The effects of increased ground moisture on permafrost sustainability

Kerr, M., Roy-Leveillee, P. 2018. The effects of increased ground moisture on permafrost sustainability. 2018 Biology Graduate Seminar at Laurentian University, April 2018, Sudbury, ON. doi:10.6084/m9.figshare.6167927

Early stages of permafrost degradation and thermokarst development in Arctic and subarctic lowlands are often characterized by increased soil moisture due to thawing ground ice. In the field, increased soil moisture has been linked to two contradictory effects on ground temperatures: a cooling effect due to the high thermal conductivity of ice compared to water, and a warming effect due to the latent heat of ground moisture slowing ground-frost penetration in early winter. However, the factors controlling which effect will dominate at a given site, and whether increased soil moisture will facilitate or inhibit further permafrost degradation remain unclear. This research investigates the response of increased soil moisture on permafrost temperatures under different climatic conditions using numerical modelling and field data. It aims to identify the conditions under which increasing soil moisture transitions from having a ground cooling effect to having a warming effect that may facilitate continuous thermokarst development. A one-dimensional, heat conduction numerical model will be used to predict active layer depth and mean annual temperature at the top of permafrost based on air temperature, snow pack development, and ground thermal properties. The model will be calibrated with field data from monitoring stations located in peatlands of the discontinuous and continuous permafrost zones in three latitudinal gradients of Northern Canada. This will allow us to examine the effects of current increasing ground moisture, snow cover and air temperature. This research aims to improve the understanding of positive and negative feedback cycles that contribute to permafrost degradation during the early stages of thermokarst development and provide new insights into the timeline of these events. Knowledge of thermokarst development will better inform future restoration and adaptive management practices in response to climate change.