Modeling the Recent Changes of Phytoplankton Blooms Dynamics in the Arctic Ocean

In recent decades, Arctic Ocean (AO) sea ice has experienced intense climate-related modifications, which coincide with earlier melting in spring and delayed formation in the fall. In this study, we use the ECCO2-Darwin ocean biogeochemistry model to gain a mechanistic understanding of how changes in sea-ice seasonality impact the phenology of AO phytoplankton blooms. We use a 2006-2013 simulation to show that early sea-ice melt in 2007 and 2012 triggers earlier phytoplankton blooms (similar to 1 month earlier compared to other years) and that the blooms dissipate earlier due to more rapid nutrient depletion in the surface AO. Our simulation also confirms that delayed formation of sea ice during fall triggers second fall blooms, in agreement with observations. These results suggest that in a warmer and changing climate, further changes to sea-ice extent could drastically impact AO phytoplankton, with important consequences for Arctic marine ecosystems.