Recent Arctic tundra fire initiates widespread thermokarst development.

Benjamin M Jones,Lin Liu,Eric Miller,Guido Grosse,Daniel J Hayes,Christopher D Arp,Christopher F Larsen

doi:10.1038/srep15865

Abstract

Fire-induced permafrost degradation is well documented in boreal forests, but the role of fires in initiating thermokarst development in Arctic tundra is less well understood. Here we show that Arctic tundra fires may induce widespread thaw subsidence of permafrost terrain in the first seven years following the disturbance. Quantitative analysis of airborne LiDAR data acquired two and seven years post-fire, detected permafrost thaw subsidence across 34% of the burned tundra area studied, compared to less than 1% in similar undisturbed, ice-rich tundra terrain units. The variability in thermokarst development appears to be influenced by the interaction of tundra fire burn severity and near-surface, ground-ice content. Subsidence was greatest in severely burned, ice-rich upland terrain (yedoma), accounting for ~50% of the detected subsidence, despite representing only 30% of the fire disturbed study area. Microtopography increased by 340% in this terrain unit as a result of ice wedge degradation. Increases in the frequency, magnitude, and severity of tundra fires will contribute to future thermokarst development and associated landscape change in Arctic tundra regions.

Highlights

Considered one of the primary disturbance mechanisms in boreal forests[27,33]
We investigate the impact of the Anaktuvuk River tundra fire on potential, post-fire thermokarst development and how this might vary given differences in burn severity and inferred ground-ice content at the landscape-scale
The development of thaw-related landforms was observed in the field during the first two summers following the Anaktuvuk River tundra fire (Fig. 2)

Summary

Introduction

Considered one of the primary disturbance mechanisms in boreal forests[27,33]. Recent shifts in the boreal forest fire regime have resulted in carbon emissions that exceed decadal-scale carbon storage during the past 60 years[29,34]. We investigate the impact of the Anaktuvuk River tundra fire on potential, post-fire thermokarst development and how this might vary given differences in burn severity and inferred ground-ice content at the landscape-scale To address these questions, we used two airborne LiDAR datasets, acquired two and seven years following the large and severe Anaktuvuk River tundra fire, to quantify the landscape scale impacts of the fire on Arctic permafrost terrain. A Landsat-derived burn severity metric was used to further analyze spatial differences in the response of the landscape to the tundra fire event To our knowledge, this is the first study to demonstrate the utility of multi-temporal airborne LiDAR data for documenting landscape-scale, fire-induced thermokarst terrain formation in the Arctic or Boreal region. Our results indicate that the impact of tundra fires for initiating widespread thermokarst development in regions with ice-rich permafrost in the Arctic has been underestimated

Methods

Results

Conclusion