Annual primary production in Antarctic sea ice during 2005–2006 from a sea ice state estimate

Abstract

AbstractUsing the data‐bounded Sea Ice Ecosystem State (SIESTA) model, we estimate total Antarctic sea ice algal primary production to be 23.7 Tg C a−1 for the period July 2005–June 2006, of which 80% occurred in the bottom 0.2 m of ice. Simulated sea ice primary production would constitute 12% of total annual primary production in the Antarctic sea ice zone, and ∼1% of annual Southern Ocean primary production. Model sea ice algal growth was net nutrient limited, rather than light limited, for the vast majority of the sunlit season. The seasonal distribution of integrated ice algal biomass matches available observations. The vertical algal distribution was weighted toward the ice bottom compared to observations, indicating that interior ice algal communities may be under‐predicted in the model, and that nutrient delivery via gravity‐induced convection is not sufficient to sustain summertime algal biomass. Bottom ice algae were most productive in ice of 0.36 m thickness, whereas interior algal communities were most productive in ice of 1.10 m thickness. Sensitivity analyses that tested different atmospheric forcing inputs, sea ice parameterizations, and nutrient availability caused mean and regional shifts in sea ice state and ice algal production even when sea extent and motion was specified. The spatial heterogeneity of both ice state and algal production highlight the sensitivity of the sea ice ecosystem to physical perturbation, and demonstrate the importance of quality input data and appropriate parameterizations to models of sea ice and associated biology.