Response of CO2 fluxes to the ocean-atmosphere interaction processes in the Fernando de Noronha island
Résumé
This study investigates thermodynamic conditions and air-sea CO2fluxes in the Fernando de Noronha Island region. The analyses were based on coupled ocean-atmosphere modeling results for three periods of oceanographic cruises, Camadas Finas I, Camadas Finas II, and Camadas Finas IV, in 2010, 2012, and 2014. The ocean-atmosphere modeling results correspond well with data from three oceanographic cruises around the island. The modeled wind correlated well with the wind speed and direction values at 10m, with a statistical significance of 95%. The presence of the island modifies the sea surface temperature and surface currents. On the island's west side, ocean currents are weakened due to the physical barrier, and the sea surface temperature increases, indicating an island effect. The island effect is also observed when analyzing vertical sections. Weather conditions in 2010 show that the air temperature was higher than in 2012 and 2014. The atmosphere also exhibits an island effect, with the wind skirting the island's upper terrain and weakening on the leeward side. The oceanic part shows the warming of the upper waters and the convergence of currents on the island's west side. Modeled ocean temperatures underestimate (~ -0.3 °C) observations, except to the west of the island (~ +0.3 °C), where model temperatures are higher than measurements. Calculation of the FCO2 bias (fCO2is the CO2fugacity with unit atm, and FCO2is the CO2flux) shows that the model underestimates the measurements by about 20 mmol m-2d-1. The ocean was a source of CO2 during the three oceanographic cruise periods.