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The flux and provenance of dust delivered to the SW Pacific during the Last Glacial Maximum

The flux and provenance of dust delivered to the SW Pacific during the Last Glacial Maximum
The flux and provenance of dust delivered to the SW Pacific during the Last Glacial Maximum

Atmospheric dust is a primary source of iron (Fe) to the open ocean, and its flux is particularly important in the high nutrient, low chlorophyll (HNLC) Southern Ocean where Fe currently limits productivity. Alleviation of this Fe limitation in the Subantarctic Zone of the Atlantic by increased dust-borne Fe supply during glacial periods has been shown to increase primary productivity. However, previous work has found no such increase in productivity in the Pacific sector. In order to constrain the relative importance of Southern Ocean Fe fertilization on glacial-interglacial carbon cycles, records of dust fluxes outside of the Atlantic sector of the Southern Ocean at the Last Glacial Maximum (LGM) are required. Here we use grain size and U-series analyses to reconstruct lithogenic and CaCO 3 fluxes and Nd, Sr, and Pb isotopes to ascertain the provenance of terrigenous material delivered to four deep water cores in the SW Pacific Ocean over the last ~30 kyr. We find evidence for an increase in the relative proportion of fine-grained (0.5–12 μm) terrigenous sediment and higher detrital fluxes during the LGM compared to the Holocene. The provenance of the LGM dust varied spatially, with an older, more “continental” signature (low ε Nd, high 87Sr/ 86Sr) sourced from Australia in the northern cores, and a younger, more volcanogenic source in the southern cores (high ε Nd, low 87Sr/ 86Sr), likely sourced locally from New Zealand. Given this increase in lithogenic flux to the HNLC subantarctic Pacific Southern Ocean during the LGM, factors besides Fe supply must have regulated the biological productivity here.

Last Glacial Maximum, Nd, Sr, Pb isotopes, SW Pacific, Subantarctic Zone, Th fluxes, dust provenance
2572-4517
Trudgill, M. D.
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Shuttleworth, R.
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Bostock, H. C.
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Burke, A.
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Cooper, M. J.
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Greenop, R.
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Foster, G. L.
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Trudgill, M. D.
e02e0439-03d4-4eda-985a-225721d4611a
Shuttleworth, R.
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Bostock, H. C.
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Burke, A.
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Cooper, M. J.
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Greenop, R.
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Foster, G. L.
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Trudgill, M. D., Shuttleworth, R., Bostock, H. C., Burke, A., Cooper, M. J., Greenop, R. and Foster, G. L. (2020) The flux and provenance of dust delivered to the SW Pacific during the Last Glacial Maximum. Paleoceanography and Paleoclimatology, 35 (12), [e2020PA003869]. (doi:10.1029/2020PA003869).

Record type: Article

Abstract

Atmospheric dust is a primary source of iron (Fe) to the open ocean, and its flux is particularly important in the high nutrient, low chlorophyll (HNLC) Southern Ocean where Fe currently limits productivity. Alleviation of this Fe limitation in the Subantarctic Zone of the Atlantic by increased dust-borne Fe supply during glacial periods has been shown to increase primary productivity. However, previous work has found no such increase in productivity in the Pacific sector. In order to constrain the relative importance of Southern Ocean Fe fertilization on glacial-interglacial carbon cycles, records of dust fluxes outside of the Atlantic sector of the Southern Ocean at the Last Glacial Maximum (LGM) are required. Here we use grain size and U-series analyses to reconstruct lithogenic and CaCO 3 fluxes and Nd, Sr, and Pb isotopes to ascertain the provenance of terrigenous material delivered to four deep water cores in the SW Pacific Ocean over the last ~30 kyr. We find evidence for an increase in the relative proportion of fine-grained (0.5–12 μm) terrigenous sediment and higher detrital fluxes during the LGM compared to the Holocene. The provenance of the LGM dust varied spatially, with an older, more “continental” signature (low ε Nd, high 87Sr/ 86Sr) sourced from Australia in the northern cores, and a younger, more volcanogenic source in the southern cores (high ε Nd, low 87Sr/ 86Sr), likely sourced locally from New Zealand. Given this increase in lithogenic flux to the HNLC subantarctic Pacific Southern Ocean during the LGM, factors besides Fe supply must have regulated the biological productivity here.

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Accepted/In Press date: 16 November 2020
e-pub ahead of print date: 23 November 2020
Published date: 1 December 2020
Keywords: Last Glacial Maximum, Nd, Sr, Pb isotopes, SW Pacific, Subantarctic Zone, Th fluxes, dust provenance

Identifiers

Local EPrints ID: 445728
URI: http://eprints.soton.ac.uk/id/eprint/445728
ISSN: 2572-4517
PURE UUID: b71fa431-a197-47d0-880d-7833d2c1c419
ORCID for M. J. Cooper: ORCID iD orcid.org/0000-0002-2130-2759
ORCID for G. L. Foster: ORCID iD orcid.org/0000-0003-3688-9668

Catalogue record

Date deposited: 06 Jan 2021 17:43
Last modified: 26 Nov 2021 06:17

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Contributors

Author: M. D. Trudgill
Author: R. Shuttleworth
Author: H. C. Bostock
Author: A. Burke
Author: M. J. Cooper ORCID iD
Author: R. Greenop
Author: G. L. Foster ORCID iD

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