Timing and structure of Mega‐SACZ events during Heinrich Stadial 1

Stríkis, Nicolás Misailidis; Chiessi, Cristiano Mazur; Cruz, F. W.; Vuille, Mathias; Cheng, Hai; Barreto, Eline A de Souza; Mollenhauer, Gesine; Kasten, Sabine; Karmann, Ivo; Edwards, R. Lawrence; Bernal, Juan Pablo; Sales, Hamilton dos Reis

doi:10.1002/2015gl064048

Cited by 125 publications

(133 citation statements)

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“…Fe/Ca and Ti/Ca ratios have hence been used to trace changes in terrigenous input of fluvial origin, particularly offshore northeastern Brazil, where repeated authors pointed out increases in the terrigenous input during Heinrich events due to southward shifts of the ITCZ Nace et al, 2014;Stríkis et al, 2015;Zhang et al, 2015).…”

Section: Oppo Et Al 2015)mentioning

confidence: 99%

“…This is a particularly relevant sector of the continental margin for reconstructing the strength of the SASM. Oxygen isotopic oscillations from stalagmites have provided a glimpse of how continental climate responded to past millennial scale abrupt events (Wang et al, 2008a;Stríkis et al, 2015). However the several other areas of the continent and proximal marine environments are still not resolved.…”

Section: Introduction / Introduçãomentioning

confidence: 99%

“…Within the continent, stalagmite δ 18 O records from caves in southeastern SA related 54 negative  18 O excursions with intensification in the SASM during Heinrich events (Cruz et 55 al., 2006;Stríkis et al, 2015;. 56…”

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confidence: 99%

“…Hemisphere it migrated further southward of the Equator, with increased moisture influx to 145 SASM related to southward shifts on ITCZ (Deplazes et al, 2013; L. C. Peterson et al, 146 2000;Stríkis et al, 2015). 147…”

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confidence: 99%

“…Raw radiocarbon ages were 189 calibrated for the reservoir effect (Bard, 1988; and for variations on the 190 original 14 C concentration in the atmosphere (Reimer et al, 2013) using the online software 191 Calib 7.0.2 and the Marine13 calibration curve (Reimer et al, 192 2013 Minnesota, USA, following the procedures described by (Shen et al, 2002). All of the total 199 26 datings yield errors <1% (Table 1), and of these, 14 had already been published by 200 (Stríkis et al, 2015). The age model was linearly interpolated between U-Th ages for the 201 entire record.…”

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Climatic evolution of eastern South America during the last deglaciation: a paleoceanographic approach

Catunda¹

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Autorizo a reprodução e divulgação total ou parcial deste trabalho, por qualquer meio convencional ou eletrônico, para fins de estudo e pesquisa, desde que citada a fonte. ii AbstractTo support the current debate and actions to be taken about climatic consequences of anthropogenic release of CO2, a refined understanding about past climatic and oceanographic changes is necessary. The Atlantic Meridional Overturning Circulation (AMOC) plays a fundamental role in the oceanography and climate of the Atlantic realm, directly controlling stratification and distribution of water masses, the amount of heat that is transported by the ocean, and the cycling and storage of chemical species, such as carbon dioxide in the deep sea. The formation and circulation of Antarctic Intermediate Water (AAIW) is an important component of the upper branch of the AMOC, involved in the transport of heat and salt within the Southern Hemisphere subtropical gyre and driving high-low latitude climatic teleconnections. Reconstructing intermediate water properties is, therefore, important for understanding feedbacks within the ocean-climate system. However, information on AAIW evolution remains limited. AMOC oscillations and changes in heat distribution have strong implications for the South American climate, influencing moisture influx availability for the South American Summer Monsoon (SASM), via sea surface temperatures and Intertropical Convergence Zone positioning. Here we reconstruct AAIW isotopic signature during marine isotope stages 2 and 3 (41-12 cal kyr BP) using carbon and oxygen isotopes from benthic foraminifera (Cibicidoides and Uvigerina genera) of a radiocarbon dated marine sediment core (1100m water depth and 20S, off the Brazilian coast). We find that AAIW's physical and chemical properties changed Heinrich stadials 3 and 4, probably as a consequence of AMOC decreased strength during these periods. We also reconstruct Last Glacial Maximum and deglacial (23-12 cal kyr BP) continental conditions over eastern Brazil based on Ti/Ca of our marine sediment core as a proxy for Doce River (draining eastern Brazil) terrigenous input. Most of the rainfall in the Doce River Basin is related to the activity of the SASM. Our Ti/Ca record together with a speleothem  18 O composite from Lapa Sem Fim Cave, also in eastern Brazil, suggests a major decrease in precipitation during the Bølling-Allerød interstadial, likely related to a weakening of the SASM. We further compared our Ti/Ca results with the output of the SYNTRACE run of the CCSM3 fully-coupled climate model with transient forcing for the last deglaciation. Geochemical records and model output show consistent results and suggest that eastern South America experienced the driest period of the whole last deglaciation during the Bølling-Allerød and that this dry spell was likely related to decreased SAMS intensity.Keywords: paleoclimatology, paleoceanography, Quaternary, geochemistry, foraminifera, AMOC, millennial events, precipitation.iii ResumoPara dar suporte ao atual debate so...

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Section: Introduction / Introduçãomentioning

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Climatic evolution of eastern South America during the last deglaciation: a paleoceanographic approach

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Investigating the Direct Meltwater Effect in Terrestrial Oxygen‐Isotope Paleoclimate Records Using an Isotope‐Enabled Earth System Model

Zhu

Liu

Brady

et al. 2017

Geophysical Research Letters

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Variations in terrestrial oxygen-isotope reconstructions from ice cores and speleothems have been primarily attributed to climatic changes of surface air temperature, precipitation amount, or atmospheric circulation. Here we demonstrate with the fully coupled isotope-enabled Community Earth System Model an additional process contributing to the oxygen-isotope variations during glacial meltwater events. This process, termed "the direct meltwater effect," involves propagating large amounts of isotopically depleted meltwater throughout the hydrological cycle and is independent of climatic changes. We find that the direct meltwater effect can make up 15-35% of the δ 18 O signals in precipitation over Greenland and eastern Brazil for large freshwater forcings (0.25-0.50 sverdrup (10 6 m 3 /s)). Model simulations further demonstrate that the direct meltwater effect increases with the magnitude and duration of the freshwater forcing and is sensitive to both the location and shape of the meltwater. These new modeling results have important implications for past climate interpretations of δ 18 O.

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Persistent link between Caribbean precipitation and Atlantic Ocean circulation during the Last Glacial revealed by a speleothem record from Puerto Rico

Warken

Vieten

Winter

et al. 2020

Preprint

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The sensitivity of tropical Atlantic precipitation patterns to the mean position of the Intertropical Convergence Zone (ITCZ) at different time scales is well-known. However, recent research suggests a more complex behavior of the northern hemispheric tropical rain belt related to the ITCZ in the western tropical Atlantic. Here we present a precisely dated speleothem multi-proxy record from a well-monitored cave in Puerto Rico, covering the period between 46.2 and 15.3 ka. The stable isotope and trace element records document a pronounced response of regional rainfall to abrupt climatic excursions in the North Atlantic across the Last Glacial such as Heinrich stadials and Dansgaard/Oeschger events. The annual to multidecadal resolution of the proxy time series allows substructural investigations of the recorded events. Spectral analysis suggests that multidecadal to centennial variability persisted in the regional hydroclimate mainly during interstadial conditions but also during the Last Glacial Maximum. In particular, we observe a strong agreement between the speleothem proxy data and the strength of the Atlantic meridional overturning circulation, supporting a persistent link of oceanic forcing to regional precipitation. Comparison to other paleo-precipitation records enables the reconstruction of past changes in position, strength, and extent of the ITCZ in the western tropical Atlantic in response to millennial-and orbital-scale global climate change.Plain Language Summary It is important to understand the climatic circumstances of how rainfall in the western tropical Atlantic varies under a changing climate to better manage the water supply for millions of people. However, it is not well understood how rainfall varied in the past, especially during the Last Glacial period, a time of strong climate variability and abrupt climate changes. Here, we use a stalagmite from Puerto Rico to create a new record of past changes in rainfall in this region. For this purpose, we analyzed proxy data that reveal a series of wet and dry periods during the Last Glacial corresponding to rapid global climate shifts. Our rainfall-sensitive stalagmite record captured changes of the tropical rain belt on various timescales and shows that this variability in rainfall is closely connected to changes in the strength of the ocean circulation. This suggests that the link between the ocean and the atmosphere is more robust than previously assumed. The comparison of our record with other rainfall-sensitive records from Central America and the northern Caribbean allows for a detailed reconstruction of the spatial and temporal changes of the western tropical Atlantic rain belt.

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Timing and structure of Mega‐SACZ events during Heinrich Stadial 1

Cited by 125 publications

References 51 publications

Climatic evolution of eastern South America during the last deglaciation: a paleoceanographic approach

Climatic evolution of eastern South America during the last deglaciation: a paleoceanographic approach

Investigating the Direct Meltwater Effect in Terrestrial Oxygen‐Isotope Paleoclimate Records Using an Isotope‐Enabled Earth System Model

Persistent link between Caribbean precipitation and Atlantic Ocean circulation during the Last Glacial revealed by a speleothem record from Puerto Rico

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