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

A high‐resolution mooring record from the Changjiang River plume (45‐m depth) is used to investigate how air‐sea CO 2 flux responds to typhoon in the productive plume. With strong wind, surface partial pressure of carbon dioxide ( p CO 2 ) increased sharply from 369 to 606 μatm due to entrainment of high‐CO 2 subsurface water. Though it was followed by p CO 2 decrease of 250 μatm and Chl a increase days after the typhoon, the typhoon caused a net CO 2 efflux overall. The maximum CO 2 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 CO 2 efflux to be +0.27 Tg C/year, which can cancel 18% of summer CO 2 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 CO 2 flux.