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Climate-sensitive northern lakes and ponds are critical components of methane release
Stockholm University, Faculty of Science, Department of Geological Sciences.
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2016 (English)In: Nature Geoscience, ISSN 1752-0894, E-ISSN 1752-0908, Vol. 9, 99-105 p.Article, review/survey (Refereed) Published
Abstract [en]

Lakes and ponds represent one of the largest natural sources of the greenhouse gas methane. By surface area, almost half of these waters are located in the boreal region and northwards. A synthesis of measurements of methane emissions from 733 lakes and ponds north of ~50° N, combined with new inventories of inland waters, reveals that emissions from these high latitudes amount to around 16.5 Tg CH4 yr−1 (12.4 Tg CH4-C yr−1). This estimate — from lakes and ponds alone — is equivalent to roughly two-thirds of the inverse model calculation of all natural methane sources in the region. Thermokarst water bodies have received attention for their high emission rates, but we find that post-glacial lakes are a larger regional source due to their larger areal extent. Water body depth, sediment type and ecoclimatic region are also important in explaining variation in methane fluxes. Depending on whether warming and permafrost thaw cause expansion or contraction of lake and pond areal coverage, we estimate that annual water body emissions will increase by 20–54% before the end of the century if ice-free seasons are extended by 20 days. We conclude that lakes and ponds are a dominant methane source at high northern latitudes.

Place, publisher, year, edition, pages
2016. Vol. 9, 99-105 p.
Keyword [en]
Biogeochemistry, Climate-change impacts
National Category
Earth and Related Environmental Sciences
Research subject
Geochemistry
Identifiers
URN: urn:nbn:se:su:diva-126816DOI: 10.1038/ngeo2578ISI: 000369324600010OAI: oai:DiVA.org:su-126816DiVA: diva2:903484
Funder
Swedish Research Council, 2007-4547
Available from: 2016-02-16 Created: 2016-02-16 Last updated: 2016-03-22Bibliographically approved
In thesis
1. Emission of methane from northern lakes and ponds
Open this publication in new window or tab >>Emission of methane from northern lakes and ponds
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Northern lakes and ponds are abundant and emit large amounts of the potent climate forcer methane to the atmosphere at rates prone to change with amplified Arctic warming. In spite of being important, fluxes from surface waters are not well understood. Long-term measurements are lacking and the dominant and irregular transport mode ebullition (bubbling) is rarely quantified, which complicate the inclusion of lakes and ponds in the global methane budget. This thesis focuses on variations in emissions on both local and regional scales. A synthesis of methane fluxes from almost all studied sites constrains uncertainties and demonstrates that northern lakes and ponds are a dominant source at high latitudes. Per unit area variations in flux magnitudes among different types of water bodies are mainly linked to water depth and type of sediment. When extrapolated, total area is key and thus post-glacial lakes dominate emissions over water bodies formed by peat degradation or thermokarst processes. Further, consistent multiyear measurements in three post-glacial lakes in Stordalen, northern Sweden, reveal that seasonal ebullition, primarily driven by fermentation of acetate, can be predicted by easily measured parameters such as temperature and heat energy input over the ice-free season. Assuming that most water bodies respond similarly to warming, this thesis also suggests that northern lakes and ponds will release substantially more methane before the end of the century, primarily as a result of longer ice-free seasons. Improved uncertainty reductions of both current and future estimates rely on increased knowledge of landscape-level processes related to changes in aquatic systems and organic loading with permafrost thaw, as well as more high-quality measurements, seldom seen in contemporary data. Sampling distributed over entire ice-free seasons and across different depth zones is crucial for accurately quantifying methane emissions from northern lakes and ponds.

Place, publisher, year, edition, pages
Stockholm: Institutionen för geologiska vetenskaper, 2016. 42 p.
Series
Meddelanden från Stockholms universitets institution för geologiska vetenskaper, 361
Keyword
lakes, ponds, water bodies, methane, fluxes, ebullition, stable isotopes, arctic, subarctic, carbon cycling, climate change
National Category
Earth and Related Environmental Sciences
Research subject
Geochemistry
Identifiers
urn:nbn:se:su:diva-126823 (URN)978-91-7649-362-5 (ISBN)
Public defence
2016-04-29, William-Olssonsalen, Geovetenskapens hus, Svante Arrhenius väg 14, Stockholm, 10:00 (English)
Opponent
Supervisors
Funder
Swedish Research Council, 2007–4547
Note

At the time of the doctoral defense, the following paper was unpublished and had a status as follows: Paper 4: Manuscript.

Available from: 2016-04-06 Created: 2016-02-16 Last updated: 2016-03-23Bibliographically approved

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