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British Columbian continental shelf as a source of dissolved iron to the subarctic northeast Pacific Ocean
Author(s) -
Cullen Jay T.,
Chong Marina,
Ianson Debby
Publication year - 2009
Publication title -
global biogeochemical cycles
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.512
H-Index - 187
eISSN - 1944-9224
pISSN - 0886-6236
DOI - 10.1029/2008gb003326
Subject(s) - oceanography , continental shelf , geology , upwelling , downwelling , isopycnal , subarctic climate , submarine pipeline , water mass
The distribution of dissolved (<0.4 μ m) iron (Fe) across the continental shelf and slope of Queen Charlotte Sound on the west coast of Canada was examined to estimate the potential of these waters as a source of Fe to the Fe‐limited waters of the subarctic northeast Pacific. Iron profiles obtained in shelf, slope, and offshore waters demonstrate decreasing concentrations of Fe with distance from the continent. Within 50 m of the shelf sediments dissolved Fe concentrations were 5.3 ± 0.3 nM. This signal was detected, although attenuated by 80%, along the isopycnal surface at offshore stations 40–50 km seaward of the shelf break, strongly suggesting cross‐shelf transport of an Fe‐rich plume originating in low dissolved oxygen (<3 ml L −1 , <130 μ mol kg −1 ) waters in subsurface water over the continental shelf. Several physical mechanisms that may cause these Fe‐enriched waters to advect offshore in this region (i.e., tidal currents and Ekman transport in the bottom boundary layer, coastal downwelling/relaxation from upwelling, and the formation of anticyclonic, westward‐propagating, coastal eddies) are discussed. We suggest that strong tidal currents over broad continental shelves may play a key role in Fe supply to ocean basins.