 |
Center for Nonlinear Studies |
Open Ocean Polynyas (OOPs) in the Southern Ocean are ice-free areas within the winter ice pack that are associated with deep convection, ventilation of intermediate and bottom waters. They can significantly contribute to the formation of Antarctic Bottom Water, with implications on the Atlantic Meridional Overturning Circulation. The ‘Great Weddell Polynya’ is a term that describes a series of spatially large OOPs that were observed during the austral winters of 1974-1976 in the Weddell Sea. Smaller short-lived OOPs have been observed intermittently including during the austral winters of 2016 and 2017. Here we investigate OOPs that emerge in this 131-years long simulation with preindustrial radiative forcing, which is part of the Energy Exascale Earth System Model project. Persistent winter OOPs emerged in the Weddell Sea (large Weddell Sea Polynya; WSP) and over the Maud Rise-Astrid Ridge complex (small Maud Rise Polynya; MRP) in a high-resolution fully-coupled simulation, similar to what has been observed. The simulated WSPs are initiated over the Maud Rise-Astrid Ridge complex and propagate steadily westward to the central Weddell Sea over the course of a few consecutive winters. We find that the preconditioning and formation of MRPs requires HR to simulate the detailed flow around the Maud Rise-Astrid Ridge complex through Taylor cap dynamics. A realistic simulation of WSPs requires anomalous negative wind stress curl and the ability of the model to produce MRPs as the latter create high surface salinity anomalies that propagate westward with the background flow of the Weddell Gyre, triggering the formation of WSPs and a strong pulse of newly formed Antarctic Bottom Water.
Host: Milena Veneziani