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Publication Date
1 April 2021

On the Generation of Weddell Sea Polynyas in a High-Resolution Earth System Model

Study explores how Weddell Sea polynyas form out of Maud Rise polynyas, within the framework of a high-resolution, fully-coupled earth system model simulation.
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Polynyas are large ice-free areas along a coast or amid the winter sea ice pack and are found in the north and south polar oceans in the winter. They play an essential role in modulating the global climate. Due to the complex nature of these processes and lack of observations, they are poorly represented in climate models. Our study helps untangle the different small- and large-scale processes that go into realistically simulating open ocean polynyas in high-resolution climate models and understand their impact on the deep ocean.


Polynyas are an important determinant while evaluating the role of the high-latitudes in the global climate. Polynyas play an important role in modulating global climate by impacting the global ocean thermohaline circulation, and they release heat into the atmosphere and modify mesoscale atmospheric motions. A good understanding of Antarctic polynyas is necessary to know under-ice shelf circulation in changing climatic regimes, which is critical to answering if Antarctica's major ice shelves will remain intact in a warmer climatic regime. Our study has for the first time explained the pre-conditioning and formation mechanisms of Weddell Sea Polynyas in a global high-resolution Earth system model.


This study investigates the processes that explain the occasional westward expansion of Maud Rise polynyas (MRP) into larger Weddell Sea polynyas (WSP) as observed in several winters of the mid-70s. This process is -to some extent- also represented in the pre-industrial simulation with the high-resolution coupled E3SMv0-HR, as analyzed here. WSPs tend to follow periods of a prolonged build-up of a heat reservoir at depth and weakly negative wind-stress curl that is associated with an anomalously northern position of the core of the southern hemisphere westerlies. While this scenario also leads to drier conditions over the central Weddell Sea, which some previous work claims to be a necessary condition for the formation of WSPs, our model results indicate that open-ocean polynyas do not occur during periods of weakly negative wind-stress curl, despite drier atmospheric conditions. Our study supports the hypothesis noted in earlier studies that a shift from a weakly negative to a strongly negative wind-stress curl over the Weddell Sea is a prerequisite for WSPs to form, together with a large heat reservoir at depth. However, the ultimate trigger is a pronounced MRP; convection associated with MRPs creates high surface salinity anomalies that propagate westward with the flow of the Weddell Gyre. If large enough, these anomalies trigger the formation of a WSP and a pulse of newly formed Antarctic bottom water.

Point of Contact
Prajvala Kurtakoti
Los Alamos National Laboratory (LANL)
Funding Program Area(s)