Subsurface Initiation of Deep Convection near Maud Rise

Abstract. In 2016 and 2017, an open-ocean polynya appeared over Maud Rise. The formation of these polynyas has been attributed to the occurrence of intense winter storms. However, the evolution and lifetime of the two polynyas was quite different. Here, we use model output of a century long high-resolution climate model simulation to explain the differences between the 2016 and 2017 Maud Rise polynyas. Analysis of the results, using convective available potential energy to measure subsurface convection, leads us to the interpretation that the first polynya event is (partly) initiated by subsurface static instabilities, leading to subsurface convection. Subsurface convection associated with the formation of the 2016 polynya preconditioned the Maud Rise region, resulting in a weakly stable surface layer and eventually leading to the 2017 polynya event. Based on this, we argue that, apart from atmospheric variability, subsurface convection is important to initiate a Maud Rise polynya.