CL5.1.3
Novel and quantitative methods for reconstructing continental palaeoenvironments, palaeohydrology and palaeofire

CL5.1.3

EDI
Novel and quantitative methods for reconstructing continental palaeoenvironments, palaeohydrology and palaeofire
Convener: Ola Kwiecien | Co-conveners: Elisabeth Dietze, Benjamin Keenan, Sebastian F.M. Breitenbach, Cindy De Jonge
Presentations
| Thu, 26 May, 08:30–11:50 (CEST), 13:20–14:50 (CEST)
 
Room 0.49/50

Presentations: Thu, 26 May | Room 0.49/50

Chairpersons: Ola Kwiecien, Elisabeth Dietze, Cindy De Jonge
08:30–08:33
08:33–08:43
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EGU22-4159
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solicited
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Virtual presentation
Ryuji Asami, Rikuto Hondo, Ryu Uemura, Masaki Fujita, Shinji Yamasaki, Chuan-Chou Shen, Chung-Che Wu, Xiuyang Jiang, Hideko Takayanagi, Ryuichi Shinjo, Akihiro Kano, and Yasufumi Iryu

We applied a new geoarchaeological method with two carbonate archives, which are fossil snails from Sakitari Cave and stalagmites from Gyokusen Cave, on Okinawa Island, Japan, to reconstruct surface air temperature changes over the northwestern Pacific since the last glacial period. Oxygen isotope ratios of modern and fossil freshwater snail shells were determined to infer annual and seasonal temperature variations. The observational and analytical data confirm that oxygen isotopic values of fluid inclusion waters in the stalagmite can be regarded as those of spring waters at the sites where snails lived. Our results indicate that the annual mean, summer, and winter air temperatures were lower by 67 °C at ca. 23 thousand years ago (ka) and 45 °C at ca. 1613 ka than those of the present day. Our reconstruction implies that surface air cooling was possibly two times greater than that of seawater around the Ryukyu Islands during the Last Glacial Maximum, which potentially enhanced the development of the East Asian summer monsoon during the last deglaciation. Considering the potential uncertainties in the temperature estimations, the climatic interpretations of this study are not necessarily definitive due to the limited number of samples. Nevertheless, our new geoarchaeological approach using coupled isotopic determinations of fossil snails and stalagmite fluid inclusion waters will be useful for reconstructing snapshots of seasonally resolved time series of air temperatures during the Quaternary.

How to cite: Asami, R., Hondo, R., Uemura, R., Fujita, M., Yamasaki, S., Shen, C.-C., Wu, C.-C., Jiang, X., Takayanagi, H., Shinjo, R., Kano, A., and Iryu, Y.: A geoarchaeological approach for reconstructing last glacial temperatures using coupled isotopic analyses of fossil snails and stalagmites from limestone caves in Okinawa, Japan, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4159, https://doi.org/10.5194/egusphere-egu22-4159, 2022.

08:43–08:48
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EGU22-11970
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Virtual presentation
Inga Labuhn, Dan Hammarlund, and Ulrich von Grafenstein

Carbonate shells from lacustrine organisms provide proxy records of past climatic changes. Their oxygen isotopic composition (δ18O) is controlled by the δ18O of the lake water and by water temperature during carbonate precipitation. The lake water δ18O depends on the δ18O of precipitation in the catchment, which is positively correlated with air temperature in high latitudes. An increasing air temperature therefore leads to an increase in carbonate δ18O. However, the proxy interpretation is complicated by the fact that an increasing water temperature during carbonate precipitation leads to a decrease in carbonate δ18O because of the temperature dependency of isotope fractionation. In the profundal parts of deep lakes, this water temperature change is minimal, and biogenic carbonates mainly reflect lake water δ18O. However, carbonate remains are often much more abundant in shallow water, where water temperature variations can be large.

In this study, we evaluate the possibility to quantitatively reconstruct seasonal temperature changes by combining sediment cores from littoral and profundal Holocene sediments of Lake Locknesjön, Sweden. We measured the isotopic composition of ostracod and mollusk shells and of encrustations from calcifying algae.

In the shallow water sediments, the differences in the mean carbonate δ18O between species can mainly be attributed to seasonal water temperature changes. The lowest δ18O values are observed in Chara encrustations formed during the summer months, and the highest values in adult ostracods, which calcify their valves during the cold season. First isotope measurements on deep water sediments show that the δ18O is higher and less variable than in the shallow sediments. The offsets between species, and between deep and shallow sediments are not constant throughout the Holocene. Assuming a water temperature near 4 °C, biogenic carbonates in the profundal sediments can give insights into the δ18O of lake water and might allow – combined with the abundant measurements from the shallow water cores – a quantification of the seasonal temperature range.

How to cite: Labuhn, I., Hammarlund, D., and von Grafenstein, U.: Seasonal climate reconstruction using biogenic carbonates from shallow and deep water lake sediments, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11970, https://doi.org/10.5194/egusphere-egu22-11970, 2022.

08:48–08:53
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EGU22-2907
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Presentation form not yet defined
Lacustrine diatom oxygen isotopes as Holocene palaeo precipitation proxy for the Polar Urals, Russia
(withdrawn)
Hanno Meyer, Svetlana S. Kostrova, Meister Philip, Lenz Marlene M., Nazarova Larisa, Kuhn Gerhard, Syrykh Luidmila S., and Dvornikov Yuri
08:53–09:02
09:02–09:07
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EGU22-1370
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ECS
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On-site presentation
Lucía Martegani, Fernando Gázquez, Ana Moreno, Blas Valero-Garcés, Mario Morellón, Miguel Bartolomé, Celia Martín-Puertas, and Miguel Rodríguez-Rodríguez

Centimeter-thick layers of gypsum (CaSO4·2H2O) were deposited at the bottom of Laguna de Zoñar (Córdoba Province, southern Spain) from ~2120 to ~1900 cal yr BP [1], coinciding with the apogee of the Roman Empire in the Iberian Peninsula. The presence of gypsum deposits in lake sediments is generally interpreted as evidence of dry climatic periods in the past [2]; however, gypsum in Laguna de Zoñar formed during the so-called Iberian Roman Humid Period (IRHP, 2600-1600 cal yr BP), the wettest episode of the last 4000 years in the southern Iberian Peninsula. At present, the lake is fed by two springs (~3.5 and ~1.1 l/s on average) and direct rainfall, extends over 37 ha and is up to 15 m deep, being the deepest natural water body in this region. Water salinity is relatively low (~1 g/l), dominated by Cl-, SO42- and Na+ and it is undersaturated in gypsum (SIgyp<-1.9).

The oxygen and hydrogen stable isotopes (δ18O and δ2H) of lake waters are sensitive to long-term changes in hydrological conditions (e.g. relative humidity, evaporation/outflow ratio, etc.). Here we determine the isotopic composition of Laguna de Zoñar at the time of gypsum precipitation from stable isotopes of hydration water in this mineral. The δ18O and δ2H values of the paleo-lake at 2122, 2051 and 1897 cal yr BP were significantly higher (mean values of 9.7±0.2‰ and 31.2±0.5‰, respectively) than those of the modern lake waters (δ18O<4.5‰ and δ2H<4.1‰), suggesting that during some stages of the IRHP the evaporation/outflow ratio of the lake was much higher than at present.

From a paleoclimatic perspective, the gypsum layers in Laguna de Zoñar formed during the transition from the wettest stage of the IRHP (2400 to 2000 cal yr BP) to the subsequent relatively drier phase (2000 to 1600 cal yr BP) [1]. Our results suggest that the second half of the IRHP was drier than the previous and later stages of the late-Holocene in this region. Also, it is possible that, at least during some periods of the Roman occupation, the hydrological regime of the lake was artificially modified by diverting the feeding creeks for urban supply. This could explain the significant increase in water salinity that led to gypsum precipitation. In the southern Iberian Peninsula, where few permanent lakes are present, Laguna de Zoñar may have been an essential water source for the Roman development in the surrounding areas, including the nearby Roman city of Ipagrum (3 km away). Combined detailed archaeological surveys of the area and analyses of anthropogenic proxies at higher resolution in the core may help to solve the relative role of water diversion and short-term aridification phases during the last centuries of the Roman Age in Hispania.

 [1] Martín-Puertas, C. et al. (2008), The Holocene, 18, 907–921; [2] Evans, N.P. et al. (2018), Science, 361, 6401, 498-501.

 

Acknowledgement

This study was supported by project PY18-871 of the Junta de Andalucía. Dr. Fernando Gázquez acknowledges the Ramón y Cajal fellowship, RYC2020-029811-I.

 

How to cite: Martegani, L., Gázquez, F., Moreno, A., Valero-Garcés, B., Morellón, M., Bartolomé, M., Martín-Puertas, C., and Rodríguez-Rodríguez, M.: Abrupt lowstands of Laguna de Zoñar (southern Spain) during the Iberian Roman Humid Period recorded by stable isotopes of gypsum hydration water, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1370, https://doi.org/10.5194/egusphere-egu22-1370, 2022.

09:07–09:12
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EGU22-3147
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Presentation form not yet defined
Fernando Gázquez, Aurora Castillo-Baquera, Antonio García-Alix, Gonzalo Jiménez-Moreno, Francisco Jiménez-Espejo, Lucia Martegani, and Miguel Rodríguez-Rodríguez

The North Atlantic Oscillation (NAO) has a major effect on the modern precipitation patterns in the southern Iberian Peninsula and also controlled the hydroclimate of this region in the past [1,2]. The oxygen and hydrogen stable isotopes (δ18O and δD) of lake waters are sensitive to long-term changes in hydrological conditions (e.g. relative humidity, evaporation/outflow ratio, etc.). Here we reconstruct the δ18O and δD values of Laguna Grande de Archidona Lake (Málaga Province, southern Spain) from the stable isotopes of hydration water of gypsum (CaSO4·2H2O) [3] that precipitated and deposited in the lake from 2.7 to 1.4 ka BP.

The maximum δ18O and δD of values of the lake water (7.8‰ and 23.9‰, respectively) were recorded at 2.7 ka BP (~700 BCE), suggesting that relatively dry conditions prevailed during the Early Iron Age in southern Iberia. Subsequently, the δ18O and δD of the lake decreased to minimum values (3.0 and -2.2‰, respectively) at 2.4 ka BP, during the early stages of the Iberian Roman Humid Period (~600 BCE to ~400 CE). A relatively arid phase was also recorded at 2.2 ka BP, which preceded a wetter stage at 2.0 ka BP. A longer drier phase occurred later on, from 1.6 ka to 1.4 ka BP, coinciding with the decline of the Western Roman Empire (395-476 CE).

The comparison of our paleo-humidity proxy with long-term NAO index [4] shows that the lake water was isotopically enriched during periods of persistent NAO+ mode, suggesting drier and more evaporative conditions and probably lake level lowstands. In contrast, lower δ18O and δD of values of the lake water occurred during periods of NAO- configuration, resulting in wetter and less evaporative conditions and lake level highstands. In summary, our results indicate that the hydrologic balance of Laguna Grande de Archidona during the Iberian Roman Humid Period was controlled by the strength of the long-term NAO and that stable isotopes of gypsum hydration water are a powerful tool for paleo-hydrologic reconstructions.

 

 

[1] Toney et al. (2020), Quat. Sci. Rev. 106395; [2] Martín-Puertas et al. (2009), Quat. Res. 71, 108–120; [3] Gázquez et al. (2018), Earth Plan. Sci. Lett. 48, 177–188; [4] Faust et al., (2016), Earth Plan. Sci. Lett. 435, 84-93.

Acknowledgement

This study was supported by projects PY18-871 and Retos P20_00059 of the Junta de Andalucía, the project CGL2017-85415-R of the Ministerio de Economía y Competitividad of Spain and Fondo Europeo de Desarrollo Regional FEDER and the project B-RNM-144-UGR18. Dr. Antonio García-Alix acknowledges the Ramón y Cajal fellowship, RYC-2015-18966. Dr. Fernando Gázquez acknowledges the Ramón y Cajal fellowship, RYC2020-029811-I.

How to cite: Gázquez, F., Castillo-Baquera, A., García-Alix, A., Jiménez-Moreno, G., Jiménez-Espejo, F., Martegani, L., and Rodríguez-Rodríguez, M.: NAO control on the hydrology of Laguna Grande de Archidona (southern Spain) during the Iberian Roman Humid Period recorded by stable isotopes (δ18O and δD) of gypsum hydration water, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3147, https://doi.org/10.5194/egusphere-egu22-3147, 2022.

09:12–09:17
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EGU22-5109
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Virtual presentation
Sonja Lojen, Tea Zuliani, Klara Nagode, Polona Vreča, Tjaša Kanduč, Jure Tičar, Matija Zorn, and Matej Lipar

The accuracy and uncertainty of paleoclimate interpretations of geochemical and isotopic proxies from stalagmites depend critically on how accurately isotopic signals are transmitted through the vadose zone of the aquifer and how the elemental composition of the groundwater feeding the stalagmite changes as it passes through the aquifer.

Results of the first year (2021) of drip-water monitoring at 15 drip sites in the Jama v Dovčku Cave in SE Slovenia are presented. Cumulative monthly samples were analysed for δ18O of water, δ13C of dissolved inorganic carbon (DIC), elemental composition of drip-water and concentration and δ13C of CO2 in the cave atmosphere. While the seasonal variability of δ18O of precipitation in 2021 at the nearest meteorological station exceeded 10 ‰ (from –15.42 ‰ in January to –5.28 in June), the intra-annual variability of δ18O of drip-water was reduced to 0.18–1.28 ‰ and showed no correlation with the thickness of the roof, which varied between >1 and 49 m. A discernible annual cyclicity was observed at some drip sites, with the highest δ18O values determined in winter and the lowest in late summer. Dissolved inorganic carbon (DIC) δ13C values exhibited a wide range (between –15.5 and –5.0 ‰), and drip sites could be divided into two groups: some drip sites exhibited large seasonal variability (up to 9.9 %) with low values in the warmer season, while the others varied within <3 ‰ with no apparent seasonality. The CO2 concentration in the cave atmosphere was significantly higher from May to October, about 4000 to 8000 ppm, while it fluctuated between 700 and 1500 ppm in the colder part of the year. The δ13C values of CO2 varied between –23.8 and –15.2 ‰ and decreased exponentially with CO2 concentration. Similar to CO2, the δ13C values of DIC also decreased exponentially with increasing DIC concentration. The δ13C value of “added” CO2 in the atmosphere obtained from the δ13C x (C/C0-1) vs. (C/C0-1) plot (Sayles &% Curry, 1988) was –23.4 ± 2.6 ‰, which is almost identical to the CO2 added to the drip-water estimated from DIC concentration and δ13C values of DIC (–23.9 ± 3.4 ‰, considering the isotopic fractionation factor between CO2(g) and HCO3- from Mook et al. 1974). Chemical analysis showed that drip sites with a large seasonality of δ13C values have significantly lower saturation indices with respect to calcite in the warmer part of the year and that earlier calcite precipitation is most likely to occur at drip sites with lower drip rates.

 

Reference:

Mook et al., 1974, Earth Planet. Sci. Lett. 22,169–186.

Sayles & Curry, 1988, Geochim. Cosmochim. Acta 52, 2963–2978.

 

ACKNOWLEDGEMENT: We acknowledge the financial support of Slovenian Research Agency (J1-2478).

How to cite: Lojen, S., Zuliani, T., Nagode, K., Vreča, P., Kanduč, T., Tičar, J., Zorn, M., and Lipar, M.: Temporal and spatial variability of isotopic and hydrochemical parameters in cave drip-water feeding stalagmites: a case study from SE Slovenia, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5109, https://doi.org/10.5194/egusphere-egu22-5109, 2022.

09:17–09:22
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EGU22-12265
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ECS
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Virtual presentation
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Sebastian Höpker, Bedartha Goswami, Megan Grainger, Sebastian F. M. Breitenbach, and Adam Hartland

Speleothems (secondary cave carbonates) are exceptional archives for the study of past climate and environments over a range of temporal and spatial scales. Conventional speleothem proxies, such as stable oxygen isotopes (δ18O), are increasingly bolstered by trace element to Ca ratios, providing increased certainty regarding local/regional hydroclimatic dynamics.

Most studies utilising trace element records limit analyses to the alkaline earth metals (primarily Mg, Sr, Ba), which are most commonly interpreted to reflect drying and wetting within the karst system. This interpretation is based on the susceptibility of these elements to prior carbonate precipitation (PCP) and their relatively predictable partitioning between infiltrating water and the carbonate crystal phase. However, this approach rarely allows for quantitative hydroclimate reconstructions, and in many cases may unperceivably be compromised by similar chemical signals generated by other processes in the karst (e.g., incongruent calcite dissolution). While numerous other trace elements are incorporated into speleothems, their systematics and controls are far less constrained, and typically require statistical models to derive any potential links with environmental processes.

Here we aim to develop a more mechanistic understanding of the partitioning of selected transition metals (Ni, Co, Cu) with view to establishing a novel quantitative hydrological proxy. The transport of these elements from the surface to the cave is governed by binding to organic matter present in percolating waters. The rate of dissociation, or “decay”, of such organic metal complexes (OMCs) at the dripwater-stalagmite interface is suggested to determine the availability of these elements for inclusion into the carbonate (Hartland & Zitoun, 2018). By extension, this link between OMC dissociation and metal availability for capture by stalagmites offers an opportunity to quantify past drip rates because the resulting carbonate metal concentrations are time-dependent.

We present results from a series of Competitive Ligand Exchange (CLE) experiments aimed to assess OMC dissociation kinetics in water samples collected from various New Zealand caves. Our study demonstrates how organic ligands constrain transition metal partitioning from dripwaters to speleothems, and provides first quantitative estimates of the time-dependent release of metals for the inclusion in the latter. We argue that in absence of detrital contamination, this kinetic control presents the overriding mechanism for metal availability at stalagmite surfaces, and thus effectively dictates M/Ca ratios in stalagmites.

References:

Hartland, A., Zitoun, R. (2018) Transition metal availability to speleothems controlled by organic binding ligands. Geochem. Persp. Let. 8, 22–25.

How to cite: Höpker, S., Goswami, B., Grainger, M., Breitenbach, S. F. M., and Hartland, A.: Kinetic metals: reconstructing past cave drip rates using the “decay” of organic metal complexes (OMCs), EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12265, https://doi.org/10.5194/egusphere-egu22-12265, 2022.

09:22–09:31
09:31–09:36
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EGU22-5857
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ECS
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On-site presentation
Laura Bergmann, Emma Finestone, Tobias Braun, Yanjun Cai, Pete Scott, Stuart Umbo, Martin Trappe, Michael Petraglia, Nicole Boivin, and Sebastian F.M. Breitenbach

The archaeological record suggests that multiple groups of hominins occupied and dispersed across Central Asia periodically during the middle Pleistocene (Ranov et al., 1995; Derevianko et al. 2003; Vishnyatsky 1999). It is likely that early transcontinental migrations were tightly interwoven with environmental conditions, and especially water availability. To gain insights into the impact of climatic changes and associated regional environmental responses on hominin dispersal in inner Asia, high-resolution palaeoenvironmental reconstructions are vital. Here we utilize a stalagmite-based multi-proxy record from Uzbekistan to shed light on environmental changes in Central Asia during the end of Marine Isotope Stage 11, ca. 390 ka before present.

We analysed stable isotopes (δ13C and δ18O), grey values (reflecting matrix density), and trace elements on a broken stalagmite segment (S-12-4) collected in 2012 in Amir Timur Cave, Uzbekistan. The cave is in the arid westernmost reaches of the Zaravshan mountain ranges south of Samarkand, with hot and arid summers and cold and humid winters. The cave is developed in marble at an altitude of 1813 m a.s.l. and exposed to western air masses. Backward trajectory modelling shows that moisture is derived mainly from the west and north-west. U/Th dating and stable isotope samples were taken at the Max Planck Institute for the Science of Human History, Jena. Six U/Th samples were measured by MC-ICP-MS at the Institute of Global Environmental Change, Xi'an Jiaotong University. Stable isotope analysis was carried out at Northumbria University. The stalagmite covers the period between 405±8 ka BP and 387.8±7 ka BP. To improve the uncertainty of the U-Th chronology we counted 682 visible layers with an average thickness of 71.4 μm that are presumably of seasonal origin. The δ13C values vary between -8.21 and -4.14 ‰ VPDB, while δ18O ranges from -11.06 to -8.5 ‰ VPDB. Both isotope ratios covary on multi-decadal scale and correlate positively with Mg. Stable isotopes, grey values, and trace elements (Sr, U, Ba, and S) reveal changes in local moisture supply, with one prominent drying event at ca. 388±8 kyr BP. Although the cause of this prominent event remains unclear, we hypothesize that it could be the expression of local drying in response to a large volcanic eruption in the northern hemisphere, like that associated with the Campanian cryptotephra TP09-70.45 of Vakhrameeva et al. (2018). Ongoing work focuses on potential changes in seasonality and climate volatility, which might have affected the suitability of this region for middle Pleistocene hominin occupation.

References

Ranov, V. A., Carbonell, E., & Rodriguez, X. P. (1995). Current Anthropology 36, 337-346.

Derevianko, A. P. (Ed.) (2003). Novosibirsk: Institute of Archaeology and Ethnography SB RAS press.

Vishnyatsky, L. B. (1999). Journal of World Prehistory 13, 69-122.

Vakhrameeva et al. (2018). Quaternary Science Reviews 200, 313-333.

How to cite: Bergmann, L., Finestone, E., Braun, T., Cai, Y., Scott, P., Umbo, S., Trappe, M., Petraglia, M., Boivin, N., and Breitenbach, S. F. M.: A tentative stalagmite-based multi-proxy reconstruction of environmental changes at the end of Marine Isotope Stage 11 in Uzbekistan, Central Asia, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5857, https://doi.org/10.5194/egusphere-egu22-5857, 2022.

09:36–09:41
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EGU22-7459
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Virtual presentation
Krisztina Sebe, Zsófia Ruszkiczay-Rüdiger, Gergely Surányi, Ágnes Novothny, Márton Bauer, and Gábor Csillag

The karst region of the Western Mecsek Mts. is a hilly area with a maximum elevation of ~600 m a.s.l. The karst has developed on Triassic limestones, with part of the drainage basins on lower Triassic sandstones and conglomerates. Our main objective was to constrain the karst development in time, to identify karstification periods with respect to climate, and to obtain data on landscape evolution. Cave geometries were surveyed, and speleothems and allochthonous siliciclastic sediments were extensively sampled for U-series, cosmogenic radionuclide (CRN) burial and optically stimulated luminescence (OSL) age determination.

Cave passage orientations are dominantly controlled by tectonic fractures and bedding. Most cavities formed in the vadose zone, only a few passages show features possibly referring to the phreatic zone. No obvious geomorphic levels could be identified within the caves. Cave sediments include reworked loess (dominant), coarse gravels and sands from Triassic red sandstones, red clay, reworked speleothems (dripstones, carbonate tuff from cave streams), and fragments of the host rocks. Though several passages used to be filled with fluvially transported sediments, at present none of the spring caves issues clastic deposits, thus the deep karst system apparently acts as sediment sink.

The CRN burial age of the oldest cave sediments is ~2.5 Ma, in a sinkhole cave now in a valley-side position. The burial ages of sediments in caves with entrances at or close to present-day valley floors are Middle Pleistocene to recent.

According to the U-series ages, speleothems precipitated at least from the Middle Pleistocene to the Holocene, with most data concentrating in the last glacial maximum and in the Holocene, but several ages exceeding the limits of the measurement method. They formed under all climatic conditions, from glacials to interglacials. They underwent repeated phases of precipitation and dissolution. Widespread submerged stalagmites refer to oscillations of the karst water table; measured ages of ~3 ka and 40-50 ka indicate formation during milder climates, with still lower-than-present water tables. Based on OSL ages, loess was washed into the caves under both cold and mild climates in the Late Pleistocene and Holocene. The ages obtained by the different age determination methods do not allow to distinguish periods with different types of karst activities, they suggest that both speleothem genesis and sediment transport happened under all climate types and simultaneously.

The burial age of the clastic infill of the oldest dated cave, which now can practically lacks a drainage area, be used to infer local incision rate. 2 Ma ago it still received sediment (coarse sand and sandstone) from non-karstic rocks. Supposing a valley-floor position for that time at the recent cave entrance gives a valley incision rate of ~15 mm/ky. Pre- and post-burial surface denudation rates calculated using the CRN data vary between ~12-35 mm/ky.

Sandstone cobbles in a cave now lacking non-karstic rocks in the catchment area indicate drastic drainage changes, the capture of the upper catchment by the neighbouring watercourse.

Research was supported by PURAM, Mecsekérc Ltd. and NKFIH project FK 124807.

How to cite: Sebe, K., Ruszkiczay-Rüdiger, Z., Surányi, G., Novothny, Á., Bauer, M., and Csillag, G.: Karst development and geochronology of cave sediments and speleothems in the Western Mecsek Mts., Hungary, Pannonian Basin, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7459, https://doi.org/10.5194/egusphere-egu22-7459, 2022.

09:41–09:46
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EGU22-254
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ECS
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Virtual presentation
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Torsa Sengupta, Arati Deshpande-Mukherjee, Ravi Bhushan, and Anindya Sarkar

Laser-based online carbonate analyses open up a simple yet efficient way to explore high-resolution (~125 µm) investigation of different biogenic (viz. bivalves, fish otolith) and abiogenic (viz. speleothem, varves) carbonates for deciphering climatic signals. Stable isotopic sclerochronological analyses on biogenic carbonates that had formed in equilibrium with the ambient water effectively record the temporal changes in the environmental parameters like temperature, salinity and isotopic composition. Similar analysis on archaeological fossil assemblages helps to understand past climate, precipitation variability with respect to cultural changes observed in the archaeological site.

Dholavira, a UNESCO world heritage site, was a magnificent seven-staged Harappan metropolitan, situated within the Rann of Kutch, Gujarat, India. The city witnessed cultural evolution from Pre- to Post- Harappan (Indus valley civilisation) culture with some minor desertion periods during the late Mature- and early Late-Harappan stages. A previous study has already proposed an estuarine environment, with the presence of a glacial-fed river (ancient Indus distributary), which mixed with the intruding seawater in the Early Harappan Rann. Here, with the high-resolution laser-based technique, we further examined this proposition by analysing and deciphering monthly climatic changes from a 4.6 Kilo year old otolith of a migrating estuarine catfish, Arius dussumieri and a 5.2 Kilo year old freshwater bivalve, Parreysia corruguta. The ẟ18O of the otolith carbonate ranges from ~-9 ‰ to ~-1 ‰ (VPDB), corroborating the presence of a highly depleted (ẟ18Owater(VSMOW)~-12 ‰ ) freshwater river debouching into an ancient estuary during summer/monsoonal times. The enriched ẟ18O values during winter/ non-monsoonal months result due to evaporative enrichment, reduction in riverine discharge in the semi-enclosed estuarine environment. The winter migration of the fish into deeper water might enrich the otolith ẟ18O values further. The monthly climatic signal from the typically freshwater bivalve with a ẟ18O variation from ~-10 ‰ to ~-7 ‰ (VPDB) might indicate a presence of a freshwater body (lake/ponds?) receiving monsoonal recharge with ~-7 ‰ (VSMOW; compared to annual weighted modern ẟ18Oprecipitation(VSMOW) of -5 ‰) and a slight evaporative enrichment during winter months during Pre- to Early Harappan times. High-resolution climatic studies from different biogenic carbonates thus suggest that the agricultural society of Dholavira flourished in a more conducive environment with riverine discharges and slightly higher precipitation, in contrast to the present day inhabitable arid climate.

How to cite: Sengupta, T., Deshpande-Mukherjee, A., Bhushan, R., and Sarkar, A.: Laser-based stable isotopic analyses of carbonates to obtain high-resolution climatic signals and its application to understand Early Harappan climate, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-254, https://doi.org/10.5194/egusphere-egu22-254, 2022.

09:46–09:51
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EGU22-5061
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On-site presentation
Ola Kwiecien, Sebastian Breitenbach, and Magdalena Kozielska

Like many of our fellow geoscientists, the early 2020 outbreak of the COVID pandemic caught us moving countries and universities. With field work cancelled and access to laboratories restricted, many research projects came to a pause. Working from home in a new, and not yet explored scientific and (sub)urban landscape presented serious challenges but also previously overlooked opportunities.

Here we report the results of a nearly two-year long monitoring of local temperature and isotopic composition of precipitation coupled with observations on the activity of the brown garden snail (Cornu aspersum) in Great Park, Newcastle upon Tyne, northeastern UK. Land snail shells are often used as archives of past environmental conditions (temperature and/or precipitation), but untested assumptions on when they form their shells might bias the interpretation. Snails precipitate their carbonate shell only during the active growth phases, while they remain dormant when conditions are too cold (hibernation) or too dry (aestivation). Thus, depending on the regional/ local conditions snail shells constitute a seasonally biased environmental archive, but this fact is often either oversimplified or completely overlooked.

The Köppen-Geiger climate classification defines UK climate as oceanic (Cfb temperate climate without dry season, but warm summers). Northeast England experiences maximum temperatures in summer (JJA) and lowest in winter (DJF), whereas precipitation is relatively homogenously distributed throughout the year, with highest rainfall in autumn and winter (SONDJF). Our local observations confirm that C. aspersum is most active during the night and directly after rainfall. As expected, the Great Park snail population does not aestivate during summer but hibernates in winter, starting when temperatures drop below ca. 7°C in late November. Contrary to expectations, the emergence from hibernation does not seem to be temperature- but precipitation-driven, and commences after the first heavy rainfall in May, independent of air temperature. Our ongoing monitoring work calls for careful assessment when interpreting the isotopic composition of fossil shells in terms of mean annual conditions.

How to cite: Kwiecien, O., Breitenbach, S., and Kozielska, M.: Monitoring annual snail activity cycles: field-testing paleoenvironmental assumptions, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5061, https://doi.org/10.5194/egusphere-egu22-5061, 2022.

09:51–10:00
Coffee break
Chairpersons: Cindy De Jonge, Sebastian F.M. Breitenbach, Ola Kwiecien
10:20–10:25
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EGU22-3598
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Virtual presentation
Jan Šafanda, Petr Dědeček, Tomáš Uxa, and Vladimír Čermák

Litoměřice borehole located in the Lowland of the Northern Czechia was drilled in 2007 to the depth of 2 km and repeatedly logged in the period 2007−2020. The analysis of the obtained data enabled us to reconstruct the temperature-depth record undisturbed by the drilling and to recognize a robust past climate signal. Whereas this signal is hidden by the temperature gradient variations caused by heterogeneous thermal properties of the sedimentary/volcanic rock strata in the uppermost 950 m, below this depth the temperature-depth profile clearly indicates a warming at the end of the last glacial. Numerical solution of the transient heat conduction equation shows that the temperature gradient increase by about 3 K/km observed in the homogenous mica schist section between 1000−1500 m depth is consistent with the ground surface temperature warming of about 10 K. The numerical simulations also suggest that the permafrost occurrence, at least in the coldest periods of the last glacial, was highly probable in the Central European lowlands.

How to cite: Šafanda, J., Dědeček, P., Uxa, T., and Čermák, V.: Glacial/Interglacial temperature signal in 2 km deep borehole Litoměřice, Czechia, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3598, https://doi.org/10.5194/egusphere-egu22-3598, 2022.

10:25–10:30
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EGU22-5017
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ECS
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Virtual presentation
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Viorica Nagavciuc, Cătălin-Constantin Roibu, Andrei Mursa, Marian Ionuț Știrbu, Ionel Popa, and Monica Ionita

Paleoclimate reconstructions are increasingly used to characterize climate variability and change prior to the instrumental record, in order to improve our estimates of climate extremes and to provide a baseline for climate change projections. Most of these reconstructions are focused on temperature, precipitation, and/or drought indices, and to a lesser extent to reconstruct streamflow variability. In this study, a regional tree-ring width chronology (i.e. Quercus petraea), from Caraorman forest (Danube Delta, Romania), was used to reconstruct the last ~250 years of annual (from November previous year to July current year) streamflow of the Lower Danube River. The obtained results indicate a stable and significant correlation between the measured tree-ring width from Caraorman forest and Danube streamflow at Ceatal Izmail hydrologic station situated in the south-eastern part of Europe. The statistical parameters of the reconstruction model confirm that our model is stable and robust, explaining 44.9 % of the variance of the Lower Danube streamflow over the period 1920 – 2013. Interannual streamflow variation for the analyzed period indicates 11 extremely high flow years, with streamflow greater than 9200 m3/s (1170, 1771, 1799, 1836, 1838, 1839, 1871, 1876, 1877, 1940, and 2010) and 11 extremely low flow years, with streamflow lower than 5200 m3/s (1750, 1753, 1753, 1773, 1794, 1832, 1843, 1882, 1921, 1964, and 1994). The influence of the large-scale atmospheric circulation on the TRW variability was analyzed using the composite maps of the geopotential height at 500 mb (Z500) and sea surface temperature (SST). High TRW values (e.g. high streamflow periods) from the Caraorman forest are associated with a low-pressure system centered over Europe and positive SST anomalies over the Atlantic Ocean and negative SST anomalies over the Baltic, North, and Mediterranean Seas. These large-scale conditions favor the advection of moist air from the Mediterranean and the Black Sea towards the south-eastern part of Romania, which in turn leads to high precipitation rates over this region. Opposite to this, low TRW values (e.g. low streamflow periods) are associated with a high-pressure system centered over Europe, a northward shift of the storm tracks and negative SST anomalies over the Atlantic Ocean, and positive SST anomalies over the Baltic, North, and Mediterranean Seas. Based on our results we argue that the reconstruction of river streamflow data based on the tree-ring width has important scientific and practical implications for a better understanding of the streamflow variation of the past, necessary for water resource management, and environmental-hydrological protection.

How to cite: Nagavciuc, V., Roibu, C.-C., Mursa, A., Știrbu, M. I., Popa, I., and Ionita, M.: Tree-ring width as an indicator for hydroclimate variability in the Lower Danube region, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5017, https://doi.org/10.5194/egusphere-egu22-5017, 2022.

10:30–10:35
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EGU22-13234
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Virtual presentation
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Manuel Chevalier

Statistical climate reconstruction techniques are fundamental tools to study past climate variability from fossil proxy data. In particular, the methods based on probability density functions (or PDFs) have the potential to be used in various environments and with different climate proxies because they rely on elementary calibration data (i.e. modern geolocalised presence data). However, the access and curation of these calibration data, as well as the complexity of interpreting probabilistic results, often limit their use in palaeoclimatological studies. I introduce a new R package (crestr) to apply the CREST method (Climate REconstruction SofTware) on diverse palaeoecological datasets and address these problems. crestr includes a globally curated calibration dataset for six common climate proxies (i.e. plants, beetles, chironomids, rodents, foraminifera, and dinoflagellate cysts) associated with an extensive range of climate variables that enables its use in most terrestrial and marine environments. Private data collections can also be used instead of, or in combination with, the provided calibration dataset. The package includes a suite of graphical diagnostic tools to represent the data at each step of the reconstruction process and provide insights into the effect of the different modelling assumptions and external factors that underlie a reconstruction. With this R package, the CREST method can now be used in a scriptable environment, thus simplifying its use and integration in existing workflows. It is hoped that crestr will contribute to producing the much-needed quantified records from the many regions where climate reconstructions are currently lacking, despite the availability of suitable fossil records. The use of the package will be illustrated with a recent application to produce a 790,000 year long mean annual temperature reconstruction based on a pollen record from southeastern Africa.

How to cite: Chevalier, M.: crestr An R package to perform probabilistic climate reconstructions using fossil proxies, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13234, https://doi.org/10.5194/egusphere-egu22-13234, 2022.

10:35–10:40
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EGU22-11983
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Presentation form not yet defined
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Ulrike Herzschuh, Thomas Boehmer, Chenzhi Li, Xianyong Cao, Manuel Chevalier, and Anne Dallmeyer

Mismatch in model- and proxy-based Holocene climate change, known as the Holocene Conundrum, may partially originate from the poor spatial coverage of climate reconstructions e.g. in Asia, limiting the number of grid cells for model-data comparison. Here we investigate pollen-based reconstructions of mean annual, mean July temperature, and annual precipitation from 2594 sites in  the northern hemisphere extratropics that were set up with a harmonized calibration method and were presented with revised chronologies. Temperature trends show strong latitudinal pattern and differ between (sub-)continents. While Europe and eastern North America show a pronounced mid-Holocene temperature maximum, western North America shows only weak changes and Asia a continuous Holocene temperature increase but with strong latitudinal differences. While on hemisphere scale, temperature and precipitation show similar trends (i.e. a Holocene toward the late mid-Holocene increase until followed by a slight decline until present), on continental and regional scale positive, negative and non-correlation are found. Particularly in Asia strong latitudinal pattern of precipitation is found.  Finally, we merged our data with the data of Kaufman et al 2020 doubling the number of records in this data base and presented a revised global temperature curve.

How to cite: Herzschuh, U., Boehmer, T., Li, C., Cao, X., Chevalier, M., and Dallmeyer, A.: Pollen-based Holocene temperature and precipitation pattern of the Northern Hemisphere regions in the light of the global temperature trend, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11983, https://doi.org/10.5194/egusphere-egu22-11983, 2022.

10:40–10:45
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EGU22-12224
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ECS
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On-site presentation
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Laura Schild, Peter Ewald, Thomas Böhmer, Alexander Karl Postl, Chenzhi Li, Thomas Laepple, and Ulrike Herzschuh

Data on past vegetation compositions is crucial not only for understanding past vegetation dynamics and environmental interactions but also for predicting potential future vegetation trajectories and thus their feedback on climate and society. Pollen records from sediment cores provide temporally resolved data on pollen frequencies. These allow for inferences of taxa presence, but biased pollen deposition due to taxa-specific pollen productivity and dispersal prohibit direct inference of taxa abundance.

The model for Regional Estimates of Vegetation Abundance from Large Sites (REVEALS) corrects for these taxa-specific parameters and produces more realistic regional vegetation abundances. Previously applied in many regions such as North America, Southern Sweden, Norway, and more recently the entirety of Europe, REVEALS has performed well in providing estimates for large vegetation units as well as individual taxa. 

With this data set, we present reconstructed past regional vegetation for more than 2200 sites across the Northern Hemisphere. The REVEALS model was applied by using a harmonized pollen dataset for the entire Northern Hemisphere, taxa-specific pollen productivity estimates, pollen fall speeds, as well as pollen dispersal models. First validations show an improved fit of the reconstructed vegetation with remotely sensed tree cover compared to pure pollen percentages. For validation tree cover datasets from the CONSENSUS global 1-km land cover product were used. The pollen source areas were defined to include 80% of the area from which deposited pollen originated.

This first-time reconstruction for the entire Northern Hemisphere will allow for detailed analysis of vegetation dynamics and trajectories ultimately improving our understanding of climate-vegetation interactions, and may even act as input and validation for other vegetation and climate models and proxies.

How to cite: Schild, L., Ewald, P., Böhmer, T., Postl, A. K., Li, C., Laepple, T., and Herzschuh, U.: Pollen-based reconstruction of regional vegetation and land cover in the Northern Hemisphere, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12224, https://doi.org/10.5194/egusphere-egu22-12224, 2022.

10:45–10:54
10:54–10:59
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EGU22-12651
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ECS
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Virtual presentation
Chéïma Barhoumi, Sébastien Joannin, Adam A. Ali, Guillemette Ménot, Yulia Golubeva, Dmitri Subetto, Alexander Kryshen, Igor Drobyshev, and Odile Peyron

The functioning of the boreal forests of Russia is still little documented and little understood. It is governed by complex mechanisms that link climate, vegetation and disturbances, such as fires or human impact.In this presentation, we aim to provide robust reconstructions of the Holocene climate (temperatures and precipitation) of the Vychegda River basin in the Republic of Komi region, based on two different proxies: pollen assemblages and GDGTs (Glycerol Dialkyl Glycerol Tetraethers). This first study of GDGTs in this area corresponds to a preliminary step for the calibration of this proxy in peats. Higher temperatures and precipitation are recorded between 7000 and 4000 cal. yr BP (mean annual temperatures around 3°C and precipitation between 600 and 700 mm per year). This climatic optimum is in agreement with previous pollen-based climate reconstructions, and climate patterns in the neighboring Russian and Fennoscandia (Komi Republic - previous study-, Arctic Russia, Siberia and Northern Europe, Andreev and Klimanov, 2000; Golubeva, 2008; Seppä et al., 2009a). These results, in conjunction with the reconstruction of fire activity and vegetation dynamics in this region, led to a better understanding of the crossed influences of these factors. In particular, vegetation is mainly controlled by climate during the first part of the Holocene, while a threshold is reached on in fire frequency after 3500 cal. yr BP and this parameter has a greater impact on vegetation than climate. Over the past 600 years, the intensification of human activities led to overexploitation of the forest and an increase in its fire activity.

How to cite: Barhoumi, C., Joannin, S., Ali, A. A., Ménot, G., Golubeva, Y., Subetto, D., Kryshen, A., Drobyshev, I., and Peyron, O.: Holocene climate in Northern Urals (Komi Republic, Russia): a multi-proxy approach based on pollen and brGDGTs, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12651, https://doi.org/10.5194/egusphere-egu22-12651, 2022.

10:59–11:04
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EGU22-13242
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On-site presentation
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Petter Hällberg, Antonio Martínez Cortizas, Anggi Hapsari, Hamidi Rifai, Steffen Eisele, Caroline Bouvet de Maisonneuve, Malin Kylander, Frederik Schenk, and Rienk Smittenberg

Despite immense progress in the last decades, the Holocene climate evolution is still poorly resolved, in particular in the tropics, and especially from a terrestrial perspective. Here we reconstruct 11 000 years of paleo-climate and environment in the western Indo-Pacific Warm Pool – “the heat and steam engine of the world” – by analysing biomarker and geochemical proxies in peat sediments from Sumatra.

We discuss the composition of archaeal and bacterial membrane lipids (branched and isoprenoid glycerol dialkyl glycerol tetraethers; GDGTs) and their relationship with temperature and other environmental conditions. By analysing the hydrogen isotopes of leaf waxes (dDwax) we reconstruct past rainfall amounts.

X-Ray Fluorescence (XRF) derived geochemical composition reveals changes in erosional regimes. Additionally, we use long-chain n-alkane distributions, carbon and nitrogen analysis, and attenuated reflectance Fourier-Transform Infrared analysis (FTIR-ATR) to investigate changes in vegetation on the peatland.

Three main climate-environmental phases emerge in our record: 1) Relatively cold, dry and unstable conditions during the Early Holocene which is marked by high detrital input into the peatland. 2) Warm, wet and stable conditions coincided with the mid-Holocene period, 8.2 – 3.2 ka BP. Using a global peat-specific temperature calibration based on branched GDGTs (Naafs et al., 2017), we derive mean annual air temperatures peaking at 4.8 ka BP that are ~3 °C warmer compared to core-top and modern local weather station data. The warmest period is also the wettest according to dDwax, which is further supported by GDGT and alkane distributions, and d13C values indicating aquatic biomass production. 3) At 3.2 ka BP, the climate abruptly deteriorated into colder and drier conditions and re-intensified erosion.

Surprisingly, slope wash events resulting in input of coarse detrital material into the core were most frequent during the dry periods. We suggest that this is related to a more variable hydroclimate with droughts and episodic heavy rains, likely associated with ENSO variability, causing increased erosion during the Early and Late Holocene.

 

How to cite: Hällberg, P., Martínez Cortizas, A., Hapsari, A., Rifai, H., Eisele, S., Bouvet de Maisonneuve, C., Kylander, M., Schenk, F., and Smittenberg, R.: Intense mid-Holocene warming on highland Sumatra: insights from biomarker proxies, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13242, https://doi.org/10.5194/egusphere-egu22-13242, 2022.

11:04–11:09
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EGU22-7376
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Virtual presentation
S. Nemiah Ladd, Daniel B. Nelson, Blake Matthews, Shannon Dyer, Anita Narwani, Nathalie Dubois, and Carsten Schubert

Phytoplankton are an important biogeochemical force, collectively impacting nutrient cycling as well as atmospheric and aquatic chemistry. However, it remains challenging to reconstruct changes in algal productivity and community assembly throughout the geologic past. Here, we lay the foundation for a sensitive proxy of past algal ecology based on compound-specific hydrogen isotope compositions (δ2H values) of common algal lipids. While such measurements have previously been used as indicators of water hydrogen isotope ratios, our results from laboratory cultures and experimental ponds demonstrate that changes in the δ2H values of ubiquitous lipids such as palmitic acid associated with taxonomic changes are an order of magnitude greater than those caused by hydrologic change. These results indicate that δ2H values of algal lipids, and the relative offset of these values among different compounds, can be used to reconstruct past changes in algal community assemblages, including those driven by changes in nutrient supply.

We apply this approach to a ~180 year sedimentary record from Lake Greifen, a lake in the central Swiss Plateau that underwent well-documented eutrophication and partial recovery in the second half of the 20th century. As total phosphorus concentrations in the lake increased from > 100 mg/L to ~ 500 mg/L in the 1950s-1970s, palmitic acid d2H values increased by 40 ‰ and phytol δ2H values by 20 ‰;  δ2H values of both compounds subsequently declined with total P following maximum values in the early 1980s. During this entire time interval, mean annual precipitation δ2H values fluctuated within a ~10 ‰ range and are not correlated with the changes in lipid δ2H values. Additionally, the decline in lipid δ2H values is correlated with declining relative abundance of green algae as the eutrophication pressure on Lake Greifen receded in the past decades. This correlation matches the prediction from our culturing and mesocosm results, where green algae produced exceptionally 2H-enriched fatty acids, and indicates that lipid δ2H can be applied to reconstruct nutrient induced shifts in algal populations.

How to cite: Ladd, S. N., Nelson, D. B., Matthews, B., Dyer, S., Narwani, A., Dubois, N., and Schubert, C.: Hydrogen isotopes from lipid biomarkers record eutrophication induced changes in algal community assemblages, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7376, https://doi.org/10.5194/egusphere-egu22-7376, 2022.

11:09–11:14
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EGU22-5562
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ECS
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On-site presentation
Céline Martin, Nora Richter, Carsten Schubert, Francesco Pomati, Linda Amaral-Zettler, and Nathalie Dubois

Past temperature records are key tools for inferring climate dynamics and provide empirical data for testing climate models to improve our mechanistic understanding of natural climate variability. Unfortunately, very few quantitative records of pre-historic continental temperatures exist in Europe. Moreover, existing paleothermometers mainly provide mean annual or warm season temperatures, limiting our understanding of climate variability during the transitional seasons and winter. Alkenones are temperature-sensitive lipids produced by Isochrysidales algae, which have been used for decades to reconstruct quantitative changes in sea-surface temperatures. In lakes, they are not ubiquitous, but they have been increasingly reported in both saline and freshwater lakes worldwide, suggesting that there is great potential for alkenone-based paleotemperature reconstructions in lacustrine settings. Lacustrine alkenones have already been successfuly used to reconstruct paleotemperatures in high-latitude lakes. Depending on the timing of ice-out, they record winter/spring or summer temperatures. In our study, we found that a significant number of Swiss lakes contain lacustrine alkenones. Other studies in mid-latitude European lakes suggest that the peak of alkenone production occurs in spring. The monitoring of Lake St Moritz, an alpine lake in the South East of Switzerland, will allow determining the seasonality of alkenone production in mid-latitute high altitude lakes. Combining genetic analyses and the monitoring of physico-chemical parameters will provide more information about the ecology of the alkenone producers. Our first results suggest that we will be able to improve the understanding of alkenone production in freshwater lakes and to develop the first spring lake temperature reconstruction in Switzerland that extends beyond existing historical records.

How to cite: Martin, C., Richter, N., Schubert, C., Pomati, F., Amaral-Zettler, L., and Dubois, N.: Potential of lacustrine alkenones as a novel proxy for spring temperatures in mid-latitude European lakes, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5562, https://doi.org/10.5194/egusphere-egu22-5562, 2022.

11:14–11:22
11:22–11:27
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EGU22-5083
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ECS
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Presentation form not yet defined
Amy Cromartie, Mary Robles, Sébastien Joannin, Lucas Dugerdil, Odile Peyron, and Guillemette Ménot
The arid and semi-arid mountainous environment of the Southern Caucasus lies between the Black and Caspian Sea with elevations from below sea level to over 5000 m asl and has annual temperatures from -6˚ to 16˚C and precipitation between 200 - 2200 mm a year. Due to the large elevation changes in this mountainous zone, temperature and precipitation shifts occur quickly over short distances. The semi-arid regions here host a number of wetland contexts available for paleo-environmental research. However, recent investigations of branched glycerol dialkyl glycerol tetraethers (brGDGTs) records from a large wetland from the region note the changes in wetland development, from lake to peatland, impact the distribution of brGDGTs and the temperature reconstructions (Robles et al. 2022). To overcome these challenges Robles et al. (2022) applied a combination of global lake and soil calibrations to each section. New research on smaller wetlands, however, have found that these wetland transformations are not always as well defined and include periods of erosional soil inputs, open lake contexts, and eventual transformation to a wetland. In addition, soils from the region record a similar trend found in Gao et al., (2021) who found a temperature relationship with the MBT'6me suggesting the MBT'5me reconstructions do not fully capture the temperature profile. To address these issues we propose two avenues to reconstruct temperature and present our results. First, we evaluate the feasibility of utilizing a stepwise selection model for local configuration based on mixed samples (lake, wetland, soils) to overcome problems with changes in sediment overtime while capturing the temperature relationships between both the 5-methyl and 6-methyl brGDGT groups. Second, we utilize a probability based machine learning approach to estimate changes in source sediment distribution as the wetland transitions through time. We test both of these applications on downcore wetland sediments to evaluate our results. These results are compared with pollen reconstructions, aquatic pollen, non-pollen polymorphs, and XRF data in order to evaluate their success. We find that both methods can help provide better information for reconstructions.
 

Robles, Mary, et al. "Impact of climate changes on vegetation and human societies during the Holocene in the South Caucasus (Vanevan, Armenia): A multiproxy approach including pollen, NPPs and brGDGTs." Quaternary Science Reviews 277 (2022): 107297. 

Guo, Jingjing, et al. "Soil pH and aridity influence distributions of branched tetraether lipids in grassland soils along an aridity transect." Organic Geochemistry (2021): 104347. APA  

 

How to cite: Cromartie, A., Robles, M., Joannin, S., Dugerdil, L., Peyron, O., and Ménot, G.: Problems and Solutions: brGDGTs distributions and calibrations for semi-arid environments and application to the wetlands of the Southern Caucasus., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5083, https://doi.org/10.5194/egusphere-egu22-5083, 2022.

11:27–11:32
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EGU22-9336
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ECS
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On-site presentation
Izabella Baisheva, Luidmila Pestryakova, Boris Biskaborn, Stuart Vyse, Sardana Levina, Ramesh Glückler, Ulrike Herzschuh, and Kathleen Stoof-Leichsenring
The permafrost-shaped landscape of Central Yakutia is particularly rich in thermokarst lakes, which provide important cultural and ecosystem services to the local population. Climate warming and an intensification of agriculture in alaas systems (i.e. mostly drained basins of large thaw lakes formed during the early Holocene under warm climatic conditions) in the Central Yakutian Lowlands may lead to pronounced changes in water resources, water quality, nutrient loading and biodiversity. This could in turn threaten the livelihoods of affected communities, who depend on functional alaas ecosystems. To better foresee potential future impacts of environmental changes on internal lake ecological processes, it is important to gain a better understanding of how thermokarst lakes reacted to such changes in the past.
 
Here, we present a new paleoenvironmental reconstruction of ecological changes within Lake Satagay (N 63.078, E 117.998, Nyurbinsky District), covering the last ca. 10,800 years. We use sedimentological and XRF-derived geochemical parameters, in addition to the metabarcoding of sedimentary ancient DNA (sedDNA) for diatoms and aquatic plants, and microscopic diatom analyses, to evaluate sedimentological and biodiversity shifts throughout the Holocene. Our study revealed 53 diatom DNA sequence types and 53 species morphologically. High distributions of Stephanodiscus and Fragilaria, among multiple other diatom genera in the early Holocene, indicate that initial formation of this typical alaas lake occurred earlier than expected (i.e. before 10,800 BP). In recent millennia diatom abundance decreased and their community is almost exclusively composed of Pseudostaurosira and Fragilaria. Composition of aquatic plants show an overall dominance of Ceratophyllaceae and strong fluctuations in Potamogetonaceae likely related to lake level and water chemical changes. All proxies investigated support that lake conditions and biotic composition has been resilient since 4,000 BP, but youngest samples since 47 BP indicate that land use influence has been crucial for the lake quality. This study represents a step towards a better understanding of climate and human-impacted alaas lake development and its consequences for their ecosystem services in eastern Siberia in the near future.

How to cite: Baisheva, I., Pestryakova, L., Biskaborn, B., Vyse, S., Levina, S., Glückler, R., Herzschuh, U., and Stoof-Leichsenring, K.: Long-term thermokarst lake development and internal ecological feedbacks: A new reconstruction from Lake Satagay (Yakutia, Siberia), EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9336, https://doi.org/10.5194/egusphere-egu22-9336, 2022.

11:32–11:37
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EGU22-2967
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ECS
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Presentation form not yet defined
Franziska A Lechleitner, Sarah Rowan, Jan Strähl, Martin Rauber, Susan Q Lang, and Sönke Szidat

The response of terrestrial ecosystems to anthropogenic climate change remains poorly understood and constitutes a major source of uncertainty in future climate projections. Stalagmites are a well-established terrestrial climate archive (Wong and Breecker, 2015), and may also serve as a sensitive recorder of surface ecosystem processes, as they are fed by dripping water that percolates through the soil zone. Coupled climate-ecosystem paleorecords from stalagmites could prove invaluable sources of information on the response of terrestrial ecosystems to past climatic shifts and their sensitivity to climate variability exceeding the instrumental range.

Here we present results from a method development study carried out at the Laboratory for the Analysis of Radiocarbon with AMS (LARA) at the University of Bern. Our results are based on a previous protocol by Lechleitner et al. (2019), which describes a rapid, low contamination method for carbon isotope analysis (δ13C and 14C) of the speleothem non-purgeable organic carbon (NPOC) fraction for small samples (<150 mg CaCO3). Decarbonation of acid digested carbonate samples is followed by wet chemical oxidation of the NPOC and analysis of the resulting headspace CO2 via mass spectrometry to determine its isotopic composition.

We have made significant progress in resolving the main issues that precluded the routine application of the method as presented in Lechleitner et al. (2019), namely incomplete removal of inorganic carbon from the sample solutions, and contamination from extraneous carbon at different method stages. Apart from an updated pre-cleaning protocol for stalagmite samples and extensive blank assessment, a new needle setup was installed, allowing reduction of the sample amount needed, and the CO2 flow is now being monitored during decarbonation to ensure complete removal of inorganic carbon prior to the oxidation step.

These results reiterate the great promise of this method to provide accurate, ecosystem-level information on past terrestrial environments at comparatively high temporal resolution.

 

References:

Lechleitner, F.A., Lang, S.Q., Haghipour, N., McIntyre, C., Baldini, J.U.L., Prufer, K.M., Eglinton, T.I., 2019. Towards organic carbon isotope records from stalagmites: coupled d13C and 14C analysis using wet chemical oxidation. Radiocarbon 61, 749–764. doi:10.1017/RDC.2019.35

Wong, C.I., Breecker, D.O., 2015. Advancements in the use of speleothems as climate archives. Quat. Sci. Rev. 127, 1–18. doi:10.1016/j.quascirev.2015.07.019

How to cite: Lechleitner, F. A., Rowan, S., Strähl, J., Rauber, M., Lang, S. Q., and Szidat, S.: Speleothem organic carbon isotopes as a novel tracer for terrestrial ecosystem change – new method developments, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2967, https://doi.org/10.5194/egusphere-egu22-2967, 2022.

11:37–11:42
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EGU22-487
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ECS
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Presentation form not yet defined
Wendy Khumalo, Vincent Hare, Kelly Kirsten, John Parkington, and Robyn Pickering

The hydrology of the Last Glacial Maximum (LGM) in South Africa has been an active area of research over the last six decades due to the richness of many proxy records and the high preservation potential of deposits of this age at sites recording human occupation. Here we review the merits of using a Weighted Average – Partial Least Squares regression on the archaeological charcoal records from Elands Bay Cave (EBC) and Boomplaas Cave (BPC) to quantitatively reconstruct palaeoclimate. These sites are both spatially and temporally ideal to track the changes in the Southern Hemisphere Westerlies – the proposed driver of the change in hydroclimate and have been used to infer LGM climate conditions. A database of the modern-day distribution of the taxa identified in the stratigraphy at EBC and BPC was created using the Global Biodiversity Information Facility, this was then paired with the modern climate data from WorldClim to perform a WA-PLS regression to reconstruct Mean Annual Temperature and Total Annual Precipitation. Many of the WA-PLS regressions reconstructed temperature differences from the LGM to present close to 5°C (consistent with regional records). The TAP reconstructions suggest decreased precipitation during the LGM at BPC and despite unrealistic values for the EBC charcoal record, they suggest higher TAP values during the LGM. The TAP reconstructions posed more problems and highlighted some major flaws in the reconstructions. When compared to the pollen record from EBC, MAT  reconstructions reflect the same trend however the TAP reconstructions from pollen indicate slightly lower TAP values during the LGM. Due to the nature of these records, there are some important differences that influence the outcomes of the reconstruction. These being the biases which exist within the records themselves and propagating through to the reference databases. With the use of a Canonical Correspondence Analysis, we can compare the modern distribution of the taxa and better understand what the reconstructions are reflecting and in some cases failing to reflect. While a WA-PLS regression is widely used for reconstructions, other regressions should be compared alongside it.

How to cite: Khumalo, W., Hare, V., Kirsten, K., Parkington, J., and Pickering, R.: Fossil charcoals as a means for reconstruction of past hydroclimate variability through the Last Glacial Maximum: a case study from two archaeological sites in the Winter and Year-round Rainfall Zones, South Africa, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-487, https://doi.org/10.5194/egusphere-egu22-487, 2022.

11:42–11:50
Lunch break
Chairpersons: Benjamin Keenan, Sebastian F.M. Breitenbach, Cindy De Jonge
13:20–13:23
13:23–13:33
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EGU22-6232
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ECS
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solicited
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Virtual presentation
Richard S. Vachula, Allison Karp, Elizabeth Denis, Nicholas Balascio, Elizabeth Canuel, and Yongsong Huang

Many regions worldwide have experienced increasing wildfire activity in recent years and climate changes are predicted to result in more frequent and severe fires. Reconstruction of past fire activity offers paleoenvironmental context for modern and future burning. Pyrogenic polycyclic aromatic hydrocarbons (PAHs) have been increasingly used as a molecular biomarker for fire occurrence in the paleorecord and offer opportunity for nuanced reconstructions of fire characteristics. A suite of PAHs is produced during combustion, and the emission amount and assemblage is influenced by many variables including fuel type, fire temperature, and oxygen availability. Despite recent advances in understanding the controls and taphonomy of these biomass burning markers, the spatial scale of this proxy is unknown. Measurements of PAH fluxes preserved in a lake sediment archive from the Sierra Nevada, California were compared with a historical geographic information system dataset of area burned up to 150 km distance from the lake to determine the spatial scales for which these biomarkers are reliable proxies of burning. The PAH fluxes in the Swamp Lake sediments record a change in the relative anthropogenic and pyrogenic sourcing of PAHs. Anthropogenic pollution sources could explain why some PAHs (fluoranthene (Fl), pyrene (Py), benz[a]anthracene (BaA), retene (Ret), benzo[a]pyrene (BaP), dibenzo[a,h]anthracene (DA) and ideno[1,2,3-cd]pyrene (IP)) did not correlate with area burned within 150 km. This indicates that individual PAHs may have different efficacies in recording area burned and be more susceptible to masking of fire signals by pollution sources. Despite these complications, we find that the PAHs naphthalene (Na), acenaphthene (Ace), fluorene (F), and anthracene (An) are reliable local proxies of area burned (within 40 km), whereas the PAHs phenanthrene (Phe), chrysene (Ch), benzo[b]fluoranthene (BbF), benzo[k]fluoranthene (BkF), and benzo[g,h,i]perylene (Bghi) are both reliable local (within 36 km) as well as more regional (as much as 75 km for phenanthrene (Phe), chrysene (Ch), and benzo[g,h,i]perylene (Bghi) or 150 km for benzo[b]fluoranthene (BbF) and benzo[k]fluoranthene (BkF)) area burned proxies. Comparisons of PAH fluxes with charcoal accumulation rates in the same sediments suggest that pyrogenic particulate transport modulates low to mid-molecular weight PAHs via adsorption. Overall, the results indicate that PAH records integrate a combination of spatial signals of area burned and measurement of individual PAHs may enable cross-scale paleofire reconstructions.

How to cite: Vachula, R. S., Karp, A., Denis, E., Balascio, N., Canuel, E., and Huang, Y.: Spatially calibrating polycyclic aromatic hydrocarbons (PAHs) as proxies of area burned by vegetation fires, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6232, https://doi.org/10.5194/egusphere-egu22-6232, 2022.

13:33–13:38
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EGU22-960
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ECS
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On-site presentation
Julia Homann, Inken Heidke, Michael Weber, Denis Schloz, and Thorsten Hoffmann

Secondary mineral deposits in caves, such as stalagmites, constitute valuable paleoclimate archives because they are largely protected from degradation due to stable in-cave conditions and can be precisely dated up to 600,000 years using 230Th/U-dating. [1] In addition to established climate proxies, such as stable isotopes and trace elements, organic proxies have become increasingly attractive in recent years for investigating local vegetation and soil dynamics. [2]

 

Lignin, a biopolymer, is one of the main constituents of higher plants and consists of three monomeric units: sinapyl-, coniferyl-, and coumaryl alcohol. Lignin can be degraded into its monomeric units by alkaline CuSO4-oxidation [3]. Determination of the ratios among different oxidation products in a speleothem allows the reconstruction of the type of vegetation above the cave [4].

 

Biomass burning events are major sources of atmospheric particulate matter that influences global and local climate. [5] Investigating fire proxies in paleoclimate archives may therefore help to determine the interactions of climate, hydrology, and fire activity. Levoglucosan, an anhydrosugar, naturally only originates from the combustion of cellulose and thus constitutes a biomass burning marker. To date, no data on levoglucosan in speleothems have been published, whereas the anhydrosugar has already been utilised in other paleoclimate archives, such as sediments and ice cores. [2,5]

 

Here we present preliminary results for samples from two flowstone cores from Cueva Victoria in south-eastern Spain. The investigated samples cover MIS 1 and 7-11. Speleothems from this cave are known to have grown in intervals for at least 450 000 years. [6] Due to the semi-arid climate in this region the speleothems have mostly grown during interglacials, thereby responding and documenting changes in paleoclimate. We aim to reconstruct vegetation changes, investigate the occurrence of fires, and compare the results with existing δ13C and δ18O data.

 

[1] D. Scholz, D. Hoffmann, Quat. Sci. J. 57 (2008) 52–76 [2] A. Blyth et al. Quat. Sci. Rev. 149 (2016) 1-17. [3] G. Yan, K. Kaiser, Anal. Chem. 90 (2018) 9289–9295. [4] C.N. Jex, G.H. et.al. Quat. Sci. Rev. 87 (2014) 46–59. [5] P. Yao et al. J. of Glaciology 59 (2013) 599-611 [5] V. O. Elias et al. Geochim. et Cosmochim. Acta 65 (2001) 267-272. [6] L. Gibert, C. Ferrandez-Canadell (eds) (2015) Geology and Paleontology of Cueva Victoria (Mastia 11–13). Cartagena: Ayuntamiento de Cartagena.

How to cite: Homann, J., Heidke, I., Weber, M., Schloz, D., and Hoffmann, T.: A new record of environmental proxies for Cueva Victoria, Spain, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-960, https://doi.org/10.5194/egusphere-egu22-960, 2022.

13:38–13:43
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EGU22-10202
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On-site presentation
Jade Robinson, Julia Homann, Stuart Umbo, Pete Scott, Gernot Nehrke, Thorsten Hoffmann, Anton Vaks, Aleksandr Kononov, Alexander Osintsev, Andrew Mason, Franziska A. Lechleitner, Gideon M. Henderson, and Sebastian F. M. Breitenbach

Recent accelerating global temperature rise increases the likelihood and susceptibility of the Siberian taiga to more frequent and extreme wildfires [1] [2]. This leads to enhanced permafrost thaw and subsequent greenhouse gases emissions, in a positive feedback loop [3]. Various studies have examined these paleofires in Siberia on limited, modern timescales [4, 5], but long-term reconstructions of wildfire occurrences are scarce [6]. This study reconstructs wildfire occurrence during the Holocene using stalagmites from southern Siberia. We provide a new means for assessing Siberian wildfires during interglacial periods and the first southern Siberian Holocene wildfire record. 

Three stalagmites from Botovskaya Cave (55˚17’59”N, 105˚19’46”E) have been U/Th-dated at the Oxford geochronology laboratory. These speleothem samples were collected deep inside the poorly ventilated cave, which is overlain by 40-130 m of sandstone covered by a thin soil and boreal taiga forest. Drip sites are active year-round, and cave air temperature is stable at ca. 1.3±0.5°C. Wildfires sporadically occur above the cave.

We use novel speleothem biomarkers, levoglucosan and lignin, as tracers for wildfire activity and vegetation composition above the cave, respectively. Levoglucosan is an anhydrous monosaccharide solely produced by the combustion of cellulose, and thus an ideal proxy for wildfires. Lignin is a biopolymer with three monomers. The monomer ratio can inform on relative changes between gymnosperm vs. angiosperm plant communities. Using both proxies we can decipher not only wildfire recurrence, but also changes in vegetation (e.g., from pine forest to peatbogs or grassland).

We took subsamples between 300 and 1000 mg and attribute the levels of levoglucosan to variance of the composition of lignin monomers, corresponding with vegetation composition. The required sample size (1 g) and the low observed carbonate growth rates of ca. 4-8 mm/a mean that we can only achieve multi-centennial resolution for the Holocene. To gain complementary insights into environmental conditions we combine the biomarker information with stable isotopes and element concentrations.

 References 

[1] V. I. Kharuk, et al., "Wildfires in the Siberian Taiga," Ambio , vol. 50, pp. 1953-1974, 2021.

[2] M. B. S. Flannigan, et al., "Impact of climate change on fire acivity and fire management in the circumboreal forest," Global Change Biology, vol. 15, pp. 549-560, 2009.

[3] M. R. Turetsky, et al., "Carbon release through abrupt permafrost thaw," Nature Geoscience , vol. 13, pp. 138-143, 2020.

[4] M. M. Grieman, et al.,"Aromatic acids in a Eurasian Arctic ice core: a 2600-year proxy record of biomass burning," Climate of the Past , vol. 13, pp. 395-410, 2017.

[5] R. Glückler, et al., "Wildfire history of the boreal forest of south-western Yakutia (Siberia) over the last two millennia document by a lake-sediment charcoal record," Biogeosciences , vol. 18, pp. 4185-4209, 2021.

[6] E. Dietze, et al., "Relationships between low-temperature fires, climate and vegetation during three late glacials and interglacials of the last 430 kyr in northeastern Siberia reconstructed from monosaccharide anhydrides in Lake El'gygytygyn sediments," Climate of the Past, vol. 16, pp. 799-818, 2020.

How to cite: Robinson, J., Homann, J., Umbo, S., Scott, P., Nehrke, G., Hoffmann, T., Vaks, A., Kononov, A., Osintsev, A., Mason, A., A. Lechleitner, F., M. Henderson, G., and F. M. Breitenbach, S.: Reconstruction of Holocene wildfire occurrence using levoglucosan and lignin biomarkers from Siberian stalagmites, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10202, https://doi.org/10.5194/egusphere-egu22-10202, 2022.

13:43–13:52
13:52–13:57
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EGU22-6078
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ECS
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Presentation form not yet defined
Stuart Umbo, Julia Homann, Franziska Lechleitner, Sevi Modestou, Alexander Kononov, Alexander Osintsev, Vaks Anton, Andrew Mason, Gideon Henderson, and Sebastian Breitenbach

The Miocene provides one of the best analogues for near future anthropogenic warming — with atmospheric CO2 concentrations similar, or slightly higher than present, warmer global temperatures (Steinthorsdottir et al., 2021), and a summer ice-free Arctic (Stein et al., 2016). Yet discrepancies still persist between the proxy record and model reconstructions (Steinthorsdottir et al., 2021), highlighting the need for chronologically well constrained and sensitive proxy records to aid our understanding of the underlying forcings of Miocene palaeoclimate and regional environmental response to climatic changes. Particularly sparse proxy coverage in the Siberian Arctic (Popova et al., 2012; Pound et al., 2012; Steinthorsdottir et al., 2021) hampers reconstruction of Miocene temperatures and hydrological dynamics in the northern hemisphere, despite the region being home to the globe’s largest extent of continuous permafrost – a key climate tipping element likely to play a significant role in future climate trajectories (Steffen et al., 2018).

Here we use U/Pb dated speleothem samples from Taba Bastaakh (72°15' N, 126°56' E), situated on the eastern bank of the river Lena in northern Siberia, to gain insights into climatic conditions during the Tortonian. The calcitic speleothems most likely formed under vadose conditions and have been U/Pb dated to 8.7 ± 0.6 Ma. Our multiproxy speleothem study utilises conventional (ẟ13C, ẟ18O, and trace elements) and novel (lignin and levoglucosan biomarkers and ẟ13C of non-purgeable organic carbon) environmental indicators to derive information on atmospheric circulation, local hydrology, wildfire occurrence, and vegetation regime. Macroscopically visible layers align with cyclic isotopic shifts of ca. 0.8 ‰ in ẟ13C (-9.8 ‰ to -8.6 ‰) and 1.6 ‰ in ẟ18O (-16.6 ‰ to -15 ‰). Oxygen isotope compositions are similar to those of southern Siberia in the modern day – indicative of a warmer, strongly seasonal environment. Carbon isotopes suggest a large organic component.

Stable isotopes have been measured at NICEST lab Northumbria University, biomarkers at JGU Mainz, ẟ13C NPOC at the University of Bern, and U/Pb dating in the Oxford geochronological lab.

 

References

Popova et al. (2012). Palaeoclimate evolution in siberia and the Russian far east from the oligocene to pliocene - evidence from fruit and seed floras. Turkish Journal of Earth Sciences, 21(2), 315–334.

Pound et al. (2012). Global vegetation dynamics and latitudinal temperature gradients during the Mid to Late Miocene (15.97-5.33Ma). Earth-Science Reviews

Steffen et al. (2018). Trajectories of the Earth System in the Anthropocene. Proceedings of the National Academy of Sciences of the United States of America, 115(33), 8252–8259.

Stein et al. (2016). Evidence for ice-free summers in the late Miocene central Arctic Ocean. Nature Communications, 7.

Steinthorsdottir et al. (2021). The Miocene: The Future of the Past. Paleoceanography and Paleoclimatology, 36(4).

How to cite: Umbo, S., Homann, J., Lechleitner, F., Modestou, S., Kononov, A., Osintsev, A., Anton, V., Mason, A., Henderson, G., and Breitenbach, S.: A late Miocene seasonality and wildfire record from northern Siberia utilising novel speleothem proxies, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6078, https://doi.org/10.5194/egusphere-egu22-6078, 2022.

13:57–14:02
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EGU22-499
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ECS
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On-site presentation
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Ramesh Glückler, Rongwei Geng, Lennart Grimm, Izabella Baisheva, Ulrike Herzschuh, Stefan Kruse, Andrei Andreev, Thomas Böhmer, Stuart Vyse, Luidmila Pestryakova, and Elisabeth Dietze

The year 2021 set new records for wildfire extent in the Republic of Sakha (Yakutia) in eastern Siberia, Russia. Wildfire seasons in this unique region, characterized by its deciduous boreal forest and permafrost landforms, are becoming more intense. Some fires are threatening local communities, while their smoke covers vast stretches of land every summer, posing health risks to people even in the distance. At the same time, the larch trees of the eastern Siberian boreal forest stabilize the permafrost soils below as guardians of a continental-scale storage of terrestrial carbon. It is still largely unknown how the current trend of wildfire intensification will develop in the future, and how it will modify the structure of the boreal forests within the next decades to centuries. However, even though needed for a well-founded evaluation of long-term impacts of changing fire regimes, data on past trends of wildfire activity still remains scarce in eastern Siberia.

Here, we present a new reconstruction of boreal fire and vegetation dynamics, spanning the last ca. 10.8 ka. Continuously analyzed macroscopic charcoal particles and a REVEALS-transformed pollen record from a sediment core from Lake Satagay (N 63.078, E 117.998) give insight into long-term trends and relationships between changes in fire regime and vegetation composition and coverage. The data indicates that modern larch-dominated forests co-exist with a lower severity fire regime, whereas early Holocene open larch-birch woodlands enabled increased charcoal accumulation and thus supported a higher severity fire regime. Considering the expected increase in tree mortality caused by wildfires and insect damage, likely to thin out currently denser tree stands, this fire-vegetation relationship suggests a potential upcoming positive feedback on intensifying fire regimes.

How to cite: Glückler, R., Geng, R., Grimm, L., Baisheva, I., Herzschuh, U., Kruse, S., Andreev, A., Böhmer, T., Vyse, S., Pestryakova, L., and Dietze, E.: Fires and forests: A reconstruction of Holocene fire-vegetation relationships in Central Yakutia, Siberia, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-499, https://doi.org/10.5194/egusphere-egu22-499, 2022.

14:02–14:07
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EGU22-2792
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Virtual presentation
The Holocene climate changes, fire history and palsa peatland dynamics: case study from Yenisei Siberia
(withdrawn)
Elena Novenko, Natalia Mazei, Dmitry Kupryanov, Anatoly Prokushkin, Anton Shatunov, Rodion Andreev, Ekaterina Makarova, and Sergey Serikov
14:07–14:12
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EGU22-2937
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ECS
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On-site presentation
Alicja Bonk, Claire M. Belcher, and Wojciech Tylmann

Variations in wildfire are a hot topic due to concerns linked to the current climate crisis. Although an increasing number of studies focus on how the coupled climate and anthropogenic forcings influence fire frequency and behaviour in highly fire-prone regions, there has been less research in more temperate ecosystems.

Analyzing charcoal records yields insights into the fire regimes in a given area, including the fire frequency, type, and intensity. Recent research suggests that measuring the amount of light reflected from charcoals can provide information about the energy flux during the pyrolysis of plant material, which can be further translated into a proxy for fire intensity. To assess the use of reflectance as a post-fire tool for palaeofire intensity reconstructions, we used annually laminated (varved) sediment record from Lake Żabińskie, north-eastern Poland.

We provide both quantitative macrocharcoal, and charcoal reflectance measurements of individual charcoal particles as well as semi-quantitative morphotypes analysis. These data were compared with palynological analysis of the vegetation shifts and evidence for the impact of humans in the lake area. Our preliminary research indicates that lower reflectance measurements (mean value around 1%) most likely relate to the litter fires as the charcoals show features of biodegradation before the fire. Higher values (mean 1-3%) represent surface understory fires (undergrowth burning) while the highest reflectance values (mean >3%) can be related to the crown fires. Our measurements are the first of this kind in this part of the world.

How to cite: Bonk, A., Belcher, C. M., and Tylmann, W.: Is charcoal reflectance a palaeofire intensity proxy?, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2937, https://doi.org/10.5194/egusphere-egu22-2937, 2022.

14:12–14:21
14:21–14:26
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EGU22-7050
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Presentation form not yet defined
Angelica Feurdean and Johannes Tintner

Wildfires can have major impacts on terrestrial ecosystems and climate. The analysis of charcoal fragments in peat and lake sediments is the most widely used approach to reconstruct past biomass burning and fire regimes. This method typically relies on the quantification of the total charcoal content of the sediment. However, there is an increasing effort to use morphologies (finer anatomical features) and morphometrics (length: width ratio) of charcoal particles to advance our understanding of fuel burnt and fire types. We used experimental burnings in the laboratory for plant species from boreal Siberia, which are also commonly found in the Northern Hemisphere, to expand the reference datasets on morphological distinctions between species or fuel types. We also tested the effect of burning temperature (five temperature categories ranging from 250 to 450 °C) on char mass and morphometrics of charred plant material. We found that graminoid charcoal particles are most elongate (6.7-11.5), leaves are the shortest and bulkiest (2.1-3.5) while twigs and wood are intermediate (2.0-5.2). Our findings correspond well to the few existing comparable experimental measurements. Further, the use of fine charcoal features was successful in separating wood, graminoids, and leaves, but it was difficult to further differentiate these fuel types i.e., leaves and wood from trees and shrubs, due to overlapping features. In terms of charred mass, graminoids, Sphagnum, and wood (trunk) lose the most mass at low burn temperatures (<300°C), whereas heathland shrub leaves, brown moss, and ferns at high burn temperatures. Ongoing work applying micro-Fourier Transformed Infrared Spectroscopy (FTIR) on both modern charred particles produced at different temperature ranges and fossil charcoal will help estimate the pyrolysis temperature and fuel type. Similarly, our focus is to expand reference datasets on charcoal morphologies and FTIR to other major biomes, particularly grasslands. We also highlight the further investigations into charcoal experimental studies needed to refine the histories of past wildfires.

How to cite: Feurdean, A. and Tintner, J.: Charcoal morphologies to discriminate fuel source and fire temperatures, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7050, https://doi.org/10.5194/egusphere-egu22-7050, 2022.

14:26–14:31
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EGU22-6249
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On-site presentation
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Elisabeth Dietze, Vivien Reichel, Andrei Andreev, Simeon Lisovski, Kai Mangelsdorf, Tabea Tessendorf, Jasmin Weise, Volker Wennrich, and Ulrike Herzschuh

The ongoing intensification of forest fires in the Siberian Arctic (larger areas, longer durations, higher intensities) raises concerns if these fires might lead to biome shifts from tundra to summergreen or evergreen boreal forest – with consequences for regional to global biophysical land properties and biogeochemical cycles. Given the short time span of instrumental observations, it is unknown if fire can initiate or support biome shifts under the ongoing amplified warming or if climate drives fire regime and biome changes independently. Lake El’gygytgyn in the Russian Far East is currently surrounded by tundra, but pollen data (ICDP sediment core 5011-1A) suggests that during late Marine Isotope Stage (MIS) 12 and “superinterglacial” MIS 11, c. 375-440 kyrs ago biomes changed several times:  from a glacial steppe to interglacial summergreen and evergreen boreal forest. Here, we investigate if and which type of fire regime shifts accompanied these biome shifts.

To enable a quantitative reconstruction of changes in fire intensities and the type of biomass burnt, we used multiple fire proxies. The monosaccharide anhydrides (MAs) are specific biomass burning residues from low-temperature fires analyzed with ultra-high-performance liquid chromatography coupled to a high-resolution mass spectrometer. Sedimentary charcoal reflects mid-to-high intensity fires and was analyzed in sieved fraction > 150 μm and from pollen slides using a microscope. MA isomer ratios and charcoal morphotypes were used to reconstruct the type of biomass burnt. We established links between fire proxy composition and pollen-based vegetation composition for the MIS 11 using core 5011-1A sediments considering dating uncertainties.

To link fire proxy composition with fire regime properties, we used the same fire proxies in modern lake surface sediments from three lakes in Eastern Siberia. We assessed modern charcoal and MA source areas by modelling lake-sedimentary fire proxy transport from modern fires using fire radiative power data of the MODIS Thermal Anomalies product, plume injection heights from the MODIS Terra and Aqua MCD19A2 data and hourly wind fields from ERA5 climate data.

We find clear differences in sedimentary fire proxy composition depending on source area of charcoals and MAs in modern lake sediments. Modern types of fire regime-fire proxy-vegetation-relationships are linkable to the derived past interglacial relationships indicating that fire regime change played a role during some, but not all biome shifts. Overall, we provide new understanding of Siberian sedimentary fire proxies, crucial for a sound, i.e. quantitative reconstruction of long-term fire regime change, allowing to assess the role of fire regime intensification in biome changes during periods of stark warming.

How to cite: Dietze, E., Reichel, V., Andreev, A., Lisovski, S., Mangelsdorf, K., Tessendorf, T., Weise, J., Wennrich, V., and Herzschuh, U.: Towards quantitative interglacial fire-vegetation-climate feedbacks: linking sedimentary fire proxy composition of marine isotope stage 11 (Lake El’gygytgyn) and modern lake surfaces (E Siberia), EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6249, https://doi.org/10.5194/egusphere-egu22-6249, 2022.

14:31–14:36
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EGU22-13424
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Virtual presentation
Grant Snitker and Dexter Strother

Differentiating between natural and anthropogenic fire activity in the past remains one of the principal challenges in interpreting paleo-charcoal records and has implications for contextualizing changing fire regimes in our world today. During the Holocene, cultural burning practices throughout the globe were motivated by diverse social institutions, values, and economics; however, the frequency, seasonality, spatial distribution, and ecological severity of global anthropogenic fire likely differed enough from natural fire to generate lasting ecological effects. Similarly, prescribed fire operations conducted by federal land managing agencies in the United States are modern examples of cultural burning to achieve desired ecological outcomes. Nonetheless, relatively few studies have utilized prescribed fires as laboratories for testing methods to interpret anthropogenic fire activity in charcoal records. In this paper, we present the results of a comprehensive study of charcoal production and morphology collected during a series of highly instrumented prescribed fires that occurred during March 2021 within the Hitchiti Experimental Forest, Georgia, USA. We relate both field-collected and lab-created charcoal datasets to pre-/post-burn vegetation inventories, thermal images capturing fire behavior, and radiometric measurement of energy release collected at 12 study plots throughout the burn area. Using this approach, we seek to expand the interpretive potential of paleo-charcoal records for identifying past anthropogenic fire activity similar to the frequent, low-severity prescribed fires practiced by land managers today.

How to cite: Snitker, G. and Strother, D.: Expanding the interpretation of anthropogenic fire in the paleo-charcoal record through modern prescribed fires: A study of charcoal production and morphology during the 2021 Hitchiti Experimental Forest prescribed fire campaign, Georgia, USA, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13424, https://doi.org/10.5194/egusphere-egu22-13424, 2022.

14:36–14:41
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EGU22-4181
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ECS
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Virtual presentation
A comprehensive assessment of palaeowildfire activity across the Danian-C2 hyperthermal event by means of Raman spectroscopy-geothermometry
(withdrawn)
Thomas Theurer, David Muirhead, David Jolley, and Dmitri Mauquoy
14:41–14:50