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Titel |
Diffusive methane flux from lakes has a distinct within-lake spatial distribution |
VerfasserIn |
Jos Schilder, David Bastviken, Maarten van Hardenbroek, Paula Kankaala, Päivi Rinta, Tabea Stötter, Oliver Heiri |
Konferenz |
EGU General Assembly 2013
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Medientyp |
Artikel
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Sprache |
Englisch
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Digitales Dokument |
PDF |
Erschienen |
In: GRA - Volume 15 (2013) |
Datensatznummer |
250072118
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Zusammenfassung |
Methane (CH4) is an important greenhouse gas and lakes, while understudied, are known to
contribute significantly to natural CH4 emissions. As such, lakes play a key role in the
greenhouse gas budget of the landscape they lie in and reliable estimates of the total
greenhouse gas emissions of lakes are necessary to incorporate lakes into the terrestrial
greenhouse gas balance. Data on lake CH4 emissions are limited, however, and
whole-lake methane flux estimates inevitably depend on extrapolations of single or few
measurements on a lake, and are in the case of diffusive flux often estimated based on
measurements of wind-speed and surface water CH4 concentrations. Hence, there is a clear
need to improve our understanding of the spatial and temporal dynamics of these
emissions.
In the study we present here, we assessed the within-lake spatial variability of diffusive
methane flux from 13 lakes in Northern and Western Europe using the floating chamber
approach. We obtained a spatially resolved (4 stations along a transect) measure of
diffusive CH4 flux and the main components of diffusive flux, k (piston velocity) and
Caq (surface water CH4 concentrations). These measurements were done in late
summer and represent a period of approximately six hours (between ca. 10:00 and
16:00). Our results show a distinct within-lake spatial variability. Most notably,
we found that diffusive CH4 fluxes and kvalues were significantly (2 to 3 times)
higher in the central parts of the lakes than in the near-shore zones. In contrast, Caq
tended to be lower in the central zones. We conclude that estimates of whole-lake
diffusive CH4 flux based on extrapolations of single point measurements of diffusive
flux and Caq and/or wind speed-derived k values may lead to considerable errors. |
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