Unraveling the controls of inorganic carbon dynamics in the Gulf of Alaska with a regional three-dimensional biogeochemical model

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The Gulf of Alaska ecosystem provides significant socio-economic benefits through tourism and through subsistence and commercial fisheries. However, the combined effects of climate change and ocean acidification, which is caused by the oceanic uptake of anthropogenic carbon dioxide, are altering the habitat of commercially important species. Climate induced enhancement of glacial melting may accelerate the progression of ocean acidification in the Gulf of Alaska even further. Due to a limited number of measurements in the Gulf of Alaska, little is known about the current state and rate of change of the chemical habitat of key species. Researchers from the University of Alaska Fairbanks propose to develop models of the ocean circulation, chemistry and biology for this region that will enable better understanding of environmental controls on ocean acidification in the Gulf of Alaska. In addition to communicating the science through a collaboration with the Alaska Ocean Observing System, the project will support a field course called "Girls in Icy Fjords", which is designed to inspire young women who have had limited opportunities due to life circumstances to pursue college educations and, possibly, careers in science. This project will identify the dominant controls and patterns of high carbon dioxide environments in the northern Gulf of Alaska. The few available observations document a seasonal manifestation of aragonite undersaturation in subsurface waters on this continental shelf. Particularly if it expands in time and space, such undersaturation could engender detrimental consequences for carbon dioxide sensitive organisms and potentially lead to altered food web structures, ultimately imparting large ecosystem and socio-economic consequences. However, the currently limited spatial and temporal data coverage precludes a detailed conceptual understanding of the physical and biological mechanisms controlling the local carbon dynamics and thus impedes our ability to anticipate and mitigate future changes. In this study, researchers will conduct high-resolution physical-biogeochemical hindcast model integrations and use neural networks, dye tracers and Lagrangian floats to detangle the complex interplay of mechanisms that drive aragonite undersaturation in the study region. The proposed physical-biogeochemical model configuration, which uses carbon and nitrate as model currencies, has been extensively evaluated for the greater North Pacific region at moderate (10 km) resolution. This model will be tailored to the Gulf of Alaska with a high (1.5 km) horizontal resolution, explicit forcing of coastal freshwater discharges, and modeled iron limitation. Such improvements will make this setup an attractive choice as a foundation for many other high-latitude biogeochemical modeling applications. The proposed experiments and analytical methods will take advantage of the three-dimensional model output and will provide insights into seasonal and interannual variability of enhancing and inhibiting controls of ocean acidification.