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Climate of the Past An interactive open-access journal of the European Geosciences Union
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https://doi.org/10.5194/cp-2020-4
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/cp-2020-4
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Submitted as: research article 06 Feb 2020

Submitted as: research article | 06 Feb 2020

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This preprint is currently under review for the journal CP.

Contrasting late-glacial paleoceanographic evolution between the upper and lower continental slope of the western South Atlantic

Leticia G. Luz1, Thiago P. Santos2, Timothy I. Eglinton3, Daniel Montluçon3, Blanca Ausin3, Negar Haghipour3, Silvia M. Sousa4, Renata Nagai5, and Renato S. Carreira1 Leticia G. Luz et al.
  • 1LabMAM/Departamento de Química, Pontifícia Universidade Católica do Rio de Janeiro (PUC-Rio), Rio de Janeiro, Brasil
  • 2Programa de Geociências (Geoquímica), Universidade Federal Fluminense, Niterói, Brazil
  • 3Department of Earth Science, Geological Institute, ETH Zürich, Zürich, Switzerland
  • 4Instituto de Oceanografia, Universidade de São Paulo, São Paulo, Brasil
  • 5Centro de Estudos do Mar, Universidade Federal do Paraná (UFPR), Paraná, Brasil

Abstract. The number of sedimentary records collected along the Brazilian margin has grown significantly in recent years. However, few are useful in elucidating the paleoclimatic evolution of relatively shallow waters (< 1,000 m in depth) influenced by continental shelf areas. In this study, we present traditional and new organic and inorganic proxies (alkenones-derived SST, δD-alkenones, δ18O of planktic foraminifera and ice-volume free seawater δ18OIVF-SW) to assess changes in sea surface temperature (SST) and the salinity of two sediment cores (RJ-1501 and RJ-1502) sampled from the subtropical western South Atlantic during the end of the last glacial cycle. Although they are separated by only 40 km, these records present a contradictory climatic evolution through the study period, with the shallower (deeper) core RJ-1501 (RJ-1502) displaying consistently cold (warm) and fresh (salt) conditions toward the Last Glacial Maximum and last deglaciation. We reconciled these results considering that the RJ-1501 site was under the influence of cold and fresh waters transported northward by the Brazilian Coastal Current (BCC), which carried a signal from mid- to high-latitudes temperature and freshwater discharged by the La Plata River to the study area. Comparing the RJ-1502 results with other deeper cores collected from this area support this interpretation. Our data indicate that a steep thermal and density gradient was formed between the BCC and Brazil Current (BC) during the last climate transition, which may have generated perturbations in the air-sea heat flux, with consequences for the regional SE South America climate. In a scenario of future weakening of the Atlantic Meridional Overturning Circulation, the reconstructed gradient may become a prominent feature in the region.

Leticia G. Luz et al.

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Leticia G. Luz et al.

Leticia G. Luz et al.

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Latest update: 03 Apr 2020
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Short summary
Two sediment cores retrieved from the SE Brazilian continental margin were studied using multiple organic (e.g., alkenones) and inorganic (oxygen isotopes in carbonate shells and water) proxies to reconstruct the sea surface temperature (SST) over the last 50,000 years. The findings indicate the formation of strong thermal gradients in the region during the last climate transition, a feature that may become more frequent in the future scenario of global water circulation system changes.
Two sediment cores retrieved from the SE Brazilian continental margin were studied using...
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