@article{ComasBruHarrisonWerneretal.2019,
  author    = {Comas-Bru, Laia and Harrison, Sandy P. and Werner, Martin and Rehfeld, Kira and Scroxton, Nick and Veiga-Pires, Cristina and Ahmad, Syed Masood and Brahim, Yassine Ait and Mozhdehi, Sahar Amirnezhad and Arienzo, Monica and Atsawawaranunt, Kamolphat and Baker, Andy and Braun, Kerstin and Breitenbach, Sebastian Franz Martin and Burstyn, Yuval and Chawchai, Sakonvan and Columbu, Andrea and Deininger, Michael and Demeny, Attila and Dixon, Bronwyn and Hatvani, Istvan Gabor and Hu, Jun and Kaushal, Nikita and Kern, Zoltan and Labuhn, Inga and Lachniet, Matthew S. and Lechleitner, Franziska A. and Lorrey, Andrew and Markowska, Monika and Nehme, Carole and Novello, Valdir F. and Oster, Jessica and Perez-Mejias, Carlos and Pickering, Robyn and Sekhon, Natasha and Wang, Xianfeng and Warken, Sophie and Atkinson, Tim and Ayalon, Avner and Baldini, James and Bar-Matthews, Miryam and Bernal, Juan Pablo and Boch, Ronny and Borsato, Andrea and Boyd, Meighan and Brierley, Chris and Cai, Yanjun and Carolin, Stacy and Cheng, Hai and Constantin, Silviu and Couchoud, Isabelle and Cruz, Francisco and Denniston, Rhawn and Dragusin, Virgil and Duan, Wuhui and Ersek, Vasile and Finne, Martin and Fleitmann, Dominik and Fohlmeister, Jens Bernd and Frappier, Amy and Genty, Dominique and Holzkamper, Steffen and Hopley, Philip and Johnston, Vanessa and Kathayat, Gayatri and Keenan-Jones, Duncan and Koltai, Gabriella and Li, Ting-Yong and Lone, Mahjoor Ahmad and Luetscher, Marc and Mattey, Dave and Moreno, Ana and Moseley, Gina and Psomiadis, David and Ruan, Jiaoyang and Scholz, Denis and Sha, Lijuan and Smith, Andrew Christopher and Strikis, Nicolas and Treble, Pauline and Unal-Imer, Ezgi and Vaks, Anton and Vansteenberge, Stef and Voarintsoa, Ny Riavo G. and Wong, Corinne and Wortham, Barbara and Wurtzel, Jennifer and Zhang, Haiwei},
  title     = {Evaluating model outputs using integrated global speleothem records of climate change since the last glacial},
  series = {Climate of the past : an interactive open access journal of the European Geosciences Union},
  volume    = {15},
  journal   = {Climate of the past : an interactive open access journal of the European Geosciences Union},
  number    = {4},
  publisher = {Copernicus},
  address   = {G{\"o}ttingen},
  organization    = {SISAL Working Grp},
  issn      = {1814-9324},
  doi       = {10.5194/cp-15-1557-2019},
  pages     = {1557 -- 1579},
  year      = {2019},
  abstract  = {Although quantitative isotope data from speleothems has been used to evaluate isotope-enabled model simulations, currently no consensus exists regarding the most appropriate methodology through which to achieve this. A number of modelling groups will be running isotope-enabled palaeoclimate simulations in the framework of the Coupled Model Intercomparison Project Phase 6, so it is timely to evaluate different approaches to using the speleothem data for data-model comparisons. Here, we illustrate this using 456 globally distributed speleothem δ18O records from an updated version of the Speleothem Isotopes Synthesis and Analysis (SISAL) database and palaeoclimate simulations generated using the ECHAM5-wiso isotope-enabled atmospheric circulation model. We show that the SISAL records reproduce the first-order spatial patterns of isotopic variability in the modern day, strongly supporting the application of this dataset for evaluating model-derived isotope variability into the past. However, the discontinuous nature of many speleothem records complicates the process of procuring large numbers of records if data-model comparisons are made using the traditional approach of comparing anomalies between a control period and a given palaeoclimate experiment. To circumvent this issue, we illustrate techniques through which the absolute isotope values during any time period could be used for model evaluation. Specifically, we show that speleothem isotope records allow an assessment of a model's ability to simulate spatial isotopic trends. Our analyses provide a protocol for using speleothem isotope data for model evaluation, including screening the observations to take into account the impact of speleothem mineralogy on δ18O values, the optimum period for the modern observational baseline and the selection of an appropriate time window for creating means of the isotope data for palaeo-time-slices.},
  language  = {en}
}
@article{MarkowskaFohlmeisterTrebleetal.2019,
  author    = {Markowska, Monika and Fohlmeister, Jens Bernd and Treble, Pauline C. and Baker, Andy and Andersen, Martin S. and Hua, Quan},
  title     = {Modelling the C-14 bomb-pulse in young speleothems using a soil carbon continuum model},
  series = {Geochimica et cosmochimica acta : journal of the Geochemical Society and the Meteoritical Society},
  volume    = {261},
  journal   = {Geochimica et cosmochimica acta : journal of the Geochemical Society and the Meteoritical Society},
  publisher = {Elsevier},
  address   = {Oxford},
  issn      = {0016-7037},
  doi       = {10.1016/j.gca.2019.04.029},
  pages     = {342 -- 367},
  year      = {2019},
  abstract  = {The 'bomb-pulse' method is a chronological approach to further constrain the age of speleothems that grew between 1950 CE - present. Establishing dependable chronological constraints is crucial for modern calibration studies of speleothems to instrumental climate records, which provides the basis for paleoclimate interpretations. However, a large unknown is how 14C is transferred from the atmosphere to any individual speleothem owing to the site-specific residence times of organic matter above cave systems. Here, we employ the bomb-pulse method to build chronologies from 14C measurements in combination with a new unsaturated zone C model which considers C decomposition as a continuum, to better understand unsaturated zone 14C dynamics. The bomb-pulse curves of eight speleothems from southern Australia in three contrasting climatic regions; the semi-arid Wellington Caves site, the mediterranean Golgotha Cave site and the montane Yarrangobilly Caves site, are investigated. Overall, the modelled 14C bomb-pulse curves produce excellent fits with measured 14C speleothem data (r2 = 0.82-0.99). The C modelling reveals that unsaturated zone C is predominately young at the semi-arid site, with a weighted-mean residence time of 32 years and that tree root respiration is likely an important source of vadose CO2. At the montane site, ∼39\% of C is young (<1 years), but the weighted-mean C ages are older (145-220 years). The mediterranean site has very little contribution from young C (<12\%: 0-1 years), with weighted-mean ages between 157 and 245 years, likely due to greater adsorption of organic matter in the upper vadose zone during matrix flow, and remobilisation of C from young syngenetic karst. New end members for low speleothem Dead Carbon Proportion (DCP) are identified (2.19\% and 1.65\%, respectively) for Australian montane and semi-arid zone speleothems, where oversupply of modern CO2 in the vadose zone leads to lower DCP. It is also demonstrated that DCP can be quite variable over small time scales, that processes may be difficult to untangle and a constant DCP assumption is likely invalid. DCP variability over time is mainly controlled by the changes vadose zone CO2, where vegetation regeneration, wild-fires and karst hydrology play an important role.},
  language  = {en}
}