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Glacial influence on the geochemistry of riverine iron fluxes to the Gulf of Alaska and effects of deglaciation

Glacial influence on the geochemistry of riverine iron fluxes to the Gulf of Alaska and effects of deglaciation
Glacial influence on the geochemistry of riverine iron fluxes to the Gulf of Alaska and effects of deglaciation
Riverine iron (Fe) derived from glacial weathering is a critical micronutrient source to ecosystems of the Gulf of Alaska (GoA). Here we demonstrate that the source and chemical nature of riverine Fe input to the GoA could change dramatically due to the widespread watershed deglaciation that is underway. We examine Fe size partitioning, speciation, and isotopic composition in tributaries of the Copper River which exemplify a long-term GoA watershed evolution from one strongly influenced by glacial weathering to a boreal-forested watershed. Iron fluxes from glacierized tributaries bear high suspended sediment and colloidal Fe loads of mixed valence silicate species, with low concentrations of dissolved Fe and dissolved organic carbon (DOC). Iron isotopic composition is indicative of mechanical weathering as the Fe source. Conversely, Fe fluxes from boreal-forested systems have higher dissolved Fe concentrations corresponding to higher DOC concentrations. Iron colloids and suspended sediment consist of Fe (hydr)oxides and organic complexes. These watersheds have an iron isotopic composition indicative of an internal chemical processing source. We predict that as the GoA watershed evolves due to deglaciation, so will the source, flux, and chemical nature of riverine Fe loads, which could have significant ramifications for Alaskan marine and freshwater ecosystems.
0094-8276
L16605
Schroth, Andrew W.
1c5ebec1-01b8-4c09-87b2-c1fa1eebd94e
Crusius, John
5faf5a68-a070-41c7-8429-9b2d12a9a668
Chever, Fanny
d0e0d02e-a5c7-47e6-a510-15f7a0402eea
Bostick, Benjamin C.
5826dfb0-f9ae-47c5-87a5-052d4e025539
Rouxel, Olivier J.
c68deadf-01db-450a-9cc8-97f24ddb1d77
Schroth, Andrew W.
1c5ebec1-01b8-4c09-87b2-c1fa1eebd94e
Crusius, John
5faf5a68-a070-41c7-8429-9b2d12a9a668
Chever, Fanny
d0e0d02e-a5c7-47e6-a510-15f7a0402eea
Bostick, Benjamin C.
5826dfb0-f9ae-47c5-87a5-052d4e025539
Rouxel, Olivier J.
c68deadf-01db-450a-9cc8-97f24ddb1d77

Schroth, Andrew W., Crusius, John, Chever, Fanny, Bostick, Benjamin C. and Rouxel, Olivier J. (2011) Glacial influence on the geochemistry of riverine iron fluxes to the Gulf of Alaska and effects of deglaciation. Geophysical Research Letters, 38 (16), L16605. (doi:10.1029/2011GL048367).

Record type: Article

Abstract

Riverine iron (Fe) derived from glacial weathering is a critical micronutrient source to ecosystems of the Gulf of Alaska (GoA). Here we demonstrate that the source and chemical nature of riverine Fe input to the GoA could change dramatically due to the widespread watershed deglaciation that is underway. We examine Fe size partitioning, speciation, and isotopic composition in tributaries of the Copper River which exemplify a long-term GoA watershed evolution from one strongly influenced by glacial weathering to a boreal-forested watershed. Iron fluxes from glacierized tributaries bear high suspended sediment and colloidal Fe loads of mixed valence silicate species, with low concentrations of dissolved Fe and dissolved organic carbon (DOC). Iron isotopic composition is indicative of mechanical weathering as the Fe source. Conversely, Fe fluxes from boreal-forested systems have higher dissolved Fe concentrations corresponding to higher DOC concentrations. Iron colloids and suspended sediment consist of Fe (hydr)oxides and organic complexes. These watersheds have an iron isotopic composition indicative of an internal chemical processing source. We predict that as the GoA watershed evolves due to deglaciation, so will the source, flux, and chemical nature of riverine Fe loads, which could have significant ramifications for Alaskan marine and freshwater ecosystems.

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Published date: August 2011
Organisations: Ocean and Earth Science

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Local EPrints ID: 364762
URI: https://eprints.soton.ac.uk/id/eprint/364762
ISSN: 0094-8276
PURE UUID: 8f88bf21-d424-43cf-b604-44d72cae6dd1

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Date deposited: 09 May 2014 09:58
Last modified: 16 Jul 2019 21:06

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