Glacial-interglacial dust and export production records from the Southern Indian Ocean

Thöle, Lena; Amsler, H. Eri; Moretti, Simone; Auderset, Alexandra; Gilgannon, James; Lippold, Jörg; Vogel, Hendrik; Crosta, Xavier; Mazaud, Alain; Michel, Elisabeth; Martinez-Garcia, Alfredo; Jaccard, Samuel L. (2019). Glacial-interglacial dust and export production records from the Southern Indian Ocean. Earth and planetary science letters, 525, p. 115716. Elsevier 10.1016/j.epsl.2019.115716

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We present 230Th-normalized dust and export production fluxes for two contrasted marine sediment cores spanning the Antarctic Polar Front, close to the Kerguelen Plateau in the Southern Indian Ocean, covering the last glacial cycle. We report glacial lithogenic fluxes comparable to the South Atlantic and higher than in the South Pacific sectors of the Southern Ocean. Structural and temporal discrepancies with dust reconstructions from Antarctic ice cores and the Atlantic and Pacific sectors of the Subantarctic Zone (SAZ) point towards Southern Africa and/or the Kerguelen Plateau as an additional source of lithogenic material to the Southern Indian Ocean during the last ice age. In the SAZ, export production proxies respond to iron (Fe) fertilization with total organic carbon (TOC) fluxes as high as those previously reported from the Atlantic sector of the Southern Ocean. However, the correlation between export production and dust proxies is weaker than in the other sectors, and shows a muted response of export production during peak glacials. We hypothesize that this muted response may be related to macronutrient (co-)limitation imposed on phytoplankton growth possibly induced by a northward displacement of wind-driven upwelling and/or the polar frontal system during peak glacials. The Antarctic Zone (AZ) record depicts the typical pattern of enhanced export production during interglacials and comparatively low productivity during glacials suggesting a decrease in the supply of macronutrients to the AZ surface during ice ages compared to warm periods, as previously proposed. However, a muted response of opal fluxes during marine isotope stage (MIS) 5e argues for a southward migration of the frontal system during warmer MIS 5e, possibly causing silicic acid (co-)limitation at this site.

Item Type:

Journal Article (Original Article)

Division/Institute:

10 Strategic Research Centers > Oeschger Centre for Climate Change Research (OCCR)
08 Faculty of Science > Institute of Geological Sciences

Graduate School:

Graduate School of Climate Sciences

UniBE Contributor:

Thöle, Lena; Amsler, Helen Eri; Gilgannon, James; Vogel, Hendrik and Jaccard, Samuel

Subjects:

500 Science > 550 Earth sciences & geology

ISSN:

0012-821X

Publisher:

Elsevier

Language:

English

Submitter:

Samuel Jaccard

Date Deposited:

30 Aug 2019 16:36

Last Modified:

22 Oct 2019 20:11

Publisher DOI:

10.1016/j.epsl.2019.115716

BORIS DOI:

10.7892/boris.132669

URI:

https://boris.unibe.ch/id/eprint/132669

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