Variability of CO2 fugacity at the western edge of the tropical Atlantic Ocean from the 8 degrees N to 38 degrees W PIRATA buoy

摘要

Hourly data of CO2 fugacity (fCO(2)) at 8 degrees N-38 degrees W were analyzed from 2008 to 2011. Analyses of wind, rainfall, temperature and salinity data from the buoy indicated two distinct seasonal periods. The first period (January to July) had a mean fCO(2) of 378.9 mu atm (n=7512). During this period, in which the study area was characterized by small salinity variations, the fCO(2) is mainly controlled by sea surface temperature (SST) variations (fCO(2) =24.4*SST-281.1, r(2)=0.8). During the second period (August December), the mean fCO(2) was 421.9 atm (n = 11571). During these months, the region is subjected to the simultaneous action of (a) rainfall induced by the presence of the Intertropical Convergence Zone (ITCZ); (b) arrival of fresh water from the Amazon River plume that is transported to the east by the North Equatorial Countercurrent (NECC) after the retroflection of the North Brazil Current (NBC); and (c) vertical input of CO2-rich water due to Ekman pumping. The data indicated the existence of high-frequency fCO(2) variability (periods less than 24 h). This high variability is related to two different mechanisms. In the first mechanism, fCO(2) increases are associated to rapid increases in SST and are attributed to the diurnal cycle of solar radiation. In addition, low wind speed contributes to SST rising by inhibiting vertical mixing. In the second mechanism, fCO(2) decreases are associated to SSS decreases caused by heavy rainfall. (C) 2017 Elsevier B.V. All rights reserved.