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Research article2018Peer reviewedOpen access

Carbon Dioxide and Methane Dynamics in a Small Boreal Lake During Winter and Spring Melt Events

Denfeld, B. A.; Klaus, M.; Laudon, H.; Sponseller, R. A.; Karlsson, J.


In seasonally ice-covered lakes, carbon dioxide (CO2) and methane (CH4) emission at ice-off can account for a significant fraction of the annual budget. Yet knowledge of the mechanisms controlling below lake-ice carbon (C) dynamics and subsequent CO2 and CH4 emissions at ice-off is limited. To understand the control of below ice C dynamics, and C emissions in spring, we measured spatial variation in CO2, CH4, and dissolved inorganic and organic carbon from ice-on to ice-off, in a small boreal lake during a winter with sporadic melting events. Winter melt events were associated with decreased surface water DOC in the forest-dominated basin and increased surface water CH4 in the mire-dominated basin. At the whole-lake scale, CH4 accumulated below ice throughout the winter, whereas CO2 accumulation was greatest in early winter. Mass-balance estimates suggest that, in addition to the CO2 and CH4 accumulated duringwinter, external inputs of CO2 and CH4 and internal processing during ice-melt could represent significant sources of C gas emissions during ice-off. Moreover, internal processing of CO2 and CH4 worked in opposition, with production of CO2 and oxidation of CH4 dominating at ice-off. These findings have important implications for how small boreal lakes will respond to warmer winters in the future; increased winter melt events will likely increase external inputs below ice and thus alter the extent and timing of CO2 and CH4 emissions to the atmosphere at ice-off.Plain Language Summary Many lakes are ice-covered for a portion of the year, where ice serves as a barrier to the atmosphere, trapping greenhouse gases, like carbon dioxide and methane. At ice-off, these greenhouse gases are released into the atmosphere. Yet due to difficulties associated with sampling ice-covered lakes, there is limited information about the factors that contribute to carbon dioxide and methane release at ice-off. Moreover, projected warmer winters, with increased precipitation as rain and reduced duration of ice cover, suggest that the contributing factors may change in the future. To gain insight into greenhouse gas dynamics in ice-covered lakes, we measured carbon dioxide and methane from ice-on to ice-off in a small boreal lake during a winter with sporadic melting events. We show that winter melt events alter carbon inputs below ice with implications for the timing and type of greenhouse gases released at ice-off. Our study brings new insight to greenhouse gas dynamics in ice-covered lakes and highlights challenges in understanding the implications of changing ice-cover patterns as the climate warms.

Published in

Journal of Geophysical Research: Biogeosciences
2018, Volume: 123, number: 8, pages: 2527-2540 Publisher: AMER GEOPHYSICAL UNION