Modelling methane emissions from arctic wetlands: A comparison between two sites

Transcription

1 Faculty of Earth and Life Sciences Hydrology and Geo-Environmental Sciences Modelling methane emissions from arctic wetlands: A comparison between two sites A. M. R. Petrescu (1), T.R. Christensen (2), J. van Huissteden (1) 1. Vrije Universiteit, Faculty of Earth and Life Sciences, Amsterdam 2. Lund University, Department of Physical Geography and Ecosystems Analysis, Lund

2 Study site Kytalyk Reserve, NE Siberia Indigirka lowlands, near Chokhurdagh Kytalyk 70 o N 147 o E High arctic climate Continuous permafrost region Mire, N Sweden Eastern part of Lake Torneträsk 68 o N 19 o E, 10 KM E from Abisko Subarctic climate Discontinuous permafrost region

3 Material, Methods CH 4 measurements Kytalyk Ice wedge polygons Sedges, Eriophorum spp. Sphagnum hummocks Active Layer depth cm Eriophorum spp. Carex spp. Active Layer depth up to 130 cm Eddy correlation system for CO 2 flux since 2003 Eddy correlation tower and TDL FW2 floodplain wet site

4 The Kytalyk site shows a very large spatial variability concerning the vegetation type This study focuses the attention to the wet site Field name Vegetation Code Morphology Low backswamp mosses, Arctica fulva FW1 Backswamp sedge, Eriophorum FW2 often hummocks The mire shows a similar pattern and the study area has a similar wet site.

5 Kytalyk Chamber Photo-acoustic gas analyzer (CH 4, CO 2, N 2 O) Battery & solar panel Soil temperature sensor Plexiglas Chambers (10-30 litres) High biomass on floodplain High biomass on the wet part of the mire High biomass on the wet part of the mire, thermokarst

6 Modelling - The PEATLAND - VU Model

7 Input data and parameterization of the model Study period: Input data for PEATLAND - VU: climate (air temperature, snow ) soil parameters vegetation type ground water depth Optimization of several parameters which influence the simulations the CH 4 production rate R 0 the Q 10 value for temperature correction methane production the methane plant oxidation fraction Based on the input data, simulations were carried out and the output CH 4 fluxes were compared with the measured ones; Kytalyk: Data were obtained from Chokhurdagh weather station at the local airport. Air and soil temperature data measured on the site (Van der Molen et al., in prep) : Data were provided by the Abisko Scientific Research Station

8 Water table simulations The ground water table strongly influences the methane fluxes Two runs were performed with PEATLAND - VU Model Observed WT (from Abisko site, lake level pipes) Simulated WT (slightly changed version of G. Granberg et al., 1999, provided by A. Yurova et al., 2007, in press.) For the simulated WT several input parameters site specific were used Climate (air temperature, precipitation) Day length (web calculator) Snow (calculated based on input precipitation) Air temperature and snow pack had output the total rainfall and melt Potential evapotranspiration (Blaney-Criddle formula)

9 Results Observed WT vs. Simulated WT Kytalyk Water table in Kytalyk Measured WT Simulated WT 2 Water level (cm below ground) Measurement campaigns Simulated (red) water table depth and observed water table (black) average values from Kytalyk site for Simulated water table depth from for

10 Results CH 4 fluxes with observed WT Kytalyk Kytalyk methane fluxes (meas WT) Measured CH4 Simulated CH4 CH4 mg m-2 hr Measurement campaigns Average measured value (black) and simulated (red) methane emissions for at Kytalyk, with observed water table Measured (red) and simulated (black) methane emissions for at mire with observed (lake level) water table

11 Results CH 4 fluxes with simulated WT Kytalyk Kytalyk methane measurements (sim WT) Measured CH4 FW2 Simulated CH4 FW2 CH4 mg m-2hr Measurement camapaigns Average measured value (black) and simulated (red) methane emissions for at Kytalyk, with simulated water table Measured (red) and simulated (black) methane emissions for at mire with simulated water table

12 Kytalyk High arctic climate Discussion Sub-arctic climate Continuous permafrost Carex, Eriophorum spp. Average Air T o C AL: cm WT close to the surface (0-7 cm) Short growing season (May- September) Average CH 4 flux with simulated WT: 2.72 mg CH 4 m -2 hr -1 ( ) Large areas covered with peat mosses have low CH 4 fluxes. Sites with Carex spp. show higher fluxes and in general the floodplain has the highest CH 4 fluxes. Discontinuous permafrost Carex, Eriophorum angustifolium Average soil T +4 o C AL: up to 130 cm WT close to the surface (0-9 cm) Long growing season (April October) Average CH 4 flux with simulated WT: 3.96 mg CH 4 m -2 hr -1 ( ) Sites dominated by Eriophorum angustifloum show higher methane fluxes than the ones with Eriophorum vaginatum or Carex spp. (Ström and Cristensen, accepted)

13 Conclusions PEATLAND VU simulates the methane fluxes and matches the simulations with the observed values in spite of the site level parameter uncertainty. A simple bucket model for simulating the water table strongly improves the simulation of the fluxes in case of uncertainty of the water table. Next Improving the hydrological models for correct simulation of water table variation is promising for larger scale modelling of methane Thank you!!!