Partitioning the Export of Distinct Biogenic Carbon Pools in the Northeast Pacific Ocean Using a Biogeochemical Profiling Float

We leverage observations from chemical and bio-optical sensors mounted on a biogeochemical profiling float in the Northeast Pacific Ocean to quantify the cycling and export potential of distinct biogenic carbon pools, including particulate inorganic carbon (PIC), particulate organic carbon (POC), and dissolved organic carbon (DOC). Year-round observations reveal complex carbon cycle dynamics among these carbon pools. Net DOC production peaked during bloom initiation, about 3 months prior to the summer peak in POC production. We validate the float estimates of DOC cycling with seasonal accumulation and removal rates derived from ship-board DOC observations over the same period. By combining chemical and bio-optical tracers of POC cycling, we estimate the instantaneous POC sinking flux (FPOCsinking ${\mathrm{F}}_{{\text{POC}}_{\text{sinking}}}$). The cooccurrence of DOC consumption and POC production and sinking during fall and winter resolves the regional conundrum of a persistent particle sinking flux observed by sediment traps during a season that is known to be heterotrophic. PIC production is small, and uncertainties are large. By combining float-based estimates of instantaneous net primary production (NPP) and FPOCsinking ${\mathrm{F}}_{{\text{POC}}_{\text{sinking}}}$, we quantify a real-time carbon export ratio ([FPOCsinking ${\mathrm{F}}_{{\text{POC}}_{\text{sinking}}}$/NPP] x 100%) for the euphotic zone. Elevated export ratios during summer are associated with an increase in the fraction of particles larger than 100 mu m in size. Elevated export ratios during winter are associated with the physical redistribution of particles through seasonal deep mixing. Our study demonstrates how the combined use of multiple sensors on biogeochemical profiling floats can provide more nuanced information about upper ocean carbon cycle dynamics.

Automated summary

We investigated the cycling and export potential of different biogenic carbon pools in the Northeast Pacific Ocean using data from chemical and bio-optical sensors. Our study revealed complex carbon cycle dynamics among these carbon pools throughout the year. We also demonstrated the importance of utilizing multiple sensors on biogeochemical profiling floats for a more comprehensive understanding of upper ocean carbon cycle dynamics.