Session: Last Millennium & Past2K
Author: Igor Stivanelli Custódio / email@example.com / Institute of Astronomy, Geophysics and Atmospheric Sciences, University of São Paulo
Co-author: Tatiana Jorgetti, Institute of Astronomy, Geophysics and Atmospheric Sciences, University of São Paulo;
Pedro L. da Silva Dias, Institute of Astronomy, Geophysics and Atmospheric Sciences, University of São Paulo;
Ilana Wainer, Oceanographic Institute, University of São Paulo, SP/Brazil;
Leila M. V. Carvalho, Earth Research Institute, University of California, Santa Barbara;
Tatiana Jorgetti, Oceanographic Institute, University of São Paulo, SP/Brazil;
The natural climate variability is an important factor to be understood for exploring the predictive potential of the climate and to evaluate the role of the anthropogenic forcing. Paleoclimate records provide indications of the past variability and cover a much longer period than the instrumental era. The main purpose of this study is to evaluate the changes of the South American Monsoon System (SAMS) during the Last Millennium (LM) in the numerical simulations of PMIP3 and to verify, in general, the influence of some climatic indexes on the monsoon. Large-scale aspects associated with the SAMS are explored, as well as its relations with the indicator of the low-frequency climate variability. The analyses have been based on the Large-scale Index for South American Monsoon (LISAM) applied in the weighted average set of the climate models simulations CCSM4-M, GISS-E2-R, IPSL-CM5A-LR, MIROC-ESM, MPI-ESM-P and MRI-ESM. The LISAM is based on the analysis of combined Empirical Orthogonal Functions (EOFc) between the variables at 850 hPa: precipitation, temperature, humidity and wind. The first (second) mode of the EOFc represents the spatial patterns of the SAMS (South Atlantic Convergence Zone – SACZ). Regarding with the LISAM the patterns related of the first two modes (SAMS and SACZ, respectively) during LM were similar to those found in the historical period. The temporal variability of the expansion coefficient series of the LISAM modes showed periods of variation associated with the variability of solar cycles and sunspots, as well as the systems internal oscillations. The internal variability of the SAMS and SACZ showed strong influences of the North and South Tropical Atlantic Ocean and the Pacific Ocean. Moreover, the time series of the first mode of EOFc proved to be a good indicator of climatic transition since it was possible to determine through the application of a regime change detection test the beginning and the end years of the Climate Medieval Anomaly and the Little Ice Age. Also, it was possible to verify the influence of some of the major volcanic eruptions of the LM period.