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| Titel |
Methane and carbon dioxide emissions from 40 lakes along a north–south latitudinal transect in Alaska |
| VerfasserIn |
A. Sepulveda-Jauregui, K. M. Walter Anthony, K. Martinez-Cruz, S. Greene, F. Thalasso |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1726-4170
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| Digitales Dokument |
URL |
| Erschienen |
In: Biogeosciences ; 12, no. 11 ; Nr. 12, no. 11 (2015-06-02), S.3197-3223 |
| Datensatznummer |
250117957
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| Publikation (Nr.) |
 copernicus.org/bg-12-3197-2015.pdf |
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| Zusammenfassung |
| Uncertainties in the magnitude and seasonality of various gas emission modes,
particularly among different lake types, limit our ability to estimate
methane (CH4) and carbon dioxide (CO2) emissions from northern
lakes. Here we assessed the relationship between CH4 and CO2
emission modes in 40 lakes along a latitudinal transect in Alaska to lakes'
physicochemical properties and geographic characteristics, including
permafrost soil type surrounding lakes. Emission modes included direct
ebullition, diffusion, storage flux, and a newly identified ice-bubble
storage (IBS) flux. We found that all lakes were net sources of atmospheric
CH4 and CO2, but the climate warming impact of lake CH4
emissions was 2 times higher than that of CO2. Ebullition and
diffusion were the dominant modes of CH4 and CO2 emissions,
respectively. IBS, ~10% of total annual CH4 emissions, is
the release to the atmosphere of seasonally ice-trapped bubbles when lake ice
confining bubbles begins to melt in spring. IBS, which has not been
explicitly accounted for in regional studies, increased the estimate of
springtime emissions from our study lakes by 320%. Geographically,
CH4 emissions from stratified, mixotrophic interior Alaska thermokarst
(thaw) lakes formed in icy, organic-rich yedoma permafrost soils were 6-fold
higher than from non-yedoma lakes throughout the rest of Alaska. The
relationship between CO2 emissions and geographic parameters was weak,
suggesting high variability among sources and sinks that regulate CO2
emissions (e.g., catchment waters, pH equilibrium). Total CH4 emission
was correlated with concentrations of soluble reactive phosphorus and total
nitrogen in lake water, Secchi depth, and lake area, with yedoma lakes having
higher nutrient concentrations, shallower Secchi depth, and smaller lake
areas. Our findings suggest that permafrost type plays important roles in
determining CH4 emissions from lakes by both supplying organic matter to
methanogenesis directly from thawing permafrost and by enhancing nutrient
availability to primary production, which can also fuel decomposition and
methanogenesis. |
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