Seasonal thaw settlement at drained thermokarst lake basins, Arctic Alaska

L Liu,A Gusmeroli,K Schaefer,T Zhang,A D Parsekian,G Grosse,B M Jones,H A Zebker

doi:10.5194/tc-8-815-2014

Abstract

Abstract. Drained thermokarst lake basins (DTLBs) are ubiquitous landforms on Arctic tundra lowland. Their dynamic states are seldom investigated, despite their importance for landscape stability, hydrology, nutrient fluxes, and carbon cycling. Here we report results based on high-resolution Interferometric Synthetic Aperture Radar (InSAR) measurements using space-borne data for a study area located on the North Slope of Alaska near Prudhoe Bay, where we focus on the seasonal thaw settlement within DTLBs, averaged between 2006 and 2010. The majority (14) of the 18 DTLBs in the study area exhibited seasonal thaw settlement of 3–4 cm. However, four of the DTLBs examined exceeded 4 cm of thaw settlement, with one basin experiencing up to 12 cm. Combining the InSAR observations with the in situ active layer thickness measured using ground penetrating radar and mechanical probing, we calculated thaw strain, an index of thaw settlement strength along a transect across the basin that underwent large thaw settlement. We found thaw strains of 10–35% at the basin center, suggesting the seasonal melting of ground ice as a possible mechanism for the large settlement. These findings emphasize the dynamic nature of permafrost landforms, demonstrate the capability of the InSAR technique to remotely monitor surface deformation of individual DTLBs, and illustrate the combination of ground-based and remote sensing observations to estimate thaw strain. Our study highlights the need for better description of the spatial heterogeneity of landscape-scale processes for regional assessment of surface dynamics on Arctic coastal lowlands.

Highlights

Thermokarst lakes are ubiquitous and dynamic landscape features on Arctic tundra lowlands (Sellman et al, 1975; Mackay, 1988; Frohn et al, 2005; Hinkel et al, 2005; Grosse et al, 2013)
Many thermokarst lakes drain, leaving depressed wetland basins known as drained thermokarst lake basins (DTLBs) (Mackay, 1988; Hinkel et al, 2007; Marsh et al, 2009)
We present the active layer thickness (ALT), the seasonal subsidence, and the thaw strains along the ground penetrating radar (GPR) transect (Fig. 6)

Summary

Introduction

Thermokarst lakes (or thaw lakes) are ubiquitous and dynamic landscape features on Arctic tundra lowlands (Sellman et al, 1975; Mackay, 1988; Frohn et al, 2005; Hinkel et al, 2005; Grosse et al, 2013). These lakes form as icerich permafrost thaws. Thermokarst lakes and DTLBs cover 50–75 % of the land surface in extensive Arctic lowland regions with ice-rich permafrost (Grosse et al, 2013)

Methods

Results

Discussion

Conclusion