Under the co-ordination of Prof. Jef Vandenberghe the IPA- Action Group has terminated the project 'Permafrost extension during the Last Glacial Maximum in the northern hemisphere and derived mean annual temperatures'. The map of maximum permafrost extension towards the end of the last glacial is published in Boreas 43-3 (2014) together with a number of related papers. The project will be continued in a new action group, coordinated by Prof. Huijun Jin.
Carbon exchange from permafrost soils and ecosystems
Research on the carbon cycle and greenhouse gas emission of present-day permafrost environments is conducted by VU University Amsterdam (Prof A.J. Dolman, Dr. J. van Huissteden) and Wageningen University (Dr. M. Heijmans). The research projects in Siberia are conducted in close collaboration with Russian counterparts (Russian Academy of Sciences - IBPC, Dr. T.C. Maximov) and Zürich University in Switzerland, Dr. Schaepman-Strub.
At the Kytalyk reserve near Chokurdagh in the Indigirka lowlands (VU and Wageningen University) research focusses on CO2 and CH4 fluxes of tundra ecosystems on continuous permafrost. This site is a primary site in the EU Framework 7 PAGE21 project and moreover closely collaborates with Japanese researchers in the GRENE-TEA project who have established research sites in the tundra-taiga transition south of Kytalyk near Chokurdagh.
Starting in 2011, the CO2 and CH4 fluxes at the site have been measured with two eddy covariance towers, one fixed reference tower on an ancient drained thaw lake basin, and one roving tower, set up alternating at the edge of the river floodplain and the edge of a thaw lake (Figure 1). In 2014, the field activities for two PhD projects at Kytalyk, conducting eddy covariance and chamber flux measurements and monitoring of permafrost changes have finished. Flux measurements at the site will be continued in 2015, financed by PAGE21 and a new Dutch research programme, Netherlands Earth System Science Centre (NESSC). Within the framework of NESSC more focus will be laid on the carbon balance with thermokarst lakes. The site now has collected 11 years of CO2 flux data and 10 years of CH4 flux data. A synthesis publication is in progress.
Figure 1. Eddy covariance tower for monitoring CO2 and CH4 fluxes set up near thaw lake bank at Kytalyk research station.
The Wageningen University team continued their measurements in two long-term field experiments: a Betula nana shrub removal experiment and a soil warming experiment. Removing the shrub part of the vegetation initiated thawing of ice-rich permafrost, resulting in collapse of the originally elevated shrub patches into waterlogged depressions within five years. This thaw pond development shifted the plots from a methane sink into a methane source (Nauta et al. 2014, Nature Climate Change). By 2014, one of the 10-m diameter removal plots has become almost completely a pond (Figure 2). In the soil warming experiment, solar panels feed heating cables buried at 15 cm depth in the ground (Figure 3). This additional heating increased thawing depth with consequences for soil moisture, soil available nutrients and vegetation composition. In 2014 we sampled both above and belowground biomass to test whether relatively deep-rooting graminoids expand at the cost of shallow-rooting low shrubs with increased thawing.
Figure 2. Shrub removal plot developing into pond.
Figure 3. Soil warming experiment located in tussock tundra.
Effect of paleo-permafrost on hydraulic properties of sediments
The Dutch Geological Survey (subdivision od TNO) is conducting research on the hydraulic properties of aquifers and aquicludes in Quaternary deposits in the Netherlands. Glacial till in the northern part of the Netherlands can be an important barrier for groundwater flow. Cryoturbation locally leads to sandy intrusions in the upper part of the till, lowering the hydraulic resistance (Figure 4). Recently the excavation of a new waterway in the province of Drenthe revealed cryoturbation structures (see Figure) and allowed in-situ measurements of hydraulic resistance in these cryoturbated zones. This research uses these and other results to determine the general depth and degree of cryoturbation in till in the Netherlands, and quantify its effects on hydraulic conductivity.
Figure 4. Cryoturbatic structures in glacial till.
Report prepared by Ko van Huissteden ( firstname.lastname@example.org)