Basin-scale estimate of the sea-air CO2 flux during the 2010 warm event in the Tropical North Atlantic

• Main Authors: Lefèvre, Nathalie, Veleda, D., Tyaquica, P., Perruche, C., Diverrès, Denis, Ibanhez, J. S. P.
• Format: Text
• Language: English
• Published: 2019
• Subjects: North Atlantic
• Online Access: http://www.documentation.ird.fr/hor/fdi:010076056

Following the anomalous warming event occurring in the tropical North Atlantic in 2010, higher than usual surface fugacity of CO2 (fCO(2)) was observed. To evaluate the spatial extent of these anomalies and their drivers, and to quantify the sea-air CO2 flux at basin scale, the Mercator-Ocean model is used from 2006 to 2014 within the region 0-30 degrees N, 70-15 degrees W. Model outputs are generally in accordance with underway sea surface temperature, sea surface salinity, and surface fCO(2) recorded by two merchant ships. The anomalous warming of 2010 is well reproduced by the model and is the main driver of fCO(2) anomalies. The first coupled Empirical Orthogonal Function mode, between sea surface temperature and fCO(2), captures more than 70% of the total variance and is characterized by a basin-scale warming associated to positive fCO(2) anomalies. The corresponding principal components are correlated to the Tropical North Atlantic Index and identify 2010 as the year with the highest positive anomaly over 2006-2014. Exceptions to this general pattern are located near the African coast, where the weakening of the coastal upwelling causes negative inorganic carbon anomalies, and close to the Amazon River plume, where fCO(2) anomalies are primarily associated with sea surface salinity anomalies. Although the fCO(2) anomalies of 2010 appear mostly in spring, they affect the annual CO2 budget and lead to an increased CO2 outgassing twice as large (46.2 Tg C per year) as the mean annual flux over the 2006-2014 period (23.3 Tg C per year).