Investigating the Spatial and Temporal Scale Variability of Ebullitive Flux from a Subarctic Thaw Pond System
Arctic regions are experiencing more rapid warming than other parts of the world, leading to destabilization of carbon (C) that has been sequestered in permafrost, especially in peatlands where the C content of the peat is very high. More frequent incidence of thaw in permafrost peatlands is leading...
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University of New Hampshire Scholars' Repository
2020
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| Online Access: | https://scholars.unh.edu/dissertation/2499 https://scholars.unh.edu/cgi/viewcontent.cgi?article=3498&context=dissertation |
| Summary: | Arctic regions are experiencing more rapid warming than other parts of the world, leading to destabilization of carbon (C) that has been sequestered in permafrost, especially in peatlands where the C content of the peat is very high. More frequent incidence of thaw in permafrost peatlands is leading to the development of small thaw ponds that are known to be sources of methane (CH4) to the atmosphere, yet there is a lack in long-term studies of CH4 emission from these formations. This is of concern because CH4 has thirty-two times the global warming potential of carbon dioxide over a one-hundred-year timescale (Holmes et al., 2013). At a site in northern Sweden, we have collected over 3000 measurements of CH4 ebullition, or bubbling, from eight small thaw ponds (<0.001 km2) differing in physical and hydrological characteristics over seven growing seasons (2012-2018). We found ebullitive emission to be highly variable over space and time, with an average emission rate of 21.9 mg CH4 m-2 d-1. Between 2012 and 2015, ebullitive emission was weakly correlated with environmental conditions like atmospheric pressure and temperature and potentially more influenced by the physical characteristics of the ponds themselves. Based on their rates of daily ebullitive emission, the ponds fell into four statistically significant groups which appeared to differ from each other based on physical characteristics among the ponds within each group. This grouping, further called pond types, distinguishes ponds from one another based on vegetation presence, pond depth, and hydrologic connectivity to neighboring fen areas (or lack there-of). Type 1, with the lowest daily ebullitive emissions measured, are the shallowest ponds, they are hydrologically isolated have low instances of sedge vegetation (Carex spp. and Eriophorum spp.) and have Sphagnum spp. mosses present within them. Type 2 ponds, which emit more ebullitive CH4 than type 1, are deeper, have more sedge vegetation present and are hydrologically isolated. Type 3 ponds are ... |
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