@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 {cluett_lake_2023,
	title = {Lake Dynamics Modulate the Air Temperature Variability Recorded by Sedimentary Aquatic Biomarkers: A Holocene Case Study From Western Greenland},
	journal = {Journal of Geophysical Research: Biogeosciences},
	volume = {128},
	number = {7},
	year = {2023},
	note = {_eprint: https://onlinelibrary.wiley.com/doi/pdf/10.1029/2022JG007106},
	month = {07/2023},
	pages = {e2022JG007106},
	abstract = {Quantitative temperature reconstructions from lacustrine organic geochemical proxies including branched glycerol dialkyl glycerol tetraethers (brGDGTs) and alkenones provide key constraints on past continental climates. However, estimation of air temperatures from proxies can be impacted by non-stationarity in the relationships between seasonal air and water temperatures, a factor not yet examined in strongly seasonal high-latitude settings. We pair downcore analyses of brGDGTs and alkenones measured on the same samples through the Holocene with forward-modeled proxy values based on thermodynamic lake model simulations for a western Greenland lake. The measured brGDGT distributions suggest that stable autochthonous (aquatic) production overpowers allochthonous inputs for most samples, justifying the use of the lake model to interpret temperature-driven changes. Conventional calibration of alkenones (detected only after 5.5 thousand years BP) suggests substantially larger temperature variations than conventional calibration of brGDGTs. Comparison of proxy measurements to forward-modeled values suggests variations in brGDGT distributions monotonically reflect multi-decadal summer air temperatures changes, although the length of the ice-free season dampens the influence of air temperatures on water temperatures. Drivers of alkenone variability remain less clear; potential influences include small changes in the seasonality of proxy production or biases toward specific years, both underlain by non-linearity in water-air temperature sensitivity during relevant seasonal windows. We demonstrate that implied temperature variability can differ substantially between proxies because of differences in air-water temperature sensitivity during windows of proxy synthesis without necessitating threshold behavior in the lake or local climate, and recommend that future studies incorporate lake modeling to constrain this uncertainty.},
	keywords = {Alkenone, Arctic, biogeochemical proxies, brGDGT, data-model comparison, proxy system modeling},
	issn = {2169-8961},
	doi = {10.1029/2022JG007106},
	url = {https://onlinelibrary.wiley.com/doi/abs/10.1029/2022JG007106},
	author = {Cluett, A. A. and Thomas, E. K. and McKay, N. P. and Cowling, O. C. and Casta{\~n}eda, I. S. and Morrill, C.}
}
@article {2857,
	title = {Temperature-controlled tundra fire severity and frequency during the last millennium in the Yukon-Kuskokwim Delta, Alaska},
	journal = {The Holocene},
	volume = {29},
	year = {2019},
	month = {Jan-07-2019},
	pages = {1223 - 1233},
	abstract = {Wildfire is an important disturbance to Arctic tundra ecosystems. In the coming decades, tundra fire frequency, intensity, and extent are projected to increase because of anthropogenic climate change. To more accurately predict the effects of climate change on tundra fire regimes, it is critical to have detailed knowledge of the natural frequency and extent of past wildfires and how they responded to past climate variability. We present analyses of fire frequency and temperature from a lake sediment core from the Yukon-Kuskokwim (YK) Delta. Our ca. 1000 macroscopic charcoal record shows more frequent but possibly less severe tundra fires during the first half of the last millennium, whereas less frequent, possibly more severe fires characterize the latter half. Our temperature reconstruction, based on distributional changes of branched glycerol dialkyl glycerol tetraethers (brGDGTs), shows slightly warmer conditions from ca. AD 1000 to 1500, and cooler conditions thereafter (ca. AD 1500 to 2000), suggesting that fire frequency increases when climate is relatively warmer in this region. When wildfires occur more frequently, fire severity may decrease because of limited biomass (fuel source) accumulating between fires. The data suggest that tundra ecosystems are highly sensitive to climate change, and that a warmer climate, which is predicted to develop in the near future, will result in more frequent tundra wildfires.},
	keywords = {alaska, Arctic, charcoal, glycerol dialkyl glycerol tetraethers (GDGTs), late-holocene, Paleoclimate, Paleofire},
	issn = {0959-6836},
	doi = {10.1177/0959683619838036},
	url = {http://journals.sagepub.com/doi/10.1177/0959683619838036},
	author = {Sae-Lim, Jarunetr and Russell, James M and Vachula, Richard S and Holmes, Robert M and Mann, Paul J and Schade, John D and Natali, Susan M}
}
@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 {2786,
	title = {Younger-Dryas cooling and sea-ice feedbacks were prominent features of the Pleistocene-Holocene transition in Arctic Alaska},
	journal = {Quaternary Science Reviews},
	volume = {169},
	year = {2017},
	month = {Jan-08-2017},
	pages = {330 - 343},
	abstract = {Declining sea-ice extent is currently amplifying climate warming in the Arctic. Instrumental records at high latitudes are too short-term to provide sufficient historical context for these trends, so paleoclimate archives are needed to better understand the functioning of the sea ice-albedo feedback. Here we use the oxygen isotope values of wood cellulose in living and sub-fossil willow shrubs (δ18Owc) (Salix spp.) that have been radiocarbon-dated (14C) to produce a multi-millennial record of climatic change on Alaska{\textquoteright}s North Slope during the Pleistocene-Holocene transition (13,500{\textendash}7500 calibrated 14C years before present; 13.5{\textendash}7.5 ka). We first analyzed the spatial and temporal patterns of δ18Owc in living willows growing at upland sites and found that over the last 30 years δ18Owc values in individual growth rings correlate with local summer temperature and inter-annual variations in summer sea-ice extent. Deglacial δ18Owc values from 145 samples of subfossil willows clearly record the Aller{\o}d warm period (\~{}13.2 ka), the Younger Dryas cold period (12.9{\textendash}11.7 ka), and the Holocene Thermal Maximum (11.7{\textendash}9.0 ka). The magnitudes of isotopic changes over these rapid climate oscillations were \~{}4.5{\textperthousand}, which is about 60\% of the differences in δ18Owc between those willows growing during the last glacial period and today. Modeling of isotope-precipitation relationships based on Rayleigh distillation processes suggests that during the Younger Dryas these large shifts in δ18Owc values were caused by interactions between local temperature and changes in evaporative moisture sources, the latter controlled by sea ice extent in the Arctic Ocean and Bering Sea. Based on these results and on the effects that sea-ice have on climate today, we infer that ocean-derived feedbacks amplified temperature changes and enhanced precipitation in coastal regions of Arctic Alaska during warm times in the past. Today, isotope values in willows on the North Slope of Alaska are similar to those growing during the warmest times of the Pleistocene-Holocene transition, which were times of widespread permafrost thaw and striking ecological changes.},
	keywords = {alaska, Arctic, Bering Strait, Climate change, dendrochronology, north pacific, oxygen isotopes, Paleoclimate, Sea ice, Younger Dryas},
	issn = {02773791},
	doi = {10.1016/j.quascirev.2017.05.012},
	url = {https://linkinghub.elsevier.com/retrieve/pii/S0277379117301713},
	author = {Gaglioti, Benjamin V. and Mann, Daniel H. and Wooller, Matthew J. and Jones, Benjamin M. and Wiles, Gregory C. and Groves, Pamela and Kunz, Michael L. and Baughman, Carson A. and Reanier, Richard E.}
}
@article {2573,
	title = {Historical records of organic matter supply and degradation status in the East Siberian Sea},
	journal = {Organic Geochemistry},
	volume = {91},
	year = {2016},
	month = {Jan-01-2016},
	pages = {16 - 30},
	abstract = {Destabilization and degradation of permafrost carbon in the Arctic regions could constitute a positive feedback to climate change. A better understanding of its fate upon discharge to the Arctic shelf is therefore needed. In this study, bulk carbon isotopes as well as terrigenous and marine biomarkers were used to construct two centennial records in the East Siberian Sea. Differences in topsoil and Pleistocene Ice Complex Deposit permafrost concentrations, modeled using δ13C and Δ14C, were larger between inner and outer shelf than the changes over time. Similarly, lignin-derived phenol and cutin acid concentrations differed by a factor of ten between the two stations, but did not change significantly over time, consistent with the dual-carbon isotope model. High molecular weight (HMW) n-alkane and n-alkanoic acid concentrations displayed a smaller difference between the two stations (factor of 3{\textendash}6). By contrast, the fraction for marine OC drastically decreased during burial with a half-life of 19{\textendash}27 years. Vegetation and degradation proxies suggested supply of highly degraded gymnosperm wood tissues. Lipid Carbon Preference Index (CPI) values indicated more extensively degraded HMW n-alkanes on the outer shelf with no change over time, whereas n-alkanoic acids appeared to be less degraded toward the core top with no large differences between the stations. Taken together, our results show larger across-shelf changes than down-core trends. Further investigation is required to establish whether the observed spatial differences are due to different sources for the two depositional settings or, alternatively, a consequence of hydrodynamic sorting combined with selective degradation during cross-shelf transport.},
	keywords = {210Pb, Arctic, East Siberian Arctic Shelf, HMW wax lipids, Lignin, Monte Carlo, δ13C, Δ14C},
	issn = {01466380},
	doi = {10.1016/j.orggeochem.2015.10.008},
	url = {https://doi.org/10.1016/j.orggeochem.2015.10.008},
	author = {Broder, Lisa and Tesi, Tommaso and Andersson, August and Eglinton, Timothy I. and Semiletov, Igor P. and Dudarev, Oleg V. and Roos, Per and Gustafsson, ?rjan}
}
@book {2581,
	title = {Treatise on Geomorphology8.26 Climate Change Impacts on Cold Climates},
	year = {2013},
	pages = {430 - 459},
	publisher = {Elsevier},
	organization = {Elsevier},
	abstract = {Since the onset of Cenozoic ice sheets, cold climate regions have played a leading role in planetary energy balance, atmospheric and global oceanic circulations. Glacial and periglacial processes in polar regions act as morphogenetic agents for landscape sculpting providing landforms and deposits that represent valuable records for investigating the amplitude of key phases of Cenozoic glacial history. Glacio-eustatic sea-level variations induce revolutionary environmental changes across the entire planet. Changes in periglacial processes also influence cold region hydrology, ecosystems, and soil carbon storage. Climatic and environmental changes in cold regions cause adaptation through ecological and evolutionary responses by organisms.},
	keywords = {Ad{\'e}lie penguins, Antarctica, Arctic, Cenozoic, Climate change, Elephant seals, glacial history, Holocene, Icehouse},
	isbn = {9780080885223},
	doi = {10.1016/B978-0-12-374739-6.00222-0},
	url = {https://doi.org/10.1016/B978-0-12-374739-6.00222-0},
	author = {Baroni, C.}
}
@article {1032,
	title = {Holocene lake sediment records of Arctic hydrology},
	journal = {Journal of Paleolimnology},
	volume = {24},
	year = {2000},
	note = {id: 375},
	pages = {1-13},
	abstract = {Although paleoclimatic research in the Arctic has most often focused on variations in temperature, the Arctic has also experienced changes in hydrologic balance. Changes in Arctic precipitation and evaporation rates affects soils, permafrost, lakes, wetlands, rivers, ice and vegetation. Changes in Arctic soils, permafrost, runoff, and vegetation can influence global climate by changing atmospheric methane and carbon dioxide concentrations, thermohaline circulation, and high latitude albedo. Documenting past variations in Arctic hydrological conditions is important for understanding Arctic climate and the potential response and role of the Arctic in regards to future climate change. Methods for reconstructing past changes in Arctic hydrology from the stratigraphic, isotopic, geochemical and fossil records of lake sediments are being developed, refined and applied in a number of regions. These records suggest that hydrological variations in the Arctic have been regionally asynchronous, reflecting the impacts of different forcing factors including orbitally controlled insolation changes, changes in geography related to coastal emergence, ocean currents, sea ice extent, and atmospheric circulation. Despite considerable progress, much work remains to be done on the development of paleohydrological proxies and their application to the Arctic.},
	keywords = {Arctic, Climate change, Holocene, paleohydrology, paleolimnology},
	doi = { 10.1023/A:1008100714795},
	author = {MacDonald, G. M. and Felzer, B. and Finney, B. P. and Forman, S. L.}
}
