Interglacial Research Articles

Prediction of the potentially suitable areas of Eucommia ulmoides Oliver in China under climate change based on optimized Biomod2 and MaxEnt models

Eucommia ulmoides Oliver is a medicinal plant of significant economic importance. Its cortex has been employed for centuries to alleviate various conditions such as lumbar pain, knee pain, and osteoporosis. Additionally, E. ulmoides possesses substantial industrial value. With the growing demand for this medicinal herb, ensuring its sustainable supply has become imperative. Climate change has caused habitat restrictions or migration of medicinal plants. Therefore, predicting the impact of climate change on the distribution of E. ulmoides is crucial for its conservation and sustainable use. This study evaluated the potential distribution of E. ulmoides across China under various climate change scenarios since the last interglacial period by modeling suitable areas based on 257 distribution records and 19 major environmental factors related to E. ulmoides. The model selection process initially identified the MaxEnt model as the most suitable. The optimized MaxEnt model, with RM = 2.0 and FC = LQHPT settings, generated the most precise predictions. Results indicate that the minimum temperature of the coldest month, annual mean temperature, and annual precipitation significantly affect the distribution of E. ulmoides. Under current environmental conditions, highly suitable areas for E. ulmoides are found in Southwest and Southeast China, with a total suitable habitat area of 23.12 × 104 km2. However, the range of suitable habitat has shifted due to global warming’s negative impact. Under different climate scenarios, suitable areas for E. ulmoides have either increased or decreased, with expansions primarily in high-latitude regions. Future climate scenarios predict shifts in the centroid of suitable E. ulmoides habitat towards Yichang City in Hubei Province. The findings of this study support the development, artificial cultivation, and conservation of E. ulmoides resources.

Late Quaternary fluvial terrace characteristics and ages of the Pamir‒Tian Shan convergence zone: indications of regional climate change and tectonic uplift

The Pamir‒Tian Shan collision zone, located at the northwestern edge of the Himalaya‒Qingzang orogenic belt, provides a natural laboratory for investigating the development of fluvial terraces controlled by regional climate change and tectonic uplift. In this study, we conducted geomorphological mapping and terrestrial cosmogenic nuclide 10Be dating of fluvial terraces in the Wuheshalu syncline, within the Pamir‒Tian Shan collision zone. Four major fluvial terraces were identified in the Wuheshalu syncline, with ages of approximately 187, 141, 90, and 19 ka, respectively. These terraces were abandoned during three glacial‒interglacial transition periods (Marine Isotope Stage 6/5 (MIS6/5), cold-to-warm transition period of MIS5, and end of MIS2 or MIS2/1) and one interglacial‒glacial period (MIS7/6), and exhibit a strong correlation with regional climate change. Tectonic uplift contributed only one-third of the observed fluvial incision. These results suggest that river incision and terrace formation in the Pamir‒Tian Shan collision zone are primarily driven by periodic fluctuations in climate, with a lesser contribution from tectonic uplift.

A model estimating the level of floral transition in olive trees exposed to warm periods during winter.

Rising winter temperatures jeopardize the fruit yield of trees that require a prolonged and sufficiently cold winter to flower. Predicting the exact risk to different crop varieties is the first step in mitigating the harmful effects of climate change. This work focused on olive (Olea europaea) - a traditional crop in the Mediterranean basin whose flowering depends on the sufficiency of cold periods and the lack of warm ones during the preceding winter. Yet, a satisfactory quantitative model forecasting its expected flowering under natural temperature conditions is still lacking. The effect of different temperature regimes on olive flowering level and flowering-gene expression was empirically tested. A modified 'dynamic model' describing the response of a putative flowering factor to the temperature signal was constructed. The crucial component of the model was an unstable intermediate, produced and degraded at temperature-dependent rates. The model accounts for both the number of cold and warm hours but also for their sequence. Empirical flowering and temperature data were applied to fit the model parameters, applying numerical constrained optimization techniques; the model outcomes were successfully validated. The model accurately predicted low-to-moderate flowering under winters with warm periods and properly accounted for the effects of warm periods during winter.

Effect of Global Warming on the Fish Population Parameters in the Upper Volga Reservoirs

As a result of global warming, the average annual water temperature has significantly increased in the Upper Volga reservoirs. Warming and the subsequent deterioration of the oxygen regime had a significant effect on most of the fish populations inhabiting temperate waters. This led to changes in the population structure of many fish species. Such phenomena as the disappearance or a sharp decline in the abundance of cold-water species (European smelt, vendace, burbot and pike) in the Rybinsk reservoir coincided with the period of warming. The disappearance of European smelt in the Rybinsk Reservoir and the favorable temperature regime contributed to the appearance and rapid increase in the abundance of the Caspian invader, the Black Sea sprat, which occupied the empty niche of the European smelt and became instead the dominant species in the pelagic zone of the Upper Volga reservoirs. Warming resulted in a decrease in the abundance and the growth rate of burbot and pike. Climate warming had an indirect effect on many species through oxygen deficiency or transformation of the forage base (ruff, zander, perch, roach), which also led to a decrease in abundance and the growth rate.

Predicting trends in atmospheric CO2 across the Mid-Pleistocene Transition using existing climate archives

Abstract. During the Mid-Pleistocene Transition (MPT), ca. 1200–800 000 years ago (ka), the Earth's glacial cycles changed from 41 to 100 kyr periodicity. The emergence of this longer ice age periodicity was accompanied by higher global ice volume in glacial periods and lower global ice volume in interglacial periods. Since there is no known change in external orbital forcing across the MPT, it is generally agreed that the cause of this transition is internal to the Earth system. Resolving the climate, carbon cycle, and cryosphere processes responsible for the MPT remains a major challenge in Earth and palaeoclimate science. To address this challenge, the international ice core community has prioritised recovery of an ice core record spanning the MPT interval. Here we present results from a simple generalised least-squares (GLS) model that predicts atmospheric CO2 out to 1.8 Myr. Our prediction utilises existing records of atmospheric carbon dioxide (CO2) from Antarctic ice cores spanning the past 800 kyr along with the existing LR04 benthic δ18Ocalcite stack (Lisiecki and Raymo, 2005; hereafter “benthic δ18O stack”) from marine sediment cores. Our predictions assume that the relationship between CO2 and benthic δ18O over the past 800 000 years can be extended over the last 1.5 million years. The implicit null hypothesis is that there has been no fundamental change in feedbacks between atmospheric CO2 and the climate parameters represented by benthic δ18O, global ice volume, and ocean temperature. We test the GLS-model-predicted CO2 concentrations against observed blue ice CO2 concentrations, δ11B-based CO2 reconstructions from marine sediment cores, and δ13C of leaf-wax-based CO2 reconstructions (Higgins et al., 2015; Yan et al., 2019; Yamamoto et al., 2022). We show that there is no clear evidence from the existing blue ice or proxy CO2 data to reject our predictions or our associated null hypothesis. A definitive test and/or rejection of the null hypothesis may be provided following recovery and analysis of continuous oldest ice core records from Antarctica, which are still several years away. The record presented here should provide a useful comparison for the oldest ice core records and an opportunity for further constraints on the processes involved in the MPT.

Species distribution modeling of North American beavers from the late Pliocene into the future

Abstract Beavers have occurred in North America since at least 7 Ma, but relatively little is known about their distribution across the continent. We modeled distributions of beavers in the late Pliocene (3.3 Ma), Pleistocene (130 ka and 21 ka), and recent Holocene (1970 to 2000) to understand their dispersal across North America, predict future distributions and predict their possible response to future climate and habitat changes. Occurrence data for Castor canadensis were derived from the Global Biodiversity Information Facility. Those data were used with both modern (1970 to 2000) and modeled future (EC-Earth-Veg 2081 to 2100) bioclimatic variables from WorldClim as well as past (Pliocene Marine Isotope Stage M2, Pleistocene Last Interglacial, and Pleistocene Last Glacial Maximum) bioclimatic variables from PaleoClim to model beaver distributions through time. Fossil locality points for Castor extracted from the New and Old Worlds Database of Fossil Mammals (NOW), NEOTOMA Paleoecology Database, and Paleobiology Database were overlain on past projection models to use as validation points. Models were run using MaxEnt with post-processing in ArcGIS. Accuracy for the 5 models ranged between 59.6% and 60.2%. Results for the present model (1970 to 2000) showed habitat suitability in areas beavers inhabit today. During the Pliocene MIS M2 cooling event (3.3 Ma) and Pleistocene Last Glacial Maximum (21 ka), habitat suitability shifted further south into Mexico and peninsular Florida and away from more periglacial northern regions. During the Last Interglacial period (130 ka) and modeled future (2081 to 2100) EC-Earth-Veg 2081 to 2100, habitat suitability was higher in coastal and central regions in North America and lower in southern regions compared to their present distribution. Distributions were most affected by precipitation seasonality, isothermality, and mean annual temperature. High variability in seasonal precipitation and temperatures is likely to influence surface water availability, vegetation type, and riparian vegetation composition, which consequently may reduce available food resources and habitat for beavers. Observed shifts during warmer periods may indicate areas in the late Miocene that facilitated dispersal into North America. Future models using other predicted climatic scenarios and shared socioeconomic pathways may provide better resolution of potential future shifts in beaver distribution with best- and worst-case climate scenarios, thereby permitting at-risk areas to be prioritized for conservation in the face of climate change.

Low-Cost Sensors for the Measurement of Soil Water Content for Rainfall-Induced Shallow Landslide Early Warning Systems

Monitoring soil water content (SWC) can improve the effectiveness of early warning systems (EWSs) designed to mitigate rainfall-induced shallow landslide risk. In extensive areas, like along linear infrastructures, the adoption of cost-effective sensors is critical for the EWS implementation. The present study aims to evaluate the reliability of different low-cost SWC sensors (frequency domain reflectometry and capacitance-based) in capturing soil moisture conditions critical for EWS, without performing soil-specific calibration. The reliability of the low-cost sensors is assessed through a comparative analysis of their measurements against those from high-cost and well-established sensors (time domain reflectometry) over a two-year period in a shallow landslide-prone area of Oltrepò Pavese, Italy. Although no landslides are observed during the monitoring period, meteorological conditions are reconstructed and statistical analysis of sensor’s responses to different rainfall events is conducted. Results indicate that, despite differences in absolute readings, low-cost sensors effectively capture relative SWC variations and demonstrate sensitivity to rainfall events across both cold and warm periods. The presented low-cost sensors can serve as reliable indicators of soil infiltration and saturation levels, highlighting their potential for real-time monitoring within extensive networks for EWS.

A 903-year annual temperature reconstruction for the southeastern tibetan plateau from the tree ring widths of Juniperus saltuaria.

Precisely dated paleoclimatic records are essential for understanding natural and anthropogenic climate influences. Here, an annually resolved absolutely dated Juniperus saltuaria tree ring width chronology from the Haizi mountain, southeastern Tibetan Plateau (TP) was developed. The chronology shows the annual- to decadal-scale paleoclimatic variability of the southeastern TP over the past 903years (1115-2017 CE). The tree ring widths correlate significantly with mean annual temperature (Tmean). A linear regression model between ring width and Tmean, accounting for 57% of the variance in temperature from 1959 to 2017 CE, was used to reconstruct the past 903years of Tmean variation in the southeastern TP. The chronology aligns with other temperature records from the TP, Asia, and the Northern Hemisphere (NH), indicating a marked temperature increase since the late twentieth century, with 1998-2017 CE identified as the warmest period. The coldest thirty years occurred in 1115-1145 CE. Solar activity and the Atlantic Multidecadal Oscillation exert notable influences on temperature fluctuations in this region. Superposed epoch analysis indicates that volcanic eruptions had significantly impacted southeastern TP temperatures, causing dramatic cooling for 2-4years. Our study presents the longest width chronology developed by Juniperus saltuaria to date, offering a long-term perspective on recent climatic shifts across the southeastern TP. This work enhances understanding of historical climate variability, providing critical insights to refine projections of future climate variability.

Has There Been a Recent Warming Slowdown over North China?

The warming slowdown observed between 1998 and 2012 has raised concerns in recent years. To examine the temporal and spatial variations in annual mean temperature (Tmp) as well as 12 extreme temperature indices (ETIs), and to assess the presence of a warming slowdown in North China (NC), we analyzed homogenized daily observational datasets from 79 meteorological stations spanning 1960 to 2020. Additionally, we investigated the influences of 78 atmospheric circulation indices (ACIs) on ETIs during the period of warming slowdown. To compare temperature changes, the study area was divided into three parts based on topographic conditions: Areas I, II, and III. The results revealed significant warming trends in Tmp and the 12 ETIs from 1960 to 2020. Comparing the time frames of 1960–1998, 2012–2020, and 1998–2012, both Tmp and the 12 ETIs displayed a cooling trend in the latter period, confirming the existence of a warming slowdown in NC. Notably, indices derived from daily maximum temperature exhibited higher cooling rates during 1998–2012, with winter contributing most significantly to the cooling trend among the four seasons. The most pronounced warming slowdown was observed in Area I, followed by Area III and Area II. Furthermore, our attribution analysis of ACIs concerning the temperature change indicated that the Asia Polar Vortex Area Index may have had the greatest influence on ETIs from 1960 to 2016. Moreover, the weakening of the Tibet Plateau Index Band and the Asian Latitudinal Circulation Index, and the strengthening of the Eurasian Latitudinal Circulation Index, were closely associated with ETIs during the warming slowdown period in NC. Through this research, we aim to deepen our understanding of climate change in NC and offer a valuable reference for the sustainable development of its natural ecology and social economy.

Greening of India and revival of the South Asian summer monsoon in a warmer world

While it is accepted that the tropical hydrological cycle has intensified during past interglacial periods due to changes in insolation, greenhouse gases and ice volume, their respective influences are uncertain. Here we present a pollen record from Bengal Bay to reconstruct vegetation changes in India’s core monsoon zone during two warm periods, the current and last interglacial, comparing the data with numerical model simulations to assess the influence of different forcing mechanisms. Results show tropical forest expansion between 11.7-5 ka and 127-120 ka, defining two Indian humid periods, with the last interglacial showing the strongest monsoon activity, consistent with salinity reconstructions. Model-data comparison highlights boreal summer insolation as the primary driver of vegetation dynamics and monsoon intensity during interglacial periods, with CO2 and ice-sheets having a limited effect. Vegetation remains unaffected by pre-industrial CO2 variations above 250 ppmv, a threshold value that characterizes most interglacials of the last million years.

Cold Intermediate Water Formation in the Black Sea Triggered by March 2022 Cold Intrusions

In mid-March 2022, a Siberian High brought intense cold air masses, leading to severe weather conditions across southern Europe, including the Black Sea region. This study investigates the spatial and temporal evolution of cold intermediate water (CIW) masses in the Black Sea, with a particular focus on the successive anomalously cold episodes that occurred in March 2022. The research underscores the significance of the northwestern continental slope and cyclonic gyres, especially as the only cold-water mass observations during the warm winters of 2020 and 2021 were concentrated in these areas. Following two warm winters, the cold episodes of March 2022 revealed notable convection and simultaneous cooling, particularly in the cyclonic interior and the Rim Current periphery, excluding the northeastern periphery. Subsequently, cold waters spreading isopycnally throughout the summer months were transported laterally and reached these regions. Argo float measurements provided clear evidence of widespread replenishment of the CIW, indicating that it is not confined to specific areas. The study also highlights regional variability in the characteristics of CIW formation, which is influenced by local dynamics and preconditioning temperatures. The temperatures of CIW increased from west to east, in line with the sea surface temperature gradient. Notably, thicker and colder CIW was found in the western cyclonic gyre compared to the eastern cyclonic area. Furthermore, the study confirms that the warming trend in CIW, identified in previous research, not only continues but has intensified during the recent period analyzed. These findings, observed under the extreme conditions analyzed in this research, offer valuable insights into the widespread occurrence of CIW formation in the Black Sea. Additionally, the study confirms that the warming trend in CIW, identified in previous studies, continued in the region throughout the warm winter period and after the cold spell in 2022. These insights contribute to a deeper understanding of CIW dynamics and their response to extreme weather events in the Black Sea.

Deep north atlantic circulation strength: Glacial-interglacial variability over the last 400,000 years

Most of the high-resolution studies investigating the past variability of the deep North Atlantic circulation are focused on recent timescales, but little is known for periods older than the last glacial period. Based on magnetic, elemental and physical grain-size proxies of three pairs of sediment cores located South of Iceland, we reconstructed the past changes in grain-size and basaltic-derived grain concentration over the last 400 ka (1 ka = 1000 years). The source and grain-size proxies exhibit highly similar variations between the three sites, suggesting they are affected by the same regional process. Persistently lower concentrations and finer grain-sizes recorded in the southernmost and deeper site compared to the northern sites indicate a North to South gradient that is consistent with the southward transport of sediments from a northern basaltic source by a deep current. Therefore, we interpret changes recorded by the ensemble of proxies at the three sites as past variations in the ISOW intensity. These new results show persistent influence, over the entire 400 ka, of a southward deep-water flow in the subpolar North Atlantic, from 1800 to 2800 m water depth. The “off mode” of deep Atlantic circulation during Heinrich events suggested by many studies is therefore questioned. This study extends the previous observations made for the 20–65 ka period over the last 400 ka. Our results also show that the three studied sites are bathed by a deep-water mass formed in the Nordic Seas, during both glacial and interglacial periods, suggesting that the present-day convection areas were still active during glacial periods. Our ISOW intensity records are highly similar to those of deep-water ventilation. We propose that the strength of overflows in the North Atlantic regulates the volume of North Atlantic Deep Water (NADW) and its southward transport in the Atlantic basin. Therefore, the Southern source waters may only act as an opportunistic component of the deep Atlantic circulation, invading or retreating depending on the NADW strength.

Retreating ice sheet caused a transition from cold-dry to cold-humid conditions in arid Central Asia

Water is critical for ecological systems in arid regions, making it imperative to understand how moisture in arid Central Asia (CA) responds to anthropogenic warming. The oscillation of warming and cooling events since the Last Glacial Maximum (LGM, ∼24–19.5 ka) provides a window for exploring the relationship between moisture and temperature. Employing 109 luminescence ages derived from eight sand dune sediment cores in the Bayanbulak Basin in the CA, this study endeavors to reconstruct the evolution of sand accumulation, and by extension, moisture dynamics. We found that pre-Holocene sand accumulation was predominant during the LGM and Heinrich Stadial 1 (HS1, ∼18–14.6 ka), indicative of a cold-dry climate prevailing during these two cold stages. During the Holocene, sand accumulation during Early Holocene is significantly stronger than that during Middle-late Holocene, supporting a long-term wetting trend. Additionally, this study reveals that the colder Little Ice Age (LIA, ∼0.55–0.2 ka) exhibited a wetter condition compared to the warmer Medieval Warming Period (MWP, ∼1–0.55 ka), indicating a cold-humid climate during the LIA. Corroborated by TraCE-21ka (Transient Climate of the Last 21,000 Years) simulation, we propose that diminished evaporation over North Atlantic during the LGM and HS1 potentially led to a reduction in water vapor transported by westerlies to the CA. During the Middle and Late Holocene, increased evaporation over North Atlantic, attributed to decreased ice sheet, westerlies intensity became the primary limiting factor. Notably, stronger westerlies during the LIA could have contributed to elevated moisture levels compared to the MWP. These findings not only resolve the debate surrounding the transition from cold-dry to cold-humid conditions but also enhance our comprehension of future moisture variations.

Sedimentary provenance and paleogeographic environment of a Mississippian coal-bearing unit in South China: Constraints from detrital zircon U-Pb ages and sedimentologic and geochemical evidence

The Mississippian Xiangbai Formation in South China is one of the oldest coal-bearing sedimentary units in China. However, the sedimentary provenance, paleogeography, and coal formation patterns of the coal-bearing strata are not well constrained. We address this key issue by using a combination of detrital zircon U-Pb data, geochemical analyses of mudstone and shale, drilling data, and geologic field observations. With the exception of the early Paleozoic orogenic events (ca. 440–420 Ma) in the eastern part of the study area, the samples from the Xiangbai Formation exhibit similar detrital zircon U-Pb age distribution with major age peaks at ca. 980–960 Ma and several subordinate age peaks at ca. 800–780 and 600–500 Ma. These detrital zircon grains mainly originated from recycled sedimentary units. Field and drilling data reveal that the Xiangbai Formation was formed in a tidal flat environment with water depth gradually increasing from the bottom to the top, indicating an overall trend of transgression. The Mississippian Xiangbai Formation was deposited in an interglacial period. The Lower Xiangbai Formation was deposited in a relatively cold paleoclimate, gradually transitioning upwards to a warm and humid climate, creating favorable conditions for coal formation. The alternation of warming and cooling climates triggered high-frequency eustatic fluctuations, which led to multiple sedimentary cycles and resulted in thin, unstable coal seams within the Xiangbai Formation. Mississippian sedimentary paleogeography, palaeoclimate, and sedimentary provenance together dominate the coal-bearing clastic sediments in southwestern South China.

Indian summer monsoon history during the last glacial cycle revealed by a loess sequence from the Tibetan Plateau

The Indian Summer Monsoon (ISM) has a profound influence on the environment and people of East Asia. However, despite its importance, the variability and dynamic mechanisms of the ISM remain inadequately understood. This study investigates the evolution of the Indian Summer Monsoon (ISM) since the Last Interglacial by analyzing the well-preserved Cuoweng (CW) loess–paleosol sequence in the southeastern Tibetan Plateau. A robust chronological framework is established using quartz optically stimulated luminescence (OSL) dating and K-feldspar post-infrared infrared stimulated luminescence (pIRIR) dating. The history of the ISM over the past ~135 ka is reconstructed based on multiple environmental proxies. The results indicate that the ISM experienced significant glacial–interglacial fluctuations during the last glacial cycle, exhibiting a strengthened monsoon during warm periods and a weakened one during cold periods. Additionally, suborbital-scale cyclic variations in the ISM during the marine isotope stage (MIS) 5 are revealed, with enhanced monsoon conditions during MIS 5a, 5c, and 5e and weakened conditions during MIS 5b and 5d. These findings suggest that the ISM variations are primarily influenced by a combination of high- and low-latitude forcing. This study provides new insights into the complex responses of the ISM to climate change, enhancing our understanding of its potential future changes.

Temporal and spatial dynamics of the non-indigenous bryozoan, Amathia verticillata, and its associated invertebrate community

The widespread non-indigenous bryozoan, Amathia verticillata primarily colonizes in coastal bays and harbors on anthropogenic structures. Although this habitat-forming bryozoan is widely recognized to house a variety of marine invertebrates within its structure, little is known about their spatiotemporal dynamics and their associated invertebrate community in Southern California, USA. Thus, we undertook a comprehensive yearlong study (July 2021-2022) in an urbanized estuary (Mission Bay, San Diego) to quantify A. verticillata percent cover and abiotic conditions at 6 stations with varying environmental conditions. The seasonal and spatial gradients in temperature and salinity within Mission Bay were as expected with seasonal hypersalinity typical of Mediterranean climate regions. The percent cover of A. verticillata was positively correlated with temperature with the highest percent cover found during the warmest periods, and higher average percent cover found in the warmer, eastern parts of Mission Bay. We also collected three replicate A. verticillata colonies to characterize the marine invertebrate community associated with this non-indigenous bryozoan. We identified 25 families, 24 genera, and 19 organisms to species belonging to the taxonomic groups: amphipods, isopods, tanaids, and polychaetes. Furthermore, we identified juvenile stages and ovigerous females living within A. verticillata. None of the identified invertebrate families contributed more than 21 % to the community. The seasonal growth and annual temporal patterns of A. verticillata may prevent competitively dominant species from becoming established within the invertebrate community and allow A. verticillata to harbor a diverse invertebrate community. Sphaeromatidae isopods were the most common family found in the bryozoan colonies, likely reflecting their broad environmental tolerances. Additionally, while some of the invertebrates found within A. verticillata were also non-indigenous species, more work needs to be done to determine if A. verticillata disproportionately supports these species over native species. Collectively, our results imply that A. verticillata functions as a nursery habitat on anthropogenic structures for peracarid crustaceans and polychaetes. Furthermore, A. verticillata assemble analogous communities across their distribution, which may indicate that invasions are homogenizing biota globally.

Carbon, iron and sulfur records of lacustrine paleo-environments during the middle Eocene in eastern China

It is widely recognized that anoxic conditions facilitate the preservation of organic carbon in marine sediments. However, the specific geological factors that lead to the development of such conditions in paleo-lakes are less well understood. Owing to their smaller size, paleolakes could experience more frequent and stronger changes in geochemical conditions than oceans. Such changes, such as volcanism, hydrothermal fluids, or ocean transgressions, can also strongly affect the lacustrine organic carbon burial thereby complicating sediment diagenesis record. Here, we used total organic carbon content (TOC), organic carbon isotope (δ13Corg), iron speciation, and pyrite sulfur isotope (δ34Spy) data to establish relationships between organic carbon preservation and anoxic conditions in fine-grained sediments from the middle Eocene lacustrine depositional environments from the Shahejie Formation of the Jiyang Depression, Bohai Bay Basin, eastern China. The results reveal TOC between 1 % and 10 %, highly-reactive iron to total iron ratios >0.38, and most TOC to total sulfur ratios exceeding 2. These data indicate that the organic-rich shales of the Shahejie Formation were formed as a result of high primary productivity during the warm and humid middle Eocene period, coupled with the efficient preservation of organic matter in anoxic bottom waters. Negative δ13Corg and δ34Spy excursions recorded in the Shahejie Formation indicate water column conditions to have been influenced by transient volcanic eruptions. Positive δ13Corg and negative δ34Spy excursions may have been caused by hydrothermal fluids input whereas δ34Spy values approaching 20 ‰ suggest frequent marine transgressions. In particular, despite potential inputs of S into the paleolake by volcanism, hydrothermal fluids, or marine transgressions, bacterial sulfate reduction efficiently depleted the sulfate pool to have created ferruginous geochemistry water conditions for the effective preservation of organic carbon in sediments. Our results establish a direct link between lacustrine shale geochemical signatures and geological phenomena that impact its sedimentation.

Worldwide consequences of a mid-Holocene cold event in the Nordic Seas

The present interglacial is a relatively warm and stable period, especially compared to the preceding glacial time. However, the Holocene has seen the emergence of several remarkable cold events, some with worldwide consequences. Leveraging marine records from the Nordic Seas, we provide the first detailed account of a cold event centered around 6.8 ka BP. Utilizing paleoceanographic proxies and advanced modeling, we unveil a distinct subsurface water cooling, associated with a stepwise increase in sea-ice cover in the eastern Fram Strait. Our findings emphasize the role of Greenland Sea deep convection onset and the subsequent westward shift in Atlantic Water flow, enabling sea-ice advection from the Barents Sea. The heightened sea-ice cover weakened Atlantic Water advection, perturbing thermohaline circulation in the eastern Nordic Seas. These perturbations propagated worldwide, affecting North Atlantic deep-water circulation, inducing widespread hemispheric cooling, shifting the Intertropical Convergence Zone southward, and weakening the East Asian monsoon. Incorporating results from the Transient simulations of Climate Evolution of the last 21,000 years (TraCE-21ka) supports and augments proxy-based paleoreconstructions, underscoring sea-ice dynamics and ocean circulation's critical influence. This study highlights the potential for localized cold events within ostensibly warm climatic intervals. It underscores the need to comprehend their mechanisms for precise climate predictions and informed policymaking toward a sustainable future.

Harvesting the sun twice: Energy, food and water benefits from agrivoltaics in East Africa

Food, energy and water insecurity are concomitant challenges facing many communities in East Africa. Agrivoltaic systems – agriculture integrated with photovoltaic panels – address all three challenges, providing low carbon electricity, food production and water conservation on the same land area. Agrivoltaics have proven benefits for the food-energy-water nexus in the USA, Europe and Asia, but research is lacking in sub-Saharan Africa, where energy access remains low, and climate change and water scarcity threaten food systems. This study presents evidence for concomitant electricity generation, food production and water conservation from agrivoltaic systems in Tanzania and Kenya, demonstrating the viability of these systems for both grid-tied agribusinesses and rural, off-grid communities. Performance of some crops improved under agrivoltaics, generating higher incomes for farmers and agribusinesses while reducing energy bills and/or enhancing energy supply. Crop survivability during a warm period was greater under the agrivoltaic system, indicating potential for climate change resilience. Panel shading reduced irrigation demand, thus some crops achieved greater yields while needing less water input. Rainwater harvesting from panel runoff further reduced irrigation needs. Combining energy infrastructure with agriculture enhanced land productivity for all crops at both sites. Agrivoltaics, whether grid-tied or off-grid, could address multiple Sustainable Development Goals in East Africa simultaneously by contributing to energy security, climate change-resilient food production, and water conservation in the region.

Utilizing Paleoclimate Data to Analyze the Relationship Between Climate Change and Human Activities

Our research aims at finding the relationship between climatic cycle-changes and the human activities in ancient China. Most climatic changes show shifts in the precipitation volume and alternations between warm and cold periods. Through other research findings, we find the precipitation volume is closely connected with alternations of warm and cold periods. This report presents a linear comparison between the population of ancient China and the east Asia climate variables and chooses tree rings as the main indicator of the paleo-climate. Through the literature review and the data analysis, we find that (1) The dominant climate pattern in East Asia is East Asia Summer Monsoon system, causing centennial scaled climate periodicities, affecting the ecosystem and the society. (2) There are certain cycles of climate change, in which the warm period and the cold period have a certain influence on the population change. (3) The precipitation has a certain correlation with the population change. However, single temperature and precipitation cannot directly affect the population change, but also need to be combined with social and historical factors specific analysis.