Sea ice forms seasonally from polar waters and as such, contains the bio-chemical signature of the ocean surface from which it forms. As ice crystals are unable to incorporate most alien molecules, salt retained during initial formation is concentrated in fluid pockets and channels creating a multiphase and protected habitat for microscopic organisms and algae. Changes in both the physical and biogeochemical states of sea ice impact the polar marine carbon system. Here we present a modeling study using E3SM v1 – Energy Exa-scale Earth System Model Version 1 – which 1) identifies some of the key physical and biogeochemical sea ice properties which most influence polar marine primary production; 2) suggests a mechanistic explanation for the observed relationships; and 3) contrasts the changing roles of each mechanism in the Arctic and Southern Ocean regions. E3SM is designed for global climate applications and includes a centimeter-scale vertically resolved sea ice biogeochemical submodule (zbgc) as well as biogeochemical components in land and ocean