Influence of changing active-layer thickness on PERmafrost Peat Land trace gas Exchanges and carbon balance (PERPLEX)

Project keywords: (at least 4)

Climate change, carbon cycle, eddy covariance, discontinuous permafrost

Name of project lead: Oliver Sonnenag

Project team/partners: For each collaborator please specify: Team member name, role, organization and contact information
J. Baltzer (collaborator, Wilfrid Laurier University); M. Hayashi (collaborator, University of Calgary); W. Quinton (collaborator, Wilfrid Laurier University).

Status: In Progress

Location: Scotty Creek (61°18’48″N, 121°18’22″W)

Year and month project started: 04/2012

Anticipated completion year of project? 03/2027

Executive year of project (example, year 1 or 2 or 3…) year 2

Brief project description:

For millennia, boreal and subarctic peatlands have been acting as long-term carbon (C) sink because annually net primary production has been exceeding respiratory losses of carbon dioxide (CO2) and methane (CH4) and lateral C losses. A large portion of Canada’s northern peatlands is underlain by permanently frozen ground (permafrost) that thaws seasonally at the top over a short growing season. Increases in the thickness of this permeable and biogeochemically active top layer due to ongoing climate change will have severe consequences for peatland ecophysiological and biogeochemical processes by exposing additional organic C to microbial decomposition and by altered peatland hydrology. The impact of a deepening active layer on the fate of permafrost peatlands’ CO2 and CH4 sink-source strengths is largely unknown. The ongoing research project will shed light on how peatland-atmosphere interactions are affected by increasing active-layer thickness (maximum depth to frost table as it descends through the peat profile). The net exchanges of CO2, CH4, water and energy will be measured with the eddy covariance technique. Recent cutting-edge developments in measurement technology resulted in new robust sensors and analyzers designed for use of this technique under harsh conditions in remote locations. Ancillary hydrological and spectral measurements in combination with regular surveys of vegetation composition and structure, snow pack, and surface and frost table topography will aid in establishing the link between continued permafrost degradation and peatlands’ CO2 and CH4 sink-source strengths and C balance. This knowledge is urgently needed for including Canada’s vast peatland C store in the country’s greenhouse gas inventory.

Significance of the results (rationale): / project linkages

What are the key contributions to science/our knowledge base of northern environments

To provide process-based understanding of permafrost thawing consequences for hydrological, ecophysiological and biogeochemical peatland functioning from a climate change perspective. For example, what are the consequences of active-layer thickness, site wetness and vegetation changes for land surface energy partitioning and thus evapotranspiration? Do the reported decrease in net CO2 exchange and the corresponding increase in net CH4 exchange due to increased site wetness as a consequence of active-layer thickness hold at the ecosystem-scale? Do the net ecosystem CO2 and CH4 exchanges respond differently to higher/lower precipitation inputs, which were shown to be more important for active-layer thickness than, for example, thawing season length?

What are the key contributions to cumulative effects monitoring in the NWT?

PERPLEX is centered on eddy covariance, a relatively complex but mature micrometeorological measurement technique that was the central component of Fluxnet-Canada Research Network (FCRN) and the Canadian Carbon Program (CCP) from 2001-2011 (http://www.fluxnet- These two initiatives provided great new insights on the CO2- and CH4 sink-source strengths and water and C balances of Canada’s forest, grassland and peatland ecosystems and their links to the climate system. However, ecosystems underlain by permafrost were not a focus of FCRN/CCP. Through the tight integration of micrometeorological, hydrological and plant ecophysiological perspectives, PERPLEX will substantially improve our understanding of how these sensitive ecosystems might respond to an increasingly warmer climate.

Which decision-makers will likely be impacted by / interested in results?

Results from PERPLEX are of great relevance for policy- and decision-makers. Despite their importance for the C cycle, peatland ecosystems were not explicitly accounted for in the UNFCCC’s Kyoto Protocol. This major deficiency is expected to be remedied in future legislative efforts to adapt to climate change, thus better understanding and careful quantification of this vast C store is urgently needed for its inclusion into Canada’s greenhouse gas inventory.

What is the relevance to communities?

Better understanding of how continued permafrost thawing might affect land surface conditions (e.g., topography, vegetation composition and structure) is of fundamental importance for planning, building and maintaining northern infrastructure.

What are the project milestones? (including beginning date and anticipated end-date)

August 2012 – September 2016: Eddy covariance and ancillary measurements at Scotty Creek. The infrastructure was built in 2012, the measurements will start May 2013.

Engagement, training and capacity building

The degree to which the Mackenzie Valley currently acts and will act in the future as a carbon sink or source has substantial implications for land-use decisions in the NWT as well as policy decisions made nationally and internationally. The research is therefore likely of substantial interest to many NWT-based institutions and residents. Sonnentag will work with Wenman to organize a brown-bag lunch in October, 2013 which will provide an initial opportunity to discuss how NWT decision-makers would like to be involved in and kept updated on this research.

Links to WSIPlan and NWT Science Agenda

Key to Success 2.1 I (Water Stewardship Strategy)
Develop and implement collaborative research and monitoring programs for environmental stressors that can contribute to cumulative effects on NWT watersheds.

Key project tasks for next year (work plan pieces – research): Installation instrumentation and start making eddy covariance and ancillary measurements (May 2013).

Published Papers

Sonnentag O, et al. (2010) On the relationship between water table depth and water vapor and carbon dioxide fluxes in a minerotrophic fen. Glob Change Biol 16:1762-1776
Sonnentag O, et al. (2008) Spatially explicit simulation of peatland hydrology and carbon dioxide exchange: Influence of mesoscale topography. J Geophys Res-Biogeo 113:1-16