Long-term climate-influenced land cover change in discontinuous permafrost peatland complexes

Olivia Carpino,Kristine Haynes,James Craig,Ryan Connon,Élise Devoie,William Quinton

doi:10.5194/hess-25-3301-2021

Abstract

Abstract. The discontinuous permafrost zone is undergoing rapid transformation as a result of unprecedented permafrost thaw brought on by circumpolar climate warming. Rapid warming over recent decades has significantly decreased the area underlain by permafrost in peatland complexes. It has catalysed extensive landscape transitions in the Taiga Plains of northwestern Canada, transforming forest-dominated landscapes to those that are wetland dominated. However, the advanced stages of this landscape transition, and the hydrological and thermal mechanisms and feedbacks governing these environments, are unclear. This study explores the current trajectory of land cover change across a 300 000 km2 region of northwestern Canada's discontinuous permafrost zone by presenting a north–south space-for-time substitution that capitalizes on the region's 600 km latitudinal span. We combine extensive geomatics data across the Taiga Plains with ground-based hydrometeorological measurements collected in the Scotty Creek basin, Northwest Territories, Canada, which is located in the medial latitudes of the Taiga Plains and is undergoing rapid landscape change. These data are used to inform a new conceptual framework of landscape evolution that accounts for the observed patterns of permafrost thaw-induced land cover change and provides a basis for predicting future changes. Permafrost thaw-induced changes in hydrology promote partial drainage and drying of collapse scar wetlands, leading to areas of afforestation forming treed wetlands without underlying permafrost. Across the north–south latitudinal gradient spanning the Taiga Plains, relatively undisturbed forested plateau–wetland complexes dominate the region's higher latitudes, forest–wetland patchwork are most prevalent at the medial latitudes, and forested peatlands are increasingly present across lower latitudes. This trend reflects the progression of wetland transition occurring locally in the plateau–wetland complexes of the Scotty Creek basin and informs our understanding of the anticipated trajectory of change in the discontinuous permafrost zone.

Highlights

Northwestern Canada is one of the most rapidly warming regions on Earth (Vincent et al, 2015; Box et al, 2019), and it is transitioning to a warmer state at a rate that appears to have no analogue in the historical record (Porter et al, 2019)
The type of peatland-dominated terrain composed of peat plateau–wetland complexes separated by channel fens as described for Scotty Creek, occupy approximately 35 % of the discontinuous permafrost zones of the Taiga Plains (Fig. 4a)
In the extensivediscontinuous permafrost zone, peatlands are clustered to the west near to the Mackenzie River and are largely absent from the eastern portion of the study area in the region bounded by Great Bear Lake to the north and the Taiga Shield to the east

Summary

Introduction

Northwestern Canada is one of the most rapidly warming regions on Earth (Vincent et al, 2015; Box et al, 2019), and it is transitioning to a warmer state at a rate that appears to have no analogue in the historical record (Porter et al, 2019). This transition includes region-wide thaw and disappearance of permafrost at unprecedented rates (Rowland et al, 2010). The accelerated rates of permafrost warming and thaw observed in recent decades throughout the circumpolar region (Biskaborn et al, 2019), including all of northwestern Canada (Kokelj et al, 2017; Holloway and Lewkowiz, 2019), have dramatically transformed land covers in the southern Taiga Plains (Chasmer and Hopkinson, 2017)

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Results

Conclusion