the 22nd Pacific−Asian Marginal Seas meeting (PAMS)

The ocean biological carbon pump plays a critical role in sustaining ocean carbon sequestration and regulating the global carbon cycle and climate. However, the mechanisms governing the production, transformation, and mesopelagic transfer of particulate organic carbon (POC) remain poorly constrained. Here, we integrate high-frequency multi-biogeochemical observations from BGC-Argo floats in the Northwest Pacific with sediment trap measurements, ship-based observations, and satellite products to systematically quantify primary production, euphotic-zone carbon export, and mesopelagic transfer across major ecological regimes, including the western and eastern equatorial regions, subtropical gyres, subpolar frontal zones, and subpolar regions. We show that gravitational sinking dominates POC export at the base of the euphotic zone across all regions. In contrast, physically driven injection pathways, including the mixed-layer pump (MLP) and eddy subduction pump (ESP), exhibit pronounced seasonal pulses in subpolar and frontal regions, contributing up to 30–40% of total export flux during episodic events. Export efficiency is significantly elevated in high-latitude frontal and subpolar regions (exceeding 100% in some cases), while remaining low (~5%) in oligotrophic regions. This spatial variability is primarily regulated by nutrient supply and associated shifts in phytoplankton community structure. Notably, we identify a clear decoupling between export efficiency and mesopelagic transfer efficiency, with the highest transfer efficiency observed in transition zones and the eastern equatorial Pacific. Temperature alone cannot explain variations in particle transfer efficiency, whereas iron availability in the mesopelagic zone likely plays a key regulatory role. In addition, surface phytoplankton community composition influences particle properties and consequently modulates their transfer efficiency to depth. By integrating multi-platform observations, this study provides a process-resolving framework for understanding the regional variability and controlling mechanisms of the biological carbon pump in the Northwest Pacific, offering new observational constraints on its role in regional and global carbon cycling.

 

carbon exort; biological pump; transfer efficiency; BGC-Argo