Dissolved Fe Supply to the Central Gulf of Alaska Is Inferred to Be Derived From Alaskan Glacial Dust That Is Not Resolved by Dust Transport Models

Abstract

AbstractRe‐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.