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

January 1, 2011

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 Information

Publication Year 2011
Title Glacial influence on the geochemistry of riverine iron fluxes to the Gulf of Alaska and effects of deglaciation
DOI 10.1029/2011GL048367
Authors A.W. Schroth, John Crusius, F. Chever, B.C. Bostick, O.J. Rouxel
Publication Type Article
Publication Subtype Journal Article
Series Title Geophysical Research Letters
Series Number
Index ID 70036125
Record Source USGS Publications Warehouse
USGS Organization Woods Hole Coastal and Marine Science Center

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