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Export production in the New-Zealand region since the Last Glacial Maximum

Citation

Durand, A and Chase, Z and Noble, TL and Bostock, H and Jaccard, SL and Kitchener, P and Townsend, AT and Jansen, N and Kinsley, L and Jacobsen, G and Johnson, S and Neil, H, Export production in the New-Zealand region since the Last Glacial Maximum, Earth and Planetary Science Letters, 469 pp. 110-122. ISSN 0012-821X (2017) [Refereed Article]

Copyright Statement

S-Romeo. Creative Commons post-print to be sourced for open access after an embargo

DOI: doi:10.1016/j.epsl.2017.03.035

Abstract

Increased export production (EP) in the Subantarctic Zone (SAZ) of the Southern Ocean due to iron fertilisation has been proposed as a key mechanism for explaining carbon drawdown during the last glacial maximum (LGM). This work reconstructs marine EP since the LGM at four sites around New Zealand. For the first time in this region, 230-Thorium-normalised fluxes of biogenic opal, carbonate, excess barium, and organic carbon are presented. In Subtropical Waters and the SAZ, these flux variations show that EP has not changed markedly since the LGM. The only exception is a site currently north of the subtropical front. Here we suggest the subtropical front shifted over the core site between 18 and 12ka, driving increased EP. To understand why EP remained mostly low and constant elsewhere, lithogenic fluxes at the four sites were measured to investigate changes in dust deposition. At all sites, lithogenic fluxes were greater during the LGM compared to the Holocene. The positive temporal correlation between the Antarctic dust record and lithogenic flux at a site in the Tasman Sea shows that regionally, increased dust deposition contributed to the high glacial lithogenic fluxes. Additionally, it is inferred that lithogenic material from erosion and glacier melting deposited on the Campbell Plateau during the deglaciation (1812ka). From these observations, it is proposed that even though increased glacial dust deposition may have relieved iron limitation within the SAZ around New Zealand, the availability of silicic acid limited diatom growth and thus any resultant increase in carbon export during the LGM. Therefore, silicic acid concentrations have remained low since the LGM. This result suggests that both silicic acid and iron co-limit EP in the SAZ around New Zealand, consistent with modern process studies.

Item Details

Item Type:Refereed Article
Keywords:biological activity, productivity, carbon draw-down, 230-Thorium, dust flux, silicic acid
Research Division:Earth Sciences
Research Group:Physical Geography and Environmental Geoscience
Research Field:Palaeoclimatology
Objective Division:Expanding Knowledge
Objective Group:Expanding Knowledge
Objective Field:Expanding Knowledge in the Earth Sciences
Author:Durand, A (Mr Axel Durand)
Author:Chase, Z (Associate Professor Zanna Chase)
Author:Noble, TL (Dr Taryn Noble)
Author:Kitchener, P (Ms Priya Kitchener)
Author:Townsend, AT (Associate Professor Ashley Townsend)
Author:Jansen, N (Dr Nils Jansen)
Author:Johnson, S (Mr Sean Johnson)
ID Code:116480
Year Published:2017
Funding Support:Australian Research Council (FT120100759)
Deposited By:Centre for Oceans and Cryosphere
Deposited On:2017-05-10
Last Modified:2017-07-21
Downloads:0

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