Figure 1
From: CH4 emissions from runoff water of Alaskan mountain glaciers
Sampling and measurement locations at the meltwater outlets at glacier terminals (red arrows). For all glaciers, the flow direction in the images is from top to bottom. Yellow arrows in the lower left corner of the panels indicate the approximate north. (a) Gulkana Glacier: A few outlets were found between two red arrows, near the left bank of the glacier around the terminus. (b) Canwell Glacier: Sampling and measurements were made at two locations close to the nearby glacier tunnel exits (within 10 m). The length of the tunnel was about 300 m, and the surface of the RW was accessible around its entrance. The downstream sampling site was 500 m away from the upstream site. (c) Castner Glacier: The sampling/measurements site was within 30 m of the entrance from the outlet ice tunnel. (d) Matanuska Glacier: Sampling and measurements were conducted within 30 m of the upwelling flow center (approximately 5 m towards the water side from the red arrow point) in the proglacial lake. Close-up images of each site can be found in the Supplementary Material (Figs. S2–S6).
