Hydrological impacts of seismic lines in the wetland-dominated zone of thawing, discontinuous permafrost, Northwest Territories, Canada

Intensive seismic exploration in the Northwest Territories began in the late 1960s. Since that time, the legacy of seismic surveys - i.e. straight lines cutting through boreal forest and tundra - has remained visible throughout northern Canada and Alaska. The removal of trees and compaction of the ground surface alter the thermophysical properties of the active (i.e. seasonally thawed) layer to such an extent that the underlying permafrost seriously degrades or even disappears completely. Such a transformation along linear corridors that cut indiscriminately across different terrain types with contrasting hydrological functions has potentially serious implications to the redistribution of water and energy within and among landscape units with feedbacks to permafrost thaw, land cover change and run-off generation. This paper characterizes the flow and storage of water and energy along a seismic cut line in the high boreal zone of discontinuous permafrost in order to improve the understanding of these processes, their interactions and hydrological implications. As such, this paper lays a conceptual foundation for the development of numerical models needed to predict the hydrological and thermal impact of seismic lines in this sensitive region. We used ground-penetrating radar and multi-year ground temperatures and water levels along a seismic line to estimate the degree of permafrost degradation below it. The seismic line studied extends from a permafrost-free wetland (flat bog), over a permafrost body (peat plateau) and into another permafrost-free wetland (channel fen). It was found that once thaw had lowered the permafrost table below the ground surface elevation of the flat bog and channel fen, the seismic line forms a hydrological connection between them. It was also shown that during the permafrost thaw process, seismic lines develop a perennially thawed layer (talik) between the overlying active layer and underlying permafrost and that the talik conveys water as a conduit throughout the year. The implications of such drainage through seismic lines and networks on basin drainage in peatland-dominated regions with discontinuous permafrost are also discussed. Copyright (c) 2015 John Wiley & Sons, Ltd.