Maritime weather data contained in U.S. whaling ship logbooks are used to assess historical changes in global wind patterns. We focus on unexploited caches of archival documentation, namely U.S. whaling logbooks of voyages spanning the period 1790 to 1910 from New England archives housed by the New Bedford Whaling Museum, Nantucket Historical Association, and Providence Public Library. The logbooks, often covering multi-year voyages around the globe, contain systematic weather observations (e.g., wind strength/direction, sea state, precipitation) at daily to sub-daily temporal resolution. The qualitative, descriptive wind recordings of wind strength and direction by the whalers are quantified and compared with reanalysis products where applicable.

Following extensive quality control, we find overall good agreement in wind strength and direction for the whaling logbook wind records with reanalysis products for mean and seasonal climatologies. Variations in wind fields associated with modes of variability, such as the North Atlantic Oscillation or El Niño-Southern Oscillation, are also captured by the whaling ship recordings for North Atlantic and Pacific surface wind patterns. The quantified wind recordings are also employed to help address contemporary questions in climate science, such as long-term shifts in position and strength of the Southern Hemisphere westerlies since the late 1700s, strengthening of the Pacific equatorial trade winds since the 19^th century, as well as changes in South Asian monsoon characteristics. Our results demonstrate that the historical records provide an important long-term context for changing maritime wind patterns in remote ocean regions lacking observational records during the 19^th century.

How to cite: Ummenhofer, C., Sander, N., Muench, B., Giacoppo, T., George, T., Miah, M., and Walker, T.: New England whaling ship logbooks and reanalyses reveal shifts in global wind patterns since the late 1700s, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12241, https://doi.org/10.5194/egusphere-egu24-12241, 2024.

The flooding in Queensland and NSW over the last years has affirmed the impacts that extreme precipitation has on peoples lives and their livelihood. To be better prepared for such extremes in the future we need to know how often and under which climatic circumstances they occur. However, climate models for Australia still involve high uncertainty in predicting the likelihood of precipitation extremes that lead to large flooding events. This is attributed to the limited record of hydro-climatic paleo data across Australia. Though efforts have been made to improve the record of past precipitation extremes, previous studies have focused on high resolution at specific locations rather than a large spacial coverage.

Our project tackles this challenge by utilising the strongly link between precipitation and filling events of ephemeral lakes. The paleoenvironmental evidence collected from various ephemeral lakes in key quadrants of the country allows the establishment of a hydro-climatic paleo record on a large spatial scale. A timeframe of the last thousand years permits the comparison of frequency and magnitude to inter-annual variability of precipitation extremes in different regions across Australia. Ultimately, a comparison of the established record against other paleo data and an analysis of global climate simulations will result in an improved understanding of past precipitation extremes and the importance varying climatic drivers have in different regions across Australia.

How to cite: Grunau, S., Cohen, T., McGregor, H., and Ummenhofer, C.: Australian Precipitation Extremes over the last Millenia: How do Ephemeral Lake Records Compare Against Climate Models?, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4, https://doi.org/10.5194/egusphere-egu24-4, 2024.

This study used Reconstructed East Asian Climate Historical Encoded Series (REACHES) database (Wang et al. 2018) to reconstruct historical tropical cyclone (TC) series documented in 1368-1911. Records documented with ‘typhoon’ (Chinese character颱) or ‘hurricane’ (颶) were retrieved, with descriptions of other compounding effects such as strong wind, torrential rain and storm surge to consist of the data set. To avoid repetition and duplicate counting of the same TC event, records that have temporal (± 1 days) and spatial (±2∘degree latitude/longitude) proximity were combined accounting for one single TC event. The method was based on a systematic database approach and data quality was checked and validated through comparison with other independent reconstructed series and IBTrACS (Tropical Cyclone Best Track Data) 1884-2020. The REACHES TC series was then merged with the IBTrACS data to form a l368-2020 long TC series for Northwestern Pacific region. The reconstructed TC series demonstrates clear multi-decadal to centennial variabilities. In the last six hundred years, there were in average 3 TC documented in every year. 1600s was the most TC active period (8 TC in 1627, 7 in 1640, 7 in 1652, 6 in 1662, 7 in 1664, 9 in 1668, 12 in 1669, 10 in 1671, and 8 in 1672). The TC series was then compared with other forcings (volcanic eruption, solar, and SST) and ENSO.  All of the forcings may have a role in the frequent TC activities during Maunder Minimum. Further research from model-data comparison and simulations will shed lights on TC behaviors in the warming climate.

How to cite: Lin, K.-H. E., Tseng, W.-L., Hsu, H.-H., and Wang, P. K.: Annually resolved Northwestern Pacific tropical cyclone series since the mid-14th century: intensified activities during the Maunder Minimum , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14200, https://doi.org/10.5194/egusphere-egu24-14200, 2024.

A reconstruction of historical floods in Poland in the 11^th–18^th centuries was carried out based on a comprehensive database of documentary evidence. For this period, we collected more than 1700 weather notes describing floods. The quality of each source containing weather notes was estimated. Only the most reliable sources were used for the analysis of flood occurrences and their characteristics. For the classification of flood intensity, the two most commonly used propositions for European rivers (Barriendos and Coeur 2004; Brázdil et al. 2006) were used. The origins of floods were evaluated based on the classification presented by Lambor (1954). The results showed that the highest number of floods in Poland in the study period occurred in the 16^th century (294 cases). The number of floods in the 11^th–15^th, 17^th, and 18^th centuries were 166, 284, and 272, respectively. Most of the floods were recorded in the Oder River basin and Silesia region (western and south-western Poland). The evaluation of the intensity of floods revealed that most of the floods belong to the “above-average, or supra-regional flood” category according to the Brázdil et al. (2006) classification and the “extraordinary” category for the Barriendos and Coeur (2004) classification. The assessment of the main origin of floods demonstrated that rain and its sub-types (torrential, frontal, long-lasting, territorially widespread) constituted the main cause of floods in Poland in the 11^th–18^th centuries. The findings of this study will improve existing knowledge of historical hydrology in Europe and Poland before the 19^th century. 

The work was supported by the National Science Centre, Poland, project No. 2020/37/B/ST10/00710. 

References:

Barriendos, M., Coeur, D, 2004: Flood data reconstruction in historical times from non-instrumental sources in Spain and France. Systematic, Palaeoflood and Historical Data for the Improvement of Flood Risk Estimation. Methodological Guidelines. 

Brázdil, R., Kundzewicz, Z. W., & Benito, G., 2006: Historical hydrology for studying flood risk in Europe. Hydrological Sciences Journal, 51(5), 739–764.

Lambor, J., 1954: Klasyfikacja typów powodzi i ich przewidywanie. Gospodarka Wodna, 4, 129–131.

How to cite: Ghazi, B., Przybylak, R., Oliński, P., and Pospieszyńska, A.: Reconstruction of floods in Poland in the pre-instrumental period (1001-1800), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-99, https://doi.org/10.5194/egusphere-egu24-99, 2024.

Although the influence of Sun on climate variability is largely investigated its contribution to extreme weather and climate change remains widely questioned. Because the sample sizes of observed weather and climate extremes are typically too small, we used seasonal resolution paleo-reanalysis data as predictors to extend back in time the field of observed climate extreme indices to reliably identify the solar signal. We reconstructed the field of a two-dimensional atmospheric blocking frequency indicator in the North Atlantic region as well as the field of the frequency of extreme cold temperature and extremely high precipitation days over Europe back to the year 1600. Based on these reconstructions, we show that low (high) solar irradiance winters are associated with more (less) frequent blocking in the Atlantic-European region. This pattern was particularly strong during Maunder and Dalton solar minima. Consistent anomaly patterns are identified for the frequency of extreme low temperature and extremely high precipitation days over Europe. A numerical experiment reveals a significant increase in the blocking frequency in the Atlantic-European region during a Grand Solar Minimum relative to the 1850s solar irradiance levels. This suggests that blocking anomaly patterns associated with total solar irradiance forcing during winter, as derived from observational data, are robust in the perspective of the last four hundred years of blocking and associated weather extreme variability in the North Atlantic region. Therefore, these patterns are useful to estimate the blocking and related weather extremes under various scenarios/predictions of total solar irradiance change during next decades/centuries.

How to cite: Rimbu, N., Spiegl, T., and Lohmann, G.: Atmospheric blocking and extreme weather frequency patterns associated with solar irradiance forcing during the last 400 years, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7818, https://doi.org/10.5194/egusphere-egu24-7818, 2024.

Quantitative assessment of natural internal variability and externally forced responses of Northern Hemisphere (NH) temperatures is necessary for understanding and attributing climate change signals during past warm and cold periods. However, it remains a challenge to distinguish the robust internally generated variability from the observed variability. Here, large-ensemble (70 member) simulations, Energy Balance Model simulation, temperature ensemble reconstruction, and three dominant external forcings (volcanic, solar, and greenhouse gas) were combined to estimate the internal variability of NH summer (June–August) temperatures over the past 2000 years (1–2000 CE). Results indicate that the Medieval Climate Anomaly was predominantly attributed to centennial-scale internal oscillation, accounting for an estimated 104% of the warming anomaly. In contrast, the Current Warm Period is influenced mainly by external forcing, contributing up to 90% of the warming anomaly. Internal temperature variability offsets cooling by volcanic eruptions during the Late Antique Little Ice Age. Ultimately, this study indicates that the dominant internal climate factor driving centennial-scale fluctuations in NH summer temperatures over the last two millennia has been the AMOC, and that the primary external forcing agent is volcanic activity. These findings have important implications for the attribution of past climate variability and improvement of future climate projections.

How to cite: Shi, F.: Quantitative attribution of Northern Hemisphere summer temperaturesover the past 2000 years, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14263, https://doi.org/10.5194/egusphere-egu24-14263, 2024.

The El Niño-Southern Oscillation (ENSO) has a significant impact on the global climate through atmospheric teleconnections. It is important to understand the stability of ENSO teleconnections, not only for future weather forecasting and climate projection, but also for ENSO reconstructions based on paleo-proxies. In this study, we investigate the decadal variations of ENSO teleconnections in global land surface temperature (LST) from 850 to 2005 AD using 13 ensemble members of the Community Earth System Model-Last Millennium Ensemble (CESM-LME). The CESM can simulate the main Eurasian cooling and Arctic warming, known as the warm Arctic-cold Eurasia (WACE) pattern, during the boreal winter of an El Niño. Furthermore, it can also capture the western Antarctic warming during the developing and decaying summers of an El Niño. There is a dominant decadal variation in the ENSO-LST teleconnections, expressed as anomalous LST patterns that closely resemble those seen in the WACE pattern during boreal winter and the western Antarctic warming pattern during summer. This decadal variation of ENSO-LST teleconnections is primarily due to the varying positions of Rossby wave sources associated with distinct ENSO patterns, which are located either to the west or to the east of Hawaii. The LST response to ENSO over South Siberia, as well as the associated precipitation response over North Eurasia, even show opposite patterns at different phases of the decadal variation. The decadal variation in CESM is found to be related to the interdecadal Pacific oscillation (IPO) and is likely attributed to internal variability rather than external forcing. Our findings suggest that the decadal variation in ENSO teleconnections should be considered when using proxies from Eurasian regions to reconstruct ENSO variability.

How to cite: Han, X., Li, Y., Liu, F., Li, J., Zheng, X., Li, Y., and Feng, L.: Stability of ENSO teleconnections during the last millennium in CESM, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6923, https://doi.org/10.5194/egusphere-egu24-6923, 2024.

The climate of the eastern Mediterranean and the Middle East is well documented in natural (speleothems, tree rings, sediments and pollen) and human-historical archives. The 6th century CE is of particular interest from both a historical and climatic perspective. It is a period of prosperity for the Eastern Byzantine Empire and political stability, but also a time when there was a heavily debated plague pandemic and significant climate variability associated with a major cluster of volcanic eruptions. Dynamical downscaling can bridge the gap between palaeo-records and climate reconstructions, which can be affected by various sources of uncertainty, and the coarsely resolved Earth System Models (ESMs) with 200 km or more horizontal resolution. A transient paleo-simulation with the appropriately adjusted regional climate model COSMO-CLM (CCLM, COSMO 5.0 clm16) is carried out to investigate possible links and feedbacks between the socio-political and economic conditions and the climate variability of that period in more detail.

The state-of-the-art and CMIP6 compliant forcing reconstructions of volcanic (stratospheric aerosol optical depth), orbital (eccentricity, obliquity, precession), solar (irradiance), land-use and greenhouse-gas changes used for the MPI-ESM-LR (Jungclaus et al. 2017) are therefore implemented in the regional climate model. The simulated temperature and precipitation are compared with those of other CMIP6 models as well as with proxy records and reconstructions. In connection with the two successive volcanic eruptions in 536 and 540 CE, the annual temperature of the entire region dropped noticeably until about 550 CE. The signal for precipitation is not as clear, but the years of the eruptions are the driest of the century in the eastern Sahara and Arabian Peninsula and the wettest in the eastern Mediterranean.

How to cite: Hartmann, E., Xoplaki, E., and Wagner, S.: Climate of the eastern Mediterranean and Middle East in the 6th century CE with COSMO-CLM , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14935, https://doi.org/10.5194/egusphere-egu24-14935, 2024.

Reconstructing and analysing the climate of the past millennium has traditionally involved using statistical methods to calibrate annually resolved proxies. It also increasingly requires analysing large data sets from ensembles of long climate simulations and paleoclimate reanalysis. The accurate annual dating of most proxies and the increasingly large data sets make machine-learning methods an attractive tool to re-calibrate proxy records and investigate the causality of past climate variability, e.g. extreme events. The available log climate simulations also offer a pre-training data set for other machine-learning applications in climate research, for which the observational records are usually too short.

In this talk, I will present a few examples of the application of machine-learning methods to these goals.  Climate reconstructions based on annually resolved proxies can now be produced with methods (Gaussian Process Regression or Long Short Term Memory Networks) that can better preserve the statistical properties of the target variable, like the past amplitude of variations and serial autocorrelation. Causality analysis of past variability episodes, including extremes, can be investigated in climate simulations with  Random Forest and Layerwise Relevance Propagation in neural networks. Finally, data assimilation methods, which blend proxy and model data into a single reconstruction, can be augmented with methods of the family of K-Nearest-Neighbour, thereby also providing an attribution of past climate episodes to one external forcing.  

How to cite: Zorita, E.: Application of machine-learning methods to the climate of the past millennium, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6471, https://doi.org/10.5194/egusphere-egu24-6471, 2024.

The anthropogenically-intensified greenhouse effect causes a radiative imbalance at the top of the atmosphere. This in turn leads to an energy surplus of the Earth system, with the ocean component absorbing the greatest part and the land the second largest. The latest observational estimates based on borehole temperature profiles quantify the land contribution to the terrestrial energy surplus to be 6 % in the last five decades, whereas studies based on state-of-the-art climate models scale it down to 2 %. This underestimation stems from land surface models (LSMs) having a too shallow representation of the subsurface, which severely constrains the land heat uptake simulated by Earth System Models (ESMs). A forced simulation of the last 2000 years with the Max Planck Institute ESM (MPI-ESM) using a deep LSM captures about 4 times more heat than the standard shallow MPI-ESM simulations in the historical period, well above the estimates provided by other ESMs. However, deepening the MPI-ESM LSM does not affect the simulated temperature at the ground surface. As a consequence, it is shown that the land heat uptake values of ESMs with shallow LSM components can be corrected considering their simulated surface temperatures and propagating them with a standalone heat conduction forward model. This result is extended to all available ground surface temperature sources, such as observational data, reanalyses, and the latest generation of ESMs. This new approach yields values of 10-16 ZJ for 1971-2018, which are in close agreement with the values derived from the MPI-ESM deep simulation (12 ZJ), and relatively close to the latest borehole-based estimates (ca. 18 ZJ).

How to cite: González-Rouco, F., García-Pereira, F., Melo-Aguilar, C., Steinert, N. J., García-Bustamante, E., de Vrese, P., Jungclaus, J., Lorenz, S., Hagemann, S., Cuesta-Valero, F. J., García-García, A., and Beltrami, H.: Using a last 2k baseline to derive a first comprehensive assessment of industrial era land heat uptake, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8123, https://doi.org/10.5194/egusphere-egu24-8123, 2024.

Great Basin Bristlecone pine (Pinus longaeva) (PILO) trees are known for their old age. The longest tree-ring width (TRW) chronology covers a large part of the Holocene, and the temperature-sensitive upper treeline chronology extends back to 2575 BC. The TRW of upper treeline PILO trees is influenced by temperature variability, but the moderate strength and temporal instability of the signal is making it hard to use for reliable temperature reconstructions. Maximum Latewood Density (MXD) of conifers is known to be a good summer temperature proxy in the northern hemisphere. However, there are no PILO MXD records due to various reasons, including its location in semi-arid lower latitudes, as well as due to methodological difficulties such as narrow rings and a varying grain angle. Here, we used an X-ray Computed Tomography (X-ray CT) of 69 cross-dated cores to construct an MXD chronology of PILO from the upper treeline sites covering the last millennium, and to investigate its temperature signal. The chronology correlates significantly (r=0.63) with warm season (April to September) temperature for the period 1895-2005 and the signal is stable throughout the instrumental period. Our results demonstrate that MXD from the bristlecone pine archive can be used as a robust proxy for western North American warm season temperature variability at an unprecedented multi-millennial scale.

How to cite: Matskovsky, V., de Mil, T., Pearson, C., Corluy, L., Verschuren, L., Salzer, M., Trouet, V., Van den Bulcke, J., and Van Hoorebeke, L.: Bristlecone Pine Maximum Latewood Density as a Superior Proxy for Millennial Temperature Reconstructions , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17740, https://doi.org/10.5194/egusphere-egu24-17740, 2024.

Temperature records with a high temporal resolution and spanning the last millennium are of primordial importance to understand climate variability beyond the instrumental period at multi-decadal to multi-centennial timescales. However, such records are rare and absolute values often suffer from large uncertainties. While tree-ring records provide excellent temperature records in the mid-latitudes at an annual timescale, they are generally not well-suited for understanding centennial to multi-millennial climate variability due to biologic age trends. Here, we provide a precisely dated, 1000 year-long temperature record with a decadal resolution from varved Lake Czechowskie located in northern Poland (Europe). The reconstruction is derived from a temperature proxy, which is based on glycerol dialkyl glycerol (GDGT) membrane lipids from bacteria thriving in the lake. The temperature record presents a trend very similar to observed June to November air temperatures for the period 1840 to 1975. However, absolute values are about 2 °C colder than observed air temperature because the estimates reflect temperature near the thermocline as suggested by lake monitoring data. The temperature reconstruction indicates that temperatures were 0.5±0.5 °C warmer and 0.8±0.5 °C colder than AD 1900–1975 during the Medieval Climate Anomaly and the Little Ice Age, respectively. A frequency analysis of Lake Czechowskie record as well as other temperature records from the Northern Hemisphere mid-latitudes reveals three main periodicity bands at 55–90, 110–190 and 210–300 years. These bands are most likely related to both solar variability (80–90-year Gleissberg and 200–210-year Suess/de Vries cycles) and to the Atlantic Multidecadal Variability/Oscillation (60–90 and 140–180-year periodicities), which is known to modulate temperature in the Baltic Sea region. Lake Czechowskie record represents a unique reconstruction of temperature decadal variability in the southern Baltic lowlands and Northern Europe during the last millennium.

How to cite: Kaiser, J., Rach, O., Słowiński, M., Błaszkiewicz, M., Arz, H., and Brauer, A.: Imprint of solar and Atlantic Multidecadal Oscillation variability in a 1000 year-long water temperature record from the varved sediments of Lake Czechowskie (northern Poland), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15410, https://doi.org/10.5194/egusphere-egu24-15410, 2024.

Gravity cores of four lakes along a NE to SW transect in Altai Mountains, from Shira Lake to Manzherok Lake, to Beloye Lake and Kolyvanskoye Lake, have been precisely dated by ²¹⁰Pb, ¹³⁷Cs and AMS ¹⁴C methods. High-resolution measurements of TOC and TON by EA, and 0.5N HCl leaching (AL) and Aqua Regia dissolved (AR) elemental concentrations by ICPOES reveal lake productivity, salinity, pH, redox condition and surface runoff under climate change and human impact over the past 1500 years. All of the lake sediments contain high sedimentary organic matter (average TOC >5%). However, ¹⁴C dating on the TOC as well as aquatic plants show old carbon influence (OCI). In order to obtain correct chronology of the cores, it is necessary to make high-resolution ¹⁴C dating. Using the least OCI ¹⁴C ages and combing ²¹⁰Pb/¹³⁷Cs dating results, a reliable chronology of the sediment core can be established. The AL fraction reflects mainly changes in lake chemistry, whereas the AR fraction represents chiefly variations in terrigenous input. The AL Ca and Sr are indicators of lake salinity, alkalinity and pH, whereas the AL Mo, Fe and Al are indicators of redox condition of the lake. TOC% and C/N are proxies for lake productivity and exogenous/endogenous TOC ratio. The AL Zn and Pb concentrations shows human impact. Based on the four lake records, the climatic conditions during the past 1500 years can be identified: warm and wet during 1500~1100 cal yr BP; warm and wet during 1100~900 cal yr BP (Medieval Warm Period -- MWP); fast sedimentation rate due to strong surface runoff during 900~700 cal yr BP; cooling and drying climates during 700~500 cal yr BP; very slow sedimentation due to longer frozen surface under cold climates during 500~50 cal yr BP (Little Ice Age -- LIA).  Since AD1900, the lakes were started to resume lake productivity under warming climate with the smaller lake first, being Manzherok (0.4 km²) in AD1900, Beloye (2.97 km²) in AD1920, Kolyvanskoye (4.5 km²) in AD1940, and Shira (39 km²) in AD1950.

This study is supported by the Russian Science Foundation (RSF) (grant No.22-47-08001) to Kazan Federal University (KFU).

How to cite: Li, H.-C., Kuzina, D., Frolova, L., Shen, T.-T., Misra, S., Nigamatzyanova, G., Yusupova, A., Nigmatullin, N., Strakhovenko, V., and Nurgaliev, D.: Climate and environmental changes during the past 1,500 years in Altai, Western Siberia, Russia: elemental geochemistry from four lake cores, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2450, https://doi.org/10.5194/egusphere-egu24-2450, 2024.

While most past millennium high-resolution temperature reconstructions rely on tree-ring data, there is a notable scarcity of detailed winter-spring temperature records covering the pre-instrumental period in Europe. This gap is evident in central Scandinavia, a region otherwise well covered by tree-ring data. Although tree-ring records in this area have demonstrated a correlation with spring temperatures, the climate signal is dominated by summer temperatures. Achieving a comprehensive understanding of seasonal variations is essential for understanding climate change and variability in the past. This study employs two different sets of sources to reconstruct late-winter and spring temperatures in central Scandinavia since 1697. First, agro-phenological data, covering barley sowing dates in the central agricultural district around lake Storsjön in Jämtland, central Scandinavia, are employed. These sowing dates have been shown to correlate with spring temperatures and cover most of the period since 1699. Second, previously unpublished data are employed in the form of ice-break up dates for Lake Storsjön, extending back to 1697. While each type of data cover most of the study period (1697–2021), combined they present an almost continuous time-series of phenological dates, enabling an attempt at reconstructing late-winter and spring temperatures in central Scandinavia back to 1697.

How to cite: Skoglund, M.: Barley to Ice: Investigating late-winter and spring temperatures in Central Scandinavia for the last 300 years through agro- and cryophenological proxies , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14523, https://doi.org/10.5194/egusphere-egu24-14523, 2024.

In this investigation, we reassess the hypothesis that volcanic eruptions lead to surface warming in Eurasia during winter. This reevaluation is grounded in contemporary modeling studies that propose internal climatic variations might dominate over the volcanic-forced responses. Our analysis is centered on the Last Millennium (LM), where we combine model output, instrumental observations, tree-ring records, and ice cores, and build a new temperature reconstruction that specifically targets the boreal winter season. Utilizing the latest advancements in volcanic forcing reconstructions, we pinpoint 20 volcanic events over the LM with volcanic stratospheric sulfur injections (VSSI) exceeding those of the 1991 Pinatubo eruption.

Our analysis indicates that among the 20 major volcanic events identified, only seven resulted in warmer surface temperature anomalies in Eurasia during the initial winter following the eruption. In scrutinizing the 13 occurrences that exhibit cold post-eruption anomalies, we observe no direct correlation between the extent of winter cooling and the mass of volcanic stratospheric sulfur injections (VSSI), suggesting that significant internal climatic variability is the probable driver of these cold anomalies.

Moreover, we compare our new temperature reconstruction with two independent reconstructions, and successfully harmonize our results with those of prior research. Moving beyond the observational uncertainties and the conflation of eruptions from different latitudes and different post-eruption winters, our study challenges previous assertions of post-eruption winter warming that largely stemmed from the superposed epoch analysis, which involved averaging the effects of smaller eruptions with larger ones. Our comprehensive observational findings, encompassing the entire LM and corroborating many recent climate modeling studies, suggest that substantial low-latitude volcanic eruptions, such as the 1991 Mount Pinatubo eruption, do not lead to any notable surface warming during the winter months in Eurasia.

How to cite: Tejedor, E., Polvani, L., Steiger, N., Vuille, M., and Smerdon, J.: Absence of Winter Warming in Eurasia following large, tropical volcanic eruptions during the Last Millennium, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13168, https://doi.org/10.5194/egusphere-egu24-13168, 2024.

Some classic approaches to climate reconstruction, such as employing transfer functions, have stringent requirements for the quality and continuity of historical records. As a result of limited data sources and complex topography, it’s hard to estimate the winter temperature in southwest China. However, the Bayesian approach allows integrating probabilities into the temperature indices and assimilating documentary information with different uncertainties with climate modeling data. Some gap years with less or even absent information in narrative sources could also be evaluated.

Based on Bayes’ theory, a large-scale simulation ensemble containing 20 members called ModE-Sim serves for the estimate of prior atmospheric states. The documentary data, including abnormal phenomena records in the local history and official reports of precipitation, contain various information on snow, rainfall, flower phenomena, and personal feelings. They are used to generate Indices from extremely cold to warm as well as the associated likelihood of each winter and contribute to the reconstruction of the posterior probability. Finally, a series of winter temperature with uncertainty in southwest China during the 18^th-19^th century is generated from the prior and posterior probability.

This new 200-yr reconstruction in this study fits well with an independent dataset called ModE-RA, which is a global monthly reanalysis also employing ModE-Sim as the background state of the atmosphere. The cold winters of 1700/1701, 1783/1784, 1809/1810, and 1892/1893 and the cold late 19^th century are expressed in this reconstruction. This study presents a new application of the Bayesian approach in the historical climatology field and has the potential to contribute to the analysis of large-scale circulation in past winters in China.

How to cite: Chen, S. and Brönnimann, S.: A winter temperature reconstruction based on the Bayesian approach in southwest China during the 18th-19th century, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4774, https://doi.org/10.5194/egusphere-egu24-4774, 2024.

The Southern Patagonian Andes are located within the core zone of the Southern Hemispheric Westerlies (SHW). The North-South orientated Andean Cordillera is perpendicular to the main flow of moist airmasses triggered by different large-scale atmospheric circulation patterns like the Antarctic Oscillation (AAO). In recent decades, especially southernmost South America (50–56◦ S) has experienced a profound climate change resulting in rising temperatures, an increase in the variation of precipitation, and increased severe droughts (e.g. the recent Chilean Megadrought) that can be related to variations in atmospheric circulation over varied timescales. Up to now, a quantification of these changes in a context pre-1950´s stays difficult, due to scarce and fragmentated available climate station data. In combination with a complex regional topography and resulting scetchy ecoclimatic zones the impacts of the current environmental change are yet not well assessed. Within this study we present the up to date most dense network of d¹⁸O_tree-ring series for southern South America based on two Nothofagus tree species. We can demonstrate, that the inherent climate signals in our proxy series is a highly suitable annual resolved archive to capture variations in the AAO and therefore can capture the long-term and short-term geographical migration (North-South) of the SHW. In addition, combined analyses of large-scale synoptic weather patterns (mean weather types; Grosswetterlagen, GWL) and backward trajectory modeling clearly reveal a highly significant influence of the moisture origin on the variations of the d¹⁸O_tree-ring series.

How to cite: Meier, W. J.-H., Grießinger, J., Aravena, J. C., and Soto-Rogel, P.: The tree-ring d18O network from southernmost Patagonia: A recorder of large-scale climate modes and their spatial-temporal variability, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-22252, https://doi.org/10.5194/egusphere-egu24-22252, 2024.

Water stable isotopes signals recorded in snow, firn and ice cores were successfully used to investigate past temperatures on glacial/interglacial scales (Jouzel and Masson-Delmotte 2010, Dansgaard, 1964). However, as evidenced by Goursaud et al. (2018) in coastal Adélie Land, many uncertainties hampered the interpretation of water isotope records at sub-annual to decadal resolution as a proxy of past temperature variations only (Goursaud et al. 2018). Condensation, sublimation and/or redistribution of snow triggered by strong katabatic winds as well as precipitation intermittencies, origin of moist air masses bringing precipitation and diffusion within firn lessen the representativity of a single isotopic profile to reconstruct past temperature in this region (Grazioli et al. 2017, Khale et al. 2018, Picard et al. 2019, Casado et al. 2020, Hirsch et al. 2023). In order to mitigate the non-representativity of a single isotopic profile, a solution consists in averaging several records to increase signal to noise ratios. However, to do so, it is necessary to provide a good correspondence between the different cores of interest.

In this study, we make good use of water stable isotopes and major chemistry records from 9 firn core (20 to 40m deep) drilled at 3 sites (so called D47, Stop5 and Stop0) during the ASUMA campaign. These sites display a high mean accumulation rate of about 250 mm.weq/year and a wide range of environmental conditions with elevation ranging from 1550m to 2460m, distance from coast ranging from 103km to 423km and different katabatic winds influence. In particular, we use the Paleochrono probabilistic model with water stable isotopes signal and major chemistry records coupled with beta-gamma and RADAR data to obtain the best correspondence between the different cores. We then quantify to what extent the stacking of several cores enable to increase the signal to noise ratio at the different sites and can provide a faithful record to document variations of the temperature and/or atmospheric water cycle over the last decades in this region.

How to cite: Tcheng, T., Fourré, E., Baubant, L., Lassalle-Bernard, C., Jacob, R., Parrenin, F., Jossoud, O., Prié, F., Minster, B., Agosta, C., Leroy-Dos-Santos, C., Casado, M., Bouchet, M., Favier, V., Magand, O., Lemeur, E., Picard, G., Cauquoin, A., Werner, M., and Landais, A. and the ASUMA RAID team: Multiproxy analyses for a network of firn cores covering the last 40 years from coastal Adélie Land , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9558, https://doi.org/10.5194/egusphere-egu24-9558, 2024.

Proxies of paleoclimate are essential tools in reconstructing past Antarctic climates, understanding its natural climate variability, and providing context for change under future warming. Constraining past changes in Antarctic sea ice is particularly challenging, and current proxy records have significant temporal and spatial limitations¹. Here, we report use of a new sea-ice proxy, namely the geochemical signature of prey remains preserved in snow petrel (Pagodroma nivea) stomach oil deposits.  

Antarctica’s relatively stable Holocene climate provided a backdrop for the establishment and development of modern ecosystems. Close to the margin of the East Antarctic Ice Sheet, the Theron Mountains provided one such ecological niche in the form of a snow petrel colony, estimated to have established approximately 6,000 years ago². During each summer breeding season, snow petrel adults travelled towards the retreating sea-ice edge to hunt for food for their young, or towards areas of open water (polynyas). Prey species varied in proportion according to proximity to the continental shelf, whether proximal (fish), distal (krill) or within a polynya (increased proportion of fish)³. These dietary signatures are preserved in the form of lipid biomarkers within their fossilised stomach oil deposits, accumulated outside nest crevices during defensive regurgitation. The presence of this colony in the Holocene therefore offers a unique lens to examine the response of the Antarctic environment to fluctuating sea-ice conditions⁴. A multi-proxy methodology is employed here, comparing key elements and trace metals, fatty acid profiles and bulk isotopic (δ¹³C and δ¹⁵N) compositions. This study aims to address the uncertainties current paleoclimate proxies have, and our results show centennial-scale dietary fluctuations across the last 2,000 years in response to retreating sea-ice. We therefore offer a more comprehensive insight into reconstructing Holocene climate variability within the eastern Weddell Sea region of Antarctica.

¹Collins, M., Knutti, R., Arblaster, J., Dufresne, J.-L., Fichefet, T., Friedlingstein, P., Gao, X., Gutowski, W. J., Johns, T., Krinner, G., Shongwe, M., Tebaldi, C., Weaver, A. J., and Wehner, M.: Long-term Climate Change: Projections, Commitments, and Irreversibility, in: Climate Change 2013: The Physical Science Basis. Contribution of Working Group I to 735 the Fifth Assessment Report of the Intergovernmental Panel on Climate Change edited by: Stocker, T. F., Qin, D., Plattner, G.-K., Tignor, M., Allen, S. K., Boschung, J., Nauels, A., Xia, Y., Bex, V., and Midgley, P. M., Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA., 2013.

²Berg, S., Melles, M., Hermichen, W.-D., McClymont, E. L., Bentley, M. J., Hodgson, D. A., & Kuhn, G. (2019). Evaluation of mumiyo deposits from East Antarctica as archives for the Late Quaternary environmental and climatic history. Geochemistry, Geophysics, Geosystems, 20(1), 260– 276.

³Barbraud, C., & Weimerskirch, H. (2001). Contrasting effects of the extent of sea-ice on the breeding performance of an Antarctic top predator, the snow petrel, Pagodroma nivea. Journal of Avian Biology, 32(4), 297– 302.

⁴Delord, K., Pinet, P., Pinaud, D., Barbraud, C., De Grissac, S., Lewden, A., et al. (2016). Species-specific foraging strategies and segregation mechanisms of sympatric Antarctic fulmarine petrels throughout the annual cycle. Ibis, 158(3), 569– 586.

How to cite: Penny, C., Bentley, M., Hodgson, D., and McClymont, E.: The Use of a New Paleoclimate Archive to Reconstruct Holocene Sea-Ice Variability in the eastern Weddell Sea, Antarctica, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10796, https://doi.org/10.5194/egusphere-egu24-10796, 2024.