Eastern Atlantic deep-water circulation inferred from neodymium and carbon isotopic compositions over the past 1200 thousand years
International audience Mid-Pleistocene transition (MPT; 1200 to 800 thousand years, ky) is marked by an intensification and a shift of glacial-interglacial cycle from 41 ky to 100 ky that is not directly supported by solar insolation. These changes can be explained by combined effects of the stabili...
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ftccsdartic:oai:HAL:hal-03547530v1 2023-12-17T10:22:20+01:00 Eastern Atlantic deep-water circulation inferred from neodymium and carbon isotopic compositions over the past 1200 thousand years Kazuyo, Tachikawa Rapuc, William Vidal, Laurence Dubois-Dauphin, Quentin Guihou, Abel Westerhold, Thomas Bickert, Torsten Skonieczny, Charlotte Centre européen de recherche et d'enseignement des géosciences de l'environnement (CEREGE) Institut de Recherche pour le Développement (IRD)-Aix Marseille Université (AMU)-Collège de France (CdF (institution))-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE) Vienna, Austria 2018 https://hal.science/hal-03547530 en eng HAL CCSD hal-03547530 https://hal.science/hal-03547530 EGU2018 https://hal.science/hal-03547530 EGU2018, 2018, Vienna, Austria [SDU.STU]Sciences of the Universe [physics]/Earth Sciences info:eu-repo/semantics/conferenceObject Conference papers 2018 ftccsdartic 2023-11-19T00:16:56Z International audience Mid-Pleistocene transition (MPT; 1200 to 800 thousand years, ky) is marked by an intensification and a shift of glacial-interglacial cycle from 41 ky to 100 ky that is not directly supported by solar insolation. These changes can be explained by combined effects of the stabilization of ice sheets associated with regolith removal withatmospheric CO2 reduction caused by active biological pumping in the Southern Ocean. Significant changes in ocean circulation was also suggested.To improve the spatiotemporal coverage of past ocean circulation records, we analysed Nd isotopic ratios recorded in foraminiferal authigenic fractions and epibenthic foraminiferal stable isotopes on two cores: MD03-2705 (18◦06’N, 21◦09’W, 3085 m) in the eastern tropical Atlantic where the reconstruction based on Nd isotopes is absent for this timescale and ODP1085 (29◦22’S, 13◦59’E, 1713 m) that is located at the present boundary between a northern source water (NSW, North Atlantic Deep Water) and a southern source water (SSW, Antarctic Bottom Water).Sequential cleaning and SEM observation of foraminiferal tests of MD03-2705 indicate that Nd isotopic ratios of authigenic phases reflect seawater values despite the fact that the core is located under Saharan dust plume. Reconstructed seawater Nd values of MD03-2705 ranges between -12.7 and -10.3 with more radiogenic values during glacial periods, suggesting an increase in SSW proportion. The glacial-interglacial eNd amplitude is smaller for the MPT than for the post-MPT. Epibenthic d13C values of ODP1085 varies from -0.6 to 0.9h with a clear positive shift at MIS 13 that is not observed for core MD03-2705. These results suggest the reorganisation of Atlantic meridional overturning circulation since the MPT. The analysis of eNd for core ODP1085 is in progress.We will discuss variability in relative proportion between SSW and NSW in relation to carbon cycle by combining reconstructed seawater eNd and d13C values from the two cores with available records Conference Object Antarc* Antarctic North Atlantic Deep Water North Atlantic Southern Ocean Archive ouverte HAL (Hyper Article en Ligne, CCSD - Centre pour la Communication Scientifique Directe) Antarctic Southern Ocean |
institution |
Open Polar |
collection |
Archive ouverte HAL (Hyper Article en Ligne, CCSD - Centre pour la Communication Scientifique Directe) |
op_collection_id |
ftccsdartic |
language |
English |
topic |
[SDU.STU]Sciences of the Universe [physics]/Earth Sciences |
spellingShingle |
[SDU.STU]Sciences of the Universe [physics]/Earth Sciences Kazuyo, Tachikawa Rapuc, William Vidal, Laurence Dubois-Dauphin, Quentin Guihou, Abel Westerhold, Thomas Bickert, Torsten Skonieczny, Charlotte Eastern Atlantic deep-water circulation inferred from neodymium and carbon isotopic compositions over the past 1200 thousand years |
topic_facet |
[SDU.STU]Sciences of the Universe [physics]/Earth Sciences |
description |
International audience Mid-Pleistocene transition (MPT; 1200 to 800 thousand years, ky) is marked by an intensification and a shift of glacial-interglacial cycle from 41 ky to 100 ky that is not directly supported by solar insolation. These changes can be explained by combined effects of the stabilization of ice sheets associated with regolith removal withatmospheric CO2 reduction caused by active biological pumping in the Southern Ocean. Significant changes in ocean circulation was also suggested.To improve the spatiotemporal coverage of past ocean circulation records, we analysed Nd isotopic ratios recorded in foraminiferal authigenic fractions and epibenthic foraminiferal stable isotopes on two cores: MD03-2705 (18◦06’N, 21◦09’W, 3085 m) in the eastern tropical Atlantic where the reconstruction based on Nd isotopes is absent for this timescale and ODP1085 (29◦22’S, 13◦59’E, 1713 m) that is located at the present boundary between a northern source water (NSW, North Atlantic Deep Water) and a southern source water (SSW, Antarctic Bottom Water).Sequential cleaning and SEM observation of foraminiferal tests of MD03-2705 indicate that Nd isotopic ratios of authigenic phases reflect seawater values despite the fact that the core is located under Saharan dust plume. Reconstructed seawater Nd values of MD03-2705 ranges between -12.7 and -10.3 with more radiogenic values during glacial periods, suggesting an increase in SSW proportion. The glacial-interglacial eNd amplitude is smaller for the MPT than for the post-MPT. Epibenthic d13C values of ODP1085 varies from -0.6 to 0.9h with a clear positive shift at MIS 13 that is not observed for core MD03-2705. These results suggest the reorganisation of Atlantic meridional overturning circulation since the MPT. The analysis of eNd for core ODP1085 is in progress.We will discuss variability in relative proportion between SSW and NSW in relation to carbon cycle by combining reconstructed seawater eNd and d13C values from the two cores with available records |
author2 |
Centre européen de recherche et d'enseignement des géosciences de l'environnement (CEREGE) Institut de Recherche pour le Développement (IRD)-Aix Marseille Université (AMU)-Collège de France (CdF (institution))-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE) |
format |
Conference Object |
author |
Kazuyo, Tachikawa Rapuc, William Vidal, Laurence Dubois-Dauphin, Quentin Guihou, Abel Westerhold, Thomas Bickert, Torsten Skonieczny, Charlotte |
author_facet |
Kazuyo, Tachikawa Rapuc, William Vidal, Laurence Dubois-Dauphin, Quentin Guihou, Abel Westerhold, Thomas Bickert, Torsten Skonieczny, Charlotte |
author_sort |
Kazuyo, Tachikawa |
title |
Eastern Atlantic deep-water circulation inferred from neodymium and carbon isotopic compositions over the past 1200 thousand years |
title_short |
Eastern Atlantic deep-water circulation inferred from neodymium and carbon isotopic compositions over the past 1200 thousand years |
title_full |
Eastern Atlantic deep-water circulation inferred from neodymium and carbon isotopic compositions over the past 1200 thousand years |
title_fullStr |
Eastern Atlantic deep-water circulation inferred from neodymium and carbon isotopic compositions over the past 1200 thousand years |
title_full_unstemmed |
Eastern Atlantic deep-water circulation inferred from neodymium and carbon isotopic compositions over the past 1200 thousand years |
title_sort |
eastern atlantic deep-water circulation inferred from neodymium and carbon isotopic compositions over the past 1200 thousand years |
publisher |
HAL CCSD |
publishDate |
2018 |
url |
https://hal.science/hal-03547530 |
op_coverage |
Vienna, Austria |
geographic |
Antarctic Southern Ocean |
geographic_facet |
Antarctic Southern Ocean |
genre |
Antarc* Antarctic North Atlantic Deep Water North Atlantic Southern Ocean |
genre_facet |
Antarc* Antarctic North Atlantic Deep Water North Atlantic Southern Ocean |
op_source |
EGU2018 https://hal.science/hal-03547530 EGU2018, 2018, Vienna, Austria |
op_relation |
hal-03547530 https://hal.science/hal-03547530 |
_version_ |
1785546689579319296 |