Session CL1.2.2

[Programme]

CL1.2.2 | Climate of the last two millennia

Climate of the last two millennia

Co-sponsored by PAGES 2k

Convener: Andrea Seim | Co-conveners: Daniel BoatengECSECS, Jun HuECSECS, Hugo Beltrami, Stefan Bronnimann

Orals

| Mon, 28 Apr, 14:00–15:45 (CEST)

Room 0.31/32

Posters on site

| Attendance Mon, 28 Apr, 16:15–18:00 (CEST) | Display Mon, 28 Apr, 14:00–18:00

Hall X5

This session aims to place recently observed climate change in a long-term perspective by highlighting the importance of paleoclimate research spanning the past 2000 years. We invite presentations that provide insights into past climate variability, over decadal to millennial timescales, from different paleoclimate archives (ice cores, marine sediments, terrestrial records, historical archives and more). In particular, we are focussing on quantitative temperature and hydroclimate reconstructions, and reconstructions of large-scale modes of climate variability from local to global scales. This session also encourages presentations on the attribution of past climate variability to external drivers or internal climate processes, data syntheses, model-data comparison exercises, proxy system modelling, and novel approaches to producing multi-proxy climate field reconstructions such as data assimilation or machine learning.

The presentation by Jason Smerdon will be held online (virtual presentation).

Orals: Mon, 28 Apr | Room 0.31/32

Chairpersons: Daniel Boateng, Stefan Bronnimann, Andrea Seim

14:00–14:05

5-minute convener introduction

14:05–14:15

EGU25-2591

ECS

Highlight

On-site presentation

A shift in South Pacific hydroclimate over the last 1500 years driven by tropical Pacific variability

Daniel Skinner, Mark Peaple, Gordon Inglis, Manoj Joshi, Peter Langdon, Adrian Matthews, Timothy Osborn, Jean-Yves Meyer, and David Sear

The South Pacific Convergence Zone (SPCZ) is a critical region of intense precipitation, particularly during the austral summer (November—March), situated in the tropical Pacific Ocean. This region is known to be highly sensitive to variations in sea surface temperatures (SSTs) across the Pacific. Previous research has demonstrated that decadal-scale shifts in the SPCZ are influenced by SST variability, but our understanding of longer-term changes—spanning multi-decadal to millennial timescales—remains limited. These constraints arise from the scarcity of high-resolution hydroclimate proxy records and systemic biases in even state-of-the-art coupled climate models.

To address this knowledge gap, we combine newly developed hydroclimate proxies (from Nuku Hiva and Tahiti, French Polynesia) with previously established proxies and novel climate model simulations to explore SPCZ dynamics over the last 1500 years. Our findings provide new insights into centennial- and millennial-scale precipitation variability and its potential drivers.

Our proxy data indicate a spatial shift in SPCZ precipitation patterns from 1000 yrs BP to 200 yrs BP. During this interval, the eastern SPCZ experienced a significant increase in precipitation, whilst the western SPCZ underwent notable drying. This north-eastward shift in precipitation was likely driven by changes in Pacific SST gradients, as shown by our climate model simulations and proxy SST reconstructions. Our modelling results show that a previously hypothesised weakening of the tropical Pacific zonal SST gradient is consistent with our new proxy reconstructions and offer a plausible mechanism for the observed hydroclimatic shifts.

An intriguing corollary of our study is the coincidence of this millennial-scale hydroclimatic changes with key events in human history. The eastward shift in SPCZ precipitation overlaps temporally with the Polynesian colonization of the eastern SPCZ region, including islands such as the Marquesas, and eventually Hawaii. This suggests a potential linkage between climate-driven changes in the SPCZ and patterns of human migration and settlement. Enhanced precipitation in the eastern SPCZ would have likely improved freshwater availability, agricultural potential, and overall habitability of these islands, potentially facilitating successful colonization. Conversely, drier conditions in the western SPCZ may have influenced resource pressures, encouraging exploration and eastward movement.

Ultimately, these findings emphasize the need for continued development of high-resolution proxies and improvements in coupled climate models to deepen our understanding of long-term Pacific region climate dynamics and their societal impacts.

How to cite: Skinner, D., Peaple, M., Inglis, G., Joshi, M., Langdon, P., Matthews, A., Osborn, T., Meyer, J.-Y., and Sear, D.: A shift in South Pacific hydroclimate over the last 1500 years driven by tropical Pacific variability, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-2591, https://doi.org/10.5194/egusphere-egu25-2591, 2025.

14:15–14:25

EGU25-16236

ECS

On-site presentation

CoolinG oveR thE VicToria LAnd (GRETA): resolving the Ross Sea response to continental climate change during the last two millennia

(withdrawn)

Fiorenza Torricella, Francesca Battaglia, Simon Belt, Lucilla Capotondi, Florence Colleoni, Ester Colizza, Leonardo Langone, Patrizia Giordano, Gesine Mollenhauer, Jens Hefter Hefter, Enrico Pochini, Mathia Sabino, and Tommaso Tesi

14:25–14:35

EGU25-15801

ECS

On-site presentation

Multi-proxy speleothem record from continental Croatia as an archive of Late Holocene palaeoclimate variability

Iva Palatinuš, Petra Bajo, Vlatko Brčić, Maja Briški, Hai Cheng, Russell Neil Drysdale, John Hellstrom, Philip Hopley, Christoph Spötl, Maša Surić, Pauline Treble, Hubert Vonhof, and Jia Xue

The Late Holocene is characterized by several short-term climate anomalies recorded widely in various natural climate archives. However, the lack of consensus on their temporal and spatial occurrence (Neukom et al., 2019) highlights the need for high-resolution archive data as they may provide information on the magnitude and timing of these events, helping to address the gaps in our understanding of the climate over the past two millennia. Given the scarcity of high-resolution palaeoclimate records in South Central Europe, we aim to reconstruct the climate conditions over the past ~1500 years by using multi-proxy records of a speleothem from the Nova Grgosova Cave in Croatia.

A floating lamina-based chronology was acquired and supported by 15 U-Th dates to construct an age-depth model of the NG-2 stalagmite. The model reveals several distinct growth phases. The slowest growth rate ( ̴ 0.01 mm/yr) was observed during the period corresponding to the Little Ice Age from ca. 1625 to 1830 CE and partially overlapping the Medieval Climate Anomaly, from ca. 710 to 1060 CE. In comparison, the stalagmite grew ten times faster from ca. 1060 to 1625 CE and ca. 535 to 710 CE, while the fastest growth rate was observed during the last ca. 185 years ( ̴ 0.2 mm/yr).

Cave monitoring observations revealed that speleothem growth is enhanced during the cooler part of the year due to increased infiltration and dripwater degassing in a CO₂-depleted cave atmosphere (Bajo et al., 2024). Accordingly, the speleothem geochemical properties most likely reflect the cooler part of the year. The stable isotope data coupled with trace element records suggest that the condensed growth phases reflect drier and/or cooler environmental conditions. Alongside, petrographical analysis revealed alterations of crystal fabrics, which are presumably a result of seasonal changes in hydrological conditions and/or geochemical properties of the dripwater. Thin sections exhibit large columnar crystals, however, to construct a stratigraphic log, the columnar fabric was further subdivided into columnar compact, columnar open, columnar elongated, micrite and microsparite fabrics. The latter two suggest microbial activity and diagenetic origin (Frisia, 2015), which is yet to be discussed.

These findings, combined with other palaeoclimate records from South Central Europe and beyond, provide a better understanding of the spatial extent and duration of the regional climate conditions over the past two millennia.

References:

Bajo, P., Briški, M., Benutić, A., Piplica, A., Brčić, V., Marciuš, B., Palatinuš, I., Stroj, A. (2024): Seasonality in cave dripwater and air properties – implications for speleothem palaeoclimatology, Nova Grgosova Cave (Croatia). Geologia Croatica, 77(3), 243–251.

Frisia, S. (2015): Microstratigraphic logging of calcite fabrics in speleothems as tool for palaeoclimate studies. International Journal of Speleology, 44(1), 1–16.

Neukom, R., Steiger, N., Gómez-Navarro, J.J., Wang, J., Werner, J.P. (2019): No evidence for globally coherent warm and cold periods over the preindustrial Common Era. Nature, 571, 550–554.

How to cite: Palatinuš, I., Bajo, P., Brčić, V., Briški, M., Cheng, H., Drysdale, R. N., Hellstrom, J., Hopley, P., Spötl, C., Surić, M., Treble, P., Vonhof, H., and Xue, J.: Multi-proxy speleothem record from continental Croatia as an archive of Late Holocene palaeoclimate variability, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-15801, https://doi.org/10.5194/egusphere-egu25-15801, 2025.

14:35–14:45

EGU25-17258

ECS

On-site presentation

Reconstructed summer temperature variability in the Caucasus since 1613 CE and its relevance for continental-scale climate dynamics

Lea Schneider, Rupesh Dhyani, Dario Martin-Benito, and Ekaterina Dolgova

While temperature history has been extensively studied in other parts of the Alpide belt, such as the Pyrenees, the Alps or the Himalaya, the Caucasus region remains underrepresented in paleoclimate research. This gap is evident in large-scale proxy compilations such as the NTREND (tree-rings) or the PAGES2k (multi-proxy) datasets as well as in climate reconstructions based on these compilations. Here, we present a reconstruction of summer temperature variability extending back to 1613 CE, derived from a network of six tree-ring Blue Intensity chronologies collected from upper treelines in the Greater and Lesser Caucasus. The reconstruction explains over 50% of the observed summer temperature variability, captures the signature of global warming, and reveals volcanic forcing signals. However, the network exhibits disagreement regarding the intensity of the Little Ice Age. Our record correlates with temperature reconstructions from Greece and Turkey, but shows an inverse relationship at higher frequencies with Western European temperature records. When combined with reconstructions from northwestern Russia, our data aligns with the East Atlantic/Western Russia (EA/WR) pattern, an atmospheric mode characterized by a temperature dipole over Europe. In its positive phase, this pattern generates cold anomalies over western Russia, the Caucasus and Turkey, accompanied by above-average temperatures in France and parts of Spain. We investigate the temperature dipole associated with the EA/WR pattern during the pre-industrial period across various frequency domains. Our findings offer valuable insights into historical climate dynamics across Europe and serve as a benchmark for evaluating the representation of the EA/WR pattern in climate model simulations.

How to cite: Schneider, L., Dhyani, R., Martin-Benito, D., and Dolgova, E.: Reconstructed summer temperature variability in the Caucasus since 1613 CE and its relevance for continental-scale climate dynamics, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17258, https://doi.org/10.5194/egusphere-egu25-17258, 2025.

14:45–14:55

EGU25-19354

ECS

On-site presentation

Regional Climate of the last 2500 years in the Eastern Mediterranean and Middle East

Eva Hartmann, Elena Xoplaki, and Sebastian Wagner

The climate of the eastern Mediterranean and the Middle East is well documented through natural archives, such as speleothems, tree rings, sediments and pollen, as well as historical human records. The period from 500 BCE to 1850 CE is particularly intriguing from both historical and climatic perspectives. This era encompasses the prosperity and decline of the Byzantine and Roman Empires, the Middle Ages, the Little Ice Age, and the onset of industrialization, as well as significant events like plague pandemics and pronounced climate variability. Dynamical downscaling can bridge the gap between palaeo-records, which often contain uncertainties from different sources but may also have very high spatial resolution, and the coarsely resolved Earth System Models (ESMs). A transient paleo-simulation using the regional climate model COSMO-CLM (CCLM, COSMO 5.0 clm16) with adjusted forcings is conducted for the period 500 BCE - 1850 CE to explore potential interactions and feedbacks between climate variability and socio-political and/or economic conditions. The model as well as the driving MPI-ESM-LR incorporates forcing reconstructions based on the framework of the international climate model comparison project CMIP6, including volcanic (stratospheric aerosol optical depth), orbital (eccentricity, obliquity, precession), solar (irradiance), land-use and greenhouse-gas changes. The simulated temperature and precipitation outputs are compared with those of other CMIP6 models and validated against proxy records and reconstructions, enhancing our understanding of climate-society dynamics in this historically pivotal region.

How to cite: Hartmann, E., Xoplaki, E., and Wagner, S.: Regional Climate of the last 2500 years in the Eastern Mediterranean and Middle East , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-19354, https://doi.org/10.5194/egusphere-egu25-19354, 2025.

14:55–15:05

EGU25-3593

ECS

On-site presentation

Climate variability and the Late Bronze Age collapse in the Peloponnese: Insights from Holocene transient simulations

Katherine Power and Qiong Zhang

The Late Bronze Age (LBA) collapse (1350–1050 BCE) marked a period of profound societal upheaval across the ancient Mediterranean, including the decline of Mycenaean civilization in the Peloponnese. While traditionally attributed to invasions by the "Sea Peoples," emerging paleo-climate evidence suggests that severe and prolonged droughts played a significant role in this collapse. A key methodology for exploring unknown past climate conditions is the use of Holocene transient simulations. This study evaluates the extent to which three Holocene transient climate simulations (MPI-ESM, TraCE-21ka, and EC-Earth3 8K) capture the prolonged arid conditions observed in regional proxies during the LBA collapse. The EcEarth and MPI models agree with lake and marine sediment, stalagmite and tree ring proxy data from across the wider region, revealing a prolonged drying trend for the Balkan area from 4800 until 1000 BCE. Focusing in on the Peloponnese region, EcEarth and MPI models agree well with the Mavri Trypa Cave δ18O record, indicating an unstable climate with extended drought periods from 1600 until 1100 BCE and recording abrupt dry pulses following 1250 BCE. The TraCE simulation, however, exhibits relatively stable behaviour, showing no marked shifts toward either wet or dry extremes during the entire period. We establish that due to differences in resolution and model parametrization, MPI and EC-Earth provide a more realistic simulation of the dynamic and variable climate conditions during the Holocene period in the Aegean region, particularly with respect to capturing prolonged droughts and abrupt climatic shifts, while TraCE seems to oversimplify these variations. From the EcEarth model, we establish that droughts in the Peloponnese and Balkan region, in the period prior to and during the LBA collapse, were a result of cooling Mediterranean sea surface temperatures, that reduced moisture into the regions hydrological cycle, supporting proxy evidence. This cooling was ultimately driven by a weakening AMOC. By drawing parallels between the LBA collapse and contemporary climate challenges, the study underscores the importance of understanding how current and future climate variability could lead to similar societal disruptions, urging policymakers to incorporate historical insights into modern climate mitigation strategies.

How to cite: Power, K. and Zhang, Q.: Climate variability and the Late Bronze Age collapse in the Peloponnese: Insights from Holocene transient simulations, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3593, https://doi.org/10.5194/egusphere-egu25-3593, 2025.

15:05–15:15

EGU25-2052

On-site presentation

Reconstructions of climate during last two millennium based on data assimilation using multiple types of proxy records

Liang Ning, Zhengyu Liu, Jian Liu, Fen Wu, Wenqing Hu, Fangmiao Xing, Kefan Chen, Yanmin Qin, Mi Yan, Chuanxi Xu, Weiyi Sun, and Qin Wen

15:15–15:25

EGU25-7521

On-site presentation

An Online Paleoclimate Data Assimilation with a Deep Learning-based Network

Lili Lei, Haohao Sun, Zhengyu Liu, Liang Ning, and Zhe-Min Tan

An online paleoclimate data assimilation (PDA) that utilizes climate forecasts from a deep learning-based network (NET) along with assimilation of proxies to reconstruct surface air temperature, is investigated here. Trained on ensemble simulations from the Community Earth System Model-Last Millennium Ensemble, the NET that has nonlinear features gains better predictive skills compared to the linear inverse model (LIM). Thus, an alternative for online PDA is to couple the NET with the integrated hybrid ensemble Kalman filter (IHEnKF). Moreover, an analog blending strategy is proposed to increase ensemble spread and mitigate filter divergence, which blends the analog ensembles selected from climatological samples based on proxies and cycling ensembles advanced by NET. To account for the underestimated uncertainties of real proxy data, an observation error inflation method is applied, which inflates the proxy error variance based on the comparison between the estimated proxy error variance and its climatological innovation. Consistent results are obtained from the pseudoproxy experiments and the real proxy experiments. The more informative ensemble priors from the online PDA using NET enhance the reconstructions than the online PDA using LIM, and both outperform the offline PDA with randomly sampled climatological ensemble priors. The advantages of online PDA with NET over the online PDA with LIM and offline PDA become more pronounced, as the proxy data become sparser. Thus, during the early period of the Common Era with limited proxy data, the online PDA with NET can play an essential role to reconstruct the temperature.

How to cite: Lei, L., Sun, H., Liu, Z., Ning, L., and Tan, Z.-M.: An Online Paleoclimate Data Assimilation with a Deep Learning-based Network, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-7521, https://doi.org/10.5194/egusphere-egu25-7521, 2025.

15:25–15:35

EGU25-14714

Virtual presentation

Climate Change and Severe Famines: Exploring the Relationship between Solar Radiation and the Dynamics of Historical Migration

Mika Ichino, Satomi Kurosu, and Kooiti Masuda

Understanding the effects of past climate change on human societies and their adaptations is vital for both historical studies and modern resilience strategies. Our previous study examined the impacts of seasonal solar radiation variations, reconstructed from diary weather records across 18 locations in Japan, on rice prices and migration during the Tenpō famine (1833–1839). We found that severe weather, as reflected in these solar radiation estimates, led to high rice prices in Osaka. Consequently, higher temporal resolution data, compared to annual or limited-season data, can be more effective for studying the impacts of climate change on society.

This study further explores how climate change affects food and economics and how stresses such as famine and grain price fluctuations impact migration, using historical weather descriptions, rice prices, and migration data. The migration data were calculated based on individual-level panel data from local population registers of four communities (current Fukushima prefecture) from 1708 to 1870. The rice price series in the local market of Aizu in the same prefecture was used to measure the annual fluctuations in local agricultural output. The monthly solar radiation was reconstructed from historical weather descriptions for three locations in the target area of Moriyama, one to the north (Yamagata), and two to the south (Nikko). A comparison of the migration data with the reconstructed monthly solar radiation indicated that after the summer solar radiation decreased significantly, the number of migrations, abscondences, and deaths increased, particularly during the Tenmei (1782-1788) and Tenpo famines.

How to cite: Ichino, M., Kurosu, S., and Masuda, K.: Climate Change and Severe Famines: Exploring the Relationship between Solar Radiation and the Dynamics of Historical Migration, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14714, https://doi.org/10.5194/egusphere-egu25-14714, 2025.

15:35–15:45

EGU25-13379

On-site presentation

Reconstructions, Reconstructions Everywhere: A humble call for a Climate Reconstruction Intercomparison Project

Jason Smerdon

The number of seasonal or annual climate reconstructions targeting the last 1000-2000 years has increased significantly over the last decade, particularly climate field reconstructions (CFRs) that provide spatially explicit estimates of multiple climate state variables such as surface temperature, precipitation, or sea level pressure. This proliferation of CFRs has been driven by multiple factors, including increasing numbers of available proxies and methodological advances. These developments have created a moment of opportunity, long in the making, in which seasonal and annual CFRs that target the last several millennia can better inform climate dynamics, model assessments, historical conditions, and characterizations of climate risks. But how accurate are these CFRs, how well do they agree with each other, and how dependent are they on different methodological and data choices? The importance of these questions will be demonstrated by comparing estimates of climate responses to large tropical eruptions derived from a state-of-the-science CFR ensemble. The results of these comparisons subsequently will be used to propose a framework for developing a climate reconstruction intercomparison project to evaluate methodological choices, data dependencies, and reconstruction agreement. This framework will include an exploration of systematic reconstruction and data protocols, as well as skill and comparison diagnostics.

How to cite: Smerdon, J.: Reconstructions, Reconstructions Everywhere: A humble call for a Climate Reconstruction Intercomparison Project , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-13379, https://doi.org/10.5194/egusphere-egu25-13379, 2025.

Posters on site: Mon, 28 Apr, 16:15–18:00 | Hall X5

Display time: Mon, 28 Apr, 14:00–18:00

Chairpersons: Jun Hu, Daniel Boateng, Hugo Beltrami

X5.124

EGU25-11351

Late Holocene climate dynamics in NW Iberian Peninsula: Exploring the Atlantic-Mediterranean interactions and paleoenvironmental impacts

Roberto Bao, Uxía Fernández-Pérez, Rafael Carballeira, Alberto Sáez, Ricardo Prego, Luisa Santos, Pedro Raposeiro, Rouven Altrogge, and Armand Hernández

The northwestern Iberian Peninsula is a climatically complex region influenced by both Atlantic and Mediterranean systems, making it a key area for studying past climate dynamics. Mountain lake ecosystems in this region are particularly sensitive to climate variability, serving as valuable archives of sedimentary records that document paleoenvironmental responses to major climatic phases. This study aims to reconstruct Late Holocene climate variability in northwestern Iberian Peninsula, with focus on clarifying the uncertainties regarding its timing and extent of climatic changes in this region. Accordingly, mountain lakes are highly sensitive to climatic fluctuations, serving as critical archives for reconstructing past climate dynamics with high temporal resolution

Lake Ocelo, an oligotrophic mountain lake at 1517 m a.s.l. in the Pena Trevinca Massif (Galicia), lies at the interface of Eurosiberian and Mediterranean bioclimatic regions. In April 2021, a sediment core (OCE21-3GA, 131 cm) was retrieved using a UWITEC® gravity corer. Radiocarbon dating, alongside concentration profiles of ²¹⁰Pb and ¹³⁷Cs, established an age-depth model indicating a sequence spanning approximately 2900 years. To identify and precisely date major environmental transitions over the last millennia (ca. 3 ka), a multidisciplinary approach was used, including sedimentological (facies analysis), geochemical (XRF, TOC, TN, biogenic silica, δ¹³C_ORG, δ¹⁵N_ORG analyses), and biological proxies (diatoms and pollen). Statistical analyses, including Principal Component Analysis (PCA), were applied to reconstruct environmental conditions.

The age of the main changes in sediment composition roughly correlate with documented Late Holocene climate centennial periods, providing evidence of regional responses to larger-scale climatic events. However, our findings also reveal a complex dynamic interplay between Atlantic and Mediterranean climatic influences. The shift from drier to wetter conditions during the Older Subatlantic (ca. 800-200 BCE) likely reflect the end of the 2.8 ka event, characterized by dry conditions in the northern hemisphere. The aridity of the Roman Warm Period (ca. 200 BCE-300 CE) suggests the onset and a northward shift of the Mediterranean bioregion. Wetter conditions during the Dark Ages (ca. 300-750 CE) indicate a subsequent Atlantic dominance, whereas the arid Medieval Climate Anomaly (ca. 750-1100 CE) reflects intensified Mediterranean influence, with temporal offsets compared to other Iberian records. The Little Ice Age (LIA; ca. 1300-1900 CE) exhibits significant hydroclimatic variability, subdivided into alternating wet and dry sub-phases: LIA-I (ca. 1300-1500 CE), LIA-II (ca. 1500-1700 CE), and LIA-III (ca. 1700-1900 CE). Diatom data suggest extended and prolonged lake ice cover conditions during the LIA in the lake, leading to stronger denitrification and prolonged stratification periods, with a marked anoxia in the lake bottom. The transition of the Medieval Climate Anomaly to Little Ice Age (ca. 1100-1300 CE) marks a shift to wetter conditions. Finally, the Industrial Era (ca. 1850 CE–present) is defined by warming trends, increased lake productivity, reduced detrital inputs, and human-induced impacts such as elevated atmospheric nitrogen deposition.

This work is supported by Grants PID2019-107424RB-I00 and PID2022-139775OB funded by MCIN/AEI/10.13039/501100011033, with the latter also co-funded by “ERDF A way of making Europe”. Xunta de Galicia also supports this work through project ED431F 2022/18 and ED431B 2024/03

How to cite: Bao, R., Fernández-Pérez, U., Carballeira, R., Sáez, A., Prego, R., Santos, L., Raposeiro, P., Altrogge, R., and Hernández, A.: Late Holocene climate dynamics in NW Iberian Peninsula: Exploring the Atlantic-Mediterranean interactions and paleoenvironmental impacts, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11351, https://doi.org/10.5194/egusphere-egu25-11351, 2025.

X5.125

EGU25-19592

ECS

Late Holocene climate and environmental history based on biomarker analyses from Lake Tislit, Morocco

Svenja Scholz, Olga Schmitz, Laura Bergmann, Maximilian Prochnow, Lisa Danius, Christoph Zielhofer, and Roland Zech

The High Atlas in Morocco is sensitive to climate change and influenced by both the subtropical and mid-latitude atmospheric circulation systems, making it a key region for paleoclimate and -environmental research. Here, we present first results of lipid biomarker analyses on a ~2 m sediment core from Lake Tislit, covering approximately the last 1500 years at 30-year temporal resolution. Specifically, we aim to apply compound-specific hydrogen isotope analyses (δ²H) on n-alkanes to investigate past changes in the hydrological cycle. Further, polycyclic aromatic hydrocarbons (PAHs) are used as a proxy for paleofires. This combined approach allows us to explore the interactions between hydrological variability and (anthropogenic) fire activity during the Late Holocene.

Our preliminary results indicate that n-alkanes (n-C₂₃ - n-C₃₃) are well preserved with an odd-over-even predominance of >7. n-C₂₉ and n-C₃₁are the most abundant homologues (~1 μg g^-), likely reflecting input from terrestrial plants. Short-chain n-alkanes (n-C₂₃ and n-C₂₅), likely derived from aquatic organisms, are also abundant (~0.25 μg g^-), providing a reliable basis for compound-specific δ²H analyses. Therefore, we will run these measurements in the coming weeks to investigate paleohydrological changes.

PAHs are consistently present throughout the sediment core. High molecular weight PAHs (m/z 252 to 278) increase strongly towards the top of the core, reaching almost 1 μg g^-. This is probably indicative of high temperature combustion and the onset of industrialisation. Perylene is considered separately, as it has recently been proposed to rather serve as possible proxy for soil erosion. Perylene is often the most abundant PAH in our core and has a pronounced maximum at ~50 cm core depth, possibly indicating significant anthropogenic land use.

How to cite: Scholz, S., Schmitz, O., Bergmann, L., Prochnow, M., Danius, L., Zielhofer, C., and Zech, R.: Late Holocene climate and environmental history based on biomarker analyses from Lake Tislit, Morocco, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-19592, https://doi.org/10.5194/egusphere-egu25-19592, 2025.

X5.126

EGU25-1403

ECS

A 2000 year record of hydroclimate variability inferred from oxygen isotopes in lake sediments on Kangaroo Island, South Australia

Mahfuzur Rahman, Lucinda Duxbury, Haidee Cadd, Robert Klaebe, Geraldine Jacobsen, John Tibby, and Jonathan Tyler

High resolution records of past hydroclimate are crucial for understanding the recurrence of extreme climatic events (prolonged droughts and deluges) and for robust decision making around environmental and economic sustainability. The current study presents a ~sub-decadal-scale hydroclimate reconstruction based on oxygen isotope analysis of lake sediment ostracod shells, extracted from the sediments of Lashmars Lagoon, Kangaroo Island, South Australia. Spanning the last ~2000 years, the oxygen isotope record records a series of multi-decadal wet and dry periods, manifest in the relative precipitation-evaporation balance of the lake. Of note, the record implies periods of prolonged declines in water balance, tentatively interpreted as droughts, during the periods 525-575 CE, 770-790 CE, 825-850 CE, and 980-1020 CE. By contrast, the periods from ~150-450 CE and 600-750 CE were relatively wet. Unfortunately, ostracods were absent within the sediments deposited between 1250-1590 CE, possibly due to a reduction in lake water or sediment pH following a notable increase in charcoal deposition. The period from ~1590-1800 CE appears to have been notably dry, prior to an increase in effective moisture during the last 200 years. The Lashmars Lagoon record exhibits similar trends to a record from Blue Lake, Mt. Gambier, approx. 500 km to the southeast. However, these records contrast with other hydroclimate records from further east, implying a complex relationship with regional climate drivers. Comparison with instrumental period rainfall data, and reconstructed indices for major ocean–atmosphere interactions suggests that periods of increased moisture balance on Kangaroo Island were influenced by a combination of Southern Ocean and Indian Ocean derived climate influences.

How to cite: Rahman, M., Duxbury, L., Cadd, H., Klaebe, R., Jacobsen, G., Tibby, J., and Tyler, J.: A 2000 year record of hydroclimate variability inferred from oxygen isotopes in lake sediments on Kangaroo Island, South Australia , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-1403, https://doi.org/10.5194/egusphere-egu25-1403, 2025.

X5.127

EGU25-4888

Paleoclimate Data Assimilation of Monsoon Precipitation in China Over the Past 500 Years

Feng Shi, Zhiqiang Lyu, and Zhengtang Guo

Monsoon precipitation in China influences the livelihoods of approximately two-thirds of its population, making an understanding of its regional patterns and long-term variability essential for improving future precipitation forecasts. However, the relatively short span of instrumental records and the limited skill of climate models in simulating precipitation hinder our ability to uncover the driving mechanisms behind historical monsoon precipitation changes. To address these gaps, this study integrates multiproxy precipitation reconstructions with climate model simulations to assimilate China precipitation fields over the past 500 years. Our analysis highlights robust assimilation results in North and Southwest China, suggesting a potential teleconnection influenced by the South Asian summer monsoon. Similarly, assimilation in East China successfully captures Meiyu rainfall variations closely associated with the East Asian summer monsoon. Furthermore, our analyses indicate that precipitation in North, Southwest, and East China exhibits strong responses to interannual-scale El Niño-Southern Oscillation (ENSO) variability and decadal-scale Pacific Decadal Oscillation (PDO) fluctuations. These findings not only deepen our understanding of the mechanisms underlying China’s monsoon precipitation evolution but also provide a valuable scientific basis for refining future projections of monsoon climate in China.

How to cite: Shi, F., Lyu, Z., and Guo, Z.: Paleoclimate Data Assimilation of Monsoon Precipitation in China Over the Past 500 Years, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4888, https://doi.org/10.5194/egusphere-egu25-4888, 2025.

X5.128

EGU25-15882

ECS

Investigation of historical low-temperature events in the warm season in China based on documentary data

Siyu Chen and Stefan Brönnimann

Low-temperature events, as an important and disastrous weather process, can cause severe damage to agriculture, transportation, and economic systems. However, low-temperature events occurring during the warm season have received less attention from climatologists compared to the harsh winters, with the exception of the well-known cold summer of the post-Tambora period during 1815-1817, which resulted in terrible famines in southwest China. Documentary data have been widely used to study past climate. Aside from abnormal phenomena like snow, frost, and ice, past low-temperature events occurring in late summer and early autumn, which are key periods of rice growth, also attracted people's attention and have been documented. Through the excavation of the original literature, the presented study reconstructed a chronology of low-temperature events in the warm season over the past hundreds of years and analyzed their temporal-spatial characteristics. We also detected low-temperature events in the past decades in southwest China and discussed the corresponding circulation pattern and potential forcing using the instrumental, reanalysis (ERA5), and paleo-simulation (ModE-Sim) datasets. Volcanic eruptions are one of the most important forcings, and Superposed Epoch Analysis (SEA) results show lower temperatures in the years following eruptions in the North Hemisphere and tropical regions. The large-scale circulation anomaly composition presents as the East-Atlantic (EA) pattern. The impact of Pacific sea surface temperature (SST) is also present in both reanalysis and simulations, which could force an EA pattern by inducing a Rossby wave train. In further work, we will make a comparison between low-temperature events in China and Europe, which are both potentially influenced by the EA pattern and volcanic eruptions.

How to cite: Chen, S. and Brönnimann, S.: Investigation of historical low-temperature events in the warm season in China based on documentary data, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-15882, https://doi.org/10.5194/egusphere-egu25-15882, 2025.

X5.129

EGU25-6842

The grand Maunder Minimum and changing patterns of South and East Asian summer monsoons

Kuan-Hui Elaine Lin, Wan-Ling Tseng, Jen-Ing Lee, Cheng-Wei Lin, Huang-Hsiung Hsu, and Pao K Wang

The East Asian summer monsoon (EASM) is a distinctive component of the Asian climate system, strongly influenced by orographic forcing. Unlike Indian summer monsoon which occurs within South Asian summer monsoon (SASM) trough and presents a relative uniformity of rainfall distribution allowing for an All Indian Rainfall index to measure its variability, the definition of the EASM intensity is more complex. One of the main reasons is the vast spatial extent of the EASM encompassing tropics, subtropics and midlatitudes, making it difficult to attribute its variability. Despite the challenges, studying the evolution of the South and East Asian monsoon systems over centennial to millennial timescales is essential for developing a comprehensive understanding of both high- and low-frequency variations in monsoon behavior and their relationship with general atmospheric circulations. Many previous studies used geochemical proxy records from oceanic sediments or continental archives to reconstruct paleomonsoon indices. However, most reconstructions relied on rainfall information extracted from individual sites, facing limited spatial coverage and constrained ability to generalize findings across broader monsoon systems.

In this study, we present a novel approach to reconstruct paleo SASM and EASM indices. First, we applied the present method for estimating SASM and EASM indices (Wang et al. 2008) to calculate wind fields (zonal and meridional winds at 850hPA) from 1950 to 2020 using ERA5 data and rainfall data from NOAA Precipitation Reconstruction over Land. This approach was used to construct modern indices and investigate the relationships between rainfall and circulation anomalies. Next, the rainfall pattern was projected onto the gridded 1^ox 1^oresolution REACHES (Reconstructing East Asian Climate Historical Encoded Series) (Wang et al., 20018) precipitation index data in 1368-1911CE so that a reconstructed SASM and EASM index can be derived incorporating both temporal and spatial variability. The reconstructed indices were then compared with other indices for justification. Importantly, the reconstructed monsoon indices reveal multidecadal and centennial variabilities during the Little Ice Age. A significant phase transition from SASM dominance shifting to EASM occurred during the Maunder Minimum, coinciding with significant behavior changes of typhoons and other extreme events in East Asia.

How to cite: Lin, K.-H. E., Tseng, W.-L., Lee, J.-I., Lin, C.-W., Hsu, H.-H., and Wang, P. K.: The grand Maunder Minimum and changing patterns of South and East Asian summer monsoons, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6842, https://doi.org/10.5194/egusphere-egu25-6842, 2025.

X5.130

EGU25-7260

ECS

A long-term drought reconstruction based on oxygen isotope tree ring data for central and eastern parts of Europe (Romania)

Viorica Nagavciuc, Gerhard Helle, Maria Rădoane, Cătălin-Constantin Roibu, Mihai-Gabriel Cotos, and Monica Ionita

This study investigates the relationship between oxygen isotope ratios (δ¹⁸O) in oak tree ring cellulose and past drought variability in Letea Forest, Romania. A δ¹⁸O site chronology spanning 1803-2020 was compiled from seven individual time series. δ¹⁸O values exhibited a significant negative correlation with moisture-related variables (cloud cover, relative humidity, and precipitation) and a positive correlation with temperature and sunshine duration. This confirms that δ¹⁸O from tree rings can be a good proxy for moisture availability. The strongest correlation was found between δ¹⁸O and the August Standardized Precipitation Evapotranspiration Index for an accumulation period of 9-months (SPEI9) for central and eastern Europe. This highlights SPEI9 as a superior indicator of drought compared to individual parameters like temperature or precipitation. Using a linear regression model, we reconstructed August SPEI9 variability for the past 200 years. The reconstruction captured interannual and decadal variations, with distinct wet and dry periods. Analysis of large-scale atmospheric circulation patterns revealed a link between high δ¹⁸O values (indicating dry conditions) and a high-pressure system over the North Atlantic. Conversely, low δ¹⁸O values (indicating wet conditions) corresponded to negative pressure anomalies over Europe. Moreover, extreme values of δ¹⁸O are also associated with the prevalence of a hemispheric teleconnection pattern, namely wave number 4. This δ¹⁸O chronology and the corresponding August SPEI9 reconstruction offer valuable tools for understanding past climate variability and its relationship with large-scale atmospheric and oceanic circulation patterns.

How to cite: Nagavciuc, V., Helle, G., Rădoane, M., Roibu, C.-C., Cotos, M.-G., and Ionita, M.: A long-term drought reconstruction based on oxygen isotope tree ring data for central and eastern parts of Europe (Romania), Biogeosciences, 22, 55–69, https://doi.org/10.5194/bg-22-55-2025, 2025

Nagavciuc, V., Helle, G., Rădoane, M., Roibu, C.-C., Cotos, M.-G., and Ionita, M.: A long-term drought reconstruction (August SPEI9) based on oxygen isotope tree ring data for central and eastern parts of Europe (Romania), Zenodo [data set], https://doi.org/10.5281/zenodo.14536886, 2024.

How to cite: Nagavciuc, V., Helle, G., Rădoane, M., Roibu, C.-C., Cotos, M.-G., and Ionita, M.: A long-term drought reconstruction based on oxygen isotope tree ring data for central and eastern parts of Europe (Romania), EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-7260, https://doi.org/10.5194/egusphere-egu25-7260, 2025.

X5.131

EGU25-9136

Daily variability of the Atlantic-European Jet stream over the last 300 years

Stefan Bronnimann and Yuri Brugnara

Extreme weather events in Western and Central Europe such as cold-air outbreaks, heavy precipitation, or heat waves are strongly affected by the Atlantic-European jet stream. Hence, projected changes in the jet stream in a future climate might alter the variability of extremes. It is therefore relevant to study the past variability of the jet. A recent analysis of the Atlantic-European jet based on reconstructions since 1421 showed links with extremes but no evidence for changes in the base state. However, the monthly-to-seasonal scale precluded analysing changes in the distribution, which are relevant for extremes. In this contribution we address the daily variability of the jet stream since 1725 based on observations and compare it with climate model simulations. We use existing historical pressure series from Padova, Uppsala, London and a newly digitised and homogenised series for Berlin. The four locations are well positioned to capture the strength, tilt, and latitude of the Atlantic-European jet. The daily indices explain large fractions of temperature variability and are associated with precipitation extremes, blocks or cyclones. Extreme excursions of the jet on a 1-, 5- or 15-daily scale were associated with extreme weather. However, changes in the mean or in extremes of the jet indices are small.

How to cite: Bronnimann, S. and Brugnara, Y.: Daily variability of the Atlantic-European Jet stream over the last 300 years, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-9136, https://doi.org/10.5194/egusphere-egu25-9136, 2025.

X5.132

EGU25-10021

ECS

Greenland ice cores as proxy for European extremes

Alessandro Gagliardi, Norel Rimbu, Gerrit Lohmann, and Monica Ionita

High-resolution ice core data from the Greenland Ice Sheet offer valuable insights into past climate variations on seasonal to multidecadal scales. One key parameter for reconstructing these variations is the concentration of stable oxygen isotopes in ice cores. We present evidence that a stacked record of stable oxygen isotope concentrations from Northern Greenland ice cores is a good proxy for the recurrence of a particular synoptic patterns in the atmospheric circulation, such as atmospheric blocking. Our evidence indicates that low oxygen isotope concentrations corroborate the reoccurrence formation of high-pressure systems over Europe. In particular, during the observational period (1920 – 2011), an increase in the frequency of atmospheric blocking events from Iberian Peninsula to Scandinavia is observed, leading to significant shifts in European hydroclimatic conditions: increased precipitation along the Norwegian coast, drier conditions and decreased temperatures in southern Europe. These findings are supported by a paleo-reanalysis product, which indicates similar patterns over a longer temporal perspective (1602 – 2003).

How to cite: Gagliardi, A., Rimbu, N., Lohmann, G., and Ionita, M.: Greenland ice cores as proxy for European extremes, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-10021, https://doi.org/10.5194/egusphere-egu25-10021, 2025.

X5.133

EGU25-11129

ECS

Reconstructing historical daily weather fields using a deep-learning variational auto-encoder

Conall E. Ruth, Yannis Schmutz, and Stefan Brönnimann

To study historical weather extremes and their impacts, as well as the evolution of weather variability over time, gridded reconstructions of daily weather are of great importance. However, prior to the establishment of national meteorological services, starting in Europe in the second half of the 19^th century, observations from which to derive such reconstructions are greatly limited. As a result, traditional spatial-interpolation approaches such as inverse-distance weighting are unreliable in this context. Numerical weather prediction models that assimilate available observations are also unfavourable, because of their high computational demand. A promising alternative is the application of deep-learning models, which have already been shown to produce reliable reconstructions with relatively little cost. Given the wide range of possible deep-learning architectures, further studies into their application for historical weather reconstruction continue to be valuable.

In this study we present a deep-learning model based on a variational auto-encoder (VAE) architecture for reconstructing fields of mean daily air temperature and mean-sea-level pressure across Europe. While the use of VAEs for weather reconstruction has previously been proposed, to our knowledge no such studies have been published in the literature. Our model is trained using ERA5 data for the domain 36N-67N, 22W-41E, aggregated to a daily, 1° resolution. During training, the model’s encoder takes the complete fields of temperature and pressure for a given day and reduces them to a simplified representation within the model’s latent space. The model’s decoder then takes this as input and attempts to recreate the original fields. Once trained, the encoder is then discarded and the latent space is instead sampled iteratively such that the decoded set of output fields best matches any available observations from a given day of interest. This output then represents the reconstruction of that day.

To evaluate performance, we apply our model to reconstruct the year 1807 using 25 historical temperature records and 18 historical pressure records. The reconstruction is then compared to a separate set of hold-out records from the same year. We also apply our model to a test period of 1950-1954 using ERA5 pseudo-observations with the same availability as above. This is then compared to the corresponding complete fields of ERA5. Additionally, we examine the performance of the model relative to the daily re-analysis dataset 20CRv3 and to an existing deep-learning model WeRec3D inspired by video inpainting.

For 1807, our model performs relatively well in reconstructing the hold-out records, achieving correlations and root-mean-squared errors similar to or better than those of WeRec3D and 20CRv3 for each variable. On the other hand, when considering the entire study domain for the period 1950-1954, our model performs notably worse than WeRec3D with a greater reconstruction error, under-represented variance and overly smooth reconstructed fields. This is especially pronounced towards the edges of the domain where observations are particularly sparse. Thus, our model is ultimately not superior to an existing alternative. Nevertheless, this study successfully demonstrates the application of a VAE for the task of historical weather reconstruction and provides a foundation for further investigation.

How to cite: Ruth, C. E., Schmutz, Y., and Brönnimann, S.: Reconstructing historical daily weather fields using a deep-learning variational auto-encoder, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11129, https://doi.org/10.5194/egusphere-egu25-11129, 2025.

X5.134

EGU25-15324

ECS

Shallow Ice Borehole Thermometry: Bayesian inversion techniques for reconstructing the Antarctic temperature evolution of the last centuries

Kshema Shaju, Thomas Laepple, Nora Hirsch, and Peter Zaspel

X5.135

EGU25-18184

ECS

Extreme rainfall events recorded in stalagmites from Oman during the last two millennia

Ismini Lypiridou, Sara Plattner, Helen Foxhall Forbes, Mohammed Al Kindi, Hai Cheng, and Dominik Fleitmann

Understanding human-climate interactions over the past two millennia is critical for areas like Oman, where water has been a valuable resource and has shaped societal resilience and adaptation strategies. Oman’s unique geographical location, at the pathway of monsoonal activity and tropical cyclones, makes it an ideal area to investigate the links between climatic variability and extreme rainfall events. During the last few decades, Oman was affected by several tropical cyclones, such as cyclone Mekunu in May 2018. Furthermore, Oman is also frequently affected by flash floods, which cause severe damages to people and property. Detailed information about tropical cyclone and flash flood activity in the recent and more distant past is urgently needed to place present-day cyclone activity and flash flood frequencies into a meaningful historical context, and to detect any significant changes in their occurrence rates. Because of the brevity of historical and instrumental records in Oman, such information must be obtained from natural archives such as stalagmites, which can be used as a paleoflood archive (e.g., Denniston and Lütscher, 2017). During flooding of caves, stalagmites can be coated with sediment and biogenic particles which are then preserved as distinct detrital layers when the stalagmite growth continues.

Here we present first results of two Uranium-series dated actively-growing stalagmites from northern and southern Oman, one from Qunf Cave and Hoti Cave (Fleitmann et al., 2022) to explore the frequency of extreme rainfall events and their climatic drivers. Both cave systems are frequently affected by flooding (Al Kindi et al., 2023) and the two stalagmites show frequent detrital layers along their growth axis. Using digital image analysis of thin sections and high-resolution trace element profiles, we are able to develop a precisely dated record of cave flooding related to tropical cyclones and regional heavy rainfall events over the last two millennia.

References

Al Kindi et al., 2023. A guide to the caves of Oman – The remarkable subterranean world of the Sultanate of Oman. Nomad Publishing, 274 pages.

Denniston, R.F., Luetscher, M., 2017. Speleothems as high-resolution paleoflood archives. Quaternary Science Reviews 170, 1-13.

Fleitmann et al., 2022. Droughts and societal change: The environmental context for the emergence of Islam in late Antique Arabia. Science 376, 1317-+.

How to cite: Lypiridou, I., Plattner, S., Foxhall Forbes, H., Al Kindi, M., Cheng, H., and Fleitmann, D.: Extreme rainfall events recorded in stalagmites from Oman during the last two millennia, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-18184, https://doi.org/10.5194/egusphere-egu25-18184, 2025.

X5.136

EGU25-6761

Early-twentieth-century cold bias in ocean surface temperature observations

(withdrawn)

Sebastian Sippel, Elizabeth Kent, Nicolai Meinshausen, Duo Chan, Christopher Kadow, Raphael Neukom, Erich Fischer, Vincent Humphrey, Robert Rohde, Iris de Vries, and Reto Knutti

X5.137

EGU25-7483

Grain Size Analysis Reveals Late Holocene Climate Variability from the Halk El Menjel Lagoon (Central Mediterranean)

Najoua Gharsalli, Hamdi Omar, Rana Baydoun, and Chokri Yaich

Examining Late Holocene climate variability is crucial for understanding past environmental changes and predicting future patterns, especially in the Mediterranean, a region sensitive to climate shifts. Positioned between temperate and arid zones, the Mediterranean is vulnerable to even minor climatic fluctuations, impacting ecosystems and water systems. The Halk El Menjel lagoon in the South-Central Mediterranean is a vital paleoenvironmental archive, recording over 4000 years of climate variability through hydrological and sedimentary cycles.

Granulometric analysis is an essential tool for interpreting sediments as environmental indicators. This study focuses on grain size distribution, revealing polymodal distributions linked to specific depositional environments and transport processes, whether by water or wind. Detailed granulometric analysis of 750 sediment samples from a 150-cm core at Halk El Menjel Lagoon was conducted using Principal Component Analysis (PCA), dendrogram clustering (DC), and temporal distribution analysis. These methods help reconstruct sediment transport dynamics and investigate long-term climatic variability in this semi-arid coastal environment.

Twelve distinct grain size sub-populations (ranging from 1.2–2 µm to 1000–1350 µm) were identified, each linked to different depositional environments. PCA revealed three main sedimentary groups: aeolian (dominated by 600–1000 µm), fluvial (dominated by 250–580 µm), and hydraulic runoff (dominated by 1.2–2 µm). These groups reflect different transport processes and depositional environments, with varying levels of homogeneity. DC further refined the categorization, highlighting significant differences between aeolian and fluvial processes.

Temporal analysis, based on an age-depth model using LANDO and Bayesian Bchron scripts, revealed key climatic shifts over the 4000-year period. The analysis, visualized through various charts, showed significant changes in sediment composition linked to historical climate variability. From 3500 to 3000 BP, all twelve sub-populations coexisted, reflecting highly variable climatic conditions. During the Iron Age (IA) to Roman Classical Period (RCP), the 600–1000 µm sub-population increased, peaking during the 2.8 ka transition in the IA. This shift suggests arid conditions and growing aeolian influence.

The Roman Humid Period (RHP) exhibited alternating arid and humid phases. During arid periods, the 600–1000 µm fraction dominated, while the 250–580 µm fraction, often associated with the 2–5.2 µm fraction, prevailed in humid periods. By the RCP, the 600–1000 µm sub-population reached near-total dominance, indicating a shift toward predominant aeolian sedimentation.

In contrast, the Dark Age (DA) and Medieval Climate Anomaly (MCA) periods saw a significant increase in the 250–580 µm sub-population, exceeding 75%, indicating wetter conditions favoring fluvial sedimentation. A new component, represented by the 1.2–2 µm fraction, emerged, accounting for approximately 25% of the sediment, signaling evolving depositional environments.

The Little Ice Age (LIA) and Modern Period (MP) were dominated by the 1.2–2 µm sub-population, comprising over seven-eighths of the sediment in the MP. This reflects lagoon infilling and deposition of suspended material transported by hydrological processes.

These findings align with Mediterranean climatic events, highlighting shifts in precipitation and aeolian activity. The Halk El Menjel lagoon provides valuable insights into long-term environmental dynamics, illustrating the interplay between climate variability and sedimentary processes.

How to cite: Gharsalli, N., Omar, H., Baydoun, R., and Yaich, C.: Grain Size Analysis Reveals Late Holocene Climate Variability from the Halk El Menjel Lagoon (Central Mediterranean), EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-7483, https://doi.org/10.5194/egusphere-egu25-7483, 2025.

X5.138

EGU25-13679

Climatic effects on grain harvest variations at parish-level in Sweden c. 1665–1810

Fredrik Charpentier Ljungqvist and Martin Skoglund

Several studies have statistically assessed the relationship between climate variability and grain harvest variations in pre-modern Sweden. They have, however, either studied the relationship on a coarse geographical (county to national) scale (Ljungqvist et al., 2023) or for only an individual province (Skoglund 2022, 2023, 2024). Fine-scale (parish-level) studies are entirely lacking. The Swedish 17^th and 18^th century tithe data – i.e., a tax paid on a percentage of the harvest – for different grain types are available at parish-level and offer excellent estimates of harvest variations from year to year. Adequate palaeoclimate data, with seasonal resolution, is also available for the region and period. This has enabled us to conduct a detailed spatio-temporal investigation of the effects of climate variability on grain harvest variations at a parish-level. We have focused on the two main grain types cultivated in pre-modern Sweden, spring-sown barley and autumn-sown rye, and used 10-year high-pass filtered data to investigate short-term effects and linearly detrended data to also capture more long-term climate–harvest relationships while minimising the effects of spurious trends.

Our results show a consistent relationship in northern, and to a lesser extent also central, Sweden between summer temperature and harvest size. Warmer summers resulted in higher yields while colder summers resulted in lower yields. This effect extended further south in Sweden for the more drought-tolerant rye than for the more drought-sensitive barley. However, for both grain types southern-most coastal Sweden showed an opposite temperature–harvest relationship than the rest of the country: here, cooler summers instead promoted larger harvests than warmer ones.

We found that wetter summer conditions (higher soil moisture) mainly had a positive effect on the harvests in east-central and southern Sweden. The hydroclimatic effect on the harvests was found to be largest when considering only inter-annual variability (i.e., using high-pass filtered data), whereas the temperature-effect is more prominent when also considering relationships over longer time-scales (i.e., using linearly detrended data). Finally, we investigate the influence of soil texture and manure availability for the detected geographical climate–harvest relationship. We conclude that the climate–harvest relationships in southern-most and northern Sweden c. 1665–1810 were rather similar to those of modern times. Due to sensitivity to drought, harvests in the former region were, and still are, favoured by cooler summers, while warmer summers in the north increased, and still increase, the harvests. However, the positive effect of warmer summers in south-central Sweden was found to be much stronger c. 1665–1810 than in modern times, when larger harvests in the region rather follow cooler summers.

References

Ljungqvist, F. C., et al.: Climatic signatures in early modern European grain harvest yields, Climate of the Past, 19, 2463–2491, 2023.

Skoglund, M. K.: Climate variability and grain production in Scania, 1702–1911, Climate of the Past, 18, 405–433, 2022.

Skoglund, M. K.: Farming at the margin: climatic impacts on harvest yields and agricultural practices in central Scandinavia, c. 1560–1920, Agricultural History Review, 71, 203–233, 2023.

Skoglund, M. K.: The impact of drought on northern European pre-industrial agriculture, The Holocene, 34, 120–135, 2024.

How to cite: Charpentier Ljungqvist, F. and Skoglund, M.: Climatic effects on grain harvest variations at parish-level in Sweden c. 1665–1810, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-13679, https://doi.org/10.5194/egusphere-egu25-13679, 2025.