Abstract
The biological carbon pump (BCP) plays a critical role in sequestering atmospheric CO2 into the deep ocean; however, the influence of fine-scale oceanic processes, encompassing mesoscale and submesoscale features, on basin-scale carbon export remains poorly understood. Using a high-resolution physical-biogeochemical model and Biogeochemical-Argo (BGC-Argo) observations in the Subtropical Countercurrent (STCC) region of the Northwest Pacific, we demonstrate that fine-scale processes significantly modulate carbon export through seasonally varying impacts on nutrient supply and phytoplankton growth. BGC-Argo observations reveal that cyclonic eddies enhance and anticyclonic eddies suppress particulate organic carbon (POC) concentrations and inventories through isopycnal displacement, providing critical evidence for the localized role of eddy dynamics and an observational foundation for exploring the basin-scale impacts of fine-scale processes. Compared to lower-resolution simulations, high-resolution models reveal that baroclinic instabilities enhance nutrient supply and phytoplankton growth in summer and autumn, increasing POC export by 42.4%. In contrast, frontogenesis-induced downwelling reduces nutrients and phytoplankton growth in winter and spring, reducing export by up to 35.8%. Over a full annual cycle, these opposing effects result in a modest net basin-scale enhancement of 2.6%–5.0% from fine-scale resolution. These results reveal a seasonally opposing role of fine-scale processes in regulating carbon export through biological pathways, demonstrating that resolving mesoscale-to-submesoscale dynamics across complete seasonal cycles is essential for accurately quantifying the ocean's biological carbon pump.
Guo, M., Xiu, P.*, & Tang, S. (2025). Fine‐scale ocean dynamics modulate seasonal carbon export in the Northwest Pacific. Global Biogeochemical Cycles, 39, e2025GB008772.
https://doi.org/10.1029/2025GB008772
