@article {2817,
	title = {Deglacial temperature controls on no-analog community establishment in the Great Lakes Region},
	journal = {Quaternary Science Reviews},
	volume = {234},
	year = {2020},
	month = {Jan-04-2020},
	pages = {106245},
	abstract = {Understanding the drivers of vegetation dynamics and no-analog communities in eastern North America is hampered by a scarcity of independent temperature indicators. We present a new branched glycerol dialkyl glycerol tetraether (brGDGT) temperature record from Bonnet Lake, Ohio (18{\textendash}8 ka) and report uncertainty estimates based on Bayesian linear regression and bootstrapping. We also reanalyze a previously published brGDGT record from Silver Lake, Ohio, using improved chromatographic methods. All pollen- and brGDGT-based temperature reconstructions showed qualitatively similar deglacial trends but varying magnitudes. Separating 5- and 6- methyl brGDGTs resulted in substantially lower estimates of deglacial temperature variations (6.4 {\textdegree}C) than inferred from earlier brGDGT methods and pollen (11.8 {\textdegree}C, 12.0 {\textdegree}C respectively). Similar trends among proxies suggest good fidelity of brGDGTs to temperature, despite calibration uncertainties. At both sites, the rise and decline of no-analog communities closely track brGDGT-inferred temperatures, with a lag of 0{\textendash}150 years. The timing of temperature and ecological events varies between Bonnet and Silver Lakes, likely due to age model uncertainties. Climate sensitivity analyses indicate a linear sensitivity of vegetation composition to temperature variations, albeit noisy and significant only with a 500-year bin. The formation of no-analog plant communities in the upper Midwest is closely linked to late-glacial warming, but other factors, such as temperature seasonality or end-Pleistocene megafaunal extinctions, remain viable.},
	keywords = {biomarkers, brGDGT, Climate sensitivity, Lagoons \& swamps, lakes, No-analog, North America, paleoclimatology, Pleistocene, pollen, sedimentology, Temperature, vegetation},
	issn = {02773791},
	doi = {10.1016/j.quascirev.2020.106245},
	url = {https://linkinghub.elsevier.com/retrieve/pii/S0277379119303713},
	author = {Fastovich, David and Russell, James M. and Jackson, Stephen T. and Williams, John W.}
}
@article {2913,
	title = {Insolation and greenhouse gases drove Holocene winter and spring warming in Arctic Alaska},
	journal = {Quaternary Science Reviews},
	volume = {242},
	year = {2020},
	month = {Jan-08-2020},
	pages = {106438},
	abstract = {Global surface temperature changes and their drivers during the Holocene Epoch remain controversial. Syntheses of proxy data indicate that global mean annual temperature declined from the mid-Holocene until the Pre-industrial Era, a trend linked to decreasing Northern Hemisphere summer insolation. In contrast, global climate models simulate increasing mean annual temperatures driven by retreating ice sheets and increasing greenhouse gas concentrations. This proxy-model disagreement may originate from a warm season bias in Northern Hemisphere proxy reconstructions, highlighting the need for new proxies that quantify cold season temperature, especially in Arctic regions that were devoid of continental ice sheets during the Holocene. Here, we present a new 16,000-year winter-spring temperature reconstruction derived from the unsaturation ratio of alkenones (U-3(7)K) in a continuous sedimentary sequence from Lake E5, northern Alaska. We employ a thermodynamic lake model to convert alkenone-inferred lake temperatures into winter-spring air temperature anomalies and we contextualize our proxy reconstruction with climate model output from the region. Our reconstruction shows that winter-spring temperatures warmed rapidly during the deglaciation at 16 and 14 thousand years before present and continued to warm gradually throughout the middle and late Holocene (0.12-0.28 degrees C/thousand years) in concert with regional sea surface temperature and sea ice records. Our results are consistent with climate model simulations and we attribute Holocene warming to rising winter-spring insolation, radiative forcing from rising greenhouse gas concentrations and regional feedbacks. Our reconstructed cold season warming equaled or exceeded summer cooling according to a regional synthesis of temperature records, suggesting that seasonal biases in temperature reconstructions may account for proxy-model disagreements in Holocene temperature trends from Eastern Beringia. (C) 2020 Elsevier Ltd. All rights reserved.},
	keywords = {Alkenone, Beringia, Continental biomarkers, Holocene, North America, paleoclimatology, paleolimnology, Proxy data-model comparison, seasonality, Temperature reconstruction},
	issn = {02773791},
	doi = {10.1016/j.quascirev.2020.106438},
	url = {https://linkinghub.elsevier.com/retrieve/pii/S0277379120304005},
	author = {Longo, William M. and Huang, Yongsong and Russell, James M. and Morrill, Carrie and Daniels, William C. and Giblin, Anne E. and Crowther, Josue}
}
@article {2637,
	title = {Evidence of Ice Age humans in eastern Beringia suggests early migration to North America},
	journal = {Quaternary Science Reviews},
	volume = {205},
	year = {2019},
	month = {Jan-02-2019},
	pages = {35 - 44},
	abstract = {Our understanding of the timing and pathway of human arrival to the Americas remains an important and polarizing topic of debate in archaeology and anthropology. Traditional consensus, supported by archaeological and paleoenvironmental data, favors a {\textquoteright}swift peopling{\textquoteright} of the Americas from Asia via the Bering Land Bridge during the last Glacial termination. More recent genetic data and archaeological finds have challenged this view, proposing the {\textquoteright}Beringian standstill hypothesis{\textquoteright} (BSH), wherein a population of proto-Americans migrated from Asia during, or even prior to the Last Glacial Maximum (LGM) and lived in Beringia for thousands of years before their eventual spread across the American continents. Using a sediment archive from Lake E5 (68.641667 degrees N, 149.457706 degrees W), located on Alaska{\textquoteright}s North Slope, we present new data supporting the BSH and shedding new light on the environmental impact of these early American populations. Fecal biomarkers support human presence in the environs of the lake, and our data demonstrate elevated biomass burning in this region during the last Glacial. Elevated burning defies the expectation that natural fires would be less frequent in the Arctic during the last Glacial, thereby suggesting human ignition as the likely culprit. Our data shed new light on the pathway and timing of human migration to the Americas and demonstrate the possibility of the sustainable coexistence of humans and the Ice Age megafauna in Beringia prior to their extinction. (C) 2018 Elsevier Ltd. All rights reserved.},
	keywords = {Beringia, charcoal, Fecal sterols, Last Glacial, Paleofire, Polycyclic aromatic hydrocarbons (PAHs)},
	issn = {02773791},
	doi = {10.1016/j.quascirev.2018.12.003},
	url = {https://linkinghub.elsevier.com/retrieve/pii/S0277379118307716https://api.elsevier.com/content/article/PII:S0277379118307716?httpAccept=text/xmlhttps://api.elsevier.com/content/article/PII:S0277379118307716?httpAccept=text/plain},
	author = {Vachula, Richard S. and Huang, Yongsong and Longo, William M. and Dee, Sylvia G. and Daniels, William C. and Russell, James M.}
}
@article {2846,
	title = {Temperature variations in the southern Great Lakes during the last deglaciation: Comparison between pollen and GDGT proxies},
	journal = {Quaternary Science Reviews},
	volume = {182},
	year = {2018},
	month = {Jan-02-2018},
	pages = {78 - 92},
	abstract = {Our understanding of deglacial climate history in the southern Great Lakes region of the United States is primarily based upon fossil pollen data, with few independent and multi-proxy climate reconstructions. Here we introduce a new, well-dated fossil pollen record from Stotzel-Leis, OH, and a new deglacial temperature record based on branched glycerol dialkyl glycerol tetraethers (brGDGTs) at Silver Lake, OH. We compare these new data to previously published records and to a regional stack of pollen-based temperature reconstructions from Stotzel-Leis, Silver Lake, and three other well-dated sites. The new and previously published pollen records at Stotzel-Leis are similar, but our new age model brings vegetation events into closer alignment with known climatic events such as the Younger Dryas (YD). brGDGT-inferred temperatures correlate strongly with pollen-based regional temperature reconstructions, with the strongest correlation obtained for a global soil-based brGDGT calibration (r2 = 0.88), lending confidence to the deglacial reconstructions and the use of brGDGT and regional pollen stacks as paleotemperature proxies in eastern North America. However, individual pollen records show large differences in timing, rates, and amplitudes of inferred temperature change, indicating caution with paleoclimatic inferences based on single-site pollen records. From 16.0 to 10.0ka, both proxies indicate that regional temperatures rose by \~{}10 {\textdegree}C, roughly double the \~{}5 {\textdegree}C estimates for the Northern Hemisphere reported in prior syntheses. Change-point analysis of the pollen stack shows accelerated warming at 14.0 {\textpm} 1.2ka, cooling at 12.6 {\textpm} 0.4ka, and warming from 11.6 {\textpm} 0.5ka into the Holocene. The timing of B{\o}lling-Aller{\o}d (B-A) warming and YD onset in our records lag by \~{}300{\textendash}500 years those reported in syntheses of temperature records from the northern mid-latitudes. This discrepancy is too large to be attributed to uncertainties in radiocarbon dating, and correlation between pollen and brGDGT temperature reconstructions rules out vegetation lags as a cause. However, the YD termination appears synchronous among the brGDGT record, regional pollen stack, and Northern Hemisphere stack. The cause of the larger and lagged temperature changes in the southern Great Lakes relative to Northern Hemisphere averages remains unclear, but may be due to the effects of continentality and ice sheet extent on regional climate evolution.},
	keywords = {Continental biomarkers, GDGT, Lagoons and Swamps, lakes, North America, paleoclimatology, Pleistocene, pollen, sedimentology},
	issn = {02773791},
	doi = {10.1016/j.quascirev.2017.12.011},
	url = {https://linkinghub.elsevier.com/retrieve/pii/S0277379117306467},
	author = {Watson, Benjamin I. and Williams, John W. and Russell, James M. and Jackson, Stephen T. and Shane, Linda and Lowell, Thomas V.}
}
@article {2828,
	title = {The tropical lapse rate steepened during the Last Glacial Maximum},
	journal = {Science Advances},
	volume = {3},
	year = {2017},
	month = {Mar-01-2019},
	pages = {e1600815},
	abstract = {The gradient of air temperature with elevation (the temperature lapse rate) in the tropics is predicted to become less steep during the coming century as surface temperature rises, enhancing the threat of warming in high-mountain environments. However, the sensitivity of the lapse rate to climate change is uncertain because of poor constraints on high-elevation temperature during past climate states. We present a 25,000-year temperature reconstruction from Mount Kenya, East Africa, which demonstrates that cooling during the Last Glacial Maximum was amplified with elevation and hence that the lapse rate was significantly steeper than today. Comparison of our data with paleoclimate simulations indicates that state-of-the-art models underestimate this lapse-rate change. Consequently, future high-elevation tropical warming may be even greater than predicted.},
	doi = {10.1126/sciadv.1600815},
	url = {https://advances.sciencemag.org/lookup/doi/10.1126/sciadv.1600815},
	author = {Loomis, Shannon E. and Russell, James M. and Verschuren, Dirk and Morrill, Carrie and De Cort, Gijs and Sinninghe Damst{\'e}, Jaap S. and Olago, Daniel and Eggermont, Hilde and Street-Perrott, F. Alayne and Kelly, Meredith A.}
}
@article {244,
	title = {Late-twentieth-century warming in Lake Tanganyika unprecedented since AD 500},
	journal = {Nature Geoscience},
	volume = {3},
	year = {2010},
	note = {id: 2043; PT: J; UT: WOS:000278134100019},
	pages = {422-425},
	abstract = {Instrumental observations suggest that Lake Tanganyika, the largest rift lake in East Africa, has become warmer, increasingly stratified and less productive over the past 90 years (refs 1,2). These trends have been attributed to anthropogenic climate change. However, it remains unclear whether the decrease in productivity is linked to the temperature rise(3,4), and whether the twentieth-century trends are anomalous within the context of longer-term variability. Here, we use the TEX(86) temperature proxy, the weight per cent of biogenic silica and charcoal abundance from Lake Tanganyika sediment cores to reconstruct lake-surface temperature, productivity and regional wildfire frequency, respectively, for the past 1,500 years. We detect a negative correlation between lake-surface temperature and primary productivity, and our estimates of fire frequency, and hence humidity, preclude decreased nutrient input through runoff as a cause for observed periods of low productivity. We suggest that, throughout the past 1,500 years, rising lake-surface temperatures increased the stratification of the lake water column, preventing nutrient recharge from below and limiting primary productivity. Our records indicate that changes in the temperature of Lake Tanganyika in the past few decades exceed previous natural variability. We conclude that these unprecedented temperatures and a corresponding decrease in productivity can be attributed to anthropogenic global warming, with potentially important implications for the Lake Tanganyika fishery.},
	issn = {1752-0894},
	doi = {10.1038/NGEO865},
	author = {Tierney, Jessica E. and Mayes, Marc T. and Meyer, Natacha and Johnson, Christopher and Swarzenski, Peter W. and Cohen, Andrew S. and Russell, James M.}
}
@article {418,
	title = {Human impacts, climate change, and aquatic ecosystem response during the past 2000 yr at Lake Wandakara, Uganda},
	journal = {Quaternary Research},
	volume = {72},
	year = {2009},
	note = {id: 2052; PT: J; UT: WOS:000271254000002},
	pages = {315-324},
	abstract = {Analyses of carbon and hydrogen isotope ratios of terrestrial leaf waxes and the carbon and nitrogen abundance. ratio, and isotopic composition of bulk sediments from Like Wandakara, a crater lake in western Uganda, East Africa. document human and climatic controls on the aquatic system and oil the Surrounding terrestrial vegetation during the past two millennia Our data indicate that Wandakara was a relatively stable, productive lake Surrounded by C(3) vegetation from AD 70 to 1000. Abrupt changes in the delta(13)C of terrestrial leaf waxes indicate a series of abrupt shifts in the relative abundance of C(3) and C(4) vegetation caused by a combination of climate change and human activities around Wandakara beginning at AD 1000. Abrupt shifts in bulk sediment organic geochemistry. particularly C/N ratios and delta(15)N, indicate that human activities at this time caused permanent changes in the limnology of Lake Wandakara. including eutrophication Our results suggest that the biogeochemistry of Like Wandakara was more sensitive to shifting human impacts than to climate variations during the past millennium, highlighting the importance of understanding the intensity of pre-colonial human impacts on Africa{\textquoteright}s aquatic ecosystems (C) 2009 University of Washington Published by Elsevier Inc All rights reserved},
	issn = {0033-5894},
	doi = {10.1016/j.yqres.2009.06.008},
	author = {Russell, James M. and McCoy, S. J. and Verschuren, D. and Bessems, I. and Huang, Y.}
}
@article {335,
	title = {Northern hemisphere controls on tropical southeast African climate during the past 60,000 years},
	journal = {Science},
	volume = {322},
	year = {2008},
	note = {id: 2047; PT: J; UT: WOS:000259902300046},
	pages = {252-255},
	abstract = {The processes that control climate in the tropics are poorly understood. We applied compound-specific hydrogen isotopes (delta D) and the TEX(86) (tetraether index of 86 carbon atoms) temperature proxy to sediment cores from Lake Tanganyika to independently reconstruct precipitation and temperature variations during the past 60,000 years. Tanganyika temperatures follow Northern Hemisphere insolation and indicate that warming in tropical southeast Africa during the last glacial termination began to increase similar to 3000 years before atmospheric carbon dioxide concentrations. delta D data show that this region experienced abrupt changes in hydrology coeval with orbital and millennial-scale events recorded in Northern Hemisphere monsoonal climate records. This implies that precipitation in tropical southeast Africa is more strongly controlled by changes in Indian Ocean sea surface temperatures and the winter Indian monsoon than by migration of the Intertropical Convergence Zone.},
	issn = {0036-8075},
	doi = {10.1126/science.1160485},
	author = {Tierney, Jessica E. and Russell, James M. and Huang, Yongsong and Damste, Jaap S. Sinninghe and Hopmans, Ellen C. and Cohen, Andrew S.}
}
