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1. Main Controls on the Stable Carbon Isotope Composition of Speleothems

Author

Fohlmeister, Jens, Voarintsoa, Ny Riavo G., Lechleitner, Franziska A., Boyd, Meighan, Brandtstätter, Susanne, Jacobson, Matthew J., and Oster, Jessica

Subjects
Physics - Geophysics
Abstract

The climatic controls on the stable carbon isotopic composition (d13C) of speleothem carbonate are less often discussed in the scientific literature in contrast to the frequently used stable oxygen isotopes. Various local processes influence speleothem d13C values and confident and detailed interpretations of this proxy are often complex. A better understanding of speleothem d13C values is critical to improving the amount of information that can be gained from existing and future records. This contribution aims to disentangle the various processes governing speleothem d13C values and assess their relative importance. Using a large data set of previously published records we examine the spatial imprint of climate-related processes in speleothem d13C values deposited post-1900 CE, a period during which global temperature and climate data is readily available. Additionally, we investigate the causes for differences in average d13C values and growth rate under identical climatic conditions by analysing pairs of contemporaneously deposited speleothems from the same caves. This approach allows to focus on carbonate dissolution and fractionation processes during carbonate precipitation, which we evaluate using existing geochemical models. Our analysis of a large global data set of records reveals evidence for a temperature control, likely driven by vegetation and soil processes, on d13C values in recently deposited speleothems. Moreover, data-model intercomparison shows that calcite precipitation occurring along water flow paths prior to reaching the top of the speleothem can explain the wide d13C range observed for concurrently deposited samples from the same cave. We demonstrate that using the combined information of contemporaneously growing speleothems is a powerful tool to decipher controls on d13C values ...

Published
2020
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2. Evaluating model outputs using integrated global speleothem records of climate change since the last glacial

Author

Comas-Bru, Laia, Harrison, Sandy P., Werner, Martin, Rehfeld, Kira, Scroxton, Nick, Veiga-Pires, Cristina, Ahmad, Syed Masood, Brahim, Yassine Ait, Mozhdehi, Sahar Amirnezhad, Arienzo, Monica, Atsawawaranunt, Kamolphat, Baker, Andy, Braun, Kerstin, Breitenbach, Sebastian, Burstyn, Yuval, Chawchai, Sakonvan, Columbu, Andrea, Deininger, Michael, Demeny, Attila, Dixon, Bronwyn, Hatvani, Istvan Gabor, Hu, Jun, Kaushal, Nikita, Kern, Zoltan, Labuhn, Inga, Lachniet, Matthew S., Lechleitner, Franziska A., Lorrey, Andrew, Markowska, Monika, Nehme, Carole, Novello, Valdir F., Oster, Jessica, Perez-Mejias, Carlos, Pickering, Robyn, Sekhon, Natasha, Wang, Xianfeng, Warken, Sophie, Atkinson, Tim, Ayalon, Avner, Baldini, James, Bar-Matthews, Miryam, Bernal, Juan Pablo, Boch, Ronny, Borsato, Andrea, Boyd, Meighan, Brierley, Chris, Cai, Yanjun, Carolin, Stacy, Cheng, Hai, Constantin, Silviu, Couchoud, Isabelle, Cruz, Francisco, Denniston, Rhawn, Dragusin, Virgil, Duan, Wuhui, Ersek, Vasile, Finné, Martin, Fleitmann, Dominik, Fohlmeister, Jens, Frappier, Amy, Genty, Dominique, Holzkamper, Steffen, Hopley, Philip, Johnston, Vanessa, Kathayat, Gayatri, Keenan-Jones, Duncan, Koltai, Gabriella, Li, Ting-Yong, Lone, Mahjoor Ahmad, Luetscher, Marc, Mattey, Dave, Moreno, Ana, Moseley, Gina, Psomiadis, David, Ruan, Jiaoyang, Scholz, Denis, Sha, Lijuan, Smith, Andrew Christopher, Strikis, Nicolas, Treble, Pauline, Unal-Imer, Ezgi, Vaks, Anton, Vansteenberge, Stef, Voarintsoa, Ny Riavo G., Wong, Corinne, Wortham, Barbara, Wurtzel, Jennifer, Zhang, Haiwei, Voarintsoa, Ny Riavo, Earth Observatory of Singapore, Comas-Bru L., Harrison S.P., Werner M., Rehfeld K., Scroxton N., Veiga-Pires C., Ahmad S.M., Brahim Y.A., Mozhdehi S.A., Arienzo M., Atsawawaranunt K., Baker A., Braun K., Breitenbach S., Burstyn Y., Chawchai S., Columbu A., Deininger M., Demeny A., Dixon B., Hatvani I.G., Hu J., Kaushal N., Kern Z., Labuhn I., Lachniet M.S., Lechleitner F.A., Lorrey A., Markowska M., Nehme C., Novello V.F., Oster J., Perez-Mejias C., Pickering R., Sekhon N., Wang X., Warken S., Atkinson T., Ayalon A., Baldini J., Bar-Matthews M., Bernal J.P., Boch R., Borsato A., Boyd M., Brierley C., Cai Y., Carolin S., Cheng H., Constantin S., Couchoud I., Cruz F., Denniston R., Dragusin V., Duan W., Ersek V., Finne M., Fleitmann D., Fohlmeister J., Frappier A., Genty D., Holzkamper S., Hopley P., Johnston V., Kathayat G., Keenan-Jones D., Koltai G., Li T.-Y., Lone M.A., Luetscher M., Mattey D., Moreno A., Moseley G., Psomiadis D., Ruan J., Scholz D., Sha L., Smith A.C., Strikis N., Treble P., Unal-Imer E., Vaks A., Vansteenberge S., Voarintsoa N.R.G., Wong C., Wortham B., Wurtzel J., and Zhang H.

Subjects
010506 paleontology, Climate Research, 010504 meteorology & atmospheric sciences, δ18O, lcsh:Environmental protection, Climate Change, Stratigraphy, Speleothem, Climate change, F800, PMIP4 CONTRIBUTION, Geology [Science], 01 natural sciences, Klimatforskning, STABLE-ISOTOPE VARIATIONS, lcsh:Environmental pollution, Time windows, ddc:550, Meteorology & Atmospheric Sciences, lcsh:TD169-171.8, Speleothem Records, GENERAL-CIRCULATION MODEL, ASIAN MONSOON, Glacial period, Geosciences, Multidisciplinary, DELTA-O-18 WATER ISOTOPE, Baseline (configuration management), lcsh:Environmental sciences, 0105 earth and related environmental sciences, lcsh:GE1-350, Global and Planetary Change, geography, Coupled model intercomparison project, Science & Technology, geography.geographical_feature_category, Paleontology, Geology, GROWTH FREQUENCY VARIATIONS, NORTH-ATLANTIC, OXYGEN-ISOTOPE, 13. Climate action, Climatology, lcsh:TD172-193.5, Physical Sciences, Spatial ecology, Environmental science, Institut für Geowissenschaften, ATMOSPHERIC CIRCULATION, HIGH-RESOLUTION
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 delta O-18 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 delta O-18 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. European Geosciences Union - W2017/413; Irish Centre for Research in Applied Geosciences (iCRAG); European Association of Geochemistry (Early Career Ambassadors program 2017); Quaternary Research Association UK; Navarino Environmental Observatory, Stockholm University; University College Dublin, Savillex (UK) - SF1428; Ibn Zohr University, Morocco; University of Reading; European Research Council - 694481; Natural Environment Research Council (JPI-Belmont project "PAleao-Constraints on Monsoon Evolution and Dynamics (PACMEDY)"); Geological Survey Ireland - 2017-SC-056; Royal Irish Academy; Deutsche Forschungsgemeinschaft - RE3994/2-1; Past Global Changes (PAGES) programme; info:eu-repo/semantics/publishedVersion

Published
2019

3. Exploring the importance of inter-departmental women’s friendship in geography as resistance in the neoliberal academy

Author

Webster, Natasha, Boyd, Meighan, Webster, Natasha, and Boyd, Meighan

Abstract

Friendship has potential as a key coping and self-care strategy among early career researchers (ECR’s) and has been shown to be crucial to overall well-being and sense of belonging, but its importance as a response to career pressures is not well studied. For ECR’s, friendships within the university are situated in a specific structural and institutional context, and formigrant women, this includes an additional aspect of gendered complexity. At the same time friendships may prove difficult as heightened neoliberal metrics emphasize competition forfunding, positions and teaching requirements. Using autoethnographic intra-reflections on the authors’ own friendship, bridging human geography and physical geography, this paper examines friendship of two ECR women from a homosocial perspective where institutional hierarchies and structures may be somewhat equalized. Drawing on the exploration of the authors’ friendship during their PhD years and into their post-doc positions, we reflect on the importance of friendship as an act of support, self-care and resistance. We argue for heightening importance for examining the way friendship creates safe social spaces and offer new insights into the importance of friendships in career paths. Friendship in the neoliberal academy has transformative potential for creating a culture of well-being in geography.

Published
2019
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4. The SISAL database: a global resource to document oxygen and carbon isotope records from speleothems

Author

Atsawawaranunt, Kamolphat, Comas-Bru, Laia, Amirnezhad Mozhdehi, Sahar, Deininger, Michael, Harrison, Sandy P., Baker, Andy, Boyd, Meighan, Kaushal, Nikita, Ahmad, Syed Masood, Ait Brahim, Yassine, Arienzo, Monica, Bajo, Petra, Braun, Kerstin, Burstyn, Yuval, Chawchai, Sakonvan, Duan, Wuhui, Hatvani, István Gábor, Hu, Jun, Kern, Zoltán, Labuhn, Inga, Lachniet, Matthew, Lechleitner, Franziska A., Lorrey, Andrew, Pérez-Mejías, Carlos, Pickering, Robyn, Scroxton, Nick, Atkinson, Tim, Ayalon, Avner, Baldini, James, Bar-Matthews, Miriam, Bernal, Juan Pablo, Breitenbach, Sebastian, Boch, Ronny, Borsato, Andrea, Cai, Yanjun, Carolin, Stacy, Cheng, Hai, Columbu, Andrea, Couchoud, Isabelle, Cruz, Francisco, Demény, Attila, Domínguez-Villar, David, Drăgusin, Virgil, Drysdale, Russell, Ersek, Vasile, Finné, Martin, Fleitmann, Dominik, Fohlmeister, Jens, Frappier, Amy, Genty, Dominique, Holzkämper, Steffen, Kathayat, Gayatri, Keenan-Jones, Duncan, Koltai, Gabriella, Luetscher, Marc, Li, Ting-Yong, Lone, Mahjoor Ahmad, Markowska, Monika, Mattey, Dave, McDermott, Frank, Moreno, Ana, Moseley, Gina, Nehme, Carole, Novello, Valdir F., Psomiadis, David, Rehfeld, Kirah, Ruan, Jiaoyang, Sekhon, Natasha, Sha, Lijuan, Scholz, Denis, Shopov, Yavor, Strikis, Nicolás, Treble, Pauline, Ünal-İmer, Ezgi, Vaks, Anton, Vansteenberge, Stef, Veiga-Pires, Cristina, Voarintsoa, Ny Riavo, Wang, Xianfeng, Wong, Corinne, Wortham, Barbara, Wurtzel, Jennifer, and Zong, Baoyun

Abstract

Stable isotope records from speleothems provide information on past climate changes, most particularly information that can be used to reconstruct past changes in precipitation and atmospheric circulation. These records are increasingly being used to provide “out-of-sample” evaluations of isotope-enabled climate models. SISAL (Speleothem Isotope Synthesis and Analysis) is an international working group of the Past Global Changes (PAGES) project. The working group aims to provide a comprehensive compilation of speleothem isotope records for climate reconstruction and model evaluation. The SISAL database contains data for individual speleothems, grouped by cave system. Stable isotopes of oxygen and carbon (δ18O, δ13C) measurements are referenced by distance from the top or bottom of the speleothem. Additional tables provide information on dating, including information on the dates used to construct the original age model and sufficient information to assess the quality of each data set and to erect a standardized chronology across different speleothems. The metadata table provides location information, information on the full range of measurements carried out on each speleothem and information on the cave system that is relevant to the interpretation of the records, as well as citations for both publications and archived data. The compiled data are available at http://dx.doi.org/10.17864/1947.147 .

Published
2018

6. Late Bronze Age climate change and the destruction of the Mycenaean Palace of Nestor at Pylos

Author

Finné, Martin, Holmgren, Karin, Shen, Chuan-Chou, Hu, Hsun-Ming, Boyd, Meighan, and Stocker, Sharon

Subjects
Atmospheric Science, Composite Particles, Atoms, Climate Research, Climate Change, Rain, Social Sciences, lcsh:Medicine, Crops, Klimatforskning, Meteorology, Isotopes, Paleoclimatology, Particle Physics, lcsh:Science, Arkeologi, Climatology, Ecology, Greece, Fossils, Physics, Stable Isotopes, Ecology and Environmental Sciences, Radiometric Dating, lcsh:R, Biology and Life Sciences, Paleontology, Agriculture, Oxygen, Chemistry, Archaeology, Physical Sciences, Earth Sciences, lcsh:Q, Paleoecology, Paleobiology, Research Article, Crop Science, Chemical Elements
Abstract

This paper offers new high-resolution oxygen and carbon isotope data from Stalagmite S1 from Mavri Trypa Cave, SW Peloponnese. Our data provide the climate background to the destruction of the nearby Mycenaean Palace of Nestor at Pylos at the transition from Late Helladic (LH) IIIB to LH IIIC, similar to 3150-3130 years before present (before AD 1950, hereafter yrs BP) and the subsequent period. S1 is dated by 24 U-Th dates with an averaged precision of +/- 26 yrs (2s), providing one of the most robust paleoclimate records from the eastern Mediterranean for the end of the Late Bronze Age (LBA). The delta O-18 record shows generally wetter conditions at the time when the Palace of Nestor at Pylos was destroyed, but a brief period of drier conditions around 3200 yrs BP may have disrupted the Mycenaean agricultural system that at the time was likely operating close to its limit. Gradually developing aridity after 3150 yrs BP, i.e. subsequent to the destruction, probably reduced crop yields and helped to erode the basis for the reinstitution of a central authority and the Palace itself.

Published
2017

8. Speleothems from Warm Climates : Holocene Records from the Caribbean and Mediterranean Regions

Author

Boyd, Meighan

Subjects
U-Th dating, Caribbean, Santorini, Naturgeografi, Eastern Mediterranean, trace elements, Alepotrypa Cave, rapid climate change, Physical Geography, Mid-Holocene, Peloponnese, stalagmite, Neolithic, climate, speleothem, Stable isotopes, ITCZ
Abstract

This thesis contributes to increased knowledge on Holocene climate and environmental variability from two complex and sparsely studied areas. Using a speleothem from Gasparee Cave, Trinidad, as a paleoclimate archive, the local expression of the 8.2 ka (thousand years before 1950) climate event and associated patterns of the inter-tropical convergence zone (ITCZ) and rainfall is provided. Subsequent speleothem studies using multi-proxy analysis of stalagmites from Kapsia Cave and Alepotrypa Cave, Greece, provide records of climate, vegetation and human induced changes in the cave environment during parts of the Holocene. The speleothems from the well-studied Neolithic habitation site, Alepotrypa Cave, have produced a climate and habitation record which covers the period of 6.3-1.0 ka. The cave was inhabited between 8.0-5.2 ka and was closed by a tectonic event, which has preserved the settlement. The stable oxygen record shows the first well-dated and robust expression of the 4.2 ka dry event in the Peloponnese, places the timing of the 3.2 ka dry event within an ongoing dry period, and shows a final dry event at 1.6 ka. The North Atlantic as well as more regional drivers, such as the North Sea Caspian Pattern Index is proposed to, in a complex interplay, govern many of the climate trends and events observed. Trace element variation after the site is abandoned indicate what is interpreted as two volcanic eruptions, the Minoan eruption of Thera (Santorini) around 3.6 ka and the 2.7 ka eruption of Somma (Vesuvius). Variations in trace elements during the habitation period show clear human influence, indicating an association with specific cave activities. One of the most interesting prospects for continued work on Alepotrypa Cave is this successful marriage of speleothem studies and archeology. A framework of dates which constrain some behavior of people living in the cave is only the beginning, and there is great potential to continue finding new clues in the speleothem data. Denna avhandling bidrar till ökad kunskap om klimatets variationer och miljön i två geografiskt skilda områden på låga breddgrader och under tidsperioder inom den Holocena epoken. Genom att använda en droppsten (stalagmit) från Gasparee-grottan, Trinidad, som ett paleoklimatarkiv, har det bland annat varit möjligt att visa att Trinidad upplevde torrare förhållanden under den snabba klimatförändring som observerats ske för 8200 år sedan på många platser i världen. Denna torrare klimatsituation i Trinidad föreslås vara ett resultat av en sydlig förflyttning av den intertropiska konvergenszonen. Övriga stalagmiter som studerats för denna avhandling kommer från Kapsia-grottan och Alepotrypa-grottan som finns på Peloponnesos-halvön i Grekland. Resultaten därifrån speglar dels klimat- och vegetationsvariatoner och dels graden av mänsklig aktivitet, under tiden för ca 8000 år sedan till för 1000 år sedan. Alepotrypa-grottan är känd för att vara en av de större Neolitiska boplatserna i Grekland. Isotop- och spårämnesanalyser av stalagmiterna har bidragit med ny kunskap om tidpunkten för mänsklig aktivitet, hur människorna påverkade grott-miljön samt hur klimatet varierat efter det att grottan, genom en tektonisk händelse, stängdes för människans inverkan. Snabba klimatförändringar, för 4200 och 3200 år sedan, observerade i andra regioner, rekonstrueras här för första gången på Peloponnesos. En snabb förändring mot torrare förhållanden observeras även för 1600 år sedan. De klimatstyrande processerna föreslås vara en kombination av storskaliga processer som den nordatlantiska oscillationen och mer regionala processer som det så kallade North Sea Caspian Pattern Index. Variationer i spårämnen i stalagmiterna efter att Alepotrypa-grottan stängdes kan kopplas till två vulkaniska utbrott, nämligen det Minoiska utbrottet av Thera på ön Santorini kring 3600 år sedan och utbrottet av Somma (Vesuvius) kring 2700 år sedan. Spårämnesvariationer under bo-perioden ger tydliga indikationer på människans påverkan på grottmiljön och som delvis kan länkas till specifika aktiviteter, som eldning av dynga i grottan. Avhandlingen är ett resultat av en framgångsrik kombination av klimatstudier och arkeologisk kunskap och utgör ett viktigt underlag för fördjupat interdisciplinärt forskningssamarbete i Alepotrypa-grottan. At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 1: Manuscript. Paper 4: Manuscript. Paper 5: Manuscript. Paper 6: Manuscript.

Published
2015

9. The socio-environmental history of the Peloponnese during the Holocene : Towards an integrated understanding of the past

Author

Weiberg, Erika, Unkel, Ingmar, Kouli, Katerina, Holmgren, Karin, Avramidis, Pavlos, Bonnier, Anton, Dibble, Flint, Finné, Martin, Izdebski, Adam, Katrantsiotis, Christos, Stocker, Sharon R., Andwinge, Maria, Baika, Kalliope, Boyd, Meighan, Heymann, Christian, Weiberg, Erika, Unkel, Ingmar, Kouli, Katerina, Holmgren, Karin, Avramidis, Pavlos, Bonnier, Anton, Dibble, Flint, Finné, Martin, Izdebski, Adam, Katrantsiotis, Christos, Stocker, Sharon R., Andwinge, Maria, Baika, Kalliope, Boyd, Meighan, and Heymann, Christian

Abstract

Published archaeological, palaeoenvironmental, and palaeoclimatic data from the Peloponnese in Greece are compiled, discussed and evaluated in order to analyse the interactions between humans and the environment over the last 9000 years. Our study indicates that the number of human settlements found scattered over the peninsula have quadrupled from the prehistoric to historical periods and that this evolution occurred over periods of climate change and seismo–tectonic activity. We show that societal development occurs both during periods of harsh as well as favourable climatic conditions. At some times, some settlements develop while others decline. Well-known climate events such as the 4.2 ka and 3.2 ka events are recognizable in some of the palaeoclimatic records and a regional decline in the number and sizes of settlements occurs roughly at the same time, but their precise chronological fit with the archaeological record remains uncertain. Local socio-political processes were probably always the key drivers behind the diverse strategies that human societies took in times of changing climate. The study thus reveals considerable chronological parallels between societal development and palaeoenvironmental records, but also demonstrates the ambiguities in these correspondences and, in doing so, highlights some of the challenges that will face future interdisciplinary projects. We suggest that there can be no general association made between societal expansion phases and periods of advantageous climate. We also propose that the relevance of climatic and environmental regionality, as well as any potential impacts of seismo-tectonics on societal development, need to be part of the interpretative frameworks., Special Issue: Mediterranean Holocene Climate, Environment and Human Societies

Published
2016
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10. Can XRF scanning of speleothems be used as a non-destructive method to identify paleoflood events in caves?

Author

Finné, Martin, Kylander, Malin, Boyd, Meighan, Sundqvist, Hanna S., Löwemark, Ludvig, Finné, Martin, Kylander, Malin, Boyd, Meighan, Sundqvist, Hanna S., and Löwemark, Ludvig

Abstract

We have developed a novel, quick and non-destructive method for tracing flood events in caves through the analysis of a stalagmite thick section with an XRF core scanner. The analyzed stalagmite has multiple horizons of fine sediments from past flood events intercalated with areas of cleaner calcite. Flood events detected from the elemental XRF core scanning data show good agreement with the position of flood horizons identified in petrographic thin sections. The geochemical composition of the individual flood layers shows that in certain cases the clay horizons had a distinct geochemical fingerprint suggesting that it may be possible to distinguish individual flood layers based on their geochemistry. This presents the possibility for using flood events as marker horizons to chronologically tie different speleothems in a cave to each other., AuthorCount:5

Published
2015
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12. Climate model benchmarking with glacial and mid-Holocene climates

Author

Harrison, S. P., Bartlein, P. J., Brewer, S., Prentice, I. C., Boyd, Meighan, Hessler, I., Holmgren, Karin, Izumi, K., Willis, K., Harrison, S. P., Bartlein, P. J., Brewer, S., Prentice, I. C., Boyd, Meighan, Hessler, I., Holmgren, Karin, Izumi, K., and Willis, K.

Abstract

Past climates provide a test of models' ability to predict climate change. We present a comprehensive evaluation of state-of-the-art models against Last Glacial Maximum and mid-Holocene climates, using reconstructions of land and ocean climates and simulations from the Palaeoclimate Modelling and Coupled Modelling Intercomparison Projects. Newer models do not perform better than earlier versions despite higher resolution and complexity. Differences in climate sensitivity only weakly account for differences in model performance. In the glacial, models consistently underestimate land cooling (especially in winter) and overestimate ocean surface cooling (especially in the tropics). In the mid-Holocene, models generally underestimate the precipitation increase in the northern monsoon regions, and overestimate summer warming in central Eurasia. Models generally capture large-scale gradients of climate change but have more limited ability to reproduce spatial patterns. Despite these common biases, some models perform better than others., AuthorCount:9

Published
2014
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13. The SISAL database: a global resource to document oxygen and carbon isotope records from speleothems

Author

Atsawawaranunt, Kamolphat, Comas-Bru, Laia, Mozhdehi, Sahar Amirnezhad, Deininger, Michael, Harrison, Sandy P., Baker, Andy, Boyd, Meighan, Kaushal, Nikita, Ahmad, Syed Masood, Brahim, Yassine Ait, Arienzo, Monica, Bajo, Petra, Braun, Kerstin, Burstyn, Yuval, Chawchai, Sakonvan, Duan, Wuhui, Hatvani, Istvan Gabor, Hu, Jun, Kern, Zoltan, Labuhn, Inga, Lachniet, Matthew, Lechleitner, Franziska A., Lorrey, Andrew, Perez-Mejias, Carlos, Pickering, Robyn, Scroxton, Nick, Atkinson, Tim, Ayalon, Avner, Baldini, James, Bar-Matthews, Miriam, Pablo Bernal, Juan, Breitenbach, Sebastian, Boch, Ronny, Borsato, Andrea, Cai, Yanjun, Carolin, Stacy, Cheng, Hai, Columbu, Andrea, Couchoud, Isabelle, Cruz, Francisco, Demeny, Attila, Dominguez-Villar, David, Dragusin, Virgil, Drysdale, Russell, Ersek, Vasile, Finné, Martin, Fleitmann, Dominik, Fohlmeister, Jens, Frappier, Amy, Genty, Dominique, Holzkamper, Steffen, Hopley, Philip, Kathayat, Gayatri, Keenan-Jones, Duncan, Koltai, Gabriella, Luetscher, Marc, Li, Ting-Yong, Lone, Mahjoor Ahmad, Markowska, Monika, Mattey, Dave, McDermott, Frank, Moreno, Ana, Moseley, Gina, Nehme, Carole, Novello, Valdir F., Psomiadis, David, Rehfeld, Kira, Ruan, Jiaoyang, Sekhon, Natasha, Sha, Lijuan, Sholz, Denis, Shopov, Yavor, Smith, Andrew, Strikis, Nicolas, Treble, Pauline, Unal-Imer, Ezgi, Vaks, Anton, Vansteenberge, Stef, Veiga-Pires, Cristina, Voarintsoa, Ny Riavo, Wang, Xianfeng, Wong, Corinne, Wortham, Barbara, Wurtzel, Jennifer, Zong, Baoyun, Veiga-Pires, C., Atsawawaranunt, Kamolphat, Comas-Bru, Laia, Amirnezhad Mozhdehi, Sahar, Deininger, Michael, Harrison, Sandy P., Baker, Andy, Boyd, Meighan, Kaushal, Nikita, Ahmad, Syed Masood, Ait Brahim, Yassine, Arienzo, Monica, Bajo, Petra, Braun, Kerstin, Burstyn, Yuval, Chawchai, Sakonvan, Duan, Wuhui, Hatvani, István Gábor, Hu, Jun, Kern, Zoltán, Labuhn, Inga, Lachniet, Matthew, Lechleitner, Franziska A., Lorrey, Andrew, Pérez-Mejías, Carlo, Pickering, Robyn, Scroxton, Nick, and Tim Atkinso, Avner Ayalon, James Baldini, Miriam Bar-Matthews, Juan Pablo Bernal, Sebastian Breitenbach, Ronny Boch, Andrea Borsato, Yanjun Cai, Stacy Carolin, Hai Cheng, Andrea Columbu, Isabelle Couchoud, Francisco Cruz, Attila Demény, David Dominguez-Villar, Virgil Dragusin, Russell Drysdale, Vasile Ersek, Martin Finné, Dominik Fleitmann, Jens Fohlmeister, Amy Frappier, Dominique Genty, Steffen Holzkämper, Philip Hopley, Gayatri Kathayat, Duncan Keenan-Jones, Gabriella Koltai, Marc Luetscher, Ting-Yong Li

Subjects
010506 paleontology, Climate Research, 010504 meteorology & atmospheric sciences, Climate change, Speleothem, F800, 010502 geochemistry & geophysics, computer.software_genre, 01 natural sciences, Klimatforskning, Cave, Paleoclimatology, lcsh:Environmental sciences, 0105 earth and related environmental sciences, lcsh:GE1-350, geography, geography.geographical_feature_category, Database, Stable isotope ratio, speleothems, PALEOCLIMATOLOGIA, lcsh:QE1-996.5, lcsh:Geology, Metadata, 13. Climate action, General Earth and Planetary Sciences, Environmental science, Climate model, computer, Chronology
Abstract

Stable isotope records from speleothems provide information on past climate changes, most particularly information that can be used to reconstruct past changes in precipitation and atmospheric circulation. These records are increasingly being used to provide “out-of-sample” evaluations of isotope-enabled climate models. SISAL (Speleothem Isotope Synthesis and Analysis) is an international working group of the Past Global Changes (PAGES) project. The working group aims to provide a comprehensive compilation of speleothem isotope records for climate reconstruction and model evaluation. The SISAL database contains data for individual speleothems, grouped by cave system. Stable isotopes of oxygen and carbon (δ18O, δ13C) measurements are referenced by distance from the top or bottom of the speleothem. Additional tables provide information on dating, including information on the dates used to construct the original age model and sufficient information to assess the quality of each data set and to erect a standardized chronology across different speleothems. The metadata table provides location information, information on the full range of measurements carried out on each speleothem and information on the cave system that is relevant to the interpretation of the records, as well as citations for both publications and archived data. The compiled data are available at https://doi.org/10.17864/1947.147.

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14. Cave monitoring of the stable isotope signals transmitted to speleothems in Gibraltar.

Author

Atkinson, Tim, Boyd, Meighan, Hoffmann, Dirk, and Grassineau, Nathalie

Subjects
*SPELEOTHEMS, *STABLE isotopes, *CAVES, *SEEPAGE, *WATER distribution, *GLACIAL climates
Abstract

An eight-year cave monitoring effort in Gibraltar had the ultimate aim of reconstructing $\delta$18O in past precipitation from well-dated speleothems. We measured stable isotopes in cave waters from nine sites in New St Michael's (NSM) and Ragged Staff (RS) caves, comparing them with monthly GNIP values for Gibraltar rain. Additionally we conducted artificial tracer tests that tracked two dyes from surface to drip sites in NSM.\newline \newlineSeepage waters have a very narrow compositional range and little difference between sites when compared with the fluctuations of $\delta$18O and $\delta$2H in monthly rainfall ($\delta$18O range 12.5 \permil\). $\delta$18O varies seasonally by only tenths per mille whereas inter-annual ranges are up to 1 \permil\. The compressed seasonal variations indicate temporal mixing of rains that entered the sub-surface at different times. Comparison of exceptional variations in rainfall with subsequent seepage samples reveals a component of seepage that has been stored for at least one year. The artificial tracers indicated marked spatial mixing as water flowed from the surface to the caves. Tracers from single points on the surface above MSN formed overlapping plumes of dyed water that could be detected across 200 m horizontally. The tracer results confirm the temporal mixing and indicate residence times that are less than the three month monitoring period but exceed the initial breakthrough times of days to weeks after injection. Combined storage time indicated by stable isotopes, tracer results imply that the full residence time distribution for water in the unsaturated zone ranges from a few days to over one year. This temporally and spatially dispersive behaviour arises from the geometric properties of the fracture network that the cave seepages have passed through, so will have been broadly invariant in the past. The water isotope signal that Gibraltar speleothems capture is averaged over a period of around one year and very short events will not be recorded. \newline\newlineThe stable isotope data also show the influence of other processes than simple mixing. Seepage waters have lower values than the amount-weighted averages for rainfall, suggesting a bias towards isotopically lighter rains. Plots of $\delta$2H versus $\delta$18O show no consistent signs of modification by evaporation, despite Gibraltar's hot dry summers, so the isotopically heavier rains are completely lost to evapo-transpiration. A less easily explained feature is that the deuterium excess of seepage is higher than that of average rainfall, although lying within its overall range. This may be caused by addition of condensation water to the shallow epikarst. \newline\newlineIn the cooler climates of the Last Glacial evaporation would have been less than today and the isotopic composition of seepage may have been closer to the annual average of rainfall. Samples from speleothems often span several years even in highly-resolved records, with the implication that in cool climates the calcite $\delta$18O will reflect the average for rainfall over this time interval. In climates resembling the present it may be displaced slightly towards lighter values.\newline [ABSTRACT FROM AUTHOR]

Published
2019

15. Cave monitoring in Gibraltar and reconstruction of δ18O in Last Glacial precipitation.

Author

Atkinson, Tim, Boyd, Meighan, Mattey, Dave, Hoffmann, Dirk, Muller, Wolfgang, and Grassineau, Natalie

Subjects
*SPELEOTHEMS, *STALACTITES & stalagmites, *ISOTOPIC fractionation, *CAVES, *GENERAL circulation model, *OCEAN temperature, *HEAT storage, *SEEPAGE
Abstract

The δ18O of past rainfall is important in palaeo-climatology because it can be simulated directly by isotope-enabled General Circulation Models, enabling data-model comparisons. We describe a methodology for reconstructing it from Last Glacial speleothems in Gibraltar. Three factors determine the δ18O of dripstone calcite: the δ18O of drip water, the cave temperature (that determines equilibrium fractionation between water and calcite), plus non-equilibrium fractionation caused by CO2 degassing and/or surface reactions. Reconstructing seepage water δ18O requires independent constraints on the second and third factors. It is also necessary that the relationship between seepage δ18O and rainfall be well-constrained. A merged record from flowstone and stalagmite (Gib10d/10e) from the same chamber of Ragged Staff Cave spans 30 – 110 ka. δ18O variations between 40 and 62 ka align closely with NGRIP's GICC05modelext timescale (1) but there is divergence before and after this. We therefore restrict our reconstruction to 40-62 ka.To constrain temperature we used Uk'37 estimates of annual average sea surface temperatures (SSTs) in core ODP-977A in the Alboran Sea, after converting its original timescale to that of NGRIP (2). We assume that in coastal Gibraltar Mean Annual Air Temperatures (MATs) equalled SSTs. Cave temperatures probably lagged behind MATs due to the thermal capacity of the bedrock, but with the possibility of a much smaller lag because of heat advection from outside by cave winds. To deal with the uncertainty this imposes, we use a 1-D heat flow model to set up two bounding scenarios for the evolution of cave temperatures. In one the full effects of heat storage and conduction are computed for 100 m depth whereas in the other the lag is zero. Both scenarios are used to determine fractionation factors (3) and time-series of 'equilibrium' values for δ18O in cave water. The effects of non-equilibrium are difficult to assess. The δ18O records for the two speleothems overlay almost exactly despite their different morphologies and implied drip discharges. We take a similar approach to 'disequilibrium' as for cave temperature, defining a bounding scenario of 'no disequilibrium' but alternatively using the 'Tremaine curve' that takes disequilibrium into account (4).This approach gives rise to a 2 x 2 set of scenarios that define an 'envelope' for δ18O in palaeo-seepage. Cave monitoring shows that average seepage δ18O is currently 0.6 to 0.75 ‰ less than rainfall, because of complete evaporation of summer rains. This bias would have been less in cooler climates, so we adjust the reconstructed envelope by amounts related to prevailing SST, to obtain estimates and uncertainties for the average δ18O of palaeo-precipitation in the western Mediterranean that can be compared directly with GCM output and with other records on the NGRIP timescale. [ABSTRACT FROM AUTHOR]

Published
2019

16. Constraints from monitoring on reconstruction of Gibraltar palaeoclimate in a speleothem record covering the last glacial period.

Author

Boyd, Meighan, Hoffmann, Dirk, Atkinson, Tim, Muller, Wolfgang, and Mattey, David

Subjects
*SPELEOTHEMS, *GLACIATION, *ICE cores, *OCEAN temperature, *GREENLAND ice, *MEDITERRANEAN climate, *STABLE isotopes
Abstract

Ten years of comprehensive cave monitoring in Gibraltar provides a unique basis forinterpreting proxy records in speleothems, and in this study we discuss some of theopportunities and challenges in constructing an interpretive framework for long proxyrecords. We present a new trace element and stable isotope record spanning 30-110 kaobtained from two neighbouring speleothems from Ragged Staff Caves, Gibraltar. The agemodel is defined by over 100 U-Th dates with continuous micromilling for stable isotopes,and LA-ICPMS used for acquiring the trace element proxy record. These provide highlyresolved critical evidence for some of the main meteorological and environmental controls onpast western Mediterranean terrestrial climate at near decadal and sub-annual resolution,respectively. Our interpretations of the monitoring data highlight geochemical and hydrologicalprocesses critical to speleothem deposition. We conclude that δ13C and δ18O in speleothemcalcite are controlled by within-cave conditions that vary seasonally and are themselvescontrolled by the temperature and water balance at the ground surface. For interpretation oftrace elements, we utilize multi-annual monitoring of drip waters. The Gibraltar record showsvariations in δ13C and δ18O on timescales from multi-decadal to multi-millennial which wecompare with independently dated records of multiple proxies from marine cores,including vegetation and sea surface temperature (SST), and the Greenland ice corerecord. The precision of the Gibraltar speleothem chronology allows for greater confidence incorrelation with other records, and we particularly note a remarkable correspondence withδ18O in Greenland in the period 40-60ka, and similarity with SST records from the AlboranSea. We believe this reveals a dominant influence of North Atlantic climate at the gateway tothe Mediterranean. However, we note that in periods which there is weaker correspondencebetween speleothem and ice core δ18O, this may indicate changes in the dominant climatecontrols in the western Mediterranean. All comparisons of proxy records show a broad similarity with the cave recordover the longest timescales, i.e. δ13C and δ18O both display higher values in thecolder, drier climates of the mid-glacial, and generally lower values in the longinterstadials of the early glacial period. Superimposed on this trend are millennial-scalevariations with amplitudes of the same order of magnitude seen over stadial-interstadialtimescales. At times these fluctuations correspond closely to the variations seen in SST,pollen, and vegetation records while some excursions appear out of phase. We usemultiproxy marine core records to explore these phase differences, as the speleothemrecord may partially reflect other factors independent of those recorded throughSST and pollen proxies. Over centuries high frequency variations similar to thoseobserved on multi-annual timescales in cave monitoring and modern speleothemoccur, showing both the small and large scale applications of our monitoring data. [ABSTRACT FROM AUTHOR]

Published
2019

21. Stable isotopes and phosphorus patterns in calcite stalagmites from Alepotrypa Cave, Peloponnese, Greece as indicators of Holocene changes in rainfall and vegetation

Author

Boyd, Meighan, Holmgren, Karin, Finné, Martin, Hoffmann, Dirk, Jochum, Klaus Peter, Karkanas, Panagiotis, Papathanasiou, Anastasia, Stoll, Brigitte, Scholz, Denis, Spötl, Christoph, Boyd, Meighan, Holmgren, Karin, Finné, Martin, Hoffmann, Dirk, Jochum, Klaus Peter, Karkanas, Panagiotis, Papathanasiou, Anastasia, Stoll, Brigitte, Scholz, Denis, and Spötl, Christoph

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