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- Denfeld, Blaize, et al.
(författare)
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Regional Variability and Drivers of Below Ice CO2 in Boreal and Subarctic Lakes
- 2016
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Ingår i: Ecosystems (New York. Print). - : Springer Science and Business Media LLC. - 1432-9840 .- 1435-0629. ; 19:3, s. 461-476
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Tidskriftsartikel (refereegranskat)abstract
- Northern lakes are ice-covered for considerable portions of the year, where carbon dioxide (CO2) can accumulate below ice, subsequently leading to high CO2 emissions at ice-melt. Current knowledge on the regional control and variability of below ice partial pressure of carbon dioxide (pCO(2)) is lacking, creating a gap in our understanding of how ice cover dynamics affect the CO2 accumulation below ice and therefore CO2 emissions from inland waters during the ice-melt period. To narrow this gap, we identified the drivers of below ice pCO(2) variation across 506 Swedish and Finnish lakes using water chemistry, lake morphometry, catchment characteristics, lake position, and climate variables. We found that lake depth and trophic status were the most important variables explaining variations in below ice pCO(2) across the 506 lakes(.) Together, lake morphometry and water chemistry explained 53% of the site-to-site variation in below ice pCO(2). Regional climate (including ice cover duration) and latitude only explained 7% of the variation in below ice pCO(2). Thus, our results suggest that on a regional scale a shortening of the ice cover period on lakes may not directly affect the accumulation of CO2 below ice but rather indirectly through increased mobility of nutrients and carbon loading to lakes. Thus, given that climate-induced changes are most evident in northern ecosystems, adequately predicting the consequences of a changing climate on future CO2 emission estimates from northern lakes involves monitoring changes not only to ice cover but also to changes in the trophic status of lakes.
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| 2. |
- Weyhenmeyer, Gesa, et al.
(författare)
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Carbon Dioxide in Boreal Surface Waters : A Comparison of Lakes and Streams
- 2012
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Ingår i: Ecosystems (New York. Print). - : Springer-Verlag. - 1432-9840 .- 1435-0629. ; 15:8, s. 1295-1307
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Tidskriftsartikel (refereegranskat)abstract
- The quantity of carbon dioxide (CO2) emissions from inland waters into the atmosphere varies, depending on spatial and temporal variations in the partial pressure of CO2 (pCO2) in waters. Using 22,664 water samples from 851 boreal lakes and 64 boreal streams, taken from different water depths and during different months we found large spatial and temporal variations in pCO2, ranging from below atmospheric equilibrium to values greater than 20,000 μatm with a median value of 1048 μatm for lakes (n = 11,538 samples) and 1176 μatm for streams (n = 11,126). During the spring water mixing period in April/May, distributions of pCO2 were not significantly different between stream and lake ecosystems (P > 0.05), suggesting that pCO2 in spring is determined by processes that are common to lakes and streams. During other seasons of the year, however, pCO2 differed significantly between lake and stream ecosystems (P < 0.0001). The variable that best explained the differences in seasonal pCO2 variations between lakes and streams was the temperature difference between bottom and surface waters. Even small temperature differences resulted in a decline of pCO2 in lake surface waters. Minimum pCO2 values in lake surface waters were reached in July. Towards autumn pCO2 strongly increased again in lake surface waters reaching values close to the ones found in stream surface waters. Although pCO2 strongly increased in the upper water column towards autumn, pCO2 in lake bottom waters still exceeded the pCO2 in surface waters of lakes and streams. We conclude that throughout the year CO2 is concentrated in bottom waters of boreal lakes, although these lakes are typically shallow with short water retention times. Highly varying amounts of this CO2 reaches surface waters and evades to the atmosphere. Our findings have important implications for up-scaling CO2 fluxes from single lake and stream measurements to regional and global annual fluxes.
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