Arctic PRIZE will address a fundamental question in Arctic biology: How will projected shifts in the spatial distribution of sea ice in the Arctic Ocean modify mixing and light in the surface ocean, and what is the net effect of these physical changes on the quantities, timing and rates of PP, phytoplankton taxonomic composition, and their pelagic and benthic consumers? This project will conduct coordinated physical, chemical and biological observations of the water column within the seasonal ice zone of the Barents Sea. Arctic PRIZE has a strong seasonal perspective and focuses on the critically important but under-sampled transition from polar winter into the post-bloom summer. Data will identify controls on pelagic primary production, combining a detailed view of the physiochemical drivers with experiments resolving the role of diversity and plasticity. Zooplankton studies will likewise resolve multiple, competing impacts and the role of behavioral responses in shaping trophic transfer. Linked benthic observations will complete this picture of how energy moves from phytoplankton through the food web in response to sea-ice retreat. Biological models that capture these processes will be validated in detail, tested for portability across the Barents Sea and contrasting Pacific Arctic systems, and subsequently integrated into NEMO/MEDUSA and prominent, parallel modelling efforts in the US and Norway. These models are components of climate and earth system models. Arctic PRIZE will improve the predictive skill of these systems in terms of ecosystem function, its fate and the impact of projected sea ice retreat.