Full text
| |
| Author(s): |
Amanda Mattosinhos Spera
Total Authors: 1
|
| Document type: | Doctoral Thesis |
| Press: | São Paulo. |
| Institution: | Universidade de São Paulo (USP). Instituto Oceanográfico (IO/DIDC) |
| Defense date: | 2016-12-01 |
| Examining board members: |
Marcia Caruso Bicego;
Francisco William da Cruz Júnior;
Rafael André Lourenço;
César de Castro Martins;
Ilana Elazari Klein Coaracy Wainer
|
| Advisor: | Marcia Caruso Bicego; Rubens Cesar Lopes Figueira |
| Abstract | |
Geochemical proxies (n-alkanes, alkenones, GDGTs, δ13C, Fe / Ca and Ti / Ca) were used to evaluate the paleoclimatic and paleoceanographic changes in the Continental Shelf of São Sebastião during the Late Holocene. The age model, obtained through the combined analyses of 210Pb and 14C methods, indicated that the core used in this study covers the last 1500 years. Variations in the sea surface temperature may be related to changes in the prevailing winds, which in turn are responsible for an increase or reduction in the frequency of the upwelling events. Changes in subsurface temperature values can be related to the presence of the South Atlantic Central Water near the coastal regions, and the mixing processes in the water column. Changes in mean air temperature (MAT), in turn, are probably related to fluctuations in total solar radiation, since periods represented by higher values of MAT correspond to the periods of maximum solar irradiation known as Medieval (1100-1250 AD) and Modern Maximum (1950 - present). While the period represented by the lower MAT values can be linked to the solar minimum period known as Spörer. The evaluation of terrigenous markers allowed the identification of variations in the drainage and continental erosion, which in turn are related to changes in the precipitation of the adjacent continent. Furthermore, the Medieval Climate Anomaly was characterized by a decrease in the terrigenous input, while the Little Ice Age could be characterized as a period of increased terrestrial contribution. Overall, it was observed that the sea surface temperature gradient between the North Atlantic and the South Atlantic Oceans appears to play an important role in triggering or amplifying climate change observed in the tropics. This temperature dipole can cause changes in the position of the Intertropical Convergence Zone and the direction of prevailing winds, which in turn will influence, directly and indirectly, the marine circulation and the rainfall. (AU) | |
| FAPESP's process: | 13/08463-0 - Record of the paleoclimatic and paleoceanographic conditions of the past 2500 years in the region of São Sebastião Island, located in the Southeastern Brazilian Continetal Shelf, through the use of geochemical proxies |
| Grantee: | Amanda Mattosinhos Spera |
| Support Opportunities: | Scholarships in Brazil - Doctorate |