Contrasting late-glacial paleoceanographic evolution between the upper and lower continental slope of the western South Atlantic
<p>The number of sedimentary records collected along the Brazilian continental margin has increased significantly in recent years, but relatively few are located in shallow waters and register paleoceanographic processes in the outer shelf–middle slope prior to 10–15 ka. For instanc...
| Main Authors: | , , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2020-07-01
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| Series: | Climate of the Past |
| Online Access: | https://cp.copernicus.org/articles/16/1245/2020/cp-16-1245-2020.pdf |
| _version_ | 1819025765564416000 |
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| author | L. G. Luz T. P. Santos T. I. Eglinton D. Montluçon B. Ausin B. Ausin N. Haghipour S. M. Sousa R. H. Nagai R. S. Carreira |
| author_facet | L. G. Luz T. P. Santos T. I. Eglinton D. Montluçon B. Ausin B. Ausin N. Haghipour S. M. Sousa R. H. Nagai R. S. Carreira |
| author_sort | L. G. Luz |
| collection | DOAJ |
| description | <p>The number of sedimentary records collected along the
Brazilian continental margin has increased significantly in recent years,
but relatively few are located in shallow waters and register
paleoceanographic processes in the outer shelf–middle slope prior to 10–15 ka. For instance, the northward flow up to 23–24<span class="inline-formula"><sup>∘</sup></span> S of
cold and fresh shelf waters sourced from the Subantarctic region is an
important feature of current hydrodynamics in the subtropical western South
Atlantic Ocean, and yet limited information is available for the long-term
changes of this system. Herein, we considered a suite of organic and
inorganic proxies – alkenones-derived sea surface temperature (SST),
<span class="inline-formula"><i>δ</i>D</span>-alkenones, <span class="inline-formula"><i>δ</i><sup>18</sup>O</span> of planktonic foraminifera, and
ice-volume free seawater <span class="inline-formula"><i>δ</i><sup>18</sup>O<sub>IVF−SW</sub></span> – in sediment from
two cores (RJ-1501 and RJ-1502) collected off the Rio de Janeiro Shelf (SE
Brazilian continental shelf) to shed light on SST patterns and relative
salinity variations since the end of the last glacial cycle in the region
and the implications of these processes over a broader spatial scale. The
data indicate that, despite the proximity (<span class="inline-formula">∼40</span> km apart) of
both cores, apparently contradictory climatic evolution occurred at the two
sites, with the shallower (deeper) core RJ-1501 (RJ-1502) showing
consistently cold (warm) and fresh (salt) conditions toward the Last Glacial Maximum (LGM) and last deglaciation. This can be reconciled by considering that the RJ-1501 core registered a signal from mid- to high latitudes on the upper slope off Rio de Janeiro represented by the influence of the cold and fresh waters composed of Subantarctic Shelf Water and La Plata Plume Water transported northward by the Brazilian Coastal Current (BCC). The data from core RJ-1502 and previous information for deep-cores from the same region
support this interpretation. In addition, alkenone-derived SST and <span class="inline-formula"><i>δ</i><sup>18</sup>O<sub>IVF−SW</sub></span> suggest a steep thermal and density gradient formed
between the BCC and Brazil Current (BC) during the last climate transition
which, in turn, may have generated perturbations in the air–sea heat flux
with consequences for the regional climate of SE South America. In a
scenario of future weakening of the Atlantic Meridional Overturning
Circulation, the reconstructed gradient may become a prominent feature of
the region.</p> |
| first_indexed | 2024-12-21T05:15:53Z |
| format | Article |
| id | doaj.art-9bc067fb3a044fbfba15cea82cb71ae1 |
| institution | Directory Open Access Journal |
| issn | 1814-9324 1814-9332 |
| language | English |
| last_indexed | 2024-12-21T05:15:53Z |
| publishDate | 2020-07-01 |
| publisher | Copernicus Publications |
| record_format | Article |
| series | Climate of the Past |
| spelling | doaj.art-9bc067fb3a044fbfba15cea82cb71ae12022-12-21T19:14:56ZengCopernicus PublicationsClimate of the Past1814-93241814-93322020-07-01161245126110.5194/cp-16-1245-2020Contrasting late-glacial paleoceanographic evolution between the upper and lower continental slope of the western South AtlanticL. G. Luz0T. P. Santos1T. I. Eglinton2D. Montluçon3B. Ausin4B. Ausin5N. Haghipour6S. M. Sousa7R. H. Nagai8R. S. Carreira9LabMAM, Departamento de Química, Pontifícia Universidade Católica do Rio de Janeiro (PUC-Rio), Rio de Janeiro, BrazilPrograma de Geociências (Geoquímica), Universidade Federal Fluminense, Niterói, BrazilDepartment of Earth Sciences, Geological Institute, ETH Zürich, Zürich, SwitzerlandDepartment of Earth Sciences, Geological Institute, ETH Zürich, Zürich, SwitzerlandDepartment of Earth Sciences, Geological Institute, ETH Zürich, Zürich, SwitzerlandDepartment of Geology, University of Salamanca, Salamanca, SpainDepartment of Earth Sciences, Geological Institute, ETH Zürich, Zürich, SwitzerlandInstituto de Oceanografia, Universidade de São Paulo, São Paulo, BrazilCentro de Estudos do Mar, Universidade Federal do Paraná (UFPR), Paraná, BrazilLabMAM, Departamento de Química, Pontifícia Universidade Católica do Rio de Janeiro (PUC-Rio), Rio de Janeiro, Brazil<p>The number of sedimentary records collected along the Brazilian continental margin has increased significantly in recent years, but relatively few are located in shallow waters and register paleoceanographic processes in the outer shelf–middle slope prior to 10–15 ka. For instance, the northward flow up to 23–24<span class="inline-formula"><sup>∘</sup></span> S of cold and fresh shelf waters sourced from the Subantarctic region is an important feature of current hydrodynamics in the subtropical western South Atlantic Ocean, and yet limited information is available for the long-term changes of this system. Herein, we considered a suite of organic and inorganic proxies – alkenones-derived sea surface temperature (SST), <span class="inline-formula"><i>δ</i>D</span>-alkenones, <span class="inline-formula"><i>δ</i><sup>18</sup>O</span> of planktonic foraminifera, and ice-volume free seawater <span class="inline-formula"><i>δ</i><sup>18</sup>O<sub>IVF−SW</sub></span> – in sediment from two cores (RJ-1501 and RJ-1502) collected off the Rio de Janeiro Shelf (SE Brazilian continental shelf) to shed light on SST patterns and relative salinity variations since the end of the last glacial cycle in the region and the implications of these processes over a broader spatial scale. The data indicate that, despite the proximity (<span class="inline-formula">∼40</span> km apart) of both cores, apparently contradictory climatic evolution occurred at the two sites, with the shallower (deeper) core RJ-1501 (RJ-1502) showing consistently cold (warm) and fresh (salt) conditions toward the Last Glacial Maximum (LGM) and last deglaciation. This can be reconciled by considering that the RJ-1501 core registered a signal from mid- to high latitudes on the upper slope off Rio de Janeiro represented by the influence of the cold and fresh waters composed of Subantarctic Shelf Water and La Plata Plume Water transported northward by the Brazilian Coastal Current (BCC). The data from core RJ-1502 and previous information for deep-cores from the same region support this interpretation. In addition, alkenone-derived SST and <span class="inline-formula"><i>δ</i><sup>18</sup>O<sub>IVF−SW</sub></span> suggest a steep thermal and density gradient formed between the BCC and Brazil Current (BC) during the last climate transition which, in turn, may have generated perturbations in the air–sea heat flux with consequences for the regional climate of SE South America. In a scenario of future weakening of the Atlantic Meridional Overturning Circulation, the reconstructed gradient may become a prominent feature of the region.</p>https://cp.copernicus.org/articles/16/1245/2020/cp-16-1245-2020.pdf |
| spellingShingle | L. G. Luz T. P. Santos T. I. Eglinton D. Montluçon B. Ausin B. Ausin N. Haghipour S. M. Sousa R. H. Nagai R. S. Carreira Contrasting late-glacial paleoceanographic evolution between the upper and lower continental slope of the western South Atlantic Climate of the Past |
| title | Contrasting late-glacial paleoceanographic evolution between the upper and lower continental slope of the western South Atlantic |
| title_full | Contrasting late-glacial paleoceanographic evolution between the upper and lower continental slope of the western South Atlantic |
| title_fullStr | Contrasting late-glacial paleoceanographic evolution between the upper and lower continental slope of the western South Atlantic |
| title_full_unstemmed | Contrasting late-glacial paleoceanographic evolution between the upper and lower continental slope of the western South Atlantic |
| title_short | Contrasting late-glacial paleoceanographic evolution between the upper and lower continental slope of the western South Atlantic |
| title_sort | contrasting late glacial paleoceanographic evolution between the upper and lower continental slope of the western south atlantic |
| url | https://cp.copernicus.org/articles/16/1245/2020/cp-16-1245-2020.pdf |
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