1. Nearby Lake Environment Stream Channel Environment
Variability of Methane in Stordalen Mire Stream Sediments, Abisko, Sweden
Adam J.D. Nicastro1, Christopher D. Horruitiner2, Dylan J. Lundgren3, Samantha N. Sinclair3 Joel E. Johnson3, Ruth K.Varner3, 1Department of Geology and Environmental Earth Science, Miami University, Oxford, OH, USA 2School of Natural Resources and Environment, University of Florida, Gainesville, FL, USA 3Department of Earth Sciences, University of New Hampshire, Durham, NH, USA
Introduction
Results
Global atmospheric methane concentrations been increasing since the industrial revolution and continue to rise (Quiquet et al, 2015.)
Landscapes dominated by lakes and ponds rank high among contributors to global methane emissions. These environments most frequently occur at high latitudes (Wik et al, 2013.)
Methane emissions in Stordalen Mire in subarctic Sweden (N68°21’,E19°.02’) are increasing in part due to rising MAT in the region (Callaghan et al, 2010.)
Sediments in subarctic peatland streams have not been thoroughly investigated, but these streams are thought to be a pathway for organic C liberated from thawing permafrost. (Schuur et al, 2008.)
MS-HC-17
MS-HC-19
Nearby Lake Environment
Point Bar Environment
Stream Channel Environment
Figure 1:
MS-HC-20
Figure 6: δ13CH4 in select cores vs. depth.
MH-HC-15
(Adapted from the European Environment Agency, 2009)
Stream Depth (m)
Figure 7: Cross-plot of wt%TOC vs μg CH4 per g of dry sediment with linear regression and R2 values shown.
Figure 3: Representative drawing of the stratigraphy of core MH-HC-15, with CH4 concentrations, wt% TOC and TOC/N ratios versus depth. The maximum concentration is marked by the orange circle.
Figure 4: Representative drawing of the stratigraphy of core MS-HC-17 with CH4 concentrations, wt% TOC and TOC/N ratios plotted versus depth. Cores MS-HC-20 and MH-HC-12, which were taken in similar, point bar environments are also shown. The maximum concentration is marked by the orange circle. Purple squares mark depths where CH4 and TOC do not correlate
Figure 5: Representative drawing of the stratigraphy of core MS-HC-19 with CH4 concentrations, wt% TOC and TOC/N ratios plotted versus depth. Cores MS-HC-18,19, which were taken in similar, stream channel environments are also included. Purple squares mark depths where CH4 and TOC do not correlate
Implications
Methane and TOC do not always show positive correlation, particularly in point bar sediments, which seems to indicate that CH4 is produced in some stratigraphic intervals, but exists in others as the result of transport. This is supported by the regression analyses (See Figure 7.)
Stratigraphy and stream morphology play a clear role in CH4 concentrations. Methane is contained in high concentrations in sediments at much greater depths than is typical of the lakes in the region (See Figures 3&4, specifically MH-HC-12, 77cm.)
TOC/N ratios are consistent with the sources of organic C in fluvial and lacustrine environments (Meyers and Ishiwagari, 1993,) but it is still unclear whether or not C in the stream sediment has been recently liberated from thawing permafrost.
Figure 2: Core sites in the stream of Stordalen Mire with corresponding depth profiles, with Permafrost map of Scandinavia adapted from the European Environment Agency, 2009
This study investigates the stream flowing into Stordalen Mire as a potential source of methane production/transport, its role on carbon cycling, and the potential role of stratigraphy and stream morphology and on methane and TOC concentrations in sediment.
Methods
Figure 8: Bulk distribution of grain size throughout all samples that contained lithogenic material. Includes data from cores 10, 12, 15, 16, 17, 18, 19, 20.
Sediment cores were taken in eight locations in the Stordalen stream.
Samples were taken at 5cm intervals for Methane, CHNS, 13C and grain size analysis
Methane concentration measured using Shimadzu GC-2014 Gas Chromatograph
CHNS element content analysis measured using Perkin-Elmer CHNS Series II Elemental Analyzer 2400
Grain size measured using Malvern Mastersizer 2000
13C measured using Quantum Cascade Laser.
Acknowledgements
References
I would like to thank Alison Hobbie, Melissa Schwann, Erin Marek, Clarice Perryman, Jessica Del Greco, Eric Heim, Carmody McCalley, Michael Palace and Nathan Tomczyk for their contributions in gathering and processing data. I would like to thank Professor Patrick Crill for allowing the use of his laboratory. I would also like to thank the staff of the Abisko Scientific Research Station, The NSF, and everyone involved in orchestrating and organizing the NERU program, without whom this research would not be possible. This research has been supported by the National Science Foundations REU program: Northern Ecosystems Research for Undergraduates (EAR# ).
Callaghan, Terry V. et al.. "A New Climate Era in the Sub-Arctic: Accelerating Climate Changes and Multiple Impacts." Geophys. Res. Lett. Geophysical Research Letters 37.14 (2010): n. pag. Print.
Meyers, Philip A. et al., and Ryoshi Ishiwatari. "Lacustrine Organic Geochemistry—an Overview of Indicators of Organic Matter Sources and Diagenesis in Lake Sediments." Organic Geochemistry 20.7 (1993): Print.
Olefeldt, David, and Roulet, Nigel T. "Effects of Permafrost and Hydrology on the Composition and Transport of Dissolved Organic Carbon in a Subarctic Peatland Complex." Journal of Geophysical Research: Biogeosciences J. Geophys. Res. 117.G1 (2012): n. pag. Print.
Quiquet, A. et al. "The Relative Importance of Methane Sources and Sinks over the Last Interglacial Period and into the Last Glaciation." Quaternary Science Reviews 112 (2015): Print.
Schuur, Edward A. et al. "Vulnerability of Permafrost Carbon to Climate Change: Implications for the Global Carbon Cycle." BioScience 58.8 (2008): 701. Print.
Wik, Martin et al. "Multiyear Measurements of Ebullitive Methane Flux from Three Subarctic Lakes.” Journal of Geophysical Research: Biogeosciences J. Geophys. Res. Biogeosci. (2013): n. pag. Print.