Surface Seawater pCO2 Variation after a Typhoon Passage in the Kuroshio off Eastern Taiwan

Abstract

In this study, two cruises were conducted across the mainstream of the Kuroshio off eastern Taiwan before and after the passage of Typhoon Saola in summer 2012. The continuous underway pCO2 (i.e., partial pressure of CO2) measurements revealed that surface seawater pCO2 (SS pCO2) displayed spatial variations in response to typhoon passage. The simulated results showed that the mixed-layer deepening after typhoon passage had a minor effect on SS pCO2 variation because pCO2 decrease driven by temperature dropdown and enhanced biological production fueled by nutrients input was largely compensated by pCO2 increase caused by salinity increase and dissolved inorganic carbon input from the subsurface layer. By contrast, the advection pattern showed significant change before and after the typhoon, which could play a major role in controlling the variation of SS pCO2. In the exit area of the cyclonic eddy, SS pCO2 decreased, while in the area of its arrival, SS pCO2 increased. Besides, the discharge of freshwater and the intrusion of the South China Sea subsurface could result in SS pCO2 increase in the nearshore area. The present study highlights that more advection changes need to be considered to better understand the impact of the typhoon on SS pCO2, especially in the strong current area, such as the Kuroshio.