Evolution of a Subducted Carbon Rich Filament on the Edge of the North Atlantic Gyre

Alexis Johnson, University of Rhode Island, Oceanography, Narragansett, RI, United States and Melissa Omand, University of Rhode Island, Graduate School of Oceanography, Narragansett, RI, United States
Abstract:
The oceanic biological carbon pump encompasses a variety of mechanisms by which CO2, fixed into organic form by phytoplankton, is transported from the sunlit surface layers to the interior ocean. Here, we investigate submesoscale and mixed layer subduction, the physical arm of the biological pump, estimated to represent approximately 20% of global particulate organic carbon (POC) export. Seven biogeochemical Argo (BGC) profiling floats were analyzed for evidence of physical subduction of POC in the North Atlantic Ocean. While we do not yet have enough measurements to reveal basin wide spatial trends, a notable pattern is found in the seasonality, suggesting that while subduction events are more likely to occur during winter, the bio-optical characteristics - namely a deep local maxima in POC and O2 - are more common in the spring and summer. We hypothesize that these deep features are potentially long-lived, having been subducted in late winter or spring and persisting throughout the warm season. We focus on a notable feature, observed in ten consecutive Argo profiles on the northeastern edge of the subtropical gyre. These physical, bio-optical and biogeochemical profiles, complemented by remote sensing and Argo data products, provides insight into the history and subsequent fate of a single subducted feature. This work highlights the potential of biogeochemical Argo for process-style assessments of the biological carbon pump and the value added by increasing the number of BGC floats throughout the oceans.