The partial pressure of carbon dioxide and air–sea fluxes in the northern South China Sea in spring, summer and autumn

Abstract

The distribution of pCO 2 in the surface waters of the northern South China Sea (NSCS) was examined in the summer of 2000, the spring of 2001 and the late fall of 2002. For the offshore region >100 km away from the coastline, surface water pCO 2 varied within a range of 360–450 μatm during all the surveys. Nevertheless, they were generally higher than atmospheric pCO 2. Sea–air Δ pCO 2 ranged in 50–100 μatm in the summer, 0–50 μatm in the spring and 0–90 μatm in the late fall. Average sea-to-air CO 2 flux was 7 mmol CO 2 m −2 day −1 in the summer and 1–3 mmol CO 2 m −2 day −1 in the spring and fall. Nearshore pCO 2 showed a very dynamic pattern likely associated with the regional hydrodynamic settings, yet again pCO 2 in the surface water overall exceeded the air pCO 2. Data from this study thus suggests that the NSCS served as a source of atmospheric CO 2. Seasonal variations of the pCO 2 in the NSCS outer shelf and slope surface waters were significantly influenced by sea surface temperature.