Characterisation of short-term extreme methane fluxes related to non-turbulent mixing above an Arctic permafrost ecosystem
Methane ( CH 4 ) emissions from biogenic sources, such as Arctic permafrost wetlands, are associated with large uncertainties because of the high variability of fluxes in both space and time. This variability poses a challenge to monitoring CH 4 fluxes with the eddy covariance (EC) technique, becaus...
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ftcopernicus:oai:publications.copernicus.org:acp67353 2023-05-15T15:01:49+02:00 Characterisation of short-term extreme methane fluxes related to non-turbulent mixing above an Arctic permafrost ecosystem Schaller, Carsten Kittler, Fanny Foken, Thomas Göckede, Mathias 2019-04-01 info:eu-repo/semantics/application/pdf https://doi.org/10.5194/acp-19-4041-2019 https://www.atmos-chem-phys.net/19/4041/2019/ eng eng info:eu-repo/grantAgreement/EC/FP7/282700 info:eu-repo/grantAgreement/EC/FP7/333796 doi:10.5194/acp-19-4041-2019 https://www.atmos-chem-phys.net/19/4041/2019/ info:eu-repo/semantics/openAccess eISSN: 1680-7324 info:eu-repo/semantics/Text 2019 ftcopernicus https://doi.org/10.5194/acp-19-4041-2019 2019-12-24T09:49:21Z Methane ( CH 4 ) emissions from biogenic sources, such as Arctic permafrost wetlands, are associated with large uncertainties because of the high variability of fluxes in both space and time. This variability poses a challenge to monitoring CH 4 fluxes with the eddy covariance (EC) technique, because this approach requires stationary signals from spatially homogeneous sources. Episodic outbursts of CH 4 emissions, i.e. triggered by spontaneous outgassing of bubbles or venting of methane-rich air from lower levels due to shifts in atmospheric conditions, are particularly challenging to quantify. Such events typically last for only a few minutes, which is much shorter than the common averaging interval for EC (30 min). The steady-state assumption is jeopardised, which potentially leads to a non-negligible bias in the CH 4 flux. Based on data from Chersky, NE Siberia, we tested and evaluated a flux calculation method based on wavelet analysis, which, in contrast to regular EC data processing, does not require steady-state conditions and is allowed to obtain fluxes over averaging periods as short as 1 min. Statistics on meteorological conditions before, during, and after the detected events revealed that it is atmospheric mixing that triggered such events rather than CH 4 emission from the soil. By investigating individual events in more detail, we identified a potential influence of various mesoscale processes like gravity waves, low-level jets, weather fronts passing the site, and cold-air advection from a nearby mountain ridge as the dominating processes. The occurrence of extreme CH 4 flux events over the summer season followed a seasonal course with a maximum in early August, which is strongly correlated with the maximum soil temperature. Overall, our findings demonstrate that wavelet analysis is a powerful method for resolving highly variable flux events on the order of minutes, and can therefore support the evaluation of EC flux data quality under non-steady-state conditions. Other/Unknown Material Arctic Chersky permafrost Siberia Copernicus Publications: E-Journals Arctic Atmospheric Chemistry and Physics 19 6 4041 4059 |
institution |
Open Polar |
collection |
Copernicus Publications: E-Journals |
op_collection_id |
ftcopernicus |
language |
English |
description |
Methane ( CH 4 ) emissions from biogenic sources, such as Arctic permafrost wetlands, are associated with large uncertainties because of the high variability of fluxes in both space and time. This variability poses a challenge to monitoring CH 4 fluxes with the eddy covariance (EC) technique, because this approach requires stationary signals from spatially homogeneous sources. Episodic outbursts of CH 4 emissions, i.e. triggered by spontaneous outgassing of bubbles or venting of methane-rich air from lower levels due to shifts in atmospheric conditions, are particularly challenging to quantify. Such events typically last for only a few minutes, which is much shorter than the common averaging interval for EC (30 min). The steady-state assumption is jeopardised, which potentially leads to a non-negligible bias in the CH 4 flux. Based on data from Chersky, NE Siberia, we tested and evaluated a flux calculation method based on wavelet analysis, which, in contrast to regular EC data processing, does not require steady-state conditions and is allowed to obtain fluxes over averaging periods as short as 1 min. Statistics on meteorological conditions before, during, and after the detected events revealed that it is atmospheric mixing that triggered such events rather than CH 4 emission from the soil. By investigating individual events in more detail, we identified a potential influence of various mesoscale processes like gravity waves, low-level jets, weather fronts passing the site, and cold-air advection from a nearby mountain ridge as the dominating processes. The occurrence of extreme CH 4 flux events over the summer season followed a seasonal course with a maximum in early August, which is strongly correlated with the maximum soil temperature. Overall, our findings demonstrate that wavelet analysis is a powerful method for resolving highly variable flux events on the order of minutes, and can therefore support the evaluation of EC flux data quality under non-steady-state conditions. |
format |
Other/Unknown Material |
author |
Schaller, Carsten Kittler, Fanny Foken, Thomas Göckede, Mathias |
spellingShingle |
Schaller, Carsten Kittler, Fanny Foken, Thomas Göckede, Mathias Characterisation of short-term extreme methane fluxes related to non-turbulent mixing above an Arctic permafrost ecosystem |
author_facet |
Schaller, Carsten Kittler, Fanny Foken, Thomas Göckede, Mathias |
author_sort |
Schaller, Carsten |
title |
Characterisation of short-term extreme methane fluxes related to non-turbulent mixing above an Arctic permafrost ecosystem |
title_short |
Characterisation of short-term extreme methane fluxes related to non-turbulent mixing above an Arctic permafrost ecosystem |
title_full |
Characterisation of short-term extreme methane fluxes related to non-turbulent mixing above an Arctic permafrost ecosystem |
title_fullStr |
Characterisation of short-term extreme methane fluxes related to non-turbulent mixing above an Arctic permafrost ecosystem |
title_full_unstemmed |
Characterisation of short-term extreme methane fluxes related to non-turbulent mixing above an Arctic permafrost ecosystem |
title_sort |
characterisation of short-term extreme methane fluxes related to non-turbulent mixing above an arctic permafrost ecosystem |
publishDate |
2019 |
url |
https://doi.org/10.5194/acp-19-4041-2019 https://www.atmos-chem-phys.net/19/4041/2019/ |
geographic |
Arctic |
geographic_facet |
Arctic |
genre |
Arctic Chersky permafrost Siberia |
genre_facet |
Arctic Chersky permafrost Siberia |
op_source |
eISSN: 1680-7324 |
op_relation |
info:eu-repo/grantAgreement/EC/FP7/282700 info:eu-repo/grantAgreement/EC/FP7/333796 doi:10.5194/acp-19-4041-2019 https://www.atmos-chem-phys.net/19/4041/2019/ |
op_rights |
info:eu-repo/semantics/openAccess |
op_doi |
https://doi.org/10.5194/acp-19-4041-2019 |
container_title |
Atmospheric Chemistry and Physics |
container_volume |
19 |
container_issue |
6 |
container_start_page |
4041 |
op_container_end_page |
4059 |
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1766333830648561664 |