@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 {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 {1875,
	title = {PALEOPRODUCTIVITY VARIATION AND ITS CORRELATION WITH CLIMATE CHANGES:AN APPROACH OF LONG-CHAIN ALKENONE},
	journal = {Quaternary Sciences},
	volume = {28},
	year = {2008},
	note = {id: 1968},
	month = {2008},
	pages = {482-490},
	abstract = {The accurate reconstruction of paleoproductivity is critical for understanding the carbon cycle in the past and for predicting the fate of anthropogenic carbon in the future.Biomarkers in marine sediments are useful tools for paleoenvirionment study and have been used as proxies for total and specific phytoplankton group paleoproductivity.Based on 17 AMS14C age controlling points,we report here molecular abundance data for alkenone and organic carbon isotopic data for bulk samples from a giant piston core MD05-2908(24{\textdegree}48.04{\textquoteright}N,122{\textdegree}29.35{\textquoteright}E).The aim is to evaluate the paleoproductivity and interpret the climatic-induced controlling factors for the past 7000aB.P.The results showed that the paleoproductivity in the South Okinawa Trough(SOT)fluctuated frequently in the past 7000aB.P.By correlating with the Titanium records from Huguang Marr and Cariaco Basin,we found out that the paleoproductivity was largely controlled by the latitude migration of ITCZ.The rapid southward shift of the ITCZ might have caused longer staying of the rainfall front in the source supply area,thus,led to intensified erosion,brought increased terrigenous material into the ECS and SOT by fluvial the terrigenous materil delivers to the SOT.Terrigenous input on the one hand might have fertilized the sea surface of SOT and stimulated the production,but on the other hand might have diluted the signal of marine derived input to the sediments.The lower production periods in the SOT correlated well with those ice-drift episodes recorded in the high latitude Atlantic Ocean,suggesting the strong relationships between high and low latitude climate.},
	keywords = {Alkenone, ITCZ, paleoproductivity, SOT, the last 7000aB.P.},
	isbn = {1001-7410},
	author = {Nan, Q. and Li, T. and Chen, Jinxia and Yu, X. and Li, Q.}
}
@article {911,
	title = {Identification of a novel alkenone in Black Sea sediments},
	journal = {Organic Geochemistry},
	volume = {32},
	year = {2000},
	note = {id: 1719},
	pages = {633-645},
	abstract = {We report the identification of a novel long-chain ketone in Holocene Black Sea sediments. Based on chemical properties, and chromatographic and mass spectrometric characteristics, this compound has been identified as a di-unsaturated C36 ethyl ketone. Further analyses indicated the position and configuration of the double bonds, and the novel alkenone was determined to be hexatriaconta-(16E,21E)-dien-3-one. While this compound is present in only trace quantities in Unit I sediments, it is the most abundant alkenone in portions of Unit II. Its presence thus apparently pre-dates the invasion of Emiliania huxleyi in the Black Sea. The down-core profiles and isotopic compositions suggest that the precursor for the C36:2 alkenone may be distinct from that of the C37-39 alkenones, however the biological origin of this novel compound is presently unknown.},
	keywords = {Alkenone, Black Sea, Haptophytes, Holocene, Sediment, Structure characterization},
	doi = {10.1016/S0146-6380(01)00019-5},
	author = {Xu, L. and Reddy, C. M. and Farrington, J. W. and Frysinger, G. S. and Gaines, R. B. and Johnson, C. G. and Nelson, R. K. and Eglinton, T. I.}
}
