Supra-permafrost Subsurface Flow on the Arctic Coastal Plain of Alaska

Abstract:

Subsurface flow is often considered to be a minor component of arctic coastal water budgets due to low land surface slopes and shallow, impermeable permafrost. However, in these landscapes the ground may thaw up to a meter during summer, and microtopography on lake shores and ground ice gradients may promote subsurface flow. Using permeameter and infiltration tests coupled with lake water budgets, we test the hypothesis that subsurface flow may be an important component of arctic lake water budgets after the spring freshet. Water budgets incorporating only evaporation, precipitation, and stream discharge indicated substantial, unmeasured fluxes that varied in direction and magnitude in full and partially-drained lakes. We were able to successfully reproduce the observed fluxes with a model incorporating drainage from thawing soils, storm runoff, and lake edge evapotranspiration. Thaw drainage was the dominant flux in a full lake, and runoff and evapotranspiration became increasingly important in partially drained lake basins. Our results suggest that supra-permafrost flow is an important component of arctic lake water budgets that must be considered to accurately predict water, solute, and heat fluxes in a changing Arctic.