@article {rieb_controls_2024,
	title = {Controls on the Respiration of Ancient Carbon Draining From Permafrost Soils Into Sunlit Arctic Surface Waters},
	journal = {Journal of Geophysical Research: Biogeosciences},
	volume = {129},
	number = {5},
	year = {2024},
	note = {_eprint: https://onlinelibrary.wiley.com/doi/pdf/10.1029/2023JG007853},
	month = {05/2024},
	pages = {e2023JG007853},
	abstract = {The thawing of ancient organic carbon stored in arctic permafrost soils, and its oxidation to carbon dioxide (CO2, a greenhouse gas), is predicted to amplify global warming. However, the extent to which organic carbon in thawing permafrost soils will be released as CO2 is uncertain. A critical unknown is the extent to which dissolved organic carbon (DOC) from thawing permafrost soils is respired to CO2 by microbes upon export of freshly thawed DOC to both dark bottom waters and sunlit surface waters. In this study, we quantified the radiocarbon age and 13C composition of CO2 produced by microbial respiration of DOC that was leached from permafrost soils and either kept in the dark or exposed to ultraviolet and visible wavelengths of light. We show that permafrost DOC most labile to microbial respiration was as old or older (ages 4,000{\textendash}11,000 a BP) and more 13C-depleted than the bulk DOC in both dark and light-exposed treatments, likely indicating respiration of old, 13C-depleted lignin and lipid fractions of the permafrost DOC pool. Light exposure either increased, decreased, or had no effect on the magnitude of microbial respiration of old permafrost DOC relative to respiration in the dark, depending on both the extent of DOC oxidation during exposure to light and the wavelength of light. Together, these findings suggest that photochemical changes affecting the lability of permafrost DOC during sunlight exposure are an important control on the magnitude of microbial respiration of permafrost DOC in arctic surface waters.},
	keywords = {Arctic, dissolved organic carbon, permafrost, photochemistry, radiocarbon, respiration},
	issn = {2169-8961},
	doi = {10.1029/2023JG007853},
	url = {https://onlinelibrary.wiley.com/doi/abs/10.1029/2023JG007853},
	author = {Rieb, E. C. and Polik, C. A. and Ward, C. P. and Kling, G. W. and Cory, R. M.}
}
@article {2883,
	title = {Clumped Isotopes Link Older Carbon Substrates With Slower Rates of Methanogenesis in Northern Lakes},
	journal = {Geophysical Research Letters},
	volume = {47},
	year = {2020},
	month = {Apr-03-2022},
	abstract = {The release of long-stored carbon from thawed permafrost could fuel increased methanogenesis in northern lakes, but it remains unclear whether old carbon substrates released from permafrost are metabolized as rapidly by methanogenic microbial communities as recently produced organic carbon. Here, we apply methane (CH4) clumped isotope (Δ18) and 14C measurements to test whether rates of methanogenesis are related to carbon substrate age. Results from culture experiments indicate that Δ18 values are negatively correlated with CH4 production rate. Measurements of ebullition samples from thermokarst lakes in Alaska and glacial lakes in Sweden indicate strong negative correlations between CH4 Δ18 and the fraction modern carbon. These correlations imply that CH4 derived from older carbon substrates is produced relatively slowly. Relative rates of methanogenesis, as inferred from Δ18 values, are not positively correlated with CH4 flux estimates, highlighting the likely importance of environmental variables other than CH4 production rates in controlling ebullition fluxes.},
	keywords = {clumped isotopes, ebullition flux, lakes, methane, permafrost, radiocarbon},
	issn = {0094-8276},
	doi = {10.1029/2019GL086756},
	url = {https://onlinelibrary.wiley.com/doi/abs/10.1029/2019GL086756},
	author = {Douglas, Peter M. J. and Gonzalez Moguel, Regina and Walter Anthony, Katey M. and Wik, Martin and Crill, Patrick M. and Dawson, Katherine S. and Smith, Derek A. and Yanay, Ella and Lloyd, Max K. and Stolper, Daniel A. and Eiler, John M. and Sessions, Alex L.}
}
@article {2699,
	title = {Millennial-scale carbon accumulation and molecular transformation in a permafrost core from Interior Alaska},
	journal = {Geochimica et Cosmochimica Acta},
	volume = {253},
	year = {2019},
	month = {Jan-05-2019},
	pages = {231 - 248},
	abstract = {Organic carbon stored in high-latitude permafrost represents a potential positive feedback to climate warming as well as a valuable store of paleoenvironmental information. The below-freezing conditions have effectively removed permafrost organic material from the modern carbon cycle and preserved its pre-freezing bulk and molecular states. The conditions that lead to efficient burial of organic carbon (OC) within permafrost were investigated by measuring OC stocks, past accumulation rates, and biogeochemical composition of a permafrost core taken from Interior Alaska dating back to 40 ka. The post-glacial Marine Isotope Stage 1 is represented by the top 1.2 m of the core and contains 64.7 kg OC/m2 with an accumulation rate of 4.3 g OC/m2/yr. The sediments that accumulated around the Last Glacial Maximum contain 9.9 kg OC/m2 with an accumulation rate of 0.5 g OC/m2/yr. Carbon storage (144.7 kg OC/m2) and accumulation (26.1 g OC/m2/yr) are both observed to be greatest between 35 and 40 ka, late during the Marine Isotope Stage 3 global interstadial. The extent of OC degradation was assessed using lignin and amino acid biomarkers with both approaches indicating well-preserved contemporary active layer and interstadial OC, whereas stadial OC was highly degraded. Lignin compositional indices throughout the core appear altered by sorptive processes that confounded some expected trends in the overall organic matter composition, while amino acids provided a more integrated pattern of change. Significant correlations between carbon-normalized hydroxyproline and total lignin concentrations further support the usefulness of hydroxyproline as an indicator for the abundance of plant organic matter. A novel amino acid plant-microbial index of the ratio of microbial-specific muramic acid and diaminopimelic acid biomarkers to the plant-specific hydroxyproline biomarker, indicate a transition from plant-dominated organic matter in fresh organic soils (index values of 0.01{\textendash}0.20) to more microbial-dominated organic matter in degraded mineral soils (index values of 0.50{\textendash}2.50). The branched glycerol dialkyl glycerol tetraether composition is complex and is not immediately compatible with existing temperature transfer functions. Residence time within the active layer is interpreted to integrate key factors such as primary productivity, inorganic sediment delivery, and other climate factors that control soil organic matter degradation. The Marine Isotope Stage 3, mid-Wisconsin interstadial period at this locality was forest-dominated and suggests the currently prevailing tundra ecotone is sensitive to environmental change. The majority of buried permafrost OC is high in degradability and if thawed, would be expected to be highly vulnerable to microbial decomposition.},
	keywords = {amino acids, biomarkers, branched GDGTs, lignin phenols, organic carbon, permafrost},
	issn = {00167037},
	doi = {10.1016/j.gca.2019.03.028},
	url = {https://www.sciencedirect.com/science/article/pii/S0016703719301863},
	author = {Hutchings, J.A. and Bianchi, T.S. and Kaufman, D.S. and Kholodov, A.L. and Vaughn, D.R. and Schuur, E.A.G.}
}
@article {2738,
	title = {Remobilization of old permafrost carbon to Chukchi Sea sediments during the end of the last deglaciation},
	journal = {Global Biogeochemical Cycles},
	year = {2018},
	month = {Jan-12-2019},
	abstract = {Climate warming is expected to destabilize permafrost carbon (PF-C) by thaw-erosion and deepening of the seasonally thawed active layer and thereby promote PF-C mineralization to CO2 and CH4. A similar PF-C remobilization might have contributed to the increase in atmospheric CO2 during deglacial warming after the last glacial maximum. Using carbon isotopes and terrestrial biomarkers (Δ14C, δ13C, and lignin phenols), this study quantifies deposition of terrestrial carbon originating from permafrost in sediments from the Chukchi Sea (core SWERUS-L2-4-PC1). The sediment core reconstructs remobilization of permafrost carbon during the late Aller{\o}d warm period starting at 13,000 cal years before present (BP), the Younger Dryas, and the early Holocene warming until 11,000 cal years BP and compares this period with the late Holocene, from 3,650 years BP until present. Dual-carbon-isotope-based source apportionment demonstrates that Ice Complex Deposit{\textemdash}ice- and carbon-rich permafrost from the late Pleistocene (also referred to as Yedoma){\textemdash}was the dominant source of organic carbon (66 {\textpm} 8\%; mean {\textpm} standard deviation) to sediments during the end of the deglaciation, with fluxes more than twice as high (8.0 {\textpm} 4.6 g{\textperiodcentered}m-2{\textperiodcentered}year-1) as in the late Holocene (3.1 {\textpm} 1.0 g{\textperiodcentered}m-2{\textperiodcentered}year-1). These results are consistent with late deglacial PF-C remobilization observed in a Laptev Sea record, yet in contrast with PF-C sources, which at that location were dominated by active layer material from the Lena River watershed. Release of dormant PF-C from erosion of coastal permafrost during the end of the last deglaciation indicates vulnerability of Ice Complex Deposit in response to future warming and sea level changes.},
	keywords = {carbon isotope, climate change feedback, coastal erosion, Deglaciation, past carbon cycling, permafrost},
	issn = {0886-6236},
	doi = {10.1029/2018GB005969},
	url = {https://onlinelibrary.wiley.com/doi/abs/10.1029/2018GB005969https://onlinelibrary.wiley.com/doi/pdf/10.1029/2018GB005969https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1029\%2F2018GB005969https://onlinelibrary.wiley.com/doi/pdf/10.1029/2018GB005969},
	author = {Martens, Jannik and Wild, Birgit and Pearce, Christof and Tesi, Tommaso and Andersson, August and Broder, Lisa and O{\textquoteright}Regan, Matt and Jakobsson, Martin and Sk{\"o}ld, Martin and Gemery, Laura and Cronin, Thomas M. and Semiletov, Igor and Dudarev, Oleg V. and Gustafsson, {\"O}rjan}
}
@article {2698,
	title = {Permafrost Organic Carbon Mobilization From the Watershed to the Colville River Delta: Evidence From 14C Ramped Pyrolysis and Lignin Biomarkers},
	journal = {Geophysical Research Letters},
	volume = {44},
	year = {2017},
	month = {Apr-11-2019},
	pages = {11,491 - 11,500},
	abstract = {The deposition of terrestrial-derived permafrost particulate organic carbon (POC) has been recorded in major Arctic river deltas. However, associated transport pathways of permafrost POC from the watershed to the coast have not been well constrained. Here we utilized a combination of ramped pyrolysis-oxidation radiocarbon analysis (RPO 14C) along with lignin biomarkers, to track the linkages between soils and river and delta sediments. Surface and deep soils showed distinct RPO thermographs which may be related to degradation and organo-mineral interaction. Soil material in the bed load of the river channel was mostly derived from deep old permafrost. Both surface and deep soils were transported and deposited to the coast. Hydrodynamic sorting and barrier island protection played important roles in terrestrial-derived permafrost POC deposition near the coast. On a large scale, ice processes (e.g., ice gauging and strudel scour) and ocean currents controlled the transport and distribution of permafrost POC on the Beaufort Shelf.},
	keywords = {Arctic, carbon cycling, Colville River, Lignin, permafrost, pyrolysis},
	issn = {0094-8276},
	doi = {10.1002/grl.v44.2210.1002/2017GL075543},
	url = {https://agupubs.onlinelibrary.wiley.com/doi/full/10.1002/2017GL075543},
	author = {Zhang, Xiaowen and Bianchi, Thomas S. and Cui, Xingqian and Rosenheim, Brad E. and Ping, Chien-Lu and Hanna, Andrea J. M. and Kanevskiy, Mikhail and Schreiner, Kathryn M. and Allison, Mead A.}
}
@article {2862,
	title = {A probabilistic method of assessing carbon accumulation rate at Imnavait Creek Peatland, Arctic Long Term Ecological Research Station, Alaska},
	journal = {Journal of Quaternary Science},
	volume = {32},
	year = {2017},
	month = {Jan-07-2017},
	pages = {579 - 586},
	abstract = {Arctic peatlands are an important part of the global carbon cycle, accumulating atmospheric carbon as organic matter since the Late glacial. Current methods for understanding the changing efficiency of the peatland carbon sink rely on peatlands with an undisturbed stratigraphy. Here we present a method of estimating primary carbon accumulation rate from a site where permafrost processes have either vertically or horizontally translocated nearby carbon-rich sediment out of stratigraphic order. Briefly, our new algorithm estimates the probability of the age of deposition of a random increment of sediment in the core. The method assumes that if sediment age is measured at even depth increments, dates are more likely to occur during intervals of higher accumulation rate and vice versa. Multiplying estimated sedimentation rate by measured carbon density yields carbon accumulation rate. We perform this analysis at the Imnavait Creek Peatland, near the Arctic Long Term Ecological Research network site at Toolik Lake, Alaska. Using classical radiocarbon age modeling, we find unreasonably high rates of carbon accumulation at various Holocene intervals. With our new method, we find accumulation rate changes that are in improved agreement within the context of other sites throughout Alaska and the rest of the Circum-Arctic region.},
	keywords = {carbon accumulation, Imnavait, peatlands, permafrost, radiocarbon, Toolik LTER},
	doi = {10.1002/jqs.2952},
	url = {https://onlinelibrary.wiley.com/doi/10.1002/jqs.2952},
	author = {Nichols, Jonathan E. and Peteet, Dorothy M. and Frolking, Steve and Karavias, John}
}
@article { ISI:000348452800012,
	title = {Preferential burial of permafrost-derived organic carbon in Siberian-Arctic shelf waters},
	journal = {JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS},
	volume = {119},
	number = {{12}},
	year = {2014},
	month = {DEC},
	pages = {8410-8421},
	type = {Article},
	abstract = {The rapidly changing East Siberian Arctic Shelf (ESAS) receives large amounts of terrestrial organic carbon (OC) from coastal erosion and Russian-Arctic rivers. Climate warming increases thawing of coastal Ice Complex Deposits (ICD) and can change both the amount of released OC, as well as its propensity to be converted to greenhouse gases (fueling further global warming) or to be buried in coastal sediments. This study aimed to unravel the susceptibility to degradation, and transport and dispersal patterns of OC delivered to the ESAS. Bulk and molecular radiocarbon analyses on surface particulate matter (PM), sinking PM and underlying surface sediments illustrate the active release of old OC from coastal permafrost. Molecular tracers for recalcitrant soil OC showed ages of 3.4-13 C-14-ky in surface PM and 5.5-18 C-14-ky in surface sediments. The age difference of these markers between surface PM and surface sediments is larger (i) in regions with low OC accumulation rates, suggesting a weaker exchange between water column and sediments, and (ii) with increasing distance from the Lena River, suggesting preferential settling of fluvially derived old OC nearshore. A dual-carbon end-member mixing model showed that (i) contemporary terrestrial OC is dispersed mainly by horizontal transport while being subject to active degradation, (ii) marine OC is most affected by vertical transport and also actively degraded in the water column, and (iii) OC from ICD settles rapidly and dominates surface sediments. Preferential burial of ICD-OC released into ESAS coastal waters might therefore lower the suggested carbon cycle climate feedback from thawing ICD permafrost.},
	keywords = {biomarkers, carbon, permafrost, radiocarbon},
	issn = {2169-9275},
	doi = {10.1002/2014JC010261},
	author = {Vonk, Jorien E. and Semiletov, Igor P. and Dudarev, Oleg V. and Eglinton, Timothy I. and Andersson, August and Shakhova, Natalia and Charkin, Alexander and Heim, Birgit and Gustafsson, {\"O}rjan}
}
@article { ISI:000342993200010,
	title = {Radiocarbon age-offsets in an arctic lake reveal the long-term response of permafrost carbon to climate change},
	journal = {JOURNAL OF GEOPHYSICAL RESEARCH-BIOGEOSCIENCES},
	volume = {119},
	number = {{8}},
	year = {2014},
	month = {AUG},
	pages = {1630-1651},
	type = {Article},
	abstract = {Continued warming of the Arctic may cause permafrost to thaw and speed the decomposition of large stores of soil organic carbon (OC), thereby accentuating global warming. However, it is unclear if recent warming has raised the current rates of permafrost OC release to anomalous levels or to what extent soil carbon release is sensitive to climate forcing. Here we use a time series of radiocarbon age-offsets (C-14) between the bulk lake sediment and plant macrofossils deposited in an arctic lake as an archive for soil and permafrost OC release over the last 14,500 years. The lake traps and archives OC imported from the watershed and allows us to test whether prior warming events stimulated old carbon release and heightened age-offsets. Today, the age-offset (2ka; thousand of calibrated years before A.D. 1950) and the depositional rate of ancient OC from the watershed into the lake are relatively low and similar to those during the Younger Dryas cold interval (occurring 12.9-11.7ka). In contrast, age-offsets were higher (3.0-5.0ka) when summer air temperatures were warmer than present during the Holocene Thermal Maximum (11.7-9.0ka) and BOlling-AllerOd periods (14.5-12.9ka). During these warm times, permafrost thaw contributed to ancient OC depositional rates that were similar to 10 times greater than today. Although permafrost OC was vulnerable to climate warming in the past, we suggest surface soil organic horizons and peat are presently limiting summer thaw and carbon release. As a result, the temperature threshold to trigger widespread permafrost OC release is higher than during previous warming events.},
	keywords = {carbon cycling, lake sediment, paleoclimatology, permafrost, radiocarbon, Younger Dryas},
	issn = {2169-8953},
	doi = {10.1002/2014JG002688},
	author = {Gaglioti, Benjamin V. and Mann, Daniel H. and Jones, Benjamin M. and Pohlman, John W. and Kunz, Michael L. and Wooller, Matthew J.}
}
