Thermokarst Lake Bank Erosion & Drainage

Thaw Forcing

Summer water temperature 4.0 °C

Ground ice content (excess ice) 1.00×

Simulation speed 6 yr/s

Allow outlet-channel drainage

Basin State

Expanding

Lake area

0.09 ha

Elapsed time

0 yr

Mean water depth

0.00 m

Bank retreat rate

— m/yr

How it works

A thermokarst lake grows two ways at once. Its bank retreats sideways because standing lake water is warmer than the surrounding frozen ground, so heat conducts laterally into the ice-rich permafrost wall and melts it out — a thermo-erosional niche undercuts the bank until it collapses into the lake:

dR/dt = k · (T_water − T_f) · n_ice
R = bank position, T_f = 0°C, n_ice = excess ground-ice fraction

Its floor deepens because open water prevents the ground below from ever fully refreezing in winter, so an unfrozen talik forms and the Stefan thaw front keeps advancing year-round instead of resetting each season:

Δz_floor ≈ −c · T_water · n_ice · Δt   (talik thaw, no winter re-freeze)

When ice-rich ground thaws, the excess ice that occupied pore space melts to water and drains away, so the ground surface subsides by roughly the ice fraction times the thaw increment — this is what actually converts a thawed bank cell into new lake surface:

Δz_subsidence = n_ice · ΔX_thaw

Water temperature and ice content both multiply directly into the erosion and subsidence rates above.
If the expanding shoreline reaches the lower outlet channel cut into the terrain, the basin breaches and drains catastrophically over a few years — a real, well-documented fate of Arctic thermokarst lakes that leaves a dry drained thaw-lake basin (DTLB) behind. Uncheck the toggle to keep the lake perched instead.
Reset lake restores the original seed pond and terrain so you can compare scenarios.

This cycle — expansion, deepening over a talik, then drainage — is why large stretches of Arctic tundra are patchworks of round lakes and flat, grassy drained basins rather than a uniform frozen plain.

Frozen tundra Thawing bank Lake water Drained basin

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