Carbon system changes in the East China Sea induced by Typhoons Tina and Winnie in 1997

Abstract

A simple chemical scheme was introduced into the Meteorological Research Institute Community Ocean Model (MRI.COM) for investigating the rapid CO2 flux increase at a moored buoy in the East China Sea caused by the passages of Typhoons Tina and Winnie in 1997. MRI.COM well reproduced variations in the observed water temperature and pCO2sea at 1 m depth and in the air‐sea CO2 flux at the buoy. Even though the analyzed magnitudes of the air‐sea CO2 fluxes were of the same order, the sudden CO2 flux change occurred nearly 2 days after Tina and nearly 3 days after Winnie. The increase in pCO2sea normalized to a temperature of 29°C induced by Winnie appeared longer than that induced by Tina. The numerical simulation results showed clear differences in the oceanic response between the two typhoons. In the case of Tina, upwelling along the continental shelf played a crucial role in rapidly decreasing the water temperature and transporting seawater with low pCO2sea and high dissolved inorganic carbon (DIC) to the upper ocean. In contrast, water with relatively high pCO2sea and low DIC transported by strong horizontal advection of the Kuroshio Current was vertically mixed by the passage of Winnie, resulting in a cool, deep mixed layer at the buoy. The surface seawater hydrogen ion concentration (pH) temporarily decreased during the passages of Tina and Winnie. In the case of Tina, pH decreased by at most 0.03 and for only 1 day.