Drivers and Impacts of Southern Ocean Polynyas in High-Resolution Earth System Models
Open-ocean polynyas are ice-free regions amid the winter ice pack, and are characterized by intense ocean/atmosphere exchanges of heat and moisture. The occurrence of the large Weddell Sea Polynyas (WSPs) in the Southern Ocean is very rare, but smaller polynyas like the Maud Rise Polynya (MRPs) appear more regularly, most recently during the winters of 2016 and 2017. High-resolution coupled climate models often display active polynya behavior that alternates between quiescent periods without polynyas; episodes with realistic Maud Rise or Weddell Sea polynyas; and periods of large embayments that do not have known analogs in the observational record. Given the episodic occurrence of polynyas in state-of-the-art climate models, it is important to understand their drivers; their impacts on the coupled ocean, sea ice, and atmosphere system; and their future in a changing climate. Here we synthesize our recent work on open-ocean polynyas in the Southern Ocean as they appear in two high-resolution climate models, namely CESM1 and E3SMv0. We will discuss preconditioning and triggering mechanisms of these polynyas, and their subsequent impacts on the ocean and atmosphere.