Award: OCE-2124188

The Amundsen Sea Polynya (ASP) is the most productive region in coastal Antarctica, surrounded waters of the Southern Ocean where iron concentrations are so low that the limit the growth of algae at the base of the food chain. Previous  scientists have shown evidence of ice melt and sediments being important sources of iron to surface waters, helping to sustain high biological activity over the growing season, much of the iron is in particles that sink before organisms can get at the iron.  Dissolved iron in the reduced form, dFe(II), is the most bioavailable form but readily combines  with oxygen to the largely insoluble form, dFe(III) (the formation of rust is a good analogy).  The cold temperatures of Antarctic water help to slow the oxidation kinetics, thereby increasing the half-life of Fe(II) and allowing Fe(II) to become a powerful geochemical tracer. Here, we report the first measurements of dFe(II) distributions in the ASP in water column, sea ice, and sediments below the seafloor. This work suggests that there are enrichments of dFe(II) throughout the surface of the ASP, associated with ice melt, sunlight transformations and influences on redox chemistry from bloom-forming alga Phaeocystis antartica.  Our data show that much of the biologically essential iron comes from the seafloor itself, but is also transported by an important current below the surface that encircles the entire continent.  The resilts are part of the GEOTRACES program - which is distinguised by the simultaneous sampling of many elements in seawater that have unique behavior in the ocean. Comparing our data with the other elemnts will sterngthen our conclusions and narrow down where on the Antarctic continental margin most of the iron is coming from.  

Last Modified: 03/31/2025
Modified by: James W Moffett