Evaluation of Under-ice Phytoplankton Blooms in the Fully-coupled, High-resolution Regional Arctic System Model (RASM)

Recent studies suggest that satellite-based assessments of Arctic primary production might be significantly underestimated, as they do not include contributions of under-ice blooms. For example, a massive under-ice phytoplankton bloom was observed in the Chukchi Sea in July 2011, with depth-integrated under-ice biomass about fourfold greater than in open water. Subsequent model studies have suggested that such blooms could be more widespread than previously thought, and that they are becoming more common as a result of increasing light availability due to thinning ice and increasing prevalence of melt ponds in the Arctic Ocean.

We present results from the fully-coupled, high-resolution Regional Arctic System Model (RASM), including marine biogeochemistry (mBGC) in its ocean and sea ice components. Our analysis of results from two RASM simulations, employing different parameterizations of sea ice mBGC, focuses on the spatial and temporal evolution of under-ice Arctic blooms from 1990 through 2017. We will discuss the influence of melt pond proliferation and nutrient availability, as well as the effect of the different parameterizations of sea ice mBGC on the extent and duration of these blooms. Finally, we will present estimates of Arctic Ocean primary production that incorporate the contributions of under-ice blooms.