Estimativa do fluxo de CO2 no oceano atlântico utilizando dados de navios e satélite

Abstract

Atmospheric carbon dioxide (CO2) is responsible for more than half of the warming potential of the greenhouse effect by anthropogenic emissions, and its basis is the conversion of the balance between sources and sinks. The ocean is one of the main CO2 sinks, which can also act as a source of CO2 for an atmosphere, depending on its concentration in the ocean. An analysis of ocean temperature and salinity data and CO2 fugacity (fCO2) are essential for an estimation of the CO2 flow without an ocean-atmosphere system, which enables a better understanding of the role of the oceans without climate, as well as the Variability of atmospheric CO2. Studies have shown that the Tropical Atlantic Ocean (TAO) is an important source of CO2 for an atmosphere but little is known about seasonal and interannual variability of its flux at the ocean-atmosphere interface, as well as the impact of atmospheric CO2 flux, due, for example, to anthropogenic effects. In order to contribute to a better understanding of the CO2 flux at the ocean-atmosphere interface in the Tropical Atlantic Ocean, for the calculation of fCO2 data, sea surface temperature (SST), sea surface salinity (SSM), obtained by voluntary observation vessels, which crossed the tropical Atlantic Ocean (15º S to 20º N) during the years 2008 to 2014, and wind speed data during this period were obtained from ECMWF re-examinations (European Center for Medium-Time Forecasting). As analyzes indicated that the interannual variability of CO2 fugacity generally presents an increase in the sampled period when considered as a study area as a whole. However, a presence of the InterTropical Convergence Zone (ITCZ) caused a decrease in fCO2sw (CO2 fugacity in seawater). This decrease is related to the rainfall characteristic of the ITCZ, which causes a decrease in SSM. A correlation between fCO2sw and SSM was significant (r = 0.7 ~ 0.9), consequently, resulting in CO2 absorption causing this region of the OAT to act as a sink for atmospheric CO2. It was also verified that, in some periods, a CO2 fugacity showed no correlation with a SST and SSM, which suggests an influence of other biophysical variables in the estimation of fugacity. The region between 10 o N and 20o N presents seasonally related behavior, acting as a sink in the months in which the TSM (December to May), presents smaller values in magnitude when compared to the other periods. On the other hand, when a TSM is higher (June to October), it acts as a source of CO2 for the atmosphere. On average, the CO2 flow from the ocean to the atmosphere in the sampled period was 0.84 μmol.m-2.d-1, confirming its performance as a source of CO2 for the atmosphere. An elaboration of a single pre-launch model of fCO2sw for the entire study region proved to be infeasible because the study region was presented, for example, as being linked to the current system of currents in the region.