Résumé
An Earth System model with an oceanic biogeochemical component is shown to reproduce accurately the seasonal course of sea‐ice and chlorophyll distribution in the Arctic region. It is argued that the phytoplankton blooms that occur concomitantly with the ice retreat along the Arctic coastal shelves in spring and summer strongly impact the Arctic climate and improve the sea‐ice distribution in the model. Indeed, these blooms modify the vertical distribution of radiant heating and trap the penetrating solar heat flux at the surface in these regions. The resulting surface warming triggers a reduction of sea‐ice thickness and concentration. This reduction increases the solar energy penetrating into the ocean, therefore providing a positive feedback that further amplifies the direct biological warming. The increased melting, precipitation and runoff related to these bio‐physical feedbacks freshen the Arctic Ocean and the Greenland Sea, provoking a slight slowdown of the overturning circulation.