A boundary exchange influence on deglacial neodymium isotope records from the deep western Indian Ocean
The use of neodymium (Nd) isotopes to reconstruct past water mass mixing relies upon the quasi-conservative behaviour of this tracer, whereas recent studies in the modern oceans have suggested that boundary exchange, involving the addition of Nd from ocean margin sediments, may be an important proce...
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ftucl:oai:eprints.ucl.ac.uk.OAI2:10059420 2023-12-24T10:25:06+01:00 A boundary exchange influence on deglacial neodymium isotope records from the deep western Indian Ocean Wilson, DJ Piotrowski, AM Galy, A McCave, IN 2012-08 text https://discovery.ucl.ac.uk/id/eprint/10059420/1/Wilson%20et%20al%202012%20EPSL%20accepted.pdf https://discovery.ucl.ac.uk/id/eprint/10059420/ eng eng ELSEVIER SCIENCE BV https://discovery.ucl.ac.uk/id/eprint/10059420/1/Wilson%20et%20al%202012%20EPSL%20accepted.pdf https://discovery.ucl.ac.uk/id/eprint/10059420/ open Earth and Planetary Science Letters , 341-4 pp. 35-47. (2012) Indian Ocean Circumpolar Deep Water neodymium isotopes ocean circulation boundary exchange deglaciation Article 2012 ftucl 2023-11-27T13:07:39Z The use of neodymium (Nd) isotopes to reconstruct past water mass mixing relies upon the quasi-conservative behaviour of this tracer, whereas recent studies in the modern oceans have suggested that boundary exchange, involving the addition of Nd from ocean margin sediments, may be an important process in the Nd cycle. Here we suggest that the relative importance of water mass advection versus boundary exchange can be assessed where the deep western boundary current in the Indian Ocean flows past the Madagascan continental margin; a potential source of highly unradiogenic Nd. Foraminiferal coatings and bulk sediment reductive leachates are used to reconstruct bottom water Nd isotopic composition (εNd) in 8 Holocene age coretops, with excellent agreement between the two methods. These data record spatial variability of ∼4 εNd units along the flow path of Circumpolar Deep Water; εNd≈−8.8 in the deep southern inflow upstream of Madagascar, which evolves towards εNd≈−11.5 offshore northern Madagascar, whereas εNd≈−7.3 where deep water re-circulates in the eastern Mascarene Basin. This variability is attributed to boundary exchange and, together with measurements of detrital sediment εNd, an isotope mass balance suggests a deep water residence time for Nd of ≤400 yr along the Madagascan margin. Considering deglacial changes, a core in the deep inflow upstream of Madagascar records εNd changes that agree with previous reconstructions of the Circumpolar Deep Water composition in the Southern Ocean, consistent with a control by water mass advection and perhaps indicating a longer residence time for Nd in the open ocean away from local sediment inputs. In contrast, sites along the Madagascan margin record offset εNd values and reduced glacial–interglacial variability, underlining the importance of detecting boundary exchange before inferring water mass source changes from Nd isotope records. The extent of Madagascan boundary exchange appears to be unchanged between the Holocene and Late Glacial periods, while a consistent ... Article in Journal/Newspaper Southern Ocean University College London: UCL Discovery Southern Ocean Indian |
institution |
Open Polar |
collection |
University College London: UCL Discovery |
op_collection_id |
ftucl |
language |
English |
topic |
Indian Ocean Circumpolar Deep Water neodymium isotopes ocean circulation boundary exchange deglaciation |
spellingShingle |
Indian Ocean Circumpolar Deep Water neodymium isotopes ocean circulation boundary exchange deglaciation Wilson, DJ Piotrowski, AM Galy, A McCave, IN A boundary exchange influence on deglacial neodymium isotope records from the deep western Indian Ocean |
topic_facet |
Indian Ocean Circumpolar Deep Water neodymium isotopes ocean circulation boundary exchange deglaciation |
description |
The use of neodymium (Nd) isotopes to reconstruct past water mass mixing relies upon the quasi-conservative behaviour of this tracer, whereas recent studies in the modern oceans have suggested that boundary exchange, involving the addition of Nd from ocean margin sediments, may be an important process in the Nd cycle. Here we suggest that the relative importance of water mass advection versus boundary exchange can be assessed where the deep western boundary current in the Indian Ocean flows past the Madagascan continental margin; a potential source of highly unradiogenic Nd. Foraminiferal coatings and bulk sediment reductive leachates are used to reconstruct bottom water Nd isotopic composition (εNd) in 8 Holocene age coretops, with excellent agreement between the two methods. These data record spatial variability of ∼4 εNd units along the flow path of Circumpolar Deep Water; εNd≈−8.8 in the deep southern inflow upstream of Madagascar, which evolves towards εNd≈−11.5 offshore northern Madagascar, whereas εNd≈−7.3 where deep water re-circulates in the eastern Mascarene Basin. This variability is attributed to boundary exchange and, together with measurements of detrital sediment εNd, an isotope mass balance suggests a deep water residence time for Nd of ≤400 yr along the Madagascan margin. Considering deglacial changes, a core in the deep inflow upstream of Madagascar records εNd changes that agree with previous reconstructions of the Circumpolar Deep Water composition in the Southern Ocean, consistent with a control by water mass advection and perhaps indicating a longer residence time for Nd in the open ocean away from local sediment inputs. In contrast, sites along the Madagascan margin record offset εNd values and reduced glacial–interglacial variability, underlining the importance of detecting boundary exchange before inferring water mass source changes from Nd isotope records. The extent of Madagascan boundary exchange appears to be unchanged between the Holocene and Late Glacial periods, while a consistent ... |
format |
Article in Journal/Newspaper |
author |
Wilson, DJ Piotrowski, AM Galy, A McCave, IN |
author_facet |
Wilson, DJ Piotrowski, AM Galy, A McCave, IN |
author_sort |
Wilson, DJ |
title |
A boundary exchange influence on deglacial neodymium isotope records from the deep western Indian Ocean |
title_short |
A boundary exchange influence on deglacial neodymium isotope records from the deep western Indian Ocean |
title_full |
A boundary exchange influence on deglacial neodymium isotope records from the deep western Indian Ocean |
title_fullStr |
A boundary exchange influence on deglacial neodymium isotope records from the deep western Indian Ocean |
title_full_unstemmed |
A boundary exchange influence on deglacial neodymium isotope records from the deep western Indian Ocean |
title_sort |
boundary exchange influence on deglacial neodymium isotope records from the deep western indian ocean |
publisher |
ELSEVIER SCIENCE BV |
publishDate |
2012 |
url |
https://discovery.ucl.ac.uk/id/eprint/10059420/1/Wilson%20et%20al%202012%20EPSL%20accepted.pdf https://discovery.ucl.ac.uk/id/eprint/10059420/ |
geographic |
Southern Ocean Indian |
geographic_facet |
Southern Ocean Indian |
genre |
Southern Ocean |
genre_facet |
Southern Ocean |
op_source |
Earth and Planetary Science Letters , 341-4 pp. 35-47. (2012) |
op_relation |
https://discovery.ucl.ac.uk/id/eprint/10059420/1/Wilson%20et%20al%202012%20EPSL%20accepted.pdf https://discovery.ucl.ac.uk/id/eprint/10059420/ |
op_rights |
open |
_version_ |
1786200513392410624 |