Hypoxic Bottom Waters as a Carbon Source to Atmosphere During a Typhoon Passage Over the East China Sea

Abstract A high‐resolution mooring record from the Changjiang River plume (45‐m depth) is used to investigate how air‐sea CO2 flux responds to typhoon in the productive plume. With strong wind, surface partial pressure of carbon dioxide (pCO2) increased sharply from 369 to 606 μatm due to entrainment of high‐CO2 subsurface water. Though it was followed by pCO2 decrease of 250 μatm and Chl a increase days after the typhoon, the typhoon caused a net CO2 efflux overall. The maximum CO2 efflux (+111.6 mmol·m−2·day−1) is much greater than that under non‐typhoon condition (−2.3 to −11.7 mmol·m−2·day−1). Based on historical typhoon records, we estimate typhoon‐induced CO2 efflux to be +0.27 Tg C/year, which can cancel 18% of summer CO2 influx in the East China Sea shelf. It may likely occur in other coastal waters. Ignoring such contribution may induce large bias in estimating regional air‐sea CO2 flux.