May 12 , 2010 Guido Grosse, Thermokarst lake dynamics on the northern Seward Peninsula from 1950-2008, Geophysical Institute, University of Alaska Fairbanks

Thermokarst lake dynamics on the northern Seward Peninsula from 1950-2008

Guido Grosse
Geophysical Institute, University of Alaska Fairbanks

Thermokarst lakes (TKL) are considered an important source of atmospheric CH4 in past, current and future budgets. Previous research reports the loss of TKL area in discontinuous permafrost due to drainage, and an increase in TKL area in continuous permafrost due to thermokarst. Contrary to this current hypothesis, we observe a massive loss of TKL in ice-rich continuous permafrost in a 12,200 km2 study region on the Seward Peninsula (Alaska) using long-term remote sensing data. Several hundred TKL drained completely or partially during the 1950-2008 period. Lake area of more than 8000 ha was lost over the 58 year period. Though most TKL continuously expanded at rates of up to 1.5 m/yr, the growth did not offset the area loss from drainage. TKL formation is extremely rare in the study area and only detectable with high-resolution imagery. Our TKL drainage rates are an order of magnitude higher than any previously reported for continuous permafrost zones. Field data and remote sensing show that erosion of ice wedge polygonal networks and gully formation are central mechanisms for TKL drainage in ice-rich continuous permafrost, highlighting the potential impact of continued surface permafrost degradation on future lake drainage rates.