Understanding the remote influences of ocean weather on the episodic pulses of particulate organic carbon flux

Henry Ruhl, Monterey Bay Aquarium Research Institute, Moss Landing, CA, United States, Fred Bahr, MBARI, Moss Landing, CA, United States, Stephanie Henson, National Oceanography Centre, Southampton, United Kingdom, William B Hosking, National Oceanography Centre, Southhampton, United Kingdom, Benoit Espinola, University of Southampton, United Kingdom, Mati Kahru, Univ California San Diego, La Jolla, CA, United States, Patrick Daniel, Monterey Bay Aquarium Research Institute, United States, Patrick Drake, University of California, Santa Cruz, CA, United States and Christopher A Edwards, University of California Santa Cruz, Santa Cruz, CA, United States
The biological carbon pump has been estimated to export ~5-15 Gt C yr-1 into the deep ocean, and forms the principal deep-sea food resource. Irregular, intense pulses of particulate organic carbon (POC) have been found to make up about one-third of the overall POC fluxes at a long-term deep-sea research station influenced by coastal upwelling, Station M. However, the drivers of these pulses have been challenging to quantify. It has long been recognized that ocean currents can result in particles being advected while sinking to the point of collection by a sediment trap. Thus, a sediment trap time series can incorporate material from a dynamic catchment area, a concept sometimes referred to as a statistical funnel. This concept raises many questions including: what are the day-to-day conditions at the source locations of the sinking POC? And, how might such ‘ocean weather and related ecosystem factors influence the intense variation seen at the seafloor? Here we analyzed three-dimensional ocean currents from a Regional Ocean Modeling System (ROMS) model from 2011-2017 to trace the potential source locations of particles sinking at 1000, 100, and 50 m d-1. We then used regionally tailored satellite data products to estimate export flux of POC from these locations. The particles had origins of up to ~300 km for the 100 m d-1 speed, and nearly 1000 km for the 50 m d-1 speed. We found significant correlations between export flux of organic carbon from the estimated source locations at 100 m depth to trap-estimated POC fluxes at 3400 m depth. There was considerable inter-annual variation in source locations. Particle source locations tended to originate from the east in the summer months, with higher export and POC fluxes. Occasionally these locations were in the vicinity of highly productive ocean features nearer to the coast. These results set the stage for further investigation into sinking speed distributions, conditions at the source locations, and comparisons with mechanistic biogeochemical models and between particle tracking model frameworks.