Drainage through holes drives Arctic sea ice melt ponds to the critical percolation threshold

During the summer, vast regions of the Arctic sea ice are covered by meltwater ponds that significantly lower the ice reflectivity and accelerate melting. Ponds develop over the summer melt season through an initial stage of rapid growth followed by drainage through macroscopic holes. Recently, we showed that ponds after drainage resemble percolation clusters near a critical percolation threshold. Here, we explore the physical mechanism behind this previously-unrecognized constraint on pond evolution. We show that organization towards the percolation threshold is a consequence of pond drainage through macroscopic holes. The threshold sets the upper limit and scales the pond coverage throughout its evolution after the beginning of drainage. Furthermore, we show that, after rescaling, pond coverage fraction as a function of number of open holes follows a universal curve. This curve governs pond evolution during and after pond drainage, which allows us to formulate an equation for pond coverage evolution that captures the dependence on ice properties.