@article {puleo_younger_2022,
	title = {Younger Dryas and early Holocene climate in south Greenland inferred from oxygen isotopes of chironomids, aquatic Moss, and Moss cellulose},
	journal = {Quaternary Science Reviews},
	volume = {296},
	year = {2022},
	month = {11/2022},
	pages = {107810},
	abstract = {Ice core records have long indicated that the Younger Dryas began and ended with large, abrupt climate shifts over Greenland. Key climatic features remain unknown, including the magnitude of warming during the Younger Dryas-Holocene transition along with the seasonality and spatial variability of Younger Dryas climate changes across Greenland. Here, we use geochemical and paleoecological proxies from lake sediments at Lake N14 in south Greenland to address these outstanding questions. Radiocarbon dating and diatom assemblages confirm early deglaciation and isolation of Lake N14 before \~{}13,600~cal~yr BP, consistent with previous work. Oxygen isotope ratios (δ18O) of chironomid head capsules, bulk aquatic moss, and aquatic moss-derived cellulose are used to reconstruct oxygen isotopes of past lake water and annual precipitation. Oxygen isotope proxies indicate annual precipitation δ18O values increased by 5.9{\textendash}7.7{\textperthousand} at the end of the Younger Dryas. Following the Younger Dryas, moss and cellulose δ18O values show a clear decline in precipitation δ18O values of 2{\textendash}3{\textperthousand} from \~{}11,540{\textendash}11,340~cal~yr BP that may correspond with the Preboreal Oscillation. Reconstructed precipitation δ18O values then gradually increased from 11,300{\textendash}10,100~cal~yr BP. All three aquatic organic materials register similar shifts in precipitation δ18O values over time, and they closely parallel the δ18O shifts observed in ice cores. This evidence strongly supports the utility of these methods for reconstructing lake water δ18O, and furthermore precipitation δ18O values where lake water reflects precipitation. The relatively large shift in isotopic composition of precipitation at Lake N14 suggests that shifts in temperature, precipitation seasonality, and/or moisture sources at the end of the Younger Dryas were even larger in south Greenland than they were in central Greenland, most likely because of the proximity to major changes in North Atlantic Ocean circulation. The annual air temperature change estimated at Lake N14 at the end of the Younger Dryas is also very large (\~{}18~{\textpm}~7~{\textdegree}C) compared to the summer warming previously inferred from chironomid species assemblages there (\~{}6~{\textdegree}C). This indicates that the strongest warming at the end of the Younger Dryas occurred in the winter season, consistent with past observations of intensified Younger Dryas seasonality at Lake N14 and elsewhere in Greenland.},
	keywords = {Chironomids, Deglaciation, diatoms, Greenland, Holocene, Micropaleontology, paleoclimatology, paleolimnology, Stable isotopes, Younger Dryas},
	issn = {0277-3791},
	doi = {10.1016/j.quascirev.2022.107810},
	url = {https://www.sciencedirect.com/science/article/pii/S0277379122004413},
	author = {Puleo, Peter J. K. and Masterson, Andrew L. and Medeiros, Andrew S. and Schellinger, Grace and Steigleder, Regan and Woodroffe, Sarah and Osburn, Magdalena R. and Axford, Yarrow}
}
@article {2690,
	title = {Late glacial and Holocene paleoenvironments in the midcontinent United States, inferred from Geneva Lake leaf wax, ostracode valve, and bulk sediment chemistry},
	journal = {Quaternary Science Reviews},
	volume = {241},
	year = {2020},
	month = {Jan-08-2020},
	pages = {106384},
	abstract = {Geneva Lake in Wisconsin, USA, is > 20,000 years old and contains a 30-m thick lacustrine sediment record of mid-continent North American climate and environmental change. Here we describe a sediment record from Geneva Lake spanning the past 14,500 years. From scanning X-ray fluorescence, organic C and N concentrations and isotopes, X-ray diffraction, magnetic susceptibility, and grain size of bulk sediments, we infer changes in sediment sources over time including: abrupt decline in inputs of remobilized loess \~{}13,400 cal yr BP followed by a gradual transition to organic-rich marl deposition by \~{}10,400 cal yr BP as the landscape stabilized following a period of permafrost thaw and vegetation development; deposition of a minerogenic unit at \~{}8,200 cal yr BP that may record enhanced eolian activity during the widespread {\textquotedblleft}8.2 ka event; {\textquotedblright} and elevated zinc, lead, and arsenic from human activities following regional industrialization. Within the Holocene marl, we also use isotopic (δ18O and δ13C) and trace metal ratio (Sr/Ca and Mg/Ca) analyses of ostracode valves paired with concentrations and hydrogen isotopic composition (δ2H) of leaf wax n-alkanes to infer climate and hydrological change. Groundwater had a large but declining influence on lake water chemistry from 11,800 to 9,700 cal yr BP, precluding inferences of regional climate from our lacustrine proxies during this period. δ2H values of terrestrial n-C29 alkanes show little variability from 9,700 to present, indicating the average isotopic composition of local precipitation was relatively stable, reflecting stable condensation temperatures and source. In contrast, a gradual trend towards more δ18O- and δ2H-depleted lake water and lower lake water Sr/Ca from 9700 cal yr BP to present suggest decreasing evaporation of lake water and increasing precipitation amounts throughout the Holocene and resulting shorter lake water residence times. Lake water Mg/Ca variations over the past 9,700 years broadly parallel regional pollen-based reconstructions of summer temperatures. Neither Mg/Ca nor terrestrial leaf wax δ2H suggest long-term directional shifts in temperature at this site through the middle to late Holocene, as climate became wetter. It appears that precipitation isotopes did not track local temperatures on millennial timescales in this part of mid-continent North America through the Holocene, and instead may have covaried with changes in Northern Hemisphere latitudinal temperature gradients driven by large Arctic temperature changes.},
	keywords = {Holocene, Inorganic geochemistry, Loess, North America, Organic geochemistry, paleoclimatology, paleolimnology, Pleistocene, sedimentology, Stable isotopes},
	issn = {02773791},
	doi = {10.1016/j.quascirev.2020.106384},
	url = {https://www.sciencedirect.com/science/article/pii/S0277379120303462},
	author = {Puleo, Peter J.K. and Axford, Yarrow and McFarlin, Jamie M. and Curry, B. Brandon and Barklage, Mitchell and Osburn, Magdalena R.}
}
@article {2601,
	title = {Holocene temperatures and isotopes of precipitation in Northwest Greenland recorded in lacustrine organic materials},
	journal = {Quaternary Science Reviews},
	volume = {170},
	year = {2017},
	month = {Jan-08-2017},
	pages = {45 - 55},
	abstract = {Reconstructions of Holocene lake water isotopic composition based upon subfossil aquatic organic material offer new insights into Arctic
climate. We present quantitative estimates of warmth during the Holocene Thermal Maximum in northwest Greenland, inferred from oxygen isotopes of chironomid head capsules and aquatic moss preserved in lake sediments. delta O-18 values of chironomids from surface sediments of multiple Greenland lakes indicate that these subfossil remains record the delta O-18 values of the lake water in which they grow. Our lake water delta O-18 reconstruction is supported by downcore agreement with delta O-18 values in aquatic moss and chironomid remains. delta O-18 of both organic materials from Secret Lake decrease after 4 ka (ka = thousands of years ago) by 3 parts per thousand into the Neoglacial. We argue that lake water at Secret Lake primarily reflects precipitation delta O-18 values, which is strongly correlated with air temperature in NW Greenland, and that this signal is biased towards summer and early autumn conditions. Other factors may have influenced Secret Lake delta O-18 values through the Holocene, including evaporation of lake water and changing seasonality and source of precipitation. The maximum early Holocene summer and early autumn-biased temperature anomaly at Secret Lake is 2.5-4 degrees C warmer than present from 7.7 (the beginning of our record) to similar to 6 ka. The maximum late Holocene cold anomaly (which includes the Little Ice Age) is 1.5-3 degrees C colder than present. These ranges of possible temperature anomalies reflect uncertainty in the delta O-18 temperature relationship for precipitation at the study site through the Holocene. (C) 2017 Elsevier Ltd. All rights reserved.},
	keywords = {Chironomids, Greenland, Holocene, paleoclimatology, paleolimnology, Stable isotopes},
	issn = {02773791},
	doi = {10.1016/j.quascirev.2017.06.016},
	url = {http://linkinghub.elsevier.com/retrieve/pii/S0277379116305650http://api.elsevier.com/content/article/PII:S0277379116305650?httpAccept=text/xmlhttp://api.elsevier.com/content/article/PII:S0277379116305650?httpAccept=text/plain},
	author = {Lasher, G. Everett and Axford, Yarrow and McFarlin, Jamie M. and Kelly, Meredith A. and Osterberg, Erich C. and Berkelhammer, Max B.}
}
