Identifying multiscale zonation and assessing the relative importance of polygon geomorphology on carbon fluxes in an Arctic tundra ecosystem

Abstract

We develop a multiscale zonation approach to characterize the spatial variability of Arctic polygonal ground geomorphology and to assess the relative controls of these elements on land surface and subsurface properties and carbon fluxes. Working within an ice wedge polygonal region near Barrow, Alaska, we consider two scales of zonation: polygon features (troughs, centers, and rims of polygons) that are nested within different polygon types (high, flat, and low centered). In this study, we first delineated polygons using a digital elevation map and clustered the polygons into four types along two transects, using geophysical and kite-based landscape-imaging data sets. We extrapolated those data-defined polygon types to all the polygons over the study site, using the polygon statistics extracted from the digital elevation map. Based on the point measurements, we characterized the distribution of vegetation, hydrological, thermal, and geochemical properties, as well as carbon fluxes, all as a function of polygon types and polygon features. Results show that nested polygon geomorphic zonation-polygon types and polygon features-can be used to represent distinct distributions of carbon fluxes and associated properties, as well as covariability among those properties. Importantly, the results indicate that polygon types have more power to explain the variations in those properties than polygon features. The approach is expected to be useful for improved system understanding, site characterization, and parameterization of numerical models aimed at predicting ecosystem feedbacks to the climate.

Mapping snow depth within a tundra ecosystem using multiscale observations and Bayesian methods

“…1). This study domain has been characterized intensively in the NGEE Arctic project, leading to various ecosystem and subsurface datasets, including snow depth measurements (Wainwright et al, 2015;Dafflon et al, 2016). Mean annual air temperature at the Barrow site is −11.3 • C and mean annual precipitation is 173 mm (Liljedahl et al, 2011).…”

“…Ice-wedge polygons are prevalent in the region, including low-centered polygons in drained thaw lake basins and highcentered polygons with well-developed troughs in the upland tundra (Hinkel et al, 2003;Wainwright et al, 2015). The dominant plants are mosses (Dicranum elongatum, Sphagnum), lichens and vascular plants (such as Carex aquatilis); plant distribution at the site is governed by surface moisture variability (e.g., Hinkel et al, 2003;Zona et al, 2011).…”

“…Snowmelt water can lead to extensive inundation of low-gradient tundra and large runoff events in early summer (Bowling et al, 2003;Kane et al, 1991;Liljedahl et al, 2016). Since soil biogeochemistry and vegetation are controlled by soil moisture (Sjögersten et al, 2006;Wainwright et al, 2015), the amount of snow affects ecosystem functioning throughout the season.…”

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

“…A similar approach was taken by Hubbard et al (2013) and Wainwright et al (2015) using geophysical and remotely sensed data as input to the cluster analysis. Other studies (e.g., Hinkel et al, 2003;Zona et al, 2011), however, have only used spatial, remotely sensed data to classify the spatial heterogeneity (vegetation, microtopography, etc.…”

Terrestrial laser scanning for quantifying small-scale vertical movements of the ground surface in Artic permafrost regions

“…As the accuracy of laser scanning systems has improved, ALS and TLS 20 have been used to study lowland sub-Arctic permafrost regions (Chasmer et al, 2011;Gangodagamage et al, 2014;Wainwright et al, 2015;Nouwakpo et al, 2016). In this context, the authors point out that the small number of studies using laser scanning to consider changes in permafrost is still insufficient for an improved understanding of these frozen ground areas.…”