Has a Threshold Been Crossed in the Direction and Rate of Thermokarst Lake Drainage in the Western Canadian Arctic?

Across large regions of the Arctic, thermokarst lakes are prone to rapid, or catastrophic, drainage. Mackay (1992) showed that in the western Canadian Arctic, lakes have been draining at a rate of approximately 1/yr over the last 8,000 years. As the climate has changed over the last decades, there is increasing concern in whether the rate of lake drainage has changed and what the implications will be on flooding, safety and changes in both hydrology and aquatic ecosystems. Marsh et al. (2009) showed that for the period 1950 to 2000 in the western Canadian Arctic, the rate of lake drainage was similar to that reported by Mackay (1992) in the early decades of the study period, but by the end of the period of record the rate of lake drainage had decreased by a third. It was proposed that this decline might be related to a decrease in the rate of ice wedge cracking during the winter - a key lake drainage process described by Mackay (1992). However, our recent research has shown that from 2005 to 2019, the rate of lake drainage in the same region has increased greatly. The reason for this increase in lake drainage is unknown, but it raises significant concern about the long-term viability of these thermokarst lakes. To answer key questions related to this apparent crossing of a key tipping point in the viability of these lakes, we have initiated a new project at the Trail Valley Creek research station, north of Inuvik, NWT, to investigate the controls on thermokarst lake drainage. We will use a combination of field observations, remote sensing, and ultra high-resolution modelling of permafrost terrain and lakes, to answer key questions related to the history of lake drainage over the last 70 years and consider the future viability of these lakes. Marsh, P., et al. (2009). Hydrological Processes, 23(17), 145-158. Mackay, J. R. (1992). Aquatic Ecosystems in Semi-Arid Regions: Implications for Resource Management. Environment Canada. P. 1-26.