Please use this identifier to cite or link to this item: https://hdl.handle.net/2440/70605
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Type: Journal article
Title: Surface ocean iron fertilization: The role of airborne volcanic ash from subduction zone and hot spot volcanoes and related iron fluxes into the Pacific Ocean
Author: Olgun, N.
Duggen, S.
Croot, P.
Delmelle, P.
Dietze, H.
Schacht, U.
Oskarsson, N.
Siebe, C.
Auer, A.
Garbe-Schonberg, D.
Citation: Global Biogeochemical Cycles: an international journal of global change, 2011; 25(4):GB4001-GB4001
Publisher: Amer Geophysical Union
Issue Date: 2011
ISSN: 0886-6236
1944-9224
Statement of
Responsibility: 
Nazlı Olgun, Svend Duggen, Peter Leslie Croot, Pierre Delmelle, Heiner Dietze, Ulrike Schacht, Niels Óskarsson, Claus Siebe, Andreas Auer, Dieter Garbe-Schönberg
Abstract: Surface ocean iron (Fe) fertilization can affect the marine primary productivity (MPP), thereby impacting on CO 2 exchanges at the atmosphere-ocean interface and eventually on climate. Mineral (aeolian or desert) dust is known to be a major atmospheric source for the surface ocean biogeochemical iron cycle, but the significance of volcanic ash is poorly constrained. We present the results of geochemical experiments aimed at determining the rapid release of Fe upon contact of pristine volcanic ash with seawater, mimicking their dry deposition into the surface ocean. Our data show that volcanic ash from both subduction zone and hot spot volcanoes (n = 44 samples) rapidly mobilized significant amounts of soluble Fe into seawater (35-340 nmol/g ash), with a suggested global mean of 200 50 nmol Fe/g ash. These values are comparable to the range for desert dust in experiments at seawater pH (10-125 nmol Fe/g dust) presented in the literature (Guieu et al., 1996; Spokes et al., 1996). Combining our new Fe release data with the calculated ash flux from a selected major eruption into the ocean as a case study demonstrates that single volcanic eruptions have the potential to significantly increase the surface ocean Fe concentration within an ash fallout area. We also constrain the long-term (millennial-scale) airborne volcanic ash and mineral dust Fe flux into the Pacific Ocean by merging the Fe release data with geological flux estimates. These show that the input of volcanic ash into the Pacific Ocean (128-221 × 10 15 g/ka) is within the same order of magnitude as the mineral dust input (39-519 × 10 15 g/ka) (Mahowald et al., 2005). From the similarity in both Fe release and particle flux follows that the flux of soluble Fe related to the dry deposition of volcanic ash (3-75 × 10 9 mol/ka) is comparable to that of mineral dust (1-65 × 10 9 mol/ka). Our study therefore suggests that airborne volcanic ash is an important but hitherto underestimated atmospheric source for the Pacific surface ocean biogeochemical iron cycle. Copyright 2011 by the American Geophysical Union.
Keywords: Pacific Ocean
iron solubility
soluble iron input
surface ocean iron limitation
volcanic ash
volcanic ash flux
Rights: Copyright 2011 by the American Geophysical Union.
DOI: 10.1029/2009GB003761
Published version: http://dx.doi.org/10.1029/2009gb003761
Appears in Collections:Aurora harvest 5
Australian School of Petroleum publications

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