Impact of sampling depth on CO flux estimates

The exchange of trace gases between the atmosphere and the ocean plays a key role in the Earth's climate. Fluxes at the air-sea interface are affected mainly by wind blowing over the ocean and seawater temperature and salinity changes. This study aimed to quantify the use of CO $$ partial pressure (pCO $$ ) measurements at different depths (1, 5, and 10 m) in ocean surface layers to determine CO $$ fluxes (FCO $$ ) and to investigate the impacts of wind-sheltered and wind-exposed regions on the carbon budget. Vertical profiles of temperature, salinity, and pCO $$ were considered during a daily cycle. pCO $$ profiles exhibited relatively high values during sunny hours, associated with relatively high sea temperatures. However, the largest FCO $$ corresponded with higher wind speeds. Estimated fluxes between measurements at 1 and 10 m depths decreased by 71% in the sheltered region and 44% in the exposed region. According to the SOCAT dataset, at a depth of 5 m, the Atlantic basin emits approximately 0.29 Tg month $$ of CO $$ to the atmosphere; nevertheless, our estimates suggest that FCO $$ at the surface is 12.02 Tg month $$ , which is 97.6% greater than that at 5 m depth. Therefore, future studies should consider sampling depth to adequately estimate the FCO $$ .