Modeling snow isothermal metamorphism at the pore scale with the phase-field model Snow3D

Abstract

<p><span>Representing snow isothermal metamorphism is key to model the evolution and properties of the snow cover. Recently, a new phase-field model allowing to describe 3D microstructure induced by curvature effects has been proposed (Bretin et al, Esiam: M2an, 2019). In the present work, this model is used to simulate isothermal metamorphism of snow at the pore scale, considering the only process of moving interfaces by sublimation-deposition driven by curvatures. This model runs on real 3D microtomographic images and gives a temporal series of 3D images simulating isothermal metamorphism. </span><span>To determine t</span><span>he condensation coefficient </span><span>to use</span><span> in </span><span>the</span><span> model, </span><span>which shows complex dependencies and is still poorly known,</span> <span>we </span><span>calibrated </span><span>it </span><span>by reproducing the time evolution of the specific surface area (SSA) measured during an isothermal experimental time-series at -2&#176;C (Flin et al., Ann. Glaciol., 2004). This calibration has led to a value of the condensation coefficient </span><span>of </span><span>9.9 &#177; 0.</span><span>6</span><span> 10&#8722;4. </span><span>Using this calibration, we obtained a good agreement between simulations and an independent series of </span><span>isothermal metamorphism at -2&#176;C (Hagenmuller et al., The </span><span>C</span><span>ryosphere, 2019). </span>Finally, 4 images representing different types of snow microstructure have been chosen as input to simulate isothermal metamorphism at -2&#176;C during 75 days. <span>The obtained temporal series of 3D images were then used to calculate microstructural (porosity, SSA, covariance lengths) and physical transport properties (thermal conductivity, effective diffusion, permeability) evolution. </span><span>Comparing our numerical es</span><span>timations of physical properties </span><span>to </span><span>current parameterizations </span><span>gives overall good </span><span>agreement</span><span>. An interesting new result arising from the simulations is the conservation or enhancement of the structural anisotropy under isothermal conditions for </span><span>the samples that were initially strongly</span><span> anisotropic.</span></p><p>&#160;</p>