Impact of the Southern Atlantic on the global overturning circulation (MOC) and climate (SAMOC)

Abstract

This project has different purposes within the international research devoted to climate variability and change. The most relevant one is to develop a monitoring array in the South Atlantic, within a broad international partnership, to continue a time series started in 2004, south of Africa, in 2008 in the Drake Passage, and on the eastern and western boundaries of the South Atlantic. The main goal is to enhance the ongoing effort within a broader coordinated experimental context, focusing at the determination of an optimal observing network to monitor the global overturning circulation in the South Atlantic. This international programmer has been named SAMOC (South Atlantic Meridional Overturning Circulation). SAMOC has been positively evaluated and endorsed by the Southern Ocean Clivar/CliC/SCAR and Clivar Atlantic Panels. It is supported, in the USA, by NOAA, and the NSF. It is already receiving support in France from Ifremer and CPER Region Bretagne. In Brazil, it is endorsed by the "Instituto Nacional de Ciência e Tecnologia para Mudanças Climáticas" (INCT -MC). Observations and models indicate that variations in the Meridional Overturning Circulation (MOC) are strongly correlated to important climate changes. To date, most MOC observations have been focused in the North Atlantic. However, model studies show that the South Atlantic is not just a passive conduit for water masses formed in other regions of the world ocean. For instance, the Agulhas leakage has a strong impact on the South Atlantic and, consequently, on the Brazilian coastal zones. Its influence also reaches the northern North Atlantic, affecting the global MOC. These results highlight the need for sustained observations in the South Atlantic, which, in conjunction with modeling efforts, would improve the understanding of the processes necessary to formulate long-term climate predictions. The CLIV AR calls for a MOC monitoring array across the South Atlantic. Three SAMOC workshops were held to bring together the international community to design a suitable integrated observational program. The hypothesis is that changes in the upper ocean return flow of the MOC in the South Atlantic could significantly impact the regional and global climate, and the properties of the North Atlantic Mac. The goals are: (1) to characterize the time-mean and time-varying components of the MOC, as well as, the heat and salt carried by the MOC, in the South Atlantic; (2) to observe the changes in the ventilation characteristics and relative contributions of different water masses to the MOC and (3) to contribute with regional studies in the assessment of the sensitivity of the South American climate conditions to the SAMOC variability and changes. The overall program is a collaborative effort involving investigators from France, Brazil, the U.S., South Africa, Argentina, Russia and Germany. France, Brazil, Germany and the U.S. will provide the major instrumentation for the moored array along 34.5°S and the GoogHope line, the backbone for the SAMOC field program. South Africa, Russia, Brazil, Germany and Argentina will contribute with funds for ship-time and local-expertise for the turn-around and recovery cruises. France and Brazil will lead the development of a common strategy in regional climate models apt to downscale climate variability and assess the ocean circulation influence on climate changes and their impact over South America and Africa. This proposal seeks funds from ANR for six new bottom Current Pressure Inverted Echo Sounder moorings (C-PIES), to refit seven (7) PIES, DATA-PODS to regularly transmit via satellite mooring data to land centers and to develop and strengthen the collaborative effort between Brazil and France. In Brazil, funds are requested from F APESP and F ACEPE mainly for ship-time for the turn-around and recovery cruises, ADCP, LADCP, bottom pressure gauge and C-PIES to be deployed in the western end of the array and travel support. Broader Impact: The influence of the MOC variability on global weather patterns, marine ecosystems, terrestrial vegetation, oceanic CO2 uptake, and other components of the climate system are of important societal relevance. The proposed program aims to improve our understanding of the MOC variability in the South Atlantic and its impact on the global and regional climate. Data will be made available to the research and operational community, particularly to the modeling community, to expand our skill in reproducing the observed MOC variability, diagnose the mechanisms that produce MOC variability, and predict the future evolution of the Mac. Participation of grad students and post-docs will advance the national education goals. (AU)