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Abstract Re‐examination of previously published dissolved iron time‐series data from Ocean Station Papa in the central Gulf of Alaska (GoA) reveals 33%–70% increases in the dissolved iron inventories occurring between September and February of successive years, implying a source of Fe to this region during autumn or early winter. Because I can virtually rule out many possible iron sources at this time of year, I suggest Alaskan glacial dust is the likely iron source. Large plumes of such dust are known to be generated regularly in the autumn by anomalous offshore winds and channeled through mountain gaps, simultaneously from several locations spanning ∼1,000 km of the northern Gulf of Alaska coastline. Large dust flux events occur when below‐freezing, low‐humidity air temperatures persist for many days during the autumn. I suggest that existing state‐of‐the‐art global dust models fail to reproduce this Alaskan dust flux because the model spatial resolution is too coarse to resolve the high winds through the narrow mountain gaps that generate the dust. Future work that could help to confirm this Fe source to the central GoA includes time‐series profiles of iron concentrations, and ancillary information from sensor‐equipped profiling floats. If this mechanism of Fe supply to the central GoA were confirmed, it would imply this Alaskan dust is transported ≥1,100 km from the coast, more than twice as far as has been visually documented from satellite observations.
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Alaskan Glacial Dust Is an Important Iron Source to Surface Waters of the Gulf of Alaska
Abstract This work evaluates glacial dust as a source of sediment, and associated iron (Fe), to the Fe‐limited Gulf of Alaska (GoA). A reanalysis of GoA sediment data, using rare earth elements and thorium as provenance tracers, suggests a flux to the ocean surface of Copper River (AK) glacial dust, and associated Fe, that is comparable to the flux of dust from Asia, at least 1,000 km from the narrow mountain valley glacial dust source area. This work suggests dust from Asia may not be the largest source of Fe to the GoA. Dust models fail to accurately simulate this glacial dust transport because their coarse resolution underestimates wind speeds, and the dust flux. This work suggests that glacial dust fluxes may have been important in the geologic past (e.g., the last glacial maximum) from locations where there was more extensive coverage by glaciers than at present.
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- Award ID(s):
- 1756126
- PAR ID:
- 10614165
- Publisher / Repository:
- DOI PREFIX: 10.1029
- Date Published:
- Journal Name:
- Geophysical Research Letters
- Volume:
- 51
- Issue:
- 12
- ISSN:
- 0094-8276
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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