Challenges in Characterizing Geospatial Relationships of Topography in the Arctic

Accurate characterization of ecological process in the Arctic landscape is crucial for informing carbon dynamics of Arctic ecosystems under changing climate. Arctic processes are governed by local environmental and climatic factors such as microtopography, surficial geology, soils, hydrologic conditions, and vegetation, which need to be understood in the context of spatial scale and geomorphology. These processes make it challenging for interpreting data derived from remote sensing and requires careful characterization of geospatial relationships to understand the spatial context of ecological processes. Microtopography is a key defining feature of Arctic landscapes, driving variability in vegetation, permafrost state and other ecological processes at the 1-10 m scale. High resolution elevation datasets such as the ArcticDEM have been critical to define such topographic relationships across the Arctic domain. However, ArcticDEM is not a bare earth DEM, but is a surface model that may include vegetation height or other surface features. Depending on the region of interest and type of analysis, a vegetation bias correction may be needed for better characterization of elevation using ArcticDEM. We compared elevation derived from ArcticDEM with bare earth elevation derived from the Land, Vegetation, and Ice Sensor (LVIS), an airborne, wide-swath imaging laser altimeter for upland and lowland regions around the Mackenzie Delta, Canada. Based on the mean difference in elevation between ArcticDEM and LVIS-derived bare ground elevation, an average vegetation bias correction of 0.18 m for lowland and 0.1m for upland could help account for error due to the vegetation height in the specific study region. However, these elevation offsets are spatially variable and depend on the geomorphology of the region and scale of analysis. Identifying the geomorphological context, spatial scale of analysis, and potential impacts of vegetation on microtopography analysis, is critical to studying permafrost features and associated disturbances in Arctic landscapes.