Geophysical Investigation Into The Drivers And Implications Of Sub Lake Permafrost Thaw PDF Download

Arctic landscapes are more susceptible to stronger and earlier impacts from climate change than are the mid-latitudes. The potential for the vast amount of carbon that has been stored in permafrost soils (1400-1850 Pg, Grosse et. al, 2011) for thousands of years to be mobilized due permafrost degradation and thermokarst development in response to climate change is poorly understood and of global importance. With the prevalence of thermokarst lakes in arctic regions, thaw beneath these lakes in response to a changing climate will be an important pathway for carbon and methane release into the atmosphere. Using a lake ice regime classification based on spaceborne synthetic aperture radar over a 25-year time period, we can begin to decipher the trends in bedfast ice extent in response to differing environmental parameters and ambient conditions. Trends in the distribution of bedfast ice extent for lakes in the 0-60% bedfast ice interval emerged by applying a robust probability density function statistical methodological technique. Simple linear regression analysis revealed statistically significant slopes and good model performance in the vulnerable sub-population of lakes that are floating ice across the Inner and Outer Coastal Plains of the North Slope. Using transient electromagnetic soundings on 33 lakes, we can characterize the electrical resistivity profiles of lakes of different ice regimes. In general, bedfast ice regime lakes had the most resistive profile corresponding to little to no permafrost thaw and floating ice lakes had the least resistive profiles corresponding to associated permafrost thaw beneath them. Transitional ice lake profiles were more closely related to floating ice lake profiles than bedfast ice. In a case study of eleven transitional ice lakes in the Barrow region, we find there exists a linear relationship between the proportion of time a lake has been under floating ice conditions and the depth of the talik. Combining lake initiation age, thermal modeling using available ground material properties, and geophysical investigations we are able to independently determine talik thickness across transects of a lake with different lake shore expansion rates. Both thermal modeling and geophysical methods showed deeper talik development than previous modeling studies on the Alaskan coastal plain. The products of this work include past, present, and projected distribution of bedfast ice regime lakes in the study areas across the Alaskan North Slope and permafrost thaw associated with the change in ice regime. These results, when coupled to the permafrost-water-climate system, greatly increase our understanding of how lake rich arctic regions are responding in response to changing ambient weather conditions. This is of particular importance for expanses of lowland Alaska, Canada, and Siberia where arctic amplification has been severe and expected to continue.