Frozen ponds – production and storage of methane during the Arctic winter
Lakes and ponds play a key role in the carbon cycle of permafrost ecosystems. They are considered to be hotspots of carbon dioxide and methane emissions. However, the strength of the emissions is controlled by a variety of physical and biochemical processes whose responses to climate warming are com...
| Main Authors: | , , , , |
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| Format: | Conference Object |
| Language: | unknown |
| Published: |
2014
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| Subjects: | |
| Online Access: | https://epic.awi.de/id/eprint/35495/ https://hdl.handle.net/10013/epic.43470 |
| Summary: | Lakes and ponds play a key role in the carbon cycle of permafrost ecosystems. They are considered to be hotspots of carbon dioxide and methane emissions. However, the strength of the emissions is controlled by a variety of physical and biochemical processes whose responses to climate warming are complex and still poorly understood. In some Arctic regions up to 25% of the land surface area are occupied by free water surfaces. Often, a large fraction of these water surfaces is attributed to small lakes and ponds which are highly abundant in lowland tundra landscapes. These small water bodies are usually not accounted for in land surface classifications and calculations of the Arctic carbon balance. Nevertheless, small water bodies receive increased attention since recent studies demonstrate that ponds can strongly contribute to the CO2 and CH4 emissions of tundra ecosystems. In addition, water bodies strongly affect the thermal state of the surrounding permafrost. During the freezing period water bodies prolong the duration in which thawed soil material is available for microbial decomposition. This study presents CH4 production rates of ponds in a typical lowland tundra landscape in northern Siberia during the freezing period. For this purpose the CH4 concentrations in ice cores of different ponds are measured. The production rates of CH4 are calculated by fitting a mass balance model to the measured CH4 concentration profiles. The results reveal strong differences in CH4 production between the ponds. Shallow and intact polygonal ponds show low production rates on the order of 10-11 to 10-10 mol m-2 s-1. Whereas deeper ponds with clear signs of thermal erosion show CH4 production rates on the order of about 10-6 mol m-2 s-1. These production rates equate in magnitude to the summertime CH4 emission rates that are reported for the same site as average for the tundra landscape. Thus, strong CH4 production still occurs long after the tundra soils are completely frozen and microbial productions is supposed to be minimal. The release of the produced CH4 to the atmosphere potentially occurs during the melt period. |
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