ASABE Technical Library - Abstract

Cause of Initiation of Thermokarsts in the Arcticas a Result of Permafrost Degradation

Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan www.asabe.org

Citation:  Soil Erosion Research Under a Changing Climate, January 8-13, 2023, Aguadilla, Puerto Rico, USA  .(doi:10.13031/soil.23058)
Authors:   Debasmita Misra, Shishay Kidanu
Keywords:   Energy balance, Gully, Thaw subsidence, Thermal erosion.

Abstract

Thermokarst is a process of soil erosion that is unique to soils underlain by permafrost containing excess ice (Pollard, 2018). These are naturally occurring erosional processes that result from thawing of ice-rich permafrost in the Arctic and the sub-Arctic, and more recently have been observed in the Antarctic. However, the term has been more recently also used to describe processes and landforms associated with the thaw of all forms of ground ice (French, 2007). Thermokarsts occur when the thermal stability of the near surface ice-rich permafrost is destabilized due to increase in the depth of the active layer because of warming of surface temperature. Soil temperatures are elevated due to an increase in air temperature because of shift in climatic regimes. Thermokarsts can occur due to thermal erosion or thaw subsidence. It has been observed that thaw subsidence is primarily vertical in direction and involves downwasting, which tends to occur in flat to low relief areas that often results in surface ponding and shallow depressions (French, 2007).

Thaw subsidence related to permafrost degradation is presently responsible for damage to houses, roads, airports, military installations, pipelines, and other facilities founded on ice-rich permafrost. Thermal erosion occurs on slopes where melting of exposed ground ice results in a retrogressive thaw slump (Pollard, 2018). There is a significant lack of forensic understanding of the degree to which the surface energy balance changes in response to the disturbance that causes initiation and growth of thermokarsts. Equally important is the impact of alterations in the thermal regime of soils on physical stability and consequently, surficial morphology. This lack of understanding stems from the complex nature of the initiation of thermokarsts. Initiation of a thermokarst is a highly dynamic process involving continuous change in surface topography, surface and groundwater quantities, soil properties, vegetation, and snow that affects the energy balance and the heat transfer processes (Jorgenson, 2013). From the field evidence gathered (Figure 1; Misra et al., 2011), we hypothesized that the soil gradient (slope), percent of fine materials in soil, the soil bulk density, depth of the active layer, and the change in the thermal regime initiates a thermokarst. Additionally, the supersaturation of soil provides the hydrostatic head along with the soil moisture movement providing the hydrodynamic force to detach the soil from its matrix and transport it downstream, thus developing the eroded gully. Forensic understanding of the physical processes in initiation and development of thermokarsts in a rapidly changing climate and/or in areas of increased anthropogenic disturbance and forest fires is crucial because the understanding developed and the parameters measured could help reduce potential impacts on engineered structures or the ecosystem in the northern areas. We will present our observations from initial data collected from an emerging thermokarst near Fairbanks in Alaska.

(Download PDF)    (Export to EndNotes)