Abstract

Being highly reflective and absorptive, sea ice was often assumed to prohibit upper ocean photosynthesis - yet observations in the modern Arctic reveal widespread under-ice blooms, driven by a transition to thinner, more mobile first-year sea ice - superficially similar to that found in the Southern Ocean. No studies have quantified the potential for under-sea-ice blooms at the Southern Ocean scale. Here we examine Southern Ocean light, sea ice, and ocean conditions, using 11 climate model contributions to CMIP6 and the ICESat-2 laser altimeter. We find large areas, 4 million square kilometers or more, of the sea-ice-covered Southern Ocean are hospitable to upper ocean photosynthesis. A stronger focus on these regions through field and remote sensing studies is necessary to assess the possible impact of under-ice productivity on Southern Hemisphere carbon and nutrient cycling.