Sumner Strait and Frederick Sound region between Ketchikan and Petersburg from August 2019 until November 2020. The moorings were equipped with sensors and instruments that recorded water temperature, salinity, and current speed and direction, and collected water samples for measurement of total alkalinity and dissolved inorganic carbon concentration.
The study found that the surface waters in southeast Alaska are extremely important in taking up carbon dioxide from the atmosphere and storing it in the form of dissolved inorganic carbon, especially during the fall and spring. This process is a key component of the global carbon cycle, whereby excess carbon dioxide is absorbed from the atmosphere and transported to the deep ocean for long-term storage.
The researchers found that about half of the total dissolved inorganic carbon moving through the region during certain times of the year is transported through Frederick Sound, even though the sound occupies less than 10% of the total volume of water in southeast Alaska's waterways.
"This is probably because Frederick Sound is one of the most energetic systems in the region, and it has really deep basins compared to other water bodies in southeast Alaska," Laney said.
These basins likely trap the dissolved inorganic carbon, enhancing the storage of carbon dioxide in the fjords, he said.
The researchers used their data to develop the first models for carbon storage in the region. These models can help scientists gauge the ability of southeast Alaska's waterways to store carbon dioxide in the future, and how projected changes in ocean circulation could impact the region's overall carbon storage capacity.
"A more complete understanding of the role southeastern Alaska plays in the carbon cycle is important because of its potential to provide climate change mitigation services, and help society reach its climate goals," Laney said.
