Long-term variations of the mole fraction and carbon isotope ratio of atmospheric methane observed at Ny-Ålesund, Svalbard from 1996 to 2013

The data presented in this paper are downloadable from the website (http://caos.sakura.ne.jp/tgr/data/en).

Figures & data

Fig. 1. Temporal variations of the CH₄ mole fraction (a) and δ¹³C of CH₄ (b) observed at Ny-Ålesund, Svalbard. Also shown are their best-fit curves (solid lines) and long-term trends (broken lines).

Fig. 2. Long-term components of the CH₄ mole fraction (a) and δ¹³C (b) at Ny-Ålesund, Svalbard obtained by using the digital filtering technique in which the cut-off period was set to 5 years. Also shown are the regression lines for each segment obtained by the stepwise fitting, given the points of slope change at 2000.8 and 2005.8 (decimal year).

Table 1. The average rate of increase in CH₄ (ppb yr⁻¹) (a) and δ¹³C (‰ yr⁻¹) (b) for given periods, together with their respective standard errors (s.e.) and 95% confidence intervals (C.I.) obtained using the bootstrap analysis.

Period	Increase rate	s.e.	95% C.I.
(a)
1991.0–2000.8	4.5	0.2	[4.2, 4.8]
2000.8–2005.8	0.3	0.2	[–0.1, 0.8]
2005.8–2014.0	5.5	0.2	[5.1, 5.8]
(b)
1996.0–2000.8	0.006	0.003	[0.000, 0.012]
2000.8–2005.8	0.012	0.002	[0.008, 0.017]
2005.8–2014.0	−0.014	0.005	[–0.024, −0.004]

Fig. 3. Yearly anomalies of precipitation (open circles and triangles) and soil moisture content (solid circles and triangles) calculated for wetland and rice paddy regions (Matthews and Fung, 2003) in 44–90°N and 24°S-24°N. Soil moisture is expressed as water equivalent depth.

Matthews, E. and Fung, I. 2003. LBA Regional Wetlands Data Set, 1-Degree Data set. Oak Ridge National Laboratory Distributed Active Archive Center, Oak Ridge, TN, DOI:10.3334/ORNLDAAC/688. Online at: http://www.daac.ornl.gov

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