Tracing dust input to the global ocean using thorium isotopes in marine sediments: ThoroMap

Kienast, Stephanie; Winckler, Gisela; Lippold, Jörg; Albani, Samuel; Mahowald, Nathalie (2016). Tracing dust input to the global ocean using thorium isotopes in marine sediments: ThoroMap. Global Biogeochemical Cycles, 30(10), pp. 1526-1541. American Geophysical Union 10.1002/2016GB005408

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Continental dust input into the ocean-atmosphere system has significant ramifications for biogeochemical cycles and global climate, yet direct observations of dust deposition in the ocean remain scarce. The long-lived isotope thorium-232 (232Th) is greatly enriched in upper continental crust compared to oceanic crust and mid-ocean ridge basalt-like volcanogenic material. In open ocean sediments, away from fluvial and ice-rafted sources of continental material, 232Th is often assumed to be of predominantly eolian origin. In conjunction with flux normalization based on the particle reactive radioisotope thorium-230 (230Th), 232Th measurements in marine sediments are a promising proxy for dust accumulation in the modern and past ocean. Here we present ThoroMap, a new global data compilation of 230Th-normalized fluxes of 232Th. After careful screening, we derive dust deposition estimates in the global ocean averaged for the late Holocene (0–4 ka) and the Last Glacial Maximum (LGM, 19–23 ka). ThoroMap is compared with dust deposition estimates derived from the Community Climate System Model (CCSM3) and CCSM4, two coupled atmosphere, land, ocean, and sea ice models. Model-data correlation factors are 0.63 (CCSM3) and 0.59 (CCSM4) in the late Holocene and 0.82 (CCSM3) and 0.83 (CCSM4) in the LGM. ThoroMap is the first compilation that is built on a single, specific proxy for dust and that exclusively uses flux-normalisation to derive dust deposition rates.

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

UniBE Contributor:

Lippold, Jörg

Subjects:

500 Science > 550 Earth sciences & geology

ISSN:

0886-6236

Publisher:

American Geophysical Union

Language:

English

Submitter:

Samuel Jaccard

Date Deposited:

15 Nov 2016 15:24

Last Modified:

09 Sep 2017 10:28

Publisher DOI:

10.1002/2016GB005408

BORIS DOI:

10.7892/boris.89956

URI:

https://boris.unibe.ch/id/eprint/89956

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