Modern terrigenous sediment sources and past changes in precipitation over tropical South America recorded in terrigenous sediments deposited in the western equatorial Atlantic

Detalhes bibliográficos
Ano de defesa: 2023
Autor(a) principal: Iani, Júlia Grigolato
Orientador(a): Não Informado pela instituição
Banca de defesa: Não Informado pela instituição
Tipo de documento: Dissertação
Tipo de acesso: Acesso aberto
Idioma: eng
Instituição de defesa: Biblioteca Digitais de Teses e Dissertações da USP
Programa de Pós-Graduação: Não Informado pela instituição
Departamento: Não Informado pela instituição
País: Não Informado pela instituição
Palavras-chave em Português:
Link de acesso: https://www.teses.usp.br/teses/disponiveis/44/44142/tde-06102023-121344/
Resumo: The effect of the slowdown of the Atlantic Meridional Overturning Circulation (AMOC) on precipitation in the Amazon Basin is a crucial issue for the future of the Amazon rainforest. At the end of the Quaternary, the AMOC strength was significantly reduced during the Heinrich Stadials (HS). These millennial-scale periods of AMOC decline offer a valuable opportunity to examine and assess the impact of AMOC intensity on Amazonian precipitation. Despite the efforts made during the last decade to understand the effects of HS on the Amazon Basin, the response of this transcontinental river system to changes in AMOC strength during the most recent HS (i.e., HS0 or Younger Dryas, 12.9 11.7 cal ka BP) remains uncertain. This masters dissertation aimed at characterizing how changes in AMOC strength affected Amazonian precipitation during the last 28,000 years. To achieve this objective, in a first step, major elements in suspended sediments from the Negro, Solimões and Amazonas Rivers were analyzed by inductively coupled plasma optical emission spectrometry (ICP-OES) covering a complete annual hydrological cycle, in order to evaluate the current fluvial dynamics of the Amazon Basin. These data provide a solid basis for the second stage of the dissertation, namely the paleoclimatic reconstruction of the Amazon Basin, carried out with emphasis on the Heinrich Stadial 1 (HS1) (18.6 14.7 cal ka BP) and the Younger Dryas. The paleoclimate reconstruction was based on two marine sediment cores collected from the western equatorial Atlantic, radiocarbon dated, analyzed by energy dispersive X-ray fluorescence (ED-XRF) and interpreted with the aid of principal component analysis. Interpretation of the data produced for the Younger Dryas was also aided by a compilation of hydroclimatic records from the Amazon Basin and its surroundings, as well as outputs from the transient TraCE-21ka run of the numerical climate model CCSM3. The results show that HS1 had two distinct phases: HS1a between 18.6 and 16.7 cal ka BP and HS1b between 16.7 and 14.7 cal ka BP. HS1a is characterized by high values of ln(Ti/Ca) and ln(Ti/Al), and low values of ln(Al/K) and ln(Fe/K), whereas HS1b is characterized by relatively lower values of ln(Ti/Ca) and ln(Ti/Al), and relatively higher of ln(Al/K) and ln(Fe/K). The differences between HS1a and HS1b are related to a shift in the main locus of precipitation: the central And es during HS1a and the southeastern lowlands of the Amazon Basin during HS1b. The change in the main locus of precipitation over the Amazon Basin was likely driven by a marked decrease in AMOC strength during HS1b, that reached its lowest level during the last deglaciation. Results for the Younger Dryas suggest distinct precipitation responses over the Amazon Basin. While its beginning is marked by an increase in ln(Ti/Ca) and ln(Al/K) and a decrease in ln(Fe/K) and ln(Ti/Al), the remainder of the event presents lower values of ln(Ti/Ca) and ln(Ti/Al) and higher values of ln(Al/K) and ln(Fe/K). We suggest that the decrease in austral summer insolation that characterized the period between HS1 and the Younger Dryas weakened the South American Monsoon System, and the Intertropical Convergence Zone gradually became the main source of moisture for the Amazon Basin. These atmospheric features influence precipitation over the Amazon Basin in distinct ways. The different responses of Amazonian precipitation during HS1 and the Younger Dryas are, therefore, related to the slowdown of the AMOC and changes in austral summer insolation. The variation in precipitation response in each event and sub-event reinforces the importance of paleoclimate studies in the Amazon Basin and the need to compartmentalize it in terms of its high complexity and continental dimension.
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spelling Modern terrigenous sediment sources and past changes in precipitation over tropical South America recorded in terrigenous sediments deposited in the western equatorial AtlanticFontes modernas de sedimentos terrígenos e mudanças passadas na precipitação sobre a América do Sul tropical registradas em sedimentos terrígenos depositados no Atlântico equatorial ocidentalAmazon BasinAtlantic Meridional overturning circulationBacia AmazônicaCélula de revolvimento meridional do AtlânticoHeinrich stadialsHeinrich stadialsYounger dryasYounger dryasThe effect of the slowdown of the Atlantic Meridional Overturning Circulation (AMOC) on precipitation in the Amazon Basin is a crucial issue for the future of the Amazon rainforest. At the end of the Quaternary, the AMOC strength was significantly reduced during the Heinrich Stadials (HS). These millennial-scale periods of AMOC decline offer a valuable opportunity to examine and assess the impact of AMOC intensity on Amazonian precipitation. Despite the efforts made during the last decade to understand the effects of HS on the Amazon Basin, the response of this transcontinental river system to changes in AMOC strength during the most recent HS (i.e., HS0 or Younger Dryas, 12.9 11.7 cal ka BP) remains uncertain. This masters dissertation aimed at characterizing how changes in AMOC strength affected Amazonian precipitation during the last 28,000 years. To achieve this objective, in a first step, major elements in suspended sediments from the Negro, Solimões and Amazonas Rivers were analyzed by inductively coupled plasma optical emission spectrometry (ICP-OES) covering a complete annual hydrological cycle, in order to evaluate the current fluvial dynamics of the Amazon Basin. These data provide a solid basis for the second stage of the dissertation, namely the paleoclimatic reconstruction of the Amazon Basin, carried out with emphasis on the Heinrich Stadial 1 (HS1) (18.6 14.7 cal ka BP) and the Younger Dryas. The paleoclimate reconstruction was based on two marine sediment cores collected from the western equatorial Atlantic, radiocarbon dated, analyzed by energy dispersive X-ray fluorescence (ED-XRF) and interpreted with the aid of principal component analysis. Interpretation of the data produced for the Younger Dryas was also aided by a compilation of hydroclimatic records from the Amazon Basin and its surroundings, as well as outputs from the transient TraCE-21ka run of the numerical climate model CCSM3. The results show that HS1 had two distinct phases: HS1a between 18.6 and 16.7 cal ka BP and HS1b between 16.7 and 14.7 cal ka BP. HS1a is characterized by high values of ln(Ti/Ca) and ln(Ti/Al), and low values of ln(Al/K) and ln(Fe/K), whereas HS1b is characterized by relatively lower values of ln(Ti/Ca) and ln(Ti/Al), and relatively higher of ln(Al/K) and ln(Fe/K). The differences between HS1a and HS1b are related to a shift in the main locus of precipitation: the central And es during HS1a and the southeastern lowlands of the Amazon Basin during HS1b. The change in the main locus of precipitation over the Amazon Basin was likely driven by a marked decrease in AMOC strength during HS1b, that reached its lowest level during the last deglaciation. Results for the Younger Dryas suggest distinct precipitation responses over the Amazon Basin. While its beginning is marked by an increase in ln(Ti/Ca) and ln(Al/K) and a decrease in ln(Fe/K) and ln(Ti/Al), the remainder of the event presents lower values of ln(Ti/Ca) and ln(Ti/Al) and higher values of ln(Al/K) and ln(Fe/K). We suggest that the decrease in austral summer insolation that characterized the period between HS1 and the Younger Dryas weakened the South American Monsoon System, and the Intertropical Convergence Zone gradually became the main source of moisture for the Amazon Basin. These atmospheric features influence precipitation over the Amazon Basin in distinct ways. The different responses of Amazonian precipitation during HS1 and the Younger Dryas are, therefore, related to the slowdown of the AMOC and changes in austral summer insolation. The variation in precipitation response in each event and sub-event reinforces the importance of paleoclimate studies in the Amazon Basin and the need to compartmentalize it in terms of its high complexity and continental dimension.O efeito da desaceleração da Célula de Revolvimento Meridional do Atlântico (CRMA) sobre a precipitação na Bacia Amazônica é uma questão crucial para o futuro da floresta Amazônica. No final do Quaternário, a CRMA foi significativamente reduzida durante os Heinrich Stadials (HS). Esses períodos de diminuição da CRMA em escala milenar oferecem uma oportunidade valiosa para examinar e avaliar o impacto da intensidade da CRMA na precipitação Amazônica. Apesar do esforço investido durante a última década na compreensão dos efeitos dos HS sobre a Bacia Amazônica, a resposta deste sistema fluvial transcontinental às mudanças na intensidade da CRMA durante o HS mais recente (i.e., HS0 ou Younger Dryas, 12,9 11,7 cal ka BP) permanece incerta. Esta dissertação de mestrado teve como principal objetivo caracterizar como as mudanças na intensidade da CRMA afetaram a precipitação Amazônica durante os últimos 28.000 anos. Para atingir tal objetivo, em uma primeira etapa, elementos maiores em sedimentos suspensos dos rios Negro, Solimões e Amazonas foram analisados por espectrometria de emissão óptica com plasma indutivamente acoplado (ICP-OES, na sigla em Inglês) em amostras que cobrem um ciclo hidrológico anual completo, de modo a avaliar a dinâmica fluvial atual da Bacia Amazônica. Esses dados forneceram uma base sólida para a segunda etapa da dissertação, a saber a reconstituição paleoclimática da Bacia Amazônica, realizada com ênfase no Heinrich Stadial 1 (HS1) (18,6 14,7 cal ka BP) e no Younger Dryas. A reconstituição paleoclimática baseou-se em dois testemunhos sedimentares marinhos coletados no Atlântico equatorial ocidental, datados por radiocarbono, analisados por fluorescência de raios-X por energia dispersiva (ED-XRF, na sigla em Inglês) e interpretados com auxílio de análise de componentes principais. A interpretação dos dados produzidos para o Younger Dryas foi também auxiliada por uma compilação de registros hidroclimáticos da Bacia Amazônica e arredores, bem como com uma saída da rodada transiente TraCE-21ka do modelo numérico climático CCSM3. Os resultados obtidos mostram que o HS1 teve duas fases distintas: o HS1a entre 18,6 e 16,7 cal ka BP e o HS1b entre 16,7 e 14,7 cal ka BP. O HS1a é caracterizado por altos valores de ln(Ti/Ca) e de ln(Ti/Al) e baixos valores de ln(Al/K) e ln(Fe/K), enquanto que o HS1b é caracterizado por valores relativamente mais baixos de ln(Ti/Ca) e ln(Ti/Al) e relativamente mais altos de ln(Al/K) e ln(Fe/K). As diferenças entre HS1a e HS1b estão relacionadas a uma mudança no locus principal de precipitação: os Andes centrais durante o HS1a e as terras baixas do sudeste da Bacia Amazônica durante o HS1b. A mudança no locus principal de precipitação sobre a Bacia Amazônica foi provavelmente determinado por uma diminuição acentuada na intensidade da CRMA durante o HS1b, quando a mesma atingiu sua menor intensidade durante a última deglaciação. Os resultados para o Younger Dryas sugerem respostas distintas da precipitação sobre a Bacia Amazônica. Enquanto seu início é marcado pelo aumento de ln(Ti/Ca) e ln(Al/K) além da diminuição de ln(Fe/K) e ln(Ti/Al), o restante do evento apresenta valores menores de ln(Ti/Ca) e ln(Ti/Al) e valores maiores de ln(Al/K) e ln(Fe/K). Sugere-se que a diminuição da insolação de verão austral que caracteriza o período entre o HS1 e o Younger Dryas enfraqueceu o Sistema de Monções da América do Sul e a Zona de Convergência Intertropical tornou-se, gradativamente, a principal fonte de umidade para a Bacia Amazônica. Estas feições atmosféricas influenciam a precipitação amazônica de maneira distinta. As diferentes respostas da precipitação Amazônica durante o HS1 e o Younger Dryas estão, portanto, relacionadas à desaceleração da CRMA e à variação da insolação de verão austral. A variada resposta da precipitação em cada evento e sub-evento reforça a importância dos estudos paleoclimáticos na Bacia Amazônica e a necessidade de compartimentalizar a mesma em função da sua alta complexidade e dimensão continental.Biblioteca Digitais de Teses e Dissertações da USPChiessi, Cristiano MazurIani, Júlia Grigolato2023-09-22info:eu-repo/semantics/publishedVersioninfo:eu-repo/semantics/masterThesisapplication/pdfhttps://www.teses.usp.br/teses/disponiveis/44/44142/tde-06102023-121344/reponame:Biblioteca Digital de Teses e Dissertações da USPinstname:Universidade de São Paulo (USP)instacron:USPReter o conteúdo por motivos de patente, publicação e/ou direitos autoriais.info:eu-repo/semantics/openAccesseng2024-10-09T13:16:04Zoai:teses.usp.br:tde-06102023-121344Biblioteca Digital de Teses e Dissertaçõeshttp://www.teses.usp.br/PUBhttp://www.teses.usp.br/cgi-bin/mtd2br.plvirginia@if.usp.br|| atendimento@aguia.usp.br||virginia@if.usp.bropendoar:27212024-10-09T13:16:04Biblioteca Digital de Teses e Dissertações da USP - Universidade de São Paulo (USP)false
dc.title.none.fl_str_mv Modern terrigenous sediment sources and past changes in precipitation over tropical South America recorded in terrigenous sediments deposited in the western equatorial Atlantic
Fontes modernas de sedimentos terrígenos e mudanças passadas na precipitação sobre a América do Sul tropical registradas em sedimentos terrígenos depositados no Atlântico equatorial ocidental
title Modern terrigenous sediment sources and past changes in precipitation over tropical South America recorded in terrigenous sediments deposited in the western equatorial Atlantic
spellingShingle Modern terrigenous sediment sources and past changes in precipitation over tropical South America recorded in terrigenous sediments deposited in the western equatorial Atlantic
Iani, Júlia Grigolato
Amazon Basin
Atlantic Meridional overturning circulation
Bacia Amazônica
Célula de revolvimento meridional do Atlântico
Heinrich stadials
Heinrich stadials
Younger dryas
Younger dryas
title_short Modern terrigenous sediment sources and past changes in precipitation over tropical South America recorded in terrigenous sediments deposited in the western equatorial Atlantic
title_full Modern terrigenous sediment sources and past changes in precipitation over tropical South America recorded in terrigenous sediments deposited in the western equatorial Atlantic
title_fullStr Modern terrigenous sediment sources and past changes in precipitation over tropical South America recorded in terrigenous sediments deposited in the western equatorial Atlantic
title_full_unstemmed Modern terrigenous sediment sources and past changes in precipitation over tropical South America recorded in terrigenous sediments deposited in the western equatorial Atlantic
title_sort Modern terrigenous sediment sources and past changes in precipitation over tropical South America recorded in terrigenous sediments deposited in the western equatorial Atlantic
author Iani, Júlia Grigolato
author_facet Iani, Júlia Grigolato
author_role author
dc.contributor.none.fl_str_mv Chiessi, Cristiano Mazur
dc.contributor.author.fl_str_mv Iani, Júlia Grigolato
dc.subject.por.fl_str_mv Amazon Basin
Atlantic Meridional overturning circulation
Bacia Amazônica
Célula de revolvimento meridional do Atlântico
Heinrich stadials
Heinrich stadials
Younger dryas
Younger dryas
topic Amazon Basin
Atlantic Meridional overturning circulation
Bacia Amazônica
Célula de revolvimento meridional do Atlântico
Heinrich stadials
Heinrich stadials
Younger dryas
Younger dryas
description The effect of the slowdown of the Atlantic Meridional Overturning Circulation (AMOC) on precipitation in the Amazon Basin is a crucial issue for the future of the Amazon rainforest. At the end of the Quaternary, the AMOC strength was significantly reduced during the Heinrich Stadials (HS). These millennial-scale periods of AMOC decline offer a valuable opportunity to examine and assess the impact of AMOC intensity on Amazonian precipitation. Despite the efforts made during the last decade to understand the effects of HS on the Amazon Basin, the response of this transcontinental river system to changes in AMOC strength during the most recent HS (i.e., HS0 or Younger Dryas, 12.9 11.7 cal ka BP) remains uncertain. This masters dissertation aimed at characterizing how changes in AMOC strength affected Amazonian precipitation during the last 28,000 years. To achieve this objective, in a first step, major elements in suspended sediments from the Negro, Solimões and Amazonas Rivers were analyzed by inductively coupled plasma optical emission spectrometry (ICP-OES) covering a complete annual hydrological cycle, in order to evaluate the current fluvial dynamics of the Amazon Basin. These data provide a solid basis for the second stage of the dissertation, namely the paleoclimatic reconstruction of the Amazon Basin, carried out with emphasis on the Heinrich Stadial 1 (HS1) (18.6 14.7 cal ka BP) and the Younger Dryas. The paleoclimate reconstruction was based on two marine sediment cores collected from the western equatorial Atlantic, radiocarbon dated, analyzed by energy dispersive X-ray fluorescence (ED-XRF) and interpreted with the aid of principal component analysis. Interpretation of the data produced for the Younger Dryas was also aided by a compilation of hydroclimatic records from the Amazon Basin and its surroundings, as well as outputs from the transient TraCE-21ka run of the numerical climate model CCSM3. The results show that HS1 had two distinct phases: HS1a between 18.6 and 16.7 cal ka BP and HS1b between 16.7 and 14.7 cal ka BP. HS1a is characterized by high values of ln(Ti/Ca) and ln(Ti/Al), and low values of ln(Al/K) and ln(Fe/K), whereas HS1b is characterized by relatively lower values of ln(Ti/Ca) and ln(Ti/Al), and relatively higher of ln(Al/K) and ln(Fe/K). The differences between HS1a and HS1b are related to a shift in the main locus of precipitation: the central And es during HS1a and the southeastern lowlands of the Amazon Basin during HS1b. The change in the main locus of precipitation over the Amazon Basin was likely driven by a marked decrease in AMOC strength during HS1b, that reached its lowest level during the last deglaciation. Results for the Younger Dryas suggest distinct precipitation responses over the Amazon Basin. While its beginning is marked by an increase in ln(Ti/Ca) and ln(Al/K) and a decrease in ln(Fe/K) and ln(Ti/Al), the remainder of the event presents lower values of ln(Ti/Ca) and ln(Ti/Al) and higher values of ln(Al/K) and ln(Fe/K). We suggest that the decrease in austral summer insolation that characterized the period between HS1 and the Younger Dryas weakened the South American Monsoon System, and the Intertropical Convergence Zone gradually became the main source of moisture for the Amazon Basin. These atmospheric features influence precipitation over the Amazon Basin in distinct ways. The different responses of Amazonian precipitation during HS1 and the Younger Dryas are, therefore, related to the slowdown of the AMOC and changes in austral summer insolation. The variation in precipitation response in each event and sub-event reinforces the importance of paleoclimate studies in the Amazon Basin and the need to compartmentalize it in terms of its high complexity and continental dimension.
publishDate 2023
dc.date.none.fl_str_mv 2023-09-22
dc.type.status.fl_str_mv info:eu-repo/semantics/publishedVersion
dc.type.driver.fl_str_mv info:eu-repo/semantics/masterThesis
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rights_invalid_str_mv Reter o conteúdo por motivos de patente, publicação e/ou direitos autoriais.
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