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

Type Article
Date 2011-08
Language English
Author(s) Schroth Andrew W.1, Crusius John2, 3, Chever Fanny4, Bostick Benjamin C.5, Rouxel OlivierORCID4, 6, 7
Affiliation(s) 1 : Woods Hole Coastal and Marine Science Center, U.S. Geological Survey, Woods Hole, Massachusetts, USA
2 : Woods Hole Coastal and Marine Science Center, U.S. Geological Survey, Woods Hole, Massachusetts, USA
3 : University of Washington, Coastal and Marine Geology Program, U.S. Geological Survey, School of Oceanography, Seattle, Washington, USA
4 : European Institute for Marine Studies, University of Brest, Technopôle Brest-Iroise, Plouzané, France
5 : Lamont-Doherty Earth Observatory, Palisades, New York, USA
6 : Department of Marine Chemistry and Geochemistry, Woods Hole Oceanographic Institution, Woods Hole, Massachusetts, USA
7 : IFREMER, Centre de Brest, Plouzané, France
Source Geophysical Research Letters (0094-8276) (Amer Geophysical Union), 2011-08 , Vol. 38 , N. L16605 , P. 6 p.
DOI 10.1029/2011GL048367
WOS© Times Cited 29
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. Citation: Schroth, A. W., J. Crusius, F. Chever, B. C. Bostick, and O. J. Rouxel (2011), Glacial influence on the geochemistry of riverine iron fluxes to the Gulf of Alaska and effects of deglaciation, Geophys. Res. Lett., 38, L16605, doi:10.1029/2011GL048367.
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Schroth Andrew W., Crusius John, Chever Fanny, Bostick Benjamin C., Rouxel Olivier (2011). Glacial influence on the geochemistry of riverine iron fluxes to the Gulf of Alaska and effects of deglaciation. Geophysical Research Letters, 38(L16605), 6 p. Publisher's official version : https://doi.org/10.1029/2011GL048367 , Open Access version : https://archimer.ifremer.fr/doc/00044/15483/