Scenario-based climate change modelling for a regional permafrost probability model of the southern Yukon and northern British Columbia, Canada

Abstract

Scenario-based climate change modelling for equilibrium conditions was applied to a Regional Model of permafrost probability for the southern Yukon and northwestern British Columbia. Under a −1 K cooling scenario, permafrost area expands from 58% (present day) of the 490 000 km2 to 76%, whereas warming scenarios of +1 K, +2 K and +5 K decrease the terrain underlain by permafrost to 38%, 24% and 9% respectively. The morphology of permafrost gain/loss under these scenarios is controlled by the Surface Lapse Rate (SLR), which varies across the region below and above treeline. The SLR is an air temperature elevation gradient that that is noticeably different across the study region. As a result of this attribute three distinct patterns of loss morphology can be identified. Areas that are more maritime exhibit SLRs characteristically similar above and below treeline resulting in low probabilities of permafrost in valley bottoms. Consequently, a loss front moves to upper elevations when warming scenarios are applied (Simple Unidirectional Spatial Loss). Areas where SLRs are gentle below treeline (but normal/negative) and normal above treeline show lower permafrost probabilities with a loss front moving up mountain according to two separate SLRs (Complex Unidirectional Spatial Loss). Finally areas that display high continentally exhibit Bidirectional Spatial Loss where the loss front of lower permafrost probabilities moves up mountain above treeline and down mountain below treeline. Areas that are most affected by permafrost loss are zones with SLRs close to 0 K km−1 where permafrost is extensive, whereas the least susceptible areas to changes in MAAT are above treeline and are highly elevation dependent.