@article {lenz_evidence_2016,
	title = {Evidence of multiple thermokarst lake generations from an 11 800-year-old permafrost core on the northern Seward Peninsula, Alaska},
	journal = {Boreas},
	volume = {45},
	number = {4},
	year = {2016},
	note = {_eprint: https://onlinelibrary.wiley.com/doi/pdf/10.1111/bor.12186},
	month = {06/2016},
	pages = {584{\textendash}603},
	abstract = {Permafrost degradation influences the morphology, biogeochemical cycling and hydrology of Arctic landscapes over a range of time scales. To reconstruct temporal patterns of early to late Holocene permafrost and thermokarst dynamics, site-specific palaeo-records are needed. Here we present a multi-proxy study of a 350-cm-long permafrost core from a drained lake basin on the northern Seward Peninsula, Alaska, revealing Lateglacial to Holocene thermokarst lake dynamics in a central location of Beringia. Use of radiocarbon dating, micropalaeontology (ostracods and testaceans), sedimentology (grain-size analyses, magnetic susceptibility, tephra analyses), geochemistry (total nitrogen and carbon, total organic carbon, δ13Corg) and stable water isotopes (δ18O, δD, d excess) of ground ice allowed the reconstruction of several distinct thermokarst lake phases. These include a pre-lacustrine environment at the base of the core characterized by the Devil Mountain Maar tephra (22 800{\textpm}280 cal. a BP, Unit A), which has vertically subsided in places due to subsequent development of a deep thermokarst lake that initiated around 11 800 cal. a BP (Unit B). At about 9000 cal. a BP this lake transitioned from a stable depositional environment to a very dynamic lake system (Unit C) characterized by fluctuating lake levels, potentially intermediate wetland development, and expansion and erosion of shore deposits. Complete drainage of this lake occurred at 1060 cal. a BP, including post-drainage sediment freezing from the top down to 154 cm and gradual accumulation of terrestrial peat (Unit D), as well as uniform upward talik refreezing. This core-based reconstruction of multiple thermokarst lake generations since 11 800 cal. a BP improves our understanding of the temporal scales of thermokarst lake development from initiation to drainage, demonstrates complex landscape evolution in the ice-rich permafrost regions of Central Beringia during the Lateglacial and Holocene, and enhances our understanding of biogeochemical cycles in thermokarst-affected regions of the Arctic.},
	issn = {1502-3885},
	doi = {10.1111/bor.12186},
	url = {https://onlinelibrary.wiley.com/doi/abs/10.1111/bor.12186},
	author = {Lenz, Josefine and Wetterich, Sebastian and Jones, Benjamin M. and Meyer, Hanno and Bobrov, Anatoly and Grosse, Guido}
}
@article {2487,
	title = {Methane emissions proportional to permafrost carbon thawed in Arctic lakes since the 1950s},
	journal = {Nature Geoscience},
	volume = {9},
	year = {2016},
	month = {Oct-08-2017},
	pages = {679 - 682},
	abstract = {Permafrost thaw exposes previously frozen soil organic matter to microbial decomposition. This process generates methane and carbon dioxide, and thereby fuels a positive feedback process that leads to further warming and thaw1. Despite widespread permafrost degradation during the past ~40 years2, 3, 4, the degree to which permafrost thaw may be contributing to a feedback between warming and thaw in recent decades is not well understood. Radiocarbon evidence of modern emissions of ancient permafrost carbon is also sparse5. Here we combine radiocarbon dating of lake bubble trace-gas methane (113 measurements) and soil organic carbon (289 measurements) for lakes in Alaska, Canada, Sweden and Siberia with numerical modelling of thaw and remote sensing of thermokarst shore expansion. Methane emissions from thermokarst areas of lakes that have expanded over the past 60 years were directly proportional to the mass of soil carbon inputs to the lakes from the erosion of thawing permafrost. Radiocarbon dating indicates that methane age from lakes is nearly identical to the age of permafrost soil carbon thawing around them. Based on this evidence of landscape-scale permafrost carbon feedback, we estimate that 0.2 to 2.5 Pg permafrost carbon was released as methane and carbon dioxide in thermokarst expansion zones of pan-Arctic lakes during the past 60 years.},
	keywords = {Carbon cycle, Climate change, Cryospheric science},
	issn = {1752-0894},
	doi = {10.1038/ngeo2795},
	url = {http://www.nature.com/doifinder/10.1038/ngeo2795},
	author = {Walter Anthony, Katey and Daanen, Ronald and Anthony, Peter and Schneider von Deimling, Thomas and Ping, Chien-Lu and Chanton, Jeffrey P. and Grosse, Guido}
}
@article {2488,
	title = {Geologic methane seeps along boundaries of Arctic permafrost thaw and melting glaciers},
	journal = {Nature Geoscience},
	volume = {5},
	year = {2012},
	month = {Aug-05-2013},
	pages = {419 - 426},
	abstract = {Methane, a potent greenhouse gas, accumulates in subsurface hydrocarbon reservoirs, such as coal beds and natural gas deposits. In the Arctic, permafrost and glaciers form a {\textquoteleft}cryosphere cap{\textquoteright} that traps gas leaking from these reservoirs, restricting flow to the atmosphere. With a carbon store of over 1,200 Pg, the Arctic geologic methane reservoir is large when compared with the global atmospheric methane pool of around 5 Pg. As such, the Earth{\textquoteright}s climate is sensitive to the escape of even a small fraction of this methane. Here, we document the release of 14C-depleted methane to the atmosphere from abundant gas seeps concentrated along boundaries of permafrost thaw and receding glaciers in Alaska and Greenland, using aerial and ground surface survey data and in situ measurements of methane isotopes and flux. We mapped over 150,000 seeps, which we identified as bubble-induced open holes in lake ice. These seeps were characterized by anomalously high methane fluxes, and in Alaska by ancient radiocarbon ages and stable isotope values that matched those of coal bed and thermogenic methane accumulations. Younger seeps in Greenland were associated with zones of ice-sheet retreat since the Little Ice Age. Our findings imply that in a warming climate, disintegration of permafrost, glaciers and parts of the polar ice sheets could facilitate the transient expulsion of 14C-depleted methane trapped by the cryosphere cap.},
	keywords = {Biogeochemistry, Cryospheric science},
	issn = {1752-0894},
	doi = {10.1038/ngeo1480},
	url = {http://www.nature.com/doifinder/10.1038/ngeo1480},
	author = {Walter Anthony, Katey M. and Anthony, Peter and Grosse, Guido and Chanton, Jeffrey}
}
