Carbon Export and Fate Beneath a Dynamic Upwelled Filament off the California Coast

Abstract

Abstract. To understand the vertical variations of carbon fluxes in biologically productive waters, four autonomous Carbon Flux Explorers (CFEs) and ship-lowered CTD-interfaced particle-sensitive transmissometer and scattering sensors were deployed in a filament of offshore flowing recently upwelled water during the June 2017 California Current Ecosystem – Long Term Ecological Research process study. The Lagrangian CFEs operating at depths from 100–500 m yielded carbon flux and its partitioning with size from 30 µm–1 cm at three intense study locations within the filament and at a location outside the filament. Different particle classes (anchovy pellets, copepod pellets and > 1000 µm aggregates) dominated the 100–150 m fluxes during successive stages of the filament evolution as it progressed offshore. Fluxes were very high at all locations in the filament; below 150 m, flux was invariant or increased with depth at the two locations closer to the coast. Martin curve b factors for total particulate carbon flux were +0.1, +0.87, −0.27, and −0.39 at the three successively occupied locations within the plume, and in transitional waters, respectively. Particle transfer efficiencies between 100 to 500 m were far greater within both filament and California Current waters than calculated using a classic Martin b factor of −0.86. Interestingly, the flux profiles for all particles 90 %) of particle flux was carried by > 1000 µm sized aggregates. Mechanisms to explain a factor of three flux increase between 150 and 500 m at the mid plume location are investigated.

Transmitted Cross-Polarized Light Detection of Particulate Inorganic Carbon Concentrations and Fluxes in the Ocean Water Column: Ships to ARGO Floats

“…PIC011 was CTD deployed ~90 times during the June 2017 California Current ecosystem-Long-Term Ecological Research (CCE-LTER) project process study, aboard R/V Revelle. The study followed the biological evolutions of a biologically productive filament of upwelled cold, high-salinity westward-flowing water off the coast of California (Bourne et al, 2021;Figure 3). Figure 3 provides a spatial context for the study with satellite retrievals of PIC and POC corresponding to days 168 and 169 which bracket the timing of the 100-km-long CTD/optics Transect T2 across the filament.…”

“…Transect segments corresponding to the time and location of GP15 stations (Figure 2A) were combined to complete a synthetic transect of retrieved properties from 60 °N to 20 °S. The June 1 to July 2 2017 CCE-LTER expedition studied a filament of biologically productive upwelled water that was moving offshore in the vicinity of Morro Bay, CA. Our use of daily resolved 4-km satellite data was described by Bourne et al (2021). In this study, we used Ocean Data View (Schlitzer, 2021) to extract data within 5 km of the transect from SNPP VIIRS, and MODIS Aqua imagery on ordinal days 168 and 169 which bracketed the times of CTD Transect 2 stations 37 (day 169.118) through 47 (day 169.803).…”

“…Our ongoing work will interface the current class of sensors to the Carbon Flux Explorer (Bishop et al, 2016;Bourne et al, 2021). This float already determines the birefringent photon yield of sinking particles as they accumulate on an imaging stage.…”