Estimating Permafrost Distribution, Soil Movement and Their Controlling Factors in Arctic Environments Using Depth-Resolved Measurements of Resistivity, Temperature and Deformation

Authors

Sylvain Fiolleau1, Sebastian Uhlemann1, Stijn Wielandt1, Ian Shirley1, Chen Wang1, Joel Rowland2, Evan Thaler2, Baptiste Dafflon1* (bdafflon@lbl.gov), Colleen Iversen3

Institutions

1Lawrence Berkeley National Laboratory, Berkeley, CA; 2Los Alamos National Laboratory, Los Alamos, NM; 3Oak Ridge National Laboratory, Oak Ridge, TN

URLs

Abstract

Discontinuous permafrost environments exhibit strong spatial heterogeneity and sharp transitions in soil and permafrost thermal conditions, subsurface hydrology, and carbon (C) and energy fluxes. This heterogeneity occurs at scales too small to be driven by weather forcing alone and is regulated by several mechanisms, some still poorly represented in Earth System Models though driving significant uncertainty in the trajectory of C fluxes. A better understanding of the permafrost conditions and soil movements, as well as their controls, is needed to improve the estimates of current and future soil C storage and release.

In this study, researchers investigate the soil deformation triggers and kinematics during the thaw season along a set of adjacent hillslopes across a 2 km2 watershed located on the southern Seward Peninsula, AK. The team used collocated temperature and resistivity measurements with a supervised learning technique to map the spatial distribution of permafrost along the adjacent hillslopes. Further, researchers acquired time series of deformation and temperature data with a dense, low-cost sensor network providing depth-resolved measurements to depths up to 1.8 m at 59 locations. During a five-month monitoring period, displacements of a few millimeters to tens of centimeters were recorded. A detailed analysis of the data allowed the team to highlight the different factors controlling the movements (incline, slope, aspect, thaw layer thickness, soil moisture and permafrost conditions). This study provides a better understanding of the mechanisms controlling permafrost distribution, hillslope movement, and the possible impact on soil C distribution and landslide hazard. Further, this study offers a new window into belowground geomechanical processes that are inherently difficult to observe and can lead to large heterogeneity in C storage and release.