COG3

Climate warming, glacial melting, and iron micronutrient sources to West Antarctic shelf waters.

Abstract:
The Amundsen Sea is a coastal embayment adjacent to the fastest accelerating glaciers in West Antarctica, and has been strongly influenced by regional warming and glacial meltwater inputs over the last few decades. In austral summer, the Amundsen Sea Polynya (ASP) becomes the most productive region of all Antarctic waters, with Chl-a concentrations exceeding 40 µg/L. Since phytoplankton growth in the Southern Ocean overall is broadly limited by the availability of the micronutrient iron, the long intense bloom of the ASP must be a product of natural Fe fertilization. This talk will describe the findings of the interdisciplinary Amundsen Sea International Research Expedition (ASPIRE) and will focus on the source and delivery mechanisms that keep Fe supplied to the very green euphotic zone over the course of the weeks-long bloom in the polynya. The role of climate change, as expressed in this rapidly warming region, in the enhanced flow of warm circumpolar deepwater onto the shelf, the melting of proximal ice shelves and the flux of Fe to the polynya will also be explored. Finally, neodymium isotopes, as a tracer of continentally-derived Fe, can reveal the potential for export of bioavailable Fe off the shelf and into the surrounding Fe-limited waters of the Southern Ocean, especially during the austral winter.