Coastal Ocean Carbon Cycling during Wintertime Conditions

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As is true for many coastal regions worldwide, the Pacific Northwest margin is characterized by intense seasonal contrasts in conditions controlling carbon flux between the atmosphere, land, and ocean. During the wintertime, rapid and intense flooding of small coastal rivers and the associated inputs of freshwater, nutrients, and organic matter are commonplace in the Pacific Northwest. Impacts of these wintertime terrestrial-ocean transfers by small, flood-prone rivers on the upwelling regions, such as the Pacific Northwest, have been underestimated at both global and regional scales. In order to gain a complete and predictive understanding of carbon cycling in ocean margins, the biogeochemistry of periods of intense terrestrial-ocean transfers needs to be comprehensively studied. This project will evaluate the dynamics of organic matter cycling along an upwelling-dominated margin during the wintertime period of active terrestrial inputs and biological cycling using a combination of shipboard, glider, moored and remote measurements. New developments in ocean observational technologies through the Ocean Observatories Initiative (OOI)* and existing scientific infrastructure along the Oregon coast will be instrumental in achieving this goal. This work will provide research opportunities for undergraduate and graduate students, and outreach will be conducted through the Centers for Ocean Science Education Excellence Pacific Partnership, local coastal community colleges, and interpretative centers such as Oregon State University Hatfield Center, the Umpqua Discovery Center, and Oregon Coast Aquarium in an effort to educate students and the public about the research.Globally, most studies of carbon cycling in eastern boundary regimes have focused on the upwelling phase during the summer months, resulting in a much poorer understanding of non-upwelling periods. As is many coastal upwelling systems, wintertime conditions along the Pacific Northwest margin are characterized by southerly, downwelling-favorable winds and moisture-laden storms that result in seasonal flooding by the numerous small to medium-sized rivers in the region. Elevated discharges by these coastal rivers translate into large inputs of land-derived biogeochemical relevant constituents, including freshwater, dissolved inorganic nutrients, and dissolved and particulate organic matter, which collectively rival or exceed those of the Columbia River. To understand the impact of flood-derived terrestrial inputs on the biogeochemistry of the coastal zone along the Pacific Northwest margin, researchers will conduct a detailed investigation of biogeochemical processes in the water column along the Newport Hydrographic Line off the central Oregon coast during fall/winter conditions. The project includes an intensive field effort that takes advantage of ship-based and autonomous platforms to gain comprehensive wintertime coverage. Among the project outcomes, this effort will lead to a revised paradigm of the biogeochemical drivers of carbon cycling in coastal margins.*The Ocean Observatories Initiative (OOI) is an NSF-funded, networked infrastructure of science-driven sensor systems to measure the physical, chemical, geological and biological variables in the ocean and seafloor. For more information about OOI, please visit the website: www.oceanobservatories.org