Geophysical Research Letters
Supporting Information for
Climate-forced changes in available energy and methane bubbling from subarctic lakes
Brett F. Thornton, Martin Wik, Patrick M. Crill
Department of Geological Sciences and Bolin Centre for Climate Research, Stockholm University,
Stockholm, Sweden
Contents of this file
Text S1 – Additional Methods Text
Figures S1 & S2
Introduction
This supporting information consists of additional methods text, and two figures.
Supporting Information references are on the last page of this document.
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Text S1 – Additional Methods Text
The present manuscript has extended (Figure S1) a previously described multiyear CH
4
ebullition dataset [ Martin Wik et al.
, 2013], now containing 8215 discrete CH
4 measurements, from 3 typical lakes in Northern Sweden. The lakes are located in
Stordalen Mire (68°21’N, 19°02’E, 350 m asl), a peatland area 9 km east of the town of
Abisko. The lakes – Inre Harrsjön, Mellan Harrsjön, and Villasjön—have surface areas of
2.2, 1.1, and 17.0 ha, respectively. Water depths reach 5 and 7 m in Inre Harrsjön and
Mellan Harrsjön [ M. Wik et al.
, 2011]
, while Villasjön reaches only 1.3 m depth
[ Jackowicz-Korczynski et al.
, 2010]. Stordalen Mire is located in the sporadic permafrost
zone (though the study lakes are not thaw or thermokarst features), and the mean annual temperature in the area has recently exceeded the permafrost stability threshold
of 0° deg. C [ Callaghan et al.
, 2010]. The ice-free season lasts from May to October,
with annual variability.
Figure S1. Seasonal methane ebullition from 3 subarctic lakes. An additional year of
data has been added to Figure 1 from [ Martin Wik et al.
, 2014].
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Figure S2. Incoming shortwave (SW) climatology for Abisko Naturvetenskap Station
(ANS) at Abisko, Sweden, for 1985-2013. Red curve is maximum observed SW. Dark gray curve is average SW. White line is polynomial fit, used to generate equation (1) in the main text. Additionally, certain observed and predicted ice-out days are marked as vertical lines.
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Supplementary References
Callaghan, T. V., F. Bergholm, T. R. Christensen, C. Jonasson, U. Kokfelt, and M.
Johansson (2010), A new climate era in the sub-Arctic: Accelerating climate changes and multiple impacts, Geophys Res Lett , 37 , L14705.
Jackowicz-Korczynski, M., T. R. Christensen, K. Backstrand, P. Crill, T. Friborg, M.
Mastepanov, and L. Strom (2010), Annual cycle of methane emission from a subarctic peatland, J. Geophys. Res.-Biogeosci.
, 115 .
Wik, M., P. M. Crill, R. K. Varner, and D. Bastviken (2013), Multiyear measurements of ebullitive methane flux from three subarctic lakes, J. Geophys. Res.-Biogeosci.
, 118 (3),
1307-1321.
Wik, M., P. M. Crill, D. Bastviken, A. Danielsson, and E. Norback (2011), Bubbles trapped in arctic lake ice: Potential implications for methane emissions, J. Geophys. Res.-
Biogeosci.
, 116 , G03044.
Wik, M., B. F. Thornton, D. Bastviken, S. MacIntyre, R. K. Varner, and P. M. Crill
(2014), Energy input is primary controller of methane bubbling in subarctic lakes,
Geophys Res Lett , 2013GL058510.
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