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  • 1
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    Online Resource
    Hydrological changes related to the variability of tropical South American climate from the Cabo Frio lagoonal system (Brazil) during the last 5000 years
    SAGE Publications ; 2005
    In:  The Holocene Vol. 15, No. 4 ( 2005-05), p. 625-630
    Details
    In: The Holocene, SAGE Publications, Vol. 15, No. 4 ( 2005-05), p. 625-630
    Abstract: From west to east, the Fluminense coastline, composed of two series of lagoons, presents an aridity gradient induced by a local upwelling that is controlled by trade winds coming from the south Atlantic. The physico-chemical conditions of the lagoons are controlled by the duration of the dry season. They are characterized by hypersaline conditions with organic-carbonate sedimentation in the upwelling-influenced area, and by hyposaline conditions with organic-detrital sedimentation out of the upwelling-influenced area. On a core collected in the Brejo do Espinho hypersaline lagoon, diatom analysis supported by sedimentological data revealed a varying high water level from 4500 to 2200 14 C yr BP induced by successive freshwater inputs in to the lagoon. Two major dry events occurred during this period, probably related to relative sea-level fluctuations. At 2200 14 C yr BP, a drastic change occurred, as indicated by a carbonate nodule, carbonate-dominated sediments and polyto hypersaline diatoms, all suggesting arid conditions. The Brejo do Espinho record suggests that before 2200 14 C yr BP, the central part of the Brazilian coast was mostly subjected to south to southeasterly winds and weaker trade winds, whereas after 2200 14 C yr BP, trade winds dominated, implying drier conditions at the easternmost part of the Fluminense coastline. These results would also suggest a late Holocene increase in El Ninlo activity (after 2200 14 C yr BP), consistent with several El Nifio records from western South America.
    Type of Medium: Online Resource
    ISSN: 0959-6836 , 1477-0911
    URL: Article
    DOI: 10.1191/0959683605hl823rr
    RVK:
    RA 1000
    Language: English
    Publisher: SAGE Publications
    Publication Date: 2005
    detail.hit.zdb_id: 2027956-5
    SSG: 14
    SSG: 3,4
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  • 2
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    Late-Holocene palaeoenvironmental reconstruction from a lake in the Amazon Rainforest-Tropical Savanna (Cerrado) boundary in Brazil using a multi-proxy approach
    SAGE Publications ; 2021
    In:  The Holocene Vol. 31, No. 9 ( 2021-09), p. 1417-1429
    Details
    In: The Holocene, SAGE Publications, Vol. 31, No. 9 ( 2021-09), p. 1417-1429
    Abstract: As an ecotone, the region between the Amazon Rainforest and Tropical Savanna (Cerrado) biomes is, by definition, more susceptible to climate change. Therefore, understanding palaeoenvironmental dynamics is essential to address the future responses of such transition areas to climatic fluctuations. In this context, we present a new sediment record for the Late-Holocene retrieved from Barro-Preto, currently an oxbow lake located in an ecotone at the southern Brazilian Amazon border. Our multi-proxy data include carbon and nitrogen isotopes, as well as bulk TOC, chlorophyll derivatives, grain-size and microcharcoal analyses, all anchored on a radiocarbon-dated chronology. The sedimentary process recorded at the Barro-Preto Lake responded to both local and regional climate dynamics. It was influenced by river excursions associated to local responses to precipitation changes by the activation of the palaeochannel connecting the main-stem river and the Barro-Preto lake. This activation was evidenced by the presence of different colour lithology laminations accompanied by coarser sediments and also by climate conditions known to influence the Amazon region. Depositional processes linked to lake dynamics and different oxbow lake cycle stages were also important to explain the changes verified in the Barro-Preto record, endorsing the use of this lake formation for palaeoclimatic reconstructions. The record indicated a rising humidity trend, reflected by a progressive increase in lacustrine productivity, in accordance to other studies carried out in the Amazon region concerning the Late-Holocene, associated with a more southward displacement of the Intertropical Convergence Zone. Despite this rising humidity trend, dry episodic events during the Late-Holocene were evidenced by charcoal data, also coherent with regional Amazon studies, albeit exhibiting increased intensity, suggesting that the transitional nature of the environment might have influenced susceptibility to fires.
    Type of Medium: Online Resource
    ISSN: 0959-6836 , 1477-0911
    URL: Article
    DOI: 10.1177/09596836211019091
    RVK:
    RA 1000
    Language: English
    Publisher: SAGE Publications
    Publication Date: 2021
    detail.hit.zdb_id: 2027956-5
    SSG: 14
    SSG: 3,4
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  • 3
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    Hydroclimate reconstruction during the last 1000 years inferred from the mineralogical and geochemical composition of a sediment core from Lake-Azuei (Haiti)
    SAGE Publications ; 2023
    In:  The Holocene Vol. 33, No. 7 ( 2023-07), p. 816-826
    Details
    In: The Holocene, SAGE Publications, Vol. 33, No. 7 ( 2023-07), p. 816-826
    Abstract: This study aims to reconstruct the hydro-climatic variations over the last 1000 years in Haiti using mineralogical and geochemical composition of well dated lacustrine sediment core retrieved from Lake Azuei. The results show changes in sedimentological processes linked to environmental and climatic variations. The general pattern suggests a wetter Medieval Climate Anomaly (MCA), drier Little Ice Age (LIA), high climate variability during the MCA-LIA transition and more anthropogenic impacts that dominate natural climate during the Current Warm Period (CWP). The MCA period (~1000–1100 CE) thus appears marked by increase sedimentation rate supported by higher terrigenous input linked to erosive events particularly increases in precipitation. During the LIA, particularly from ~1450 to 1600 CE, there is a great variation toward a decrease of terrigenous input, which is related to a decrease on sedimentation rate and increase Mg-calcite precipitation, suggesting less precipitation and high evaporation respectively during dry climate conditions. The MCA-LIA transition (~1200–1400 CE) is characterized by variations between terrigenous input, Mg-calcite formation and organic matter deposition, which indicate succession of dry and humid conditions. The CWP (1800–2000 CE) shows a progressive increase on sedimentation rate and decrease of gray level, which indicate more organic matter sedimentation as consequence of anthropogenic activities in the surrounding basin of the lake. High-resolution gray level analysis, which reflects principally variations in terrigenous input, carbonate mineral formation and organic matter deposition, shows that the AMO, NAO, PDO and ENSO are the principal modes affecting the hydro-climatic changes in Haiti during the last millennium. In addition, temporal correlation of other Caribbean paleoclimate records with our geochemical and mineralogical data, suggests that trends observed in Lake Azuei were controlled by regional climate, likely associated with shifts in the position of the ITCZ.
    Type of Medium: Online Resource
    ISSN: 0959-6836 , 1477-0911
    URL: Article
    DOI: 10.1177/09596836231163512
    RVK:
    RA 1000
    Language: English
    Publisher: SAGE Publications
    Publication Date: 2023
    detail.hit.zdb_id: 2027956-5
    SSG: 14
    SSG: 3,4
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  • 4
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    Diatom-based paleoproductivity and climate change record of the Gulf of Tehuantepec (Eastern Tropical Pacific) during the last ~500 years
    SAGE Publications ; 2023
    In:  The Holocene Vol. 33, No. 10 ( 2023-10), p. 1221-1236
    Details
    In: The Holocene, SAGE Publications, Vol. 33, No. 10 ( 2023-10), p. 1221-1236
    Abstract: Changes in marine productivity of the last five centuries in the Gulf of Tehuantepec were investigated using a high-resolution record of diatoms, organic carbon (C org ), total nitrogen (TN), Ni/Al, and Cu/Al. The laminated sediments were dated by using 210 Pb and 14 C, with a bayesian age model providing a new Δ R = 247 ± 30 years for the bulk sediment. The Little Ice Age (LIA) (~1500 to ~1858 CE) was characterized by the predominance of cold-water and high productivity diatoms ( Chaetoceros spores, Thalassionema nitzschioides, Lioloma pacificum, Thalassiosira nanolineata, and Rhizossolenia setigera) and high values of geochemical productivity proxies. A transition period (~1860 to ~1919 CE) toward warmer conditions related to the end of the LIA and the beginning of the Current Warm Period (CWP), was indicated by the appearance of warm-water diatoms ( Neodelphineis pelagica, Thalassiosira tenera, and Rhizossolenia bergonii), as well as lower values of C org , TN, Ni/Al, and Cu/Al. The most recent period of the CWP (~1920 CE to today) was characterized by the increased abundance warm-water taxa ( N. pelagica, Cymatodiscus planetophorus, T. tenera, Plagiogramma minus, Nitzschia interruptestriata, and R. bergonii), and by the prevalence of low values of C org , TN, Ni/Al, and Cu/Al. These changes in productivity during the LIA and CWP were likely driven by changes in solar irradiance and the migration of the Intertropical Convergence Zone. This study highlights the spatial extent of the LIA in the Eastern Tropical North Pacific and contributes to the knowledge of the productivity response to climate in tropical regions.
    Type of Medium: Online Resource
    ISSN: 0959-6836 , 1477-0911
    URL: Article
    DOI: 10.1177/09596836231183057
    RVK:
    RA 1000
    Language: English
    Publisher: SAGE Publications
    Publication Date: 2023
    detail.hit.zdb_id: 2027956-5
    SSG: 14
    SSG: 3,4
    Location Call Number Limitation Availability
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