Paleoclimatic and paleoceanographic reconstructions in the Brazilian equatorial margin: proxy analysis and numerical modeling

Abstract

Understanding ocean circulation and past climate is crucial to anticipating future climate change and its impacts on marine ecosystems. In this context, paleoclimatic and paleoceanographic reconstructions of the Brazilian equatorial margin are extremely important since it has been positioned for at least 100 million years in a region with an equatorial climate, at practically constant latitude, being an important source of historical records. In addition, it is a key region for the study of oceanic circulation and global climate, comprising part of the Atlantic Meridional Upturning Circulation (AMOC) and the Northern Brazil Current. The investigation of past changes in AMOC can be carried out from the stratigraphy of the marine sediment, with analysis of paleoproperties. Magnetic properties in marine sediments have the potential to analyze past continental environmental changes, via changes in the terrigenous magnetic supply, but also to record past marine environmental conditions, via the formation of magnetic minerals. Due to the heterogeneous spatial distribution of data obtained from the stratigraphic analysis, numerical models are excellent tools to understand the oceanographic and climatic behavior of the area of interest, in a homogeneous way. In this way, this doctoral project intends to understand the changes in the behavior of magnetic parameters in sediment cores from the Brazilian equatorial margin in different paleoclimatic periods, such as the Last Glacial Maximum, complementing with oceanographic data obtained from numerical simulations. The magnetic susceptibility and remaining magnetizations of two cores from the Potiguar Basin (730m and 3867m of water column depth) obtained from the RETRO III project will be investigated, in order to unravel changes in the entry of terrigenous sediments, in water conditions background and sea level fluctuations. The oceanographic characterization will be performed using the Regional Ocean Modeling System (ROMS) model, with boundary conditions obtained from the global Community Earth System Model version 2 (CESM2). The simulations will be conducted during the glacial and current period. With the results of this project it is expected to understand the terrigenous contribution and the behavior of oceanic circulation in the Brazilian equatorial margin in glacial and interglacial periods. (AU)