Controls on carbon dioxide and methane fluxes from a low-center polygonal peatland in the Mackenzie River Delta, Northwest Territories

June Skeeter,Andreas Christen,Greg H.R. Henry

doi:10.1139/as-2021-0034

June Skeeter, Andreas Christen + Show 1 more

Open Access

https://doi.org/10.1139/as-2021-0034

Copy DOI

Abstract

Growing season surface–atmosphere exchange of carbon dioxide and methane were quantified at Fish Island, a wetland site in the lower northeast Mackenzie River Delta, Northwest Territories, Canada. The terrain consists of low-center polygonal tundra and is subject to infrequent flooding in high water years. Carbon dioxide and methane fluxes were continuously measured using eddy covariance and the relevance of different environmental controls were identified using neural networks. Net daily carbon dioxide uptake peaked in mid-July before gradually decreasing and transitioning to net daily emissions by September. Variations in light level and temperature were the main controls over diurnal net carbon dioxide uptake, whereas thaw depth and phenology were the main seasonal controls. Methane emissions measured at Fish Island were higher than comparable studies on river delta sites in the Arctic and were influenced by the interaction of a large number of factors including thaw and water table depth, soil temperatures, and net radiation. Spikes in methane emissions were associated with strong winds and turbulence. The Fish Island tundra was a net sink for carbon during the growing season and methane emissions only slightly reduced the overall sink strength.

Highlights

The Canadian Arctic has experienced significant recent warming: mean annual temperatures increased 2.3 K from 1948 to 2016 (Zhan et al 2019)
Variations in light level and temperature were the main controls over diurnal net carbon dioxide uptake, while thaw depth and phenology were the main seasonal controls
Methane emissions measured at Fish Island were higher than comparable studies on river delta sites in the Arctic and were influenced by the interaction of a large number of factors including thaw and water table depth, soil temperatures and net radiation

Summary

Introduction

The Canadian Arctic has experienced significant recent warming: mean annual temperatures increased 2.3 K from 1948 to 2016 (Zhan et al 2019). Warming has and will continue to have significant impacts across the Canadian Arctic, including: permafrost degradation and increased active layer thickness, decreased snow cover and longer snow free seasons, changes in surface energy balance, and tundra greening (Derksen et al 2019; Frost et al.2020). Climate change related disturbances put these shallow permafrost C stocks at risk for release into the atmosphere, as carbon dioxide (CO2) and methane (CH4) via aerobic and anaerobic respiration, respectively (Tarnocai et al, 2009; Hugelius et al, 2014; Schuur et al, 2015; Turetsky et al, 2020). Longer growing seasons, more liquid water availability, and enhanced plant growth could have the opposite effect increasing CO2 uptake in some areas (Prowse et al, 2009)

Objectives

Methods

Results

Discussion

Conclusion