Abstract
Abstract. Soils in Arctic and boreal ecosystems store twice as much carbon as the atmosphere, a portion of which may be released as high-latitude soils warm. Some of the uncertainty in the timing and magnitude of the permafrost–climate feedback stems from complex interactions between ecosystem properties and soil thermal dynamics. Terrestrial ecosystems fundamentally regulate the response of permafrost to climate change by influencing surface energy partitioning and the thermal properties of soil itself. Here we review how Arctic and boreal ecosystem processes influence thermal dynamics in permafrost soil and how these linkages may evolve in response to climate change. While many of the ecosystem characteristics and processes affecting soil thermal dynamics have been examined individually (e.g., vegetation, soil moisture, and soil structure), interactions among these processes are less understood. Changes in ecosystem type and vegetation characteristics will alter spatial patterns of interactions between climate and permafrost. In addition to shrub expansion, other vegetation responses to changes in climate and rapidly changing disturbance regimes will affect ecosystem surface energy partitioning in ways that are important for permafrost. Lastly, changes in vegetation and ecosystem distribution will lead to regional and global biophysical and biogeochemical climate feedbacks that may compound or offset local impacts on permafrost soils. Consequently, accurate prediction of the permafrost carbon climate feedback will require detailed understanding of changes in terrestrial ecosystem distribution and function, which depend on the net effects of multiple feedback processes operating across scales in space and time.
Highlights
Permafrost, or perennially frozen ground, underlies approximately 24 % of Northern Hemisphere land masses, primarily in Arctic and boreal regions (Brown et al, 1998)
We focus on how ecosystem responses to a changing climate alter the thermal balance of permafrost soils and how these thermal dynamics translate into seasonal and interannual temperature shifts
While there are a number of studies that have examined the role of variation in vegetation canopy cover, soil moisture, and ground/soil thermal properties on the permafrost thermal regime, few have fully isolated the relative contribution of each process to variation in active layer thickness or soil temperatures (Jiang et al, 2015)
Summary
Permafrost, or perennially frozen ground, underlies approximately 24 % of Northern Hemisphere land masses, primarily in Arctic and boreal regions (Brown et al, 1998). The areal distribution of permafrost may be continuous (> 90 % areal extent), whereas at lower latitudes discontinuous, sporadic, and isolated permafrost (> 50 %–90%, 10 %–50 %, and < 10 % areal extent, respectively) (Brown et al, 1998) have large areas that are not perennially frozen This general latitudinal gradient is interrupted by considerable local variability in active layer and permafrost thickness and temperature due to differences in local climate, vegetation, soil properties, hydrology, topography, and snow characteristics. Our objectives are to (1) identify and review the key mechanisms by which terrestrial ecosystem structure and function influence permafrost soil thermal dynamics; (2) characterize changes in these ecosystem properties associated with altered climate and disturbance regimes; (3) identify and characterize potential feedbacks and uncertainties arising from multiple opposing processes operating across spatial and temporal scales; and (4) identify key challenges and research questions that could improve understanding of how continued climatemediated ecosystem changes will affect soil thermal dynamics in the permafrost zone
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