Permafrost thaw induced drying of wetlands at Scotty Creek, NWT, Canada

Abstract

Northwestern Canada is one of the most rapidly warming regions on Earth. The scale and rapidity of recently observed warming-induced changes throughout this region indicate that it is particularly sensitive to climate warming and capable of rapid responses to perturbations. Unprecedented rates of permafrost thaw in the zone of discontinuous permafrost are transforming forests to wetlands, and changing the distribution and routing of water over the landscape as evidenced by recent increases in basin discharge. However, the impact of increasing basin discharge on basin water storage is not well understood. Water levels on a permafrost plateau, channel fen, and isolated and connected bogs were monitored from 2003-2017 in the Scotty Creek watershed, Northwest Territories. The water level in the channel fen did not significantly change over the period of study, sustained by inputs from the increasingly-connected network of bogs as permafrost barriers thawed. Bogs with varying levels of connection to the drainage network released from storage between 40 and 53 mm of water over the study period. The water level in the monitored isolated bog did not significantly change over this period. Estimates of moisture contributions derived directly from vertical permafrost thaw and from the lateral expansion of contributing areas account for 90% of the observed cumulative increase of 1043 mm in basin runoff between 1998-2012, leaving 109 mm of this increase unaccounted for. Increasing connectivity to the drainage network and transient wetland drainage at the landscape scale resulted from permafrost thaw-induced talik development. The similarity between the magnitude of wetland drainage and that of enhanced runoff suggests that increased connectivity of wetlands to the drainage network may contribute to increasing runoff from the Scotty Creek watershed. Permafrost thaw-induced land cover transition was found to have both short and long-term effects on runoff generation.

Hydrometeorological measurements in peatland‐dominated, discontinuous permafrost at Scotty Creek, Northwest Territories, Canada

“…The considerable observed land cover changes resulting in the loss of permafrost-cored peat plateaus (e.g. Beilman and Robinson, 2003;Pohl et al, 2009) significantly impact the cycling of water through these landscapes (Connon et al, 2014;Haynes et al, 2018b). Long-term increases in streamflow have been documented throughout the Northwest Territories (NWT), with the greatest increases in flow observed in the south-central NWT (St. Jacques and Sauchyn, 2009).…”

Ecosystem carbon response of an Arctic peatland to simulated permafrost thaw

“…In contrast, our study emphasizes the important role CH 4 uptake may play in offsetting the permafrost‐C feedback caused by CO 2 emissions, as long as conditions stay dry. This is an important finding, considering that, in fact, mounting evidence suggests that permafrost degradation will lead to a reduction in wetland extent (Avis, Weaver, & Meissner, ) by increasing runoff and drainage (Haynes, Connon, & Quinton, ; Liljedahl et al, ; Malmer et al, ; Swindles et al, ). Considering the vast Arctic landmasses, enhanced surface drying and deeper thaw is likely to increase the Arctic CH 4 sink, with potential repercussions on the global CH 4 budget.…”

Modelling the effects of permafrost loss on discharge from a wetland‐dominated, discontinuous permafrost basin

“…Channel fens convey run‐off to the basin outlet (Hayashi, Quinton, Pietroniro, & Gibson, ), whereas bogs have been considered storage features in the landscape (Quinton et al, ). However, breaches in permafrost surrounding bogs has increased wetland hydrological connectivity and facilitated the exchange of water between adjacent bogs as well as between bogs and channel fens, contributing run‐off to drainage networks (Connon, Quinton, Craig, Hanisch, & Sonnentag, ; Connon, Quinton, Craig, & Hayashi, ; Haynes, Connon, & Quinton, ). A change in the relative proportion of bog, fen, and peat plateau area in a basin influences the basin hydrograph, with increased run‐off from discontinuous permafrost watersheds attributed to the thaw‐induced increase in run‐off contributing area and transient contributions of wetland drainage (Connon et al, ; Haynes et al, ).…”

“…Predicting basin discharge along the southern margin of permafrost distribution in northwestern Canada depends upon an understanding of the individual impacts of permafrost degradation on the major land cover types and their hydrological interactions. Substantial improvements have been made in understanding the hydrological contributions from peat plateaux (Quinton & Baltzer, ; Quinton & Hayashi, ) and bogs (Connon et al, ; Haynes et al, ) to channel fens with continued permafrost degradation. Despite the functional understanding of fens as lateral transport features conveying water to the basin outlet (Quinton et al, ) and the application of roughness‐based algorithms for approximating surface discharge (Hayashi et al, ), the mechanisms by which channel fens store and transport water are not well understood.…”