Seasonal Relationship Between Net Primary and Net Community Production in the Subtropical Gyres: Insights From Satellite and Argo Profiling Float Measurements

The ratio between net community production (NCP) and net primary production (NPP) is a useful index of carbon export efficiency (e-ratio). Seasonal variations of e-ratio are poorly documented due to the lack of field measurements. In this study, the satellite-based NPP and Argo-Oxygen (O-2) based NCP were used to determine e-ratio in the subtropical gyres. Comparisons with long-term field measurements at the Hawaii Ocean Time-Series showed good agreement in annual mean and spring-summer (April-July) e-ratio. With the short-term tracer (O-2) the satellite-Argo approach revealed significant seasonal variations in NCP and e-ratio in the subtropical gyres of the North Pacific, North Atlantic, and South Pacific. The satellite-Argo-derived annual mean e-ratio in all three Northern Hemisphere sites were close to those from the temperature-based empirical model, but significantly lower in the South Pacific subtropical gyre where the sub-annual NCP variations were stronger.

Automated summary

This study utilized satellite and Argo data to determine the seasonal variations of e-ratio in subtropical gyres, showing significant seasonal changes in NCP and e-ratio in the North Pacific, North Atlantic, and South Pacific. The e-ratio was significantly lower in the South Pacific subtropical gyre, attributed to stronger sub-annual variations in NCP.