A Glacial Isostatic Model for Early- mid Holocene Iron Fertilization of Antarctic Peninsula Shelf Waters

Diatom-based proxy records from a dozen marine sediment cores recovered from the Antarctic Peninsula continental shelf document a geographically widespread episode of iron fertilization of shelf waters, that developed gradually, beginning ~8,000 years before present (ybp), and ending relatively quickly, at ~5500 ybp. We propose that a short, culminating period of post-glacial rebound and iceberg scouring served to resuspend littoral marine sediment, releasing soluble, bioavailable iron that induced high productivity. The timing and duration of the rebound event is well constrained by the chronology of near-coastal glacial recession and a very well constrained mantle viscosity, the latter determined by modern rebound associated with ice mass loss. The diatom data also document a longer open water season, characterized by a later advance of sea ice in the fall. We suggest that changes in the Southern Hemisphere westerly winds resulted in enhanced upwelling of Upper Circumpolar Deep Water (UCDW) onto the newly exposed and relatively shallow continental shelf. Warm UCDW may have driven the longer open water season, while iron may have been supplied from the re-suspension of shelf sediment, through upwelling and/or upward mixing from late season storms. A new glacial reconstruction for the Antarctic Peninsula suggests the delayed demise of ice domes and coastal deglaciation provided the final large post-glacial rebound event that is correlative to this unusual period of littoral sediment resuspension and consequent Fe-replete productivity that characterizes the early- mid Holocene.