The heterogeneous nature of Fe delivery from melting icebergs

Hopwood, Mark J., Cantoni, C., Clarke, Jennifer S., Cozzi, S. and Achterberg, Eric P. (2017) The heterogeneous nature of Fe delivery from melting icebergs Geochemical Perspectives Letters, 3 . pp. 200-209. DOI 10.7185/geochemlet.1723.

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Abstract

The micronutrient iron (Fe) can be transported from marine terminating glaciers to the ocean by icebergs. There are however few observations of iceberg Fe content, and the flux of Fe from icebergs to the offshore surface ocean is poorly constrained. Here we report the dissolved Fe (DFe), total dissolvable Fe (TdFe) and ascorbic acid extractable Fe (FeAsc) sediment content of icebergs from Kongsfjorden, Svalbard. The concentrations of DFe (range 0.63 nM – 536 nM, mean 37 nM, median 6.5 nM) and TdFe (range 46 nM – 57 µM, mean 3.6 µM, median 144 nM) both demonstrated highly heterogeneous distributions and there was no significant correlation between these two fractions. FeAsc (range 0.0042 to 0.12 wt. %) was low compared to both previous measurements in Kongsfjorden and to current estimates of the global mean. FeAsc content per volume ice did however, as expected, show a significant relationship with sediment loading (which ranged from < 0.1 – 234 g L-1 of meltwater). In the Arctic, icebergs lose their sediment load faster than ice volume due to the rapid loss of basal ice after calving. We therefore suggest that the loss of basal ice is a potent mechanism for the reduction of mean TdFe and FeAsc per volume of iceberg. Delivery of TdFe and FeAsc to the ocean is thereby biased towards coastal waters where, in Kongsfjorden, DFe (18 ± 17 nM) and TdFe (mean 8.1 µM, median 3.7 µM) concentrations were already elevated.

Document Type: Article
Keywords: icebergs, iron, Fe, Svalbard, Arctic
Research affiliation: OceanRep > GEOMAR > FB2 Marine Biogeochemistry > FB2-CH Chemical Oceanography
Kiel University
Refereed: Yes
DOI etc.: 10.7185/geochemlet.1723
ISSN: 2410-339X
Related URLs:
Projects: OCEAN-CERTAIN, pH in Svalbard
Date Deposited: 26 Jun 2017 07:31
Last Modified: 26 Jun 2017 07:32
URI: http://eprints.uni-kiel.de/id/eprint/38506

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