@article {2955,
	title = {Carbon Accumulation, Flux, and Fate in Stordalen Mire, a Permafrost Peatland in Transition},
	journal = {Global Biogeochemical Cycles},
	volume = {36},
	year = {2022},
	month = {Jan-01-2022},
	abstract = {Stordalen Mire is a peatland in the discontinuous permafrost zone in arctic Sweden that exhibits a habitat gradient from permafrost palsa, to Sphagnum bog underlain by permafrost, to Eriophorum-dominated fully thawed fen. We used three independent approaches to evaluate the annual, multi-decadal, and millennial apparent carbon accumulation rates (aCAR) across this gradient: seven years of direct semi-continuous measurement of CO2 and CH4 exchange, and 21 core profiles for 210Pb and 14C peat dating. Year-round chamber measurements indicated net carbon balance of -13 {\textpm} 8, -49 {\textpm} 15, and -91 {\textpm} 43 g C m-2 y-1 for the years 2012{\textendash}2018 in palsa, bog, and fen, respectively. Methane emission offset 2\%, 7\%, and 17\% of the CO2 uptake rate across this gradient. Recent aCAR indicates higher C accumulation rates in surface peats in the palsa and bog compared to current CO2 fluxes, but these assessments are more similar in the fen. aCAR increased from low millennial-scale levels (17{\textendash}29 g C m-2 y-1) to moderate aCAR of the past century (72{\textendash}81 g C m-2 y-1) to higher recent aCAR of 90{\textendash}147 g C m-2 y-1. Recent permafrost collapse, greater inundation and vegetation response has made the landscape a stronger CO2 sink, but this CO2 sink is increasingly offset by rising CH4 emissions, dominated by modern carbon as determined by 14C. The higher CH4 emissions result in higher net CO2-equivalent emissions, indicating that radiative forcing of this mire and similar permafrost ecosystems will exert a warming influence on future climate. Stordalen Mire, a permafrost peatland, has become a stronger carbon sink due to shifts in vegetation and inundation accompanying thaw This stronger carbon sink is offset by an increase in methane emission, resulting in higher net CO2-equivalent emissions Analysis of respiration products indicates that methane emission from the fen and bog are dominated by modern carbon Stordalen Mire, a permafrost peatland, has become a stronger carbon sink due to shifts in vegetation and inundation accompanying thaw This stronger carbon sink is offset by an increase in methane emission, resulting in higher net CO2-equivalent emissions Analysis of respiration products indicates that methane emission from the fen and bog are dominated by modern carbon},
	issn = {0886-6236},
	doi = {10.1029/2021GB007113},
	url = {https://onlinelibrary.wiley.com/doi/10.1029/2021GB007113},
	author = {Holmes, M. E. and Crill, P. M. and Burnett, W. C. and McCalley, C. K. and Wilson, R. M. and Frolking, S. and Chang, K.-Y. and Riley, W. J. and Varner, R. K. and Hodgkins, S. B. and McNichol, A. P. and Saleska, S. R. and Rich, V. I. and Chanton, J. P.}
}
@article {2477,
	title = {Greenhouse gas balance over thaw-freeze cycles in discontinuous zone permafrost},
	journal = {Journal of Geophysical Research: Biogeosciences},
	volume = {122},
	year = {2017},
	month = {Jan-02-2017},
	pages = {387 - 404},
	abstract = {Peat in the discontinuous permafrost zone contains a globally significant reservoir of carbon that has undergone multiple permafrost-thaw cycles since the end of the mid-Holocene (~3700 years before present). Periods of thaw increase C decomposition rates which leads to the release of CO2 and CH4 to the atmosphere creating potential climate feedback. To determine the magnitude and direction of such feedback, we measured CO2 and CH4 emissions and modeled C accumulation rates and radiative fluxes from measurements of two radioactive tracers with differing lifetimes to describe the C balance of the peatland over multiple permafrost-thaw cycles since the initiation of permafrost at the site. At thaw features, the balance between increased primary production and higher CH4 emission stimulated by warmer temperatures and wetter conditions favors C sequestration and enhanced peat accumulation. Flux measurements suggest that frozen plateaus may intermittently (order of years to decades) act as CO2 sources depending on temperature and net ecosystem respiration rates, but modeling results suggest that{\textemdash}despite brief periods of net C loss to the atmosphere at the initiation of thaw{\textemdash}integrated over millennia, these sites have acted as net C sinks via peat accumulation. In greenhouse gas terms, the transition from frozen permafrost to thawed wetland is accompanied by increasing CO2 uptake that is partially offset by increasing CH4 emissions. In the short-term (decadal time scale) the net effect of this transition is likely enhanced warming via increased radiative C emissions, while in the long-term (centuries) net C deposition provides a negative feedback to climate warming.},
	doi = {10.1002/jgrg.v122.210.1002/2016JG003600},
	url = {onlinelibrary.wiley.com/wol1/doi/10.1002/2016JG003600/fullpdf},
	author = {Wilson, R. M. and Fitzhugh, L. and Whiting, G. J. and Frolking, S. and Harrison, M. D. and Dimova, N. and Burnett, W. C. and Chanton, J. P.}
}
@article {2478,
	title = {Stability of peatland carbon to rising temperatures},
	journal = {Nature Communications},
	volume = {7},
	year = {2016},
	month = {Jan-12-2017},
	pages = {13723},
	abstract = {Peatlands contain one-third of soil carbon (C), mostly buried in deep, saturated anoxic zones (catotelm). The response of catotelm C to climate forcing is uncertain, because prior experiments have focused on surface warming. We show that deep peat heating of a 2 m-thick peat column results in an exponential increase in CH4 emissions. However, this response is due solely to surface processes and not degradation of catotelm peat. Incubations show that only the top 20{\textendash}30 cm of peat from experimental plots have higher CH4 production rates at elevated temperatures. Radiocarbon analyses demonstrate that CH4 and CO2 are produced primarily from decomposition of surface-derived modern photosynthate, not catotelm C. There are no differences in microbial abundances, dissolved organic matter concentrations or degradative enzyme activities among treatments. These results suggest that although surface peat will respond to increasing temperature, the large reservoir of catotelm C is stable under current anoxic conditions.},
	doi = {10.1038/ncomms13723},
	url = {http://www.nature.com/doifinder/10.1038/ncomms13723},
	author = {Wilson, R. M. and Hopple, A. M. and Tfaily, M. M. and Sebestyen, S. D. and Schadt, C. W. and Pfeifer-Meister, L. and Medvedeff, C. and McFarlane, K. J. and Kostka, J. E. and Kolton, M. and Kolka, R.K. and Kluber, L. A. and Keller, J. K. and Guilderson, T. P. and Griffiths, N. A. and Chanton, J. P. and Bridgham, S. D. and Hanson, P. J.}
}
@article { ISI:000312696400053,
	title = {Radiocarbon evidence that carbon from the Deepwater Horizon spill entered the planktonic food web of the Gulf of Mexico},
	journal = {ENVIRONMENTAL RESEARCH LETTERS},
	volume = {7},
	number = {{4}},
	year = {2012},
	month = {OCT-DEC},
	type = {Article},
	abstract = {The Deepwater Horizon (Macondo) oil spill released large volumes of oil and gas of distinct carbon isotopic composition to the northern Gulf of Mexico, allowing Graham et al (2010 Environ. Res. Lett. 5 045301) to use stable carbon isotopes (delta C-13) to infer the introduction of spilled oil into the planktonic food web. Surface ocean organic production and measured oil are separated by 5-7 parts per thousand in stable carbon isotope (delta C-13) space, while in radiocarbon (Delta C-14) space these two potential sources are separated by more than 1000 parts per thousand. Thus radiocarbon isotopes provide a more sensitive tracer by which to infer possible introduction of Macondo oil into the food web. We measured Delta C-14 and delta C-13 in plankton collected from within 100 km of the spill site as well as in coastal and offshore DIC (dissolved inorganic carbon or Sigma CO2) to constrain surface production values. On average, plankton values were depleted in C-14 relative to surface DIC, and we found a significant linear correlation between Delta C-14 and delta C-13 in plankton. Cumulatively, these results are consistent with the hypothesis that carbon released from the Deepwater Horizon spill contributed to the offshore planktonic food web. Our results support the findings of Graham et al (2010 Environ. Res. Lett. 5 045301), but we infer that methane input may be important.},
	keywords = {carbon isotope, Gulf oil spill, methane, petroleum hydrocarbon, radiocarbon},
	issn = {1748-9326},
	doi = {10.1088/1748-9326/7/4/045303},
	author = {Chanton, J. P. and Cherrier, J. and Wilson, R. M. and Sarkodee-Adoo, J. and Bosman, S. and Mickle, A. and Graham, W. M.}
}
@article {385,
	title = {Radiocarbon evidence for the importance of surface vegetation on fermentation and methanogenesis in contrasting types of boreal peatlands},
	journal = {Global Biogeochemical Cycles},
	volume = {22},
	year = {2008},
	note = {id: 1949; PT: J; UT: WOS:000262041000002},
	pages = {GB4022-GB4022},
	abstract = {We found a consistent distribution pattern for radiocarbon in dissolved organic carbon (DOC), dissolved inorganic carbon (DIC), and methane replicated across spatial and temporal scales in northern peatlands from Minnesota to Alaska. The (14)C content of DOC is relatively modern throughout the peat column, to depths of 3 m. In sedge-dominated peatlands, the (14)C contents of the products of respiration, CH(4) and DIC, are essentially the same and are similar to that of DOC. In Sphagnum- and woody plant-dominated peatlands with few sedges, however, the respiration products are similar but intermediate between the (14)C contents of the solid phase peat and the DOC. Preliminary data indicates qualitative differences in the pore water DOC, depending on the extent of sedge cover, consistent with the hypothesis that the DOC in sedge-dominated peatlands is more reactive than DOC in peatlands where Sphagnum or other vascular plants dominate. These data are supported by molecular level analysis of DOC by ultrahigh-resolution mass spectrometry that suggests more dramatic changes with depth in the composition of DOC in the sedge-dominated peatland pore waters relative to changes observed in DOC where Sphagnum dominates. The higher reactivity of DOC from sedge-dominated peatlands may be a function of either different source materials or environmental factors that are related to the abundance of sedges in peatlands.},
	issn = {0886-6236},
	doi = {10.1029/2008GB003274},
	author = {Chanton, J. P. and Glaser, P. H. and Chasar, L. S. and Burdige, D. J. and Hines, M. E. and Siegel, D. I. and Tremblay, L. B. and Cooper, W. T.}
}
@article {2160,
	title = {Radiocarbon and stable carbon isotopic evidence for transport and transformation of DOC, DIC and CH4 in a northern Minnesota peatland},
	journal = {Global Biogeochemical Cycles},
	volume = {14},
	year = {2001},
	note = {id: 98},
	month = {2001},
	pages = {1095-1105},
	author = {Chasar, L. S. and Chanton, J. P. and Glaser, P. H. and Siegel, D. I. and Rivers, J. S.}
}
