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| Titel |
Carbon trace gas dynamics in three subarctic lakes in winter and spring |
| VerfasserIn |
Joachim Jansen, Mathilde Jammet, Martin Wik, Brett Thornton, Thomas Friborg, Patrick Crill |
| Konferenz |
EGU General Assembly 2017
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 19 (2017) |
| Datensatznummer |
250137740
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| Publikation (Nr.) |
 EGU/EGU2017-547.pdf |
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| Zusammenfassung |
| Northern lakes are an important atmospheric source of radiatively active trace gases -
methane and carbon dioxide - despite being ice covered for up to 7 months of the year. As
much as 56% of annual emissions occur during ice-out in spring. Although important, this
flux is currently both poorly understood and constrained. Here we present a detailed annual
carbon gas budget for three subarctic lakes in Northern Sweden. We combine year-round
continuous eddy covariance measurements from one lake with monthly observations of the
dissolved gas content and ice-free season measurements of ebullition and turbulence-driven
diffusive fluxes in all three lakes. Dissolved methane begun to accumulate when
anoxia set in, approximately two months after ice-on. Dissolved inorganic carbon
concentrations increased throughout winter. Total CO2 accumulation exceeded total O2
consumption, pointing to an additional carbon source to the under-ice water, presumably the
sediment. A total winter accumulation of 0.9-2.8 g/m2 CH4 and 55-145 g/m2 CO2 was
measured: the largest values were from the deepest lakes. We found that while
some dissolved gas was released with ice-out, between 65 and 84% disappeared
several weeks prior in two of the study lakes, during a period of heavy snowmelt.
This suggests that hydrology plays an important part in determining the spring
carbon budget by diluting or replacing the under-ice water column. Should this
fraction reach the atmosphere, the total ice-covered season flux represents 22-61% of
the annual CH4 flux (three lakes), and reduces the annual CO2 sink by 70% (one
lake). The CH4 flux during ice-out alone represented 10-55% of the annual flux. |
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