Scaling-up permafrost thermal measurements in western Alaska using an ecotype approach

Abstract

Abstract. Permafrost temperatures are increasing in Alaska due to climate change and in some cases permafrost is thawing and degrading. In areas where degradation has already occurred the effects can be dramatic, resulting in changing ecosystems, carbon release, and damage to infrastructure. However, in many areas we lack baseline data, such as subsurface temperatures, needed to assess future changes and potential risk areas. Besides climate, the physical properties of the vegetation cover and subsurface material have a major influence on the thermal state of permafrost. These properties are often directly related to the type of ecosystem overlaying permafrost. In this paper we demonstrate that classifying the landscape into general ecotypes is an effective way to scale up permafrost thermal data collected from field monitoring sites. Additionally, we find that within some ecotypes the absence of a moss layer is indicative of the absence of near-surface permafrost. As a proof of concept, we used the ground temperature data collected from the field sites to recode an ecotype land cover map into a map of mean annual ground temperature ranges at 1 m depth based on analysis and clustering of observed thermal regimes. The map should be useful for decision making with respect to land use and understanding how the landscape might change under future climate scenarios.

Land Cover Mapping in Northern High Latitude Permafrost Regions with Satellite Data: Achievements and Remaining Challenges

“…Only general classes can be derived, and applicability has been proven in permafrost transition zones only. The relevant types are peatlands (with differentiation by vegetation cover) [73] and ecotypes that distinguish between low and tall shrubs, as well as their characteristic moss and organic layers [75]. This demand for details on shrubs coincides with statements in studies for numerical permafrost modeling [1,80].…”

“…A land cover map was produced, and values for peat thickness and vegetation height were associated with the resulting classes. Ground temperatures have been up-scaled using an ecotype land cover map (from among other sources, Landsat, stratified NDVI and unsupervised classification of Jorgenson et al [74]) on a regional scale [75]. The available classes were grouped into four clusters representing certain ground temperature ranges in a permafrost transition zone in Alaska.…”

Modeling the role of preferential snow accumulation in through talik development and hillslope groundwater flow in a transitional permafrost landscape

“…The effect of ground warming as a result of tundra shrubification has been discussed in previous studies (Lynch et al 1999, Chapin et al 2000, Cable et al 2016. However, the ramification of snow-shrub interactions is not linear and depends on multiple factors (Sturm et al 2005).…”

“…Shifting climate conditions in the Arctic are driving evolution of permafrost landscapes that include changes in, and complex interactions between, plant productivity and species distribution, permafrost degradation, hydrologic processes, and the terrestrial carbon cycle and energy balance (AMAP 2017). Increasing migration of shrubs into tundra could lead to positive changes in surface energy balance and net loss of carbon from the ecosystem (Bret-Harte et al 2002, Cable et al 2016. Shrub-snow interaction could boost winter heating by up to 70% for exposed shrubs, leading to warmer soil temperature below shrubs over winter periods (Sturm et al 2005).…”

Holocene permafrost history and cryostratigraphy in the High‐Arctic Adventdalen Valley, central Svalbard

“…) or using an ecotype approach (Cable et al . ). Upscaling of soil organic carbon in mountainous NE Greenland based on a vegetation map identified that vegetation is a poor indicator for the burial history of organic matter in areas with sedimentation (Palmtag et al .…”