Sea-level changes and global monsoon system: clues from marine cores in Brazil
Abstract
Tropical regions are a major source of heat to mid- and high-latitudes. The Atlantic Ocean-Atmosphere system is unique as it is the only system that currently transports heat across the equator. Therefore, accomplishing accurate global climate reconstructions, documentation and implementation of Atlantic climates in large-scale climate models is essential. This, however, has been hampered for most of the Cenozoic due to the lack of sufficient low-latitude sediment records. Here we propose to investigate paleoceanographic changes across the Cenozoic driven by longer and shorter term forcings from the Eocene greenhouse to icehouse conditions in the Quaternary, through the reconstruction of atmospheric, oceanographic and biological processes. The Brazilian Margin is a passive and stable continental margin that developed following the opening of the central Atlantic Ocean in mid-Cretaceous. A peculiar aspect of this margin is that it remained tectonically "passive" and approximately at the same equatorial latitude since its formation and, consequently, it has maintained continually a mainly oligotrophic inter-tropical environment. This project will take advantage of these unique attributes for obtaining high-quality sedimentological, paleoclimatic, and paleoceanographic data for the Cenozoic, proposing to drill transects across the Brazilian Margin from the uppermost part of the continental slope to the abyssal plain. The expected stratigraphic continuity along these transects will allow the detailed study of the relation between pCO2, sea-level and climate changes throughout the Cenozoic by constraining the fundamental parameters for calculating the climate sensitivity. This stratigraphic record will define the low-latitude climatic response to the major Cenozoic climatic events, such as the EECO, MECO, EOT, OMT, MCO and iNHG (see text for details). Sediments are expected to yield calcareous and organic microfossils, which will allow for studying the response of tropical ecosystems to these climatic events and also provide independent substrates for climate and carbon cycle reconstructions. Sediments will contain also fine eolian particles as well as terrigenous sediments related to increased run-off therefore more precipitations, which are associated to the South American Monsoon System as part of the Global Monsoon System. By undertaking a depth transect of sites selected from a wealth of seismic reflection data, integrated with high-resolution sedimentological records to reconstruct sea-level changes. In particular, these sites were chosen to establish a landmark for high-resolution Eocene-Recent tropical climate reconstructions, which will provide the following outcomes: 1) detail the relationship between tropical climate (temperature), sea-level and atmospheric pCO2; 2) evolution of the Atlantic Meridional Overturning Circulation driven by longer (tectonic) and shorter term (solar input) forcings and interplay with the South American Monsoon System. (AU)