Investigating the biogeochemical impact of an across-shore filament
Thomas Bryce Kelly1,2, Ralf Goericke3, Mark D Ohman4, Hajoon Song5, Sven Alexander Kranz6, Michael R Landry7 and Michael R Stukel1, (1)Florida State University, Earth, Ocean and Atmospheric Science, Tallahassee, FL, United States, (2)Center for Ocean-Atmospheric Prediction Studies, Tallahassee, FL, United States, (3)Scripps Institution of Oceanography, Integrative Oceanography, La Jolla, CA, United States, (4)Scripps Institution of Oceanography, La Jolla, CA, United States, (5)Massachusetts Institute of Technology, Seoul, South Korea, (6)Rice University, Department of Biosciences, Houston, United States, (7)Scripps Inst Oceanography, La Jolla, CA, United States
Abstract:
Here we present data from two quasi-synoptic surveys of a coastal filament (width: ~50 km) that transported upwelled coastal waters 100’s of kilometers offshore over a period of several days. Each survey consisted of ~400 SeaSoar tow-yo profiles along ~800 km of cruise track. The resultant 3D observations of T, S, O
2 and beam-transmission were merged with surface measurements of particulate organic carbon, chlorophyll, nutrients, and thorium-234 and a 3D physical, data-assimilative ocean model (4DVARS ROMS) to derive across-shore and alongshore fluxes of nutrients, biomass and carbon. We integrate these quantities into a biogeochemical box model, which is constrained by
in situ rate measurements conducted during the cruise at 4 Lagrangian stations along the filament. Observations include
primary production, sediment trap export,
234Th disequilibrium, net community production, microzooplankton grazing and mesozooplankton grazing.
Within the filament, rates of NPP were elevated with respect to proximal, non-filament waters with rates sometimes exceeding 1000 mmol C m-2 d-1. The filament transported POC and nitrate from the nearshore to otherwise oligotrophic areas, highlighting the importance of physical forcings in driving the spatiotemporal variability of the CCE. Results from the model will be compared with previous non-filament process studies in the region to quantify the impact to local biogeochemical budgets and ecosystem dynamics. With the ongoing development of higher resolution ocean models and advancements in remote sensing capability, there is a current need to improve our ecological understanding of the ecological and biogeochemical consequences of these temporally variable transport events.
