SubZero: a new discrete element sea ice model with an explicit representation of floe lifecycle

Описание: The multi-scale nature of sea ice presents a challenge for developing realistic models. At scales below 100 km, sea ice dynamics are commonly conceptualized as a collection of interacting floes of various sizes and thicknesses. To explicitly simulate the lifecycle of individual floes, including their shapes, sizes, and thicknesses, we developed a new discrete element sea ice model -- SubZero. Its elements are polygonal floes with time-evolving boundaries due to various physical processes such as fracture, welding, rafting, and ridging that are currently parameterized using idealized laws but could be improved upon direct comparison with floe-scale in-situ and remote sensing observations. The key advantage of SubZero over existing discrete element sea ice models is that it allows deformation and fractures of its elements and is capable of simulating non-convex floes, with floe size and thickness distributions being well-defined based on the model state variables. We will demonstrate the model capabilities in simulating the equilibration of winter-time sea ice with floe size and thickness distributions similar to observational estimates. We will also present the test simulation of sea ice passing through the Nares Strait in the late spring where floes are subject to only fractures and melting, thus changing their floe size and thickness distributions as they propagate through the strait. Finally, we will discuss how changes to different parameters such as the sea ice thickness, friction between the floes, and the rate of fractures impact various metrics such as the flux and floe size distribution of sea ice through the strait. With its ability to represent the lifecycle of floes, SubZero could provide a more realistic representation of floe-scale dynamics and enable a more direct utilization of floe-scale observations for purposes of model validation, development of parameterizations, data assimilation, and process studies.