Estimating variability and long-term change in sea ice primary productivity using a satellite-based light penetration index

Sea ice algae in the Southern Ocean have strong ecological and biogeochemical significance, providing a lipid-rich food-resource to keystone species such as Antarctic krill. Despite their importance, estimating seasonal or interannual changes algal production at circumpolar scale is not presently possible. We show that product of concentration irradiance penetrating into sea (Eice) explains 69% variability sector estimated from two respected models. After allowing for greater quantum yield summer than other seasons we simple light-based index potential (Pice) this explained 91% modelled production. Our results suggest between 1987 2017, has generally increased with largest increases seen off East Antarctica, Weddell Sea, western Ross Sea.