Frozen tundra
Thawing bank
Lake water
Drained basin
A small seed pond on ice-rich permafrost is rarely stable. This 2D cross-section models the same real physics as the full 3D terrain: a Stefan-problem square-root thaw front deepens the lake floor once a permanently unfrozen talik forms beneath it, while fetch-boosted lateral thermal erosion retreats the banks faster as the lake widens. Push the climate warming-rate slider up to watch water temperature climb over simulated decades, and see whether the accumulating bank erosion crosses the computed threshold distance to the outlet channel before you reset — triggering the catastrophic drainage that has turned much of the Arctic tundra into a patchwork of round lakes and flat drained lake basins.