Reconstruction of east–west deep water exchange in the low latitude Atlantic Ocean over the past 25,000 years
Radiogenic neodymium isotopes have been used as a water mass mixing proxy to investigate past changes in ocean circulation. Here we present a new depth transect of deglacial neodymium isotope records measured on uncleaned planktic foraminifera from five cores spanning from 3300 to 4900 m on the Maur...
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ftunivcam:oai:www.repository.cam.ac.uk:1810/261844 2024-02-04T10:02:15+01:00 Reconstruction of east–west deep water exchange in the low latitude Atlantic Ocean over the past 25,000 years Howe, JNW Piotrowski, AM Hu, R Bory, A 2017-01-15 application/pdf https://www.repository.cam.ac.uk/handle/1810/261844 https://doi.org/10.17863/CAM.7064 eng eng Elsevier http://dx.doi.org/10.1016/j.epsl.2016.10.048 Earth and Planetary Science Letters https://www.repository.cam.ac.uk/handle/1810/261844 doi:10.17863/CAM.7064 Attribution 4.0 International http://creativecommons.org/licenses/by/4.0/ neodymium isotopes Last Glacial Maximum eastern Atlantic western Atlantic Article 2017 ftunivcam https://doi.org/10.17863/CAM.7064 2024-01-11T23:27:38Z Radiogenic neodymium isotopes have been used as a water mass mixing proxy to investigate past changes in ocean circulation. Here we present a new depth transect of deglacial neodymium isotope records measured on uncleaned planktic foraminifera from five cores spanning from 3300 to 4900 m on the Mauritanian margin, in the tropical eastern Atlantic as well as an additional record from 4000 m on the Ceara Rise in the equatorial western Atlantic. Despite being located under the Saharan dust plume, the eastern Atlantic records differ from the composition of detrital inputs through time and exhibit similar values to the western Atlantic foraminiferal Nd across the deglaciation. Therefore we interpret the foraminiferal values as recording deep water Nd isotope changes. All six cores shift to less radiogenic values across the deglaciation, indicating that they were bathed by a lower proportion of North Atlantic Deep Water during the Last Glacial Maximum (LGM) relative to the Holocene. The eastern Atlantic records also show that a neodymium isotope gradient was present during the LGM and during the deglaciation, with more radiogenic values observed at the deepest sites. A homogeneous water mass observed below 3750 m in the deepest eastern Atlantic during the LGM is attributed to the mixing of deep water by rough topography as it passes from the western Atlantic through the fracture zones in the Mid-Atlantic Ridge. This implies that during the LGM the low latitude deep eastern Atlantic was ventilated from the western Atlantic via advection through fracture zones in the same manner as occurs in the modern ocean. Comparison with carbon isotopes indicates there was more respired carbon in the deep eastern than deep western Atlantic during the LGM, as is also seen in the modern Atlantic Ocean. Radiocarbon analyses were supported by NERC radiocarbon grant 1752.1013 and Nd isotope analyses by NERC grants NERC NE/K005235/1 and NERC NE/F006047/1 to AMP. JNWH was supported by a Rutherford Memorial Scholarship. Article in Journal/Newspaper North Atlantic Deep Water North Atlantic Apollo - University of Cambridge Repository Mid-Atlantic Ridge |
institution |
Open Polar |
collection |
Apollo - University of Cambridge Repository |
op_collection_id |
ftunivcam |
language |
English |
topic |
neodymium isotopes Last Glacial Maximum eastern Atlantic western Atlantic |
spellingShingle |
neodymium isotopes Last Glacial Maximum eastern Atlantic western Atlantic Howe, JNW Piotrowski, AM Hu, R Bory, A Reconstruction of east–west deep water exchange in the low latitude Atlantic Ocean over the past 25,000 years |
topic_facet |
neodymium isotopes Last Glacial Maximum eastern Atlantic western Atlantic |
description |
Radiogenic neodymium isotopes have been used as a water mass mixing proxy to investigate past changes in ocean circulation. Here we present a new depth transect of deglacial neodymium isotope records measured on uncleaned planktic foraminifera from five cores spanning from 3300 to 4900 m on the Mauritanian margin, in the tropical eastern Atlantic as well as an additional record from 4000 m on the Ceara Rise in the equatorial western Atlantic. Despite being located under the Saharan dust plume, the eastern Atlantic records differ from the composition of detrital inputs through time and exhibit similar values to the western Atlantic foraminiferal Nd across the deglaciation. Therefore we interpret the foraminiferal values as recording deep water Nd isotope changes. All six cores shift to less radiogenic values across the deglaciation, indicating that they were bathed by a lower proportion of North Atlantic Deep Water during the Last Glacial Maximum (LGM) relative to the Holocene. The eastern Atlantic records also show that a neodymium isotope gradient was present during the LGM and during the deglaciation, with more radiogenic values observed at the deepest sites. A homogeneous water mass observed below 3750 m in the deepest eastern Atlantic during the LGM is attributed to the mixing of deep water by rough topography as it passes from the western Atlantic through the fracture zones in the Mid-Atlantic Ridge. This implies that during the LGM the low latitude deep eastern Atlantic was ventilated from the western Atlantic via advection through fracture zones in the same manner as occurs in the modern ocean. Comparison with carbon isotopes indicates there was more respired carbon in the deep eastern than deep western Atlantic during the LGM, as is also seen in the modern Atlantic Ocean. Radiocarbon analyses were supported by NERC radiocarbon grant 1752.1013 and Nd isotope analyses by NERC grants NERC NE/K005235/1 and NERC NE/F006047/1 to AMP. JNWH was supported by a Rutherford Memorial Scholarship. |
format |
Article in Journal/Newspaper |
author |
Howe, JNW Piotrowski, AM Hu, R Bory, A |
author_facet |
Howe, JNW Piotrowski, AM Hu, R Bory, A |
author_sort |
Howe, JNW |
title |
Reconstruction of east–west deep water exchange in the low latitude Atlantic Ocean over the past 25,000 years |
title_short |
Reconstruction of east–west deep water exchange in the low latitude Atlantic Ocean over the past 25,000 years |
title_full |
Reconstruction of east–west deep water exchange in the low latitude Atlantic Ocean over the past 25,000 years |
title_fullStr |
Reconstruction of east–west deep water exchange in the low latitude Atlantic Ocean over the past 25,000 years |
title_full_unstemmed |
Reconstruction of east–west deep water exchange in the low latitude Atlantic Ocean over the past 25,000 years |
title_sort |
reconstruction of east–west deep water exchange in the low latitude atlantic ocean over the past 25,000 years |
publisher |
Elsevier |
publishDate |
2017 |
url |
https://www.repository.cam.ac.uk/handle/1810/261844 https://doi.org/10.17863/CAM.7064 |
geographic |
Mid-Atlantic Ridge |
geographic_facet |
Mid-Atlantic Ridge |
genre |
North Atlantic Deep Water North Atlantic |
genre_facet |
North Atlantic Deep Water North Atlantic |
op_relation |
https://www.repository.cam.ac.uk/handle/1810/261844 doi:10.17863/CAM.7064 |
op_rights |
Attribution 4.0 International http://creativecommons.org/licenses/by/4.0/ |
op_doi |
https://doi.org/10.17863/CAM.7064 |
_version_ |
1789968719672246272 |