CL5.1.3

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 6–7 °C at ca. 23 thousand years ago (ka) and 4–5 °C at ca. 16–13 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.

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.

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^-, SO₄^2- and Na⁺ and it is undersaturated in gypsum (SI_gyp<-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.

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.

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.

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.

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.

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.

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.

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.

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 20^th 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.

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.

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.

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.

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.

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.

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.

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.

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 

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.

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.

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.

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.

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.