Ice wedge degradation and CO2 and CH4 emissions in the Tuktoyaktuk Coastlands, Northwest Territories

Abstract

Increases in ground temperature make soil organic carbon in permafrost environments highly vulnerable to release to the atmosphere. High-centred polygonal terrain is a form of patterned ground that may act as a large source of carbon to the atmosphere because thawing ice wedges can result in increased ground temperatures, soil moisture, and thaw depth. To evaluate the effect of ice wedge degradation on carbon flux, carbon emissions were characterized at two polygonal peatlands in the Tuktoyaktuk Coastlands in northern Canada. Opaque chambers were used to measure CO2 and CH4 emissions from nine nondegraded polygon centres and nine moderately degraded troughs four times during the growing season. To measure emissions from 10 ponds resulting from severe ice wedge degradation, wind diffusion models were used to characterize fluxes using CO2 and CH4 concentration measurements made in each pond. Our field data show that degraded troughs had increased ground temperature, deeper active layers, and increased CO2 and CH4 emissions. Our study shows that rates of CO2 and CH4 emissions from high-centreed polygonal terrain are likely to increase with more widespread melt pond formation in this terrain type.

Keywords

• carbon dioxide
• methane
• permafrost
• thermokarst