Laura Endres

Last Name

Endres

First Name

Laura

ORCID

0000-0002-5013-4811

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09601 - Stoll, Heather / Stoll, Heather

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Publications1 - 8 of 8

Distinguishing the combined vegetation and soil component of δ13C variation in speleothem records from subsequent degassing and prior calcite precipitation effects
Stoll, Heather M.; Day, Chris; Lechleitner, Franziska; et al. (2023)
Climate of the Past
The carbon isotopic signature inherited from soil and epikarst processes may be modified by degassing and prior calcite precipitation (PCP) before its imprint on speleothem calcite. Despite laboratory demonstration of PCP effects on carbon isotopes and increasingly sophisticated models of the governing processes, to date, there has been limited effort to deconvolve the dual PCP and soil-epikarst components in measured speleothem isotopic time series. In this contribution, we explore the feasibility, advantages, and disadvantages of using trace element ratios and δ⁴⁴Ca to remove the overprinting effect of PCP on measured δ¹³C to infer the temporal variations in the initial δ¹³C of drip water prior to degassing and PCP. In nine examined stalagmites, the most widely utilized PCP indicators Mg/Ca and δ⁴⁴Ca covary as expected. However, Srg/gCa does not show consistent relationships with δ⁴⁴Ca so PCP is not the dominant control on Srg/gCa. From δ⁴⁴Ca and Mg/Ca, our calculation of PCP as f_Ca, the fraction of initial Ca remaining in solution at the time the stalagmite layer is deposited, yields multiple viable solutions depending on the assumed δ⁴⁴Ca fractionation factor and inferred variation in DMg. Uncertainty in the effective fractionation of δ¹³C during degassing and precipitation contributes to uncertainty in the absolute value of estimated initial δ¹³C. Nonetheless, the trends in initial δ¹³C are less sensitive to these uncertainties. In coeval stalagmites from the same cave spanning the 94 to 82 ka interval, trends in calculated initial δ¹³C are more similar than those in measured δ¹³C and reveal a common positive-Anomaly initial δ¹³C during a stadial cooling event. During deglaciations, calculated initial δ¹³C implies a trend of greater respiration rates and higher soil CO₂, although the higher interglacial drip water saturation favors more extensive PCP. Initial δ¹³C can be estimated for active and fossil speleothems from a range of settings, wherever there is confidence that Mg/Ca and/or δ⁴⁴Ca provides a quantitative indication of past changes in PCP. Further study of Mg partitioning in speleothems will improve the robustness of Mg/Ca as a PCP proxy.
Accelerated phosphorous leaching during abrupt climate transitions in a temperate Atlantic ecosystem in Northwest Spain recorded by stalagmite P / Ca variations
Tapia , Nicolas; Endres, Laura; Jaggi , Madalina; et al. (2025)
Biogeosciences
In natural ecosystems, phosphorus cycling regulates terrestrial productivity and may respond to climate variations. Seasonal to several year monitoring studies capture the short-Term controls on P release but may miss longer term feedbacks. There is an important observational gap of the centennial to millennial scale response of the P cycle to climate oscillations. Cave carbonates such as stalagmites and flowstones, which precipitate from infiltrating groundwater, may record past changes in P loss on these timescales. Here, we examine trends in P/Ca ratios in four coeval stalagmites from coastal caves in NW Iberia during two climate transitions, the Penultimate Glacial Maximum through the Last Interglacial (145 to 118 kyr BP) and an intermediate glacial climate state interrupted by an abrupt cooling event of the Greenland Stadial 22 (92 to 80 kyr BP). We conduct sensitivity tests with a model to assess the degree to which drip water pH and in-cave drip water chemical evolution could affect the stalagmite P/Ca record. Both during the last deglaciation and during Greenland Stadial 22, we find large (3-10-fold) transient increases in stalagmite P/Ca at the onset of abrupt cooling events and during the rapid recovery from some events. These increases are much larger than can be explained by variations in P incorporation due to drip water pH or in-cave chemical evolution and likely reflect significantly increased drip water P/Ca ratios at the onset and end of abrupt stadial events. Two climatic factors may contribute to this increased leaching. First, soil temperatures may reach minimum values during these transition states, if the temperature minimum leads to increased thickness and duration of snow cover which raises soil temperatures. Minimum winter soil temperature suppresses microbial recycling of P. Second, the transitions into and out of stadial events may feature the highest frequency of freeze-Thaw events which change the physical soil structure and lead to stronger spring flushing of P. Additionally, during cooling, reduced soil respiration rates may raise the pH of soil water and lead to increased mobility of P bound to soil minerals.
Relationship of seasonal variations in drip water δ13CDIC, δ18O, and trace elements with surface and physical cave conditions of La Vallina cave, NW Spain
Kost, Oliver; González-Lemos, Saúl; Rodríguez-Rodríguez, Laura; et al. (2023)
Hydrology and Earth System Sciences
Cave-monitoring studies clarify the climatic, surface vegetation, and karst processes affecting the cave system and lay the foundation for interpreting geochemical stalagmite records. Here we report the monitoring of cave air, bedrock chemistry, and drip water δ13CDIC, δ18O, and δD, as well as 16 trace elements, covering a full annual cycle spanning the 16 months between November 2019 and March 2021 in La Vallina cave in the northwestern Iberian Peninsula. While decreased rainfall and increased evapotranspiration in the summer months lead to a strong reduction in drip rates, there is little seasonal variation in δ18O and δD in a given drip, likely reflecting the discrete moderately mixed to well-mixed karst water reservoirs. Small differences in δ18O and δD between drip sites are attributed to variable evaporation intensity and/or transit times. The carbon isotope signature of the dissolved inorganic carbon of drip water (δ13CDIC) is likely driven by seasonal changes in the temperature controlling biological processes (vegetation and microbial soil activity), resulting in minimum δ13CDIC in summer and autumn months. Increased bedrock dissolution due to higher soil pCO2 in summer and autumn results in increased trace element concentrations of congruently dissolved elements. Cave air measurements (pCO2, δ13Cair, and temperature) indicate the seasonal ventilation (winter) and stagnation (summer) of cave air. The opposite effects of reduced cave air pCO2, seasonally variable biological activity, and increased drip rate limit the extent of the seasonal variation in degassing and prior calcite precipitation (PCP) supported by trace elements ( index). Estimated stalagmite growth rates using monitoring data suggest biannual phases of potential calcite precipitation in summer and winter and growth cessation during spring and autumn, depending on cave and drip water conditions and the location within the cave, which has important implications for the proxy interpretation of stalagmite records.
SISALv3: a global speleothem stable isotope and trace element database
Kaushal, Nikita; Lechleitner, Franziska A.; Wilhelm, Micah; et al. (2024)
Earth System Science Data
Palaeoclimate information on multiple climate variables at different spatiotemporal scales is becoming increasingly important to understand environmental and societal responses to climate change. A lack of high-quality reconstructions of past hydroclimate has recently been identified as a critical research gap. Speleothems, with their precise chronologies, widespread distribution, and ability to record changes in local to regional hydroclimate variability, are an ideal source of such information. Here, we present a new version of the Speleothem Isotopes Synthesis and AnaLysis database (SISALv3), which has been expanded to include trace element ratios and Sr isotopes as additional, hydroclimate-sensitive geochemical proxies. The oxygen and carbon isotope data included in previous versions of the database have been substantially expanded. SISALv3 contains speleothem data from 365 sites from across the globe, including 95 Mg / Ca , 85 Sr / Ca , 52 Ba / Ca , 25 U / Ca , 29 P / Ca , and 14 Sr-isotope records. The database also has increased spatiotemporal coverage for stable oxygen (892) and carbon (620) isotope records compared with SISALv2 (which consists of 673 and 430 stable oxygen and carbon records, respectively). Additional meta information has been added to improve the machine-readability and filtering of data. Standardized chronologies are included for all new entities along with the originally published chronologies. Thus, the SISALv3 database constitutes a unique resource of speleothem palaeoclimate information that allows regional to global palaeoclimate analyses based on multiple geochemical proxies, permitting more robust interpretations of past hydroclimate and comparisons with isotope-enabled climate models and other Earth system and hydrological models. The database can be accessed at 10.5287/ora-2nanwp4rk (Kaushal et al., 2024).
Climatic and cave settings influence on drip water fluorescent organic matter with implications for fluorescent laminations in stalagmites
Endres, Laura; Jacquin, Céline; González-Lemos, Saúl; et al. (2024)
Quaternary Research
Speleothem fluorescence can provide insights into past vegetation dynamics and stalagmite chronology. However, its origin and especially the formation of fluorescent laminations in stalagmites are poorly understood. We conducted a year-long monthly monitoring of drip water fluorescence in La Vallina Cave (northern Iberian Peninsula) and compared the results to drip water chemistry and active speleothems from the same sites. Drip waters were analyzed using fluorescence spectroscopy and parallel factor analysis (PARAFAC). The resulting five-component model indicates contributions from vegetation, microbial activity, and bedrock. Intra-site fluorescence variability is mainly influenced by changes in overlying vegetation, water reservoir time, and respiration rates. Contrary to prevailing views, we find no systematic increase in drip water fluorescence during rainy conditions across drip sites and seasonal variations in drip water fluorescence are absent at a location where present-day speleothem layers form. Our findings challenge the notion of a higher abundance of humic-like fluorescence during the rainy season as the primary cause for layer formation and suggest additional controls on drip water fluorescence, such as bedrock interaction and microbial reprocessing. We also propose that growth rate may control the dilation of the fluorescence signal in stalagmites, indicating other potential mechanisms for fluorescent layer formation.
Sound ambiences consistent with visualizations of landscape types – An evaluation
Wissen Hayek, Ulrike; Endres, Laura; Spielhofer, Reto; et al. (2018)
Journal of Digital Landscape Architecture
Using digital landscape representations for assessing people’s perceptions of the visual landscape and their preferences for alternative options of landscape change, a high simulation quality is required. Thereby, sounds can augment people’s experiencing of the demonstrated landscape. We present an approach to establish sound ambiences and to investigate their level of perceived con-sistency with visual representations of different landscape types in a laboratory experiment. The results show that sounds expected through the visual contents and sounds anticipated by partici-pants remembering similar situations need to be reproduced. For presenting a realistic sound am-bience a mix of soundmarks and of more general ambient sounds is important. Further, the sounds’ volume and dominance are decisive for the overall consistency. It is notable that people in laboratory environments seem to not always accept the volume measured in the real landscape as appropriate. Our conclusions give advice for designing audio-visual simulations. Furthermore, we provide guidance for evaluating the consistency of audio-visual stimuli for implementation in landscape preference studies.
Exploring soluble and colloidally transported trace elements in stalagmites: The strontium-yttrium connection
Sliwinski, Jakub; Kost, Oliver; Endres, Laura; et al. (2023)
Geochimica et Cosmochimica Acta
While seasonality in speleothem trace element signatures is well-documented, the parameters that control the emergence of laminations vary between elements and tend to be multi-factorial. Here, we examine a series of active and fossil stalagmites from Asturias, Spain, with a particular focus on strontium and yttrium co-variations and fluorescent laminations. Coupled confocal fluorescence scanning light microscopy (layer counting) and time scales derived from accelerated mass spectrometry (F14C) in active stalagmites confirm that fluorescent banding is annual. This banding is coincident with Y peaks and Sr troughs, which are among the most robust trace element markers of seasonality. Strontium concentrations (in particular, the strontium partition coefficient, DSr) are positively correlated with stalagmite growth rate and are likely controlled by solution supersaturation, which is in turn controlled by seasonal variations in cave ventilation. DSr can be estimated after correcting for prior calcite precipitation using coeval Mg/Ca ratios, and is consistent with both empirical and experimental values. Meanwhile, yttrium is a proxy for colloidal organic input, and its concentration in stalagmites is likely controlled by a combination of Y drip water flux, surface retention time (i.e., how long a drip and its associated organic matter are in contact with the stalagmite surface), and dilation within the matrix (hereafter referred to as “dilation”). Persistent Sr-Y anti-correlation can be explained as an interplay between the individual controls on each element, and a breakdown in this relationship may be indicative of past changes in cave ventilation and/or drip hydrology.
Miking Landscape
Schütz, Nadine; Endres, Laura (2016)
Conference Proceedings of the 29th Tonmeistertagung (tmt29)

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Laura Endres

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