Insights into carbonate environmental conditions in the Chukchi Sea

• Published in: Biogeosciences
• Main Authors: Hauri, Claudine, Irving, Brita, Dupont, Sam, Pagés, Rémi, Hauser, Donna D. W., Danielson, Seth L.
• Format: Text
• Language: English
• Published: 2024
• Subjects: Arctic; Chukchi Sea; Arctic cod; Boreogadus saida; Chukchi; Climate change; ice algae; Ocean acidification; Odobenus rosmarus; Phytoplankton; Sea ice; walrus*
• Online Access: https://doi.org/10.5194/bg-21-1135-2024; https://bg.copernicus.org/articles/21/1135/2024/

Healthy Arctic marine ecosystems are essential to the food security and sovereignty, culture, and wellbeing of Indigenous Peoples in the Arctic. At the same time, Arctic marine ecosystems are highly susceptible to impacts of climate change and ocean acidification. While increasing ocean and air temperatures and melting sea ice act as direct stressors on the ecosystem, they also indirectly enhance ocean acidification, accelerating the associated changes in the inorganic carbon system. Yet, much is to be learned about the current state and variability of the inorganic carbon system in remote, high-latitude oceans. Here, we present time series (2016–2020) of pH and the partial pressure of carbon dioxide ( p CO 2 ) from the northeast Chukchi Sea continental shelf. The Chukchi Ecosystem Observatory includes a suite of subsurface year-round moorings sited amid a biological hotspot that is characterized by high primary productivity and a rich benthic food web that in turn supports coastal Iñupiat, whales, ice seals, walrus ( Odobenus rosmarus ), and Arctic cod ( Boreogadus saida ). Our observations suggest that near-bottom waters (33 m depth, 13 m above the seafloor) are a high carbon dioxide and low pH and aragonite saturation state ( Ω arag ) environment in summer and fall, when organic material from the highly productive summer remineralizes. During this time, Ω arag can be as low as 0.4. In winter, when the site was covered by sea ice, pH was <8 and Ω arag remained undersaturated under the sea ice. There were only two short seasonal periods with relatively higher pH and Ω arag , which we term ocean acidification relaxation events. In spring, high primary production from sea ice algae and phytoplankton blooms led to spikes in pH (pH > 8) and aragonite oversaturation. In late fall, strong wind-driven mixing events that delivered low-CO 2 surface water to the shelf also led to events with elevated pH and Ω arag . Given the recent observations of high rates of ocean acidification and a sudden and dramatic ...