Trends in CO2 exchange in a high Arctic tundra

Permafrost is a solid layer of frozen rock and soil which is mainly found in heart of Arctic, where the average annual temperature lies below ~23°F (-5° C). The Arctic tundra, with underlying permafrost, is stark and treeless all year around but in summer, the topmost layer of the permafrost melts, leaving behind soggy ground and lakes. In recent years, an increase in average global temperatures has resulted in the permafrost retreating northward which has reduced its global coverage to below 20 percent. Significant rise in sea levels, acceleration of global warming and release of greenhouse gases such as CH4 and CO2 into the atmosphere are a number of issues that will contribute to the devastation of permafrost in arctic tundra.

 

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The importance of monitoring ecosystem in Greenland

Greenland Ecosystem Monitoring (GEM) is a long-term research program on ecosystems and climate change effects in the Arctic. The core of this program is designed to provide a comprehensive and long-term data collection system to understand functioning of ecosystems and their responses to climatic changes. The GEM program is currently divided into 5 subprograms; Climate basis, Marine basis, GlacioBasis, BioBasis and GeoBasis.

Zeckenberg research Station (GeoBasis data collection site), is an ecosystem research and monitoring facility at Zackenberg (74º28’ N, 20º34’ W) in Northeast Greenland, 25 km north-west of Daneborg. This facility which is one of the longest running ecosystem/climate monitoring sites in the arctic, provides a wealth of historical environmental data. It has been reported that the permafrost at the Zackenberg site has experienced strong warming and increased ecosystem respiration (Reco) during the last decade. As a result, continued arctic warming will transform the ecosystem into a source of atmospheric CO2 and thus establish a permafrost carbon feedback to the climate system.

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11 years of data collection

Magnus Lund, manager of the GeoBasis monitoring program in Zackenberg, NE Greenland and PI for Zackenberg ecosystem station which is a Danish Integrated Carbon Observation System Research Infrastructure (ICOS) site. Magnus and his team have monitored CO2 and energy fluxes using eddy covariance techniques since the year 2000. Zackenberg heath site is currently equipped with an eddy covariance system supplemented with a wide array of air and soil meteorological measurements including temperature, humidity, wind speed, NDVI, short and long-range radiation PAR, soil moisture and active layer depth. Eddy covariance footprint modeling of the area, has indicated that the majority of the detected CO2 fluxes emanated from the Cassiope heath plant community type. The Cassiope heath is the dominant plant community type in all directions surrounding the eddy covariance system except for the 0°– 90° sector, where Salix snow bed and grassland plant community types dominate.

 

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Based on 11 years of measurements (2000–2010), it was found that snow cover dynamics are an important factor controlling CO2 exchange. The start of the CO2 uptake period significantly correlated with timing of snowmelt. Furthermore, CO2 emission rates were increased in spring of the years with deep and long-lasting snowpacks. In the first part of the study period, there was an increase of approximately 8 g C /m2 yr in both accumulated gross primary production (GPP) and CO2 sink strength during summer. However, in the last few years there were no significant changes in GPP, whereas Reco increased and ecosystem CO2 sink strength weakened by approximately half. As it was expected, the interannual variations in CO2 exchanges was controlled by temperature and temperature related variables such as thaw depth and growing degree. However, as Reco continued to increase, the initial increase in GPP with temperature leveled off at the high end of observed temperature range. At this point future increases in temperature will weaken the ecosystem CO2 sink strength or even turn it into a CO2 source, depending on possible changes in vegetation structure and functioning, as a response to a changing climate.

Breaking down the problem: Eosense’s role

Mechanistic models such as dynamic vegetation, land surface and process oriented coup model are used to describe the physical and biogeochemical processes of arctic tundra in detail. Moreover, using eddy covariance, the net ecosystem exchange (NEE) can be measured and partitioned into GPP and Reco. However acquiring independent data on components of Reco into soil and plant respiration can provide valuable data on the relationship of temperature, vegetation type and carbon feedback of permafrost. Furthering the break down of the Reco into the soil and plant respiration without specialized measurement techniques like automated soil respiration systems remains a challenge.

 

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To overcome these challenges and provide a platform for partitioning the effect of each component of Reco, Zackenberg research station will use the eosFD soil CO2 flux sensor which uses Eosense’s patented Forced Diffusion technology to directly measure soil CO2 flux. Forced Diffusion (FD) dynamic chambers, contain a gas permeable membrane that passively regulates mixing of atmosphere and soil air in the chamber, in place of the active pumping system inside a regular dynamic efflux chamber system.

The eosFD soil flux sensor is better suited than other automated soil respiration systems for long-term, remote and off-grid deployments, especially in environments that have harsh environmental conditions. They also provide the advantages of being easy to put into practice, requiring only a few pieces of easy to deploy equipment, very little human intervention and are thus ideal for a remote sites like Zackenberg.

 

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For more information on technical specification of eosFD-CO2 please download our brochure.

And stay tuned for our upcoming scientific presentations and case study, which will present preliminary data collected at the Zackenberg site.