Assessment of LiDAR and Spectral Techniques for High-Resolution Mapping of Sporadic Permafrost on the Yukon-Kuskokwim Delta, Alaska

Matthew Whitley,Gerald Frost,Samantha Winder,Chris Maio,Matthew Macander,M Jorgenson

doi:10.3390/rs10020258

Abstract

Western Alaska’s Yukon-Kuskokwim Delta (YKD) spans nearly 67,200 km2 and is among the largest and most productive coastal wetland ecosystems in the pan-Arctic. Permafrost currently forms extensive elevated plateaus on abandoned floodplain deposits of the outer delta, but is vulnerable to disturbance from rising air temperatures, inland storm surges, and salt-kill of vegetation. As pan-Arctic air and ground temperatures rise, accurate baseline maps of permafrost extent are critical for a variety of applications including long-term monitoring, understanding the scale and pace of permafrost degradation processes, and estimating resultant greenhouse gas dynamics. This study assesses novel, high-resolution techniques to map permafrost distribution using LiDAR and IKONOS imagery, in tandem with field-based parameterization and validation. With LiDAR, use of a simple elevation threshold provided a permafrost map with 94.9% overall accuracy; this approach was possible due to the extremely flat coastal plain of the YKD. The addition of high spatial-resolution IKONOS satellite data yielded similar results, but did not increase model performance. The methods and the results of this study enhance high-resolution permafrost mapping efforts in tundra regions in general and deltaic landscapes in particular, and provide a baseline for remote monitoring of permafrost distribution on the YKD.

Highlights

Permafrost, or perennially frozen ground, is an important landscape feature for much of the Arctic and sub-Arctic regions of the world
29 distinct transitions from permafrost plateau to coastal meadow were observed along the transects, 27 of which were within the Light Detection And Ranging (LiDAR) swath
Permafrost was rarely encountered in the Riverine Moist Graminoid Shrub Meadow (RMGSM), Lowland Wet Sedge-Shrub Meadow (LWSSM), and Lowland Wet Graminoid Shrub Meadow (LWGSM) ecotypes; and no permafrost was encountered in the Water class (Figure 5)

Summary

Introduction

Permafrost, or perennially frozen ground, is an important landscape feature for much of the Arctic and sub-Arctic regions of the world. With increasing air and ground temperatures across the Arctic, monitoring permafrost degradation (e.g., thermokarst) is important for understanding processes at both the local and the larger regional and global scales. Since nearly half of Alaska lies within the zones of isolated permafrost (>0–10% permafrost landcover), sporadic permafrost (10–50%), or discontinuous permafrost (50–90%), large areas are at risk of being affected by permafrost thaw in the future [2]. This is especially true on the Yukon-Kuskokwim Delta (YKD), which is near the southern limit of permafrost in Alaska

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