Evaluation of the Atlantic Meridional overturning circulation under high CO2 emissions

Abstract

This thesis aimed to evaluate the impact, in the Earth Climate System, of the continuous increase of CO2 in the atmosphere. More specifically, the thesis proposed identifying tipping points in the Thermohaline Circulation and evaluating its impacts mainly in the Atlantic Ocean. The results from two numerical simulations, derived from a state-of-the-art Earth System Model, were used to achieve the proposed objectives. The control experiment aimed to represent the pre-industrial period with conditions that did not evolve, that is, without forcing, and it is called piControl. The experiment with altered conditions, on the other hand, is called 1pctCO2, started from year 501 of piControl and has as its only forcing, an increase of 1% per year in the concentration of atmospheric CO2. The piControl experiment was validated to be used as a comparison parameter with the 1pctCO2 experiment through several analyzes and comparisons with observed and reanalysis data. In the 1pctCO2 experiment, an average Global Warming in the atmosphere of more than 6°C was identified, and there was a change in the freshwater flow pattern in the North Atlantic. This change impacted the regions of deep convection and all dynamics associated with the Atlantic Meridional Overturning Circulation (AMOC). This work contributed to the knowledge about the mechanisms of AMOC and North Atlantic Deep Water dynamics in both the North and the South Atlantic Ocean.