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

Thumbnail Image
Date
2011-08-25
Authors
Schroth, Andrew W.
Crusius, John
Chever, Fanny
Bostick, Benjamin C.
Rouxel, Olivier J.
Linked Authors
Alternative Title
Date Created
Location
DOI
10.1029/2011GL048367
Replaced By
Keywords
Boreal forest
Glacier
Iron
Isotope
Nutrient
Speciation
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.
Description
This paper is not subject to U.S. copyright. The definitive version was published in Geophysical Research Letters 38 (2011): L16605, doi:10.1029/2011GL048367.
Embargo Date
Citation
Geophysical Research Letters 38 (2011): L16605
Cruises
Cruise ID
Cruise DOI
Vessel Name