  Permafrost thaw is a major concern raised by the ongoing climate change. An
understudied phenomenon possibly affecting the pace of permafrost thaw is the
onset of convective motions within the active layer caused by the density
anomaly of water. Here, we explore the effects of groundwater convection on
permafrost thawing using a model that accounts for ice - water phase
transitions, coupled with the dynamics of the temperature field transported by
the Darcy's flow across a porous matrix. Numerical simulations of this model
show that ice thawing in the presence of convection is much faster than in the
diffusive case and deepens at a constant velocity proportional to the soil
permeability. A scaling argument is able to predict correctly the asymptotic
velocity. Since in the convective regime the heat transport is mediated by the
coherent motion of thermal plumes across the thawed layer, we find that the
depth of the thawing interface becomes highly heterogeneous.
