Instrumental Observations Research Articles

ГЕОМЕХАНІЧНЕ ОБҐРУНТУВАННЯ РОЗРОБКИ ПОТУЖНИХ ТА ВЕЛЬМИ ПОТУЖНИХ ПОКЛАДІВ БАГАТИХ ЗАЛІЗНИХ РУД В УМОВАХ ЗНАЧНИХ ГЛИБИН

Purpose. Improving the quality of the mined ore mass and reducing the operating costs for the extraction of minerals by taking into account the geomechanical state of the ore-rock massif. Methods. A complex method that includes analysis and generalization of previous studies, mine instrumental observations, numerical modeling by the finite element method, analytical studies and statistical data processing. Results. It has been established that the key factors influencing the choice of stable parameters of the structural elements of the stope panels of the stope blocks are: the parameters of the stress-strain state of the stope horizon, determined by the depth of mining, the thickness and dip of the ore deposit, the shape and size of the shear zone of host rocks; the procedure for working out stope panels according to the thickness and strike of the stope block; intensity of development of stocks of compensation spaces. At the same time, the stability of transport drifts and junctions with orts-arrivals depends on the length of their location before the contact of the host rocks of the lying side with the ore deposit, the thickness of the ore deposit and the geological macrostructure of the rocks of the sides, as well as the number of contacts of the stope panel with collapsed host rocks. The maximum possible stable parameters of exposures of compensation chambers, which are formed by explosive breaking of borehole charges, depending on the thickness of the ore deposit and the location of their center from the rocks of the hanging side, have been established. Scientific novelty. For the depth range of 1200–1500 m, the dependences of the stress distribution across the pull of the ore deposit on the horizon of mining have been obtained. Power-law dependences of the equivalent span width of the bottom of the stope panel, equivalent spans of stable horizontal and vertical outcrops on the location of the center of the stope panel along the thickness of the ore deposit on the host rocks of the hanging side have been established. Practical significance. The obtained dependencies allow choosing the most rational technological schemes for the mining of rich iron ore deposits, taking into account the stress-strain state of the ore-rock mass and the location of the stope panel according to the thickness of the deposit.

Consolidating historical instrumental observations in southern Australia for assessing pre-industrial weather and climate variability

Human-induced climate change has resulted in long-term drying trends across southern Australia, particularly during the cool season, with the most pronounced impacts observed in the southwest since the 1970s. Although these trends have been linked to changes in large-scale atmospheric circulation features, the limited number of daily weather datasets that extend into the pre-industrial period have so far prevented an assessment of the long-term context of synoptic-level changes associated with global warming. To address this need, we present the development of the longest sub-daily atmospheric pressure, temperature and rainfall records for Australia beginning in 1830. We first consolidate a range of historical observations from the two southern Australian cities of Perth and Adelaide. After assessing the quality and homogeneity of these records, we verify their ability to capture the weather and climate features produced by the Southern Hemisphere’s key climate modes of variability. Our analysis shows the historical observations are sensitive to the influence of large-scale dynamical drivers of Australian climate, as well as the relationship between southwestern and southeastern Australia. Finally, we demonstrate the ability of the dataset to resolve daily weather extremes by examining three severe storms that occurred in the nineteenth century associated with westerly storm tracks that influence southern Australia. The historical dataset introduced here provides a foundation for investigating pre-industrial weather and climate variability in southern Australia, extending the potential for attribution studies of anthropogenically-influenced weather and climate extremes.

The marble envelope of the Casa delle Armi by Luigi Moretti: documentary and experimental knowledge finalized to digital modeling

The application of digital modeling for safeguarding the built heritage is a consolidated research field and carries substantial operational interest. The methodological aspects of this application are theoretically outlined but far from being commonly applied. In the perspective of delineating a more straightforward method for implementing these practices among the built heritage, modern Italian architectural production constitutes an ideal field of investigation, both for the significance of the built heritage and for the construction problems that characterize them. Indeed, in the case of stone cladding – which is typical of the Fascist period – the decay conditions and the peculiarity of the material make the investigation specific and paradigmatic of the implementation of the above-mentioned digital methodologies. The Casa delle Armi built heritage by Luigi Moretti in Rome, which has been the research subject of the Authors for years, features a marbled envelope detailed by the designer in every aspect, not only during the design phase but also during construction. This uniqueness makes the recovery of the envelope extremely challenging, as it should not alter its extremely complex nature, while today, the marble envelope is profoundly degraded by natural and anthropogenic factors. Digital modeling appears to be an optimal operational solution for guiding the recovery, but it presents many issues illustrated in this article and to which we have begun to give answers in this contribution. In particular, we delineate the knowledge of the case mentioned above study-built heritage, pursued through documentary analysis integrated by direct and instrumental observation on site.

DAGESTAN EARTHQUAKES FELT in 2016–2017

The article provides instrumental data and descriptions of macroseismic manifestations of six perceptible earthquakes that occurred on the territory of Dagestan in 2016 (Mekhelta on May 13 with KR=13.5, Ms=5.3, I0=5, Arakan on August 24 with KR=10.1, Ms =3.4, I0=4, Botlikh on November 2 with KR=9.3, Ms=3.2, I0=4, Kizilyurt-II on December 22 with KR=10.3, Ms=3.5, I0=4–5) and in 2017 (Tsurib on May 3 with KR=13.6, Ms=5.3, I0=6 and Lyakhlya on December 7 with KR=12, Ms=4.4, I0=5–6). For each of the considered earthquakes, except for the Tsurib one, isoseismal maps were compiled. All earthquakes, except for the Arakan one, are located along the seismically active ring around the calm zone. The Arakan earthquake, together with the Kichigamra-I and Kichigamra-II earthquakes on May 3, 1988, and April 3, 2013, breaks the long-term seismic calm in this zone, there-by confirming that similar seismic events can take place here in the medium term. It should be noted that the 2016 Botlikh earthquake is the only event of such magnitude within the Botlikh area for the entire instrumental observation period (since 1975). The Kizilyurt-II earthquake, despite its low mag-nitude, is of interest due to the wide-area where shakes were felt, and, together with the strong 1999 Kizilyurt-I earthquake with Ms=5.3, due to proximity to the Chiryurt hydroelectric power station.

Evolution and transformation processes of China’s educational policy and governance in 1978-2019

Since the beginning of the period of reforms and openness, the PRC has constantly promoted a phased reform of the education system to modernize educational functions, rise new builders of socialism and support economic transformations in the country. Due to the active regulatory and management work, described in detail in the article with the help of instrumental observation, China gradually achieved several important results. State educational policy shifted from focusing on expanding the scope and improving the quality of education to its connotation-based development. The study of the Chinese experience of modernization of the education system has not only theoretical, but also practical significance, since successful Chinese examples of deep and rapid transformation of the national administrative system and state functions, as well as a clear adjustment of the characteristics of educational policy to current national priorities can be considered for partial application in other countries, including Russia. In order to adapt elements of the Chinese experience to the realities of other countries, such as Russian Federation, it is necessary to fully understand the context, features and stages of the educational policy evolution of the People’s Republic of China, which is done in this article.

ГИДРОЛОГИЧЕСКИЕ ХАРАКТЕРИСТИКИ РЕК НАЦИОНАЛЬНОГО ПАРКА «БЕЛОВЕЖСКАЯ ПУЩА»

The article presents analysis of modern hydrological characteristics of the of Bialowieza Forest rivers’ during the period of instrumental observations and provides a water regime’s forecast assessment of the research territory. The database of Bialowieza Forest rivers’ hydrological characteristics was updated with the help of GIS.

A Bayesian approach to historical climatology for the Burgundian Low Countries in the 15th century

Abstract. Although collaborative efforts have been made to retrieve climate data from instrumental observations and paleoclimate records, there is still a large amount of valuable information in historical archives that has not been utilized for climate reconstruction. Due to the qualitative nature of these datasets, historical texts have been compiled and studied by historians aiming to describe the climate impact in socioeconomic aspects of human societies, but the inclusion of this information in past climate reconstructions remains fairly unexplored. Within this context, we present a novel approach to assimilate climate information contained in chronicles and annals from the 15th century to generate robust temperature and precipitation reconstructions of the Burgundian Low Countries, taking into account uncertainties associated with the descriptions of narrative sources. After data assimilation, our reconstructions present a high seasonal temperature correlation of ∼0.8 independently of the climate model employed to estimate the background state of the atmosphere. Our study aims to be a first step towards a more quantitative use of available information contained in historical texts, showing how Bayesian inference can help the climate community with this endeavor.

Pre-industrial temperature variability on the Swiss Plateau derived from the instrumental daily series of Bern and Zurich

Abstract. We describe the compilation of two early instrumental daily temperature series from Bern and Zurich, Switzerland, starting from 1760 and 1756, respectively. The series are a combination of numerous small segments from different observers at different locations within and outside the two cities that are converted to modern units and homogenized. In addition, we introduce a methodology to estimate the errors affecting daily and monthly mean values derived from early instrumental observations. Given the frequent small data gaps, we merge the two daily series into a more complete series representing the central Swiss Plateau. We finally compare the homogenized monthly series with other temperature reconstructions for Switzerland. We find significant differences before 1860, pointing to biases that might affect some of the most widely used instrumental data sets. In general, the homogenization of temperature measurements at the transition between the early instrumental and national weather service eras remains a problematic issue in historical climatology and has significant implications for other fields of climate research.

Protracted Indian monsoon droughts of the past millennium and their societal impacts

Protracted droughts lasting years to decades constitute severe threats to human welfare across the Indian subcontinent. Such events are, however, rare during the instrumental period (ca. since 1871 CE). In contrast, the historic documentary evidence indicates the repeated occurrences of protracted droughts in the region during the preinstrumental period implying that either the instrumental observations underestimate the full spectrum of monsoon variability or the historic accounts overestimate the severity and duration of the past droughts. Here we present a temporally precise speleothem-based oxygen isotope reconstruction of the Indian summer monsoon precipitation variability from Mawmluh cave located in northeast India. Our data reveal that protracted droughts, embedded within multidecadal intervals of reduced monsoon rainfall, frequently occurred over the past millennium. These extreme events are in striking temporal synchrony with the historically documented droughts, famines, mass mortality events, and geopolitical changes in the Indian subcontinent. Our findings necessitate reconsideration of the region's current water resources, sustainability, and mitigation policies that discount the possibility of protracted droughts in the future.

Early warning signal for a tipping point suggested by a millennial Atlantic Multidecadal Variability reconstruction

Atlantic multidecadal variability is a coherent mode of natural climate variability occurring in the North Atlantic Ocean, with strong impacts on human societies and ecosystems worldwide. However, its periodicity and drivers are widely debated due to the short temporal extent of instrumental observations and competing effects of both internal and external climate factors acting on North Atlantic surface temperature variability. Here, we use a paleoclimate database and an advanced statistical framework to generate, evaluate, and compare 312 reconstructions of the Atlantic multidecadal variability over the past millennium, based on different indices and regression methods. From this process, the best reconstruction is obtained with the random forest method, and its robustness is checked using climate model outputs and independent oceanic paleoclimate data. This reconstruction shows that memory in variations of Atlantic multidecadal variability have strongly increased recently—a potential early warning signal for the approach of a North Atlantic tipping point.

On the relationship between Scandinavian extreme precipitation days, atmospheric blocking and Red Sea coral oxygen isotopes

In the context of ongoing climate change towards a warmer world, it is important to gain insights into the frequency and intensity of weather and climate extreme events over longer periods of time prior to the start of instrumental observations. Reconstructions of their variability are usually hampered by the rareness of natural archives for the pre-instrumental period that document climate variability at a sub-seasonal resolution. A potential archive for extreme events are annually banded reef corals which incorporate isotopic proxies of temperature and hydrology into their carbonate skeletons at sub-seasonal resolution, grow for centuries, and overlap with the observational period. Here, we investigate the relationship between the frequency of heavy precipitation days in southwestern Scandinavia and colder conditions in the northern Red Sea during winter, as documented by a coral oxygen isotope record from the northernmost area of tropical reef growth in the European sector of the Northern Hemisphere. Statistical analysis of observational data reveals that cold conditions in the northern Red Sea are associated with an increased frequency of heavy precipitation in southwestern Scandinavia. From a synoptic-scale perspective, this teleconnection can be explained by winter atmospheric blocking over mid-latitude Europe, which is a large-scale pattern of atmospheric pressure that can be active for several days or weeks. We show that increased winter blocking activity in the European region is related to an increased frequency of extreme moisture transport by atmospheric rivers affecting southwestern Scandinavia, as well as to an increased meridional advection of cold continental air from the north towards the subtropical northern Red Sea. The coral-based Scandinavian heavy precipitation reconstruction shows strong decadal variations during the pre-instrumental period. Our results provide insights into the frequency of winter atmospheric blocking events and related daily precipitation extremes in the European region, as well as into the impact of mid-latitude climate extremes on coral reef ecosystems in the northern Red Sea, during the last centuries.

FEATURES OF THE DYNAMICS OF SEASONAL DEVELOPMENT OF NATURE IN SAINT PETERSBURG IN 2021

The abnormally warm and dry summer was the main feature of the year 2021. The average temperature of June (21,4) was the record for the whole period of instrumental meteorological observations since 1752. The phenological anomalies were evident first of all in the early dates of phenostages of the year, since the third stage of subseason "Height of Spring" till the first stage of subseason "Abatement of Summer", and especially very early dates of subseason of "Full Summer", which became the record or close to record ones. So, the warming of the climate of Saint Petersburg is continuing and strengthening. In such condition after the winter 2020/21 the majority of trees and shrubs in Peter the Great Botanic Garden (Saint Petersburg, Russia) survived the winter without damages or with small damages not more than half of annual growth. The summer drought, accompanied by hot weather, caused the early yellowing and falling of leaves on many trees and shrubs which happened to be not hardy to drought. The phenological monitoring and timely publishing of results of observations is of important significance in conditions of climatic changes.

Multiscale variability of China’s historical flood/drought index and precipitation teleconnections with ENSO using wavelet analyses

Studies of the low-frequency variabilities of key climate variables are often handicapped by the limited length of available instrumental observations. To tackle this, the use of a set of historical flood/drought index (FDI) spanning from AD 1470 to 2000 for 120 sites in China has been made to investigate the multiscale temporal variability of annual precipitation by applying wavelet methods. The analyses reveal oscillating components of the FDI time series from the decadal to multi-decadal, and to the quasi-centennial range, as well as in the interannual range. Furthermore, the relationships of the FDI with the dominant mode of oscillations in the coupled ocean–atmosphere system, i.e., the El Niño-Southern Oscillation (ENSO) index, on a range of time scales have been probed by cross wavelet transform and wavelet coherence methods. Statistically significant coherence between FDI and ENSO index time series has been found for regions in eastern China south of the Yangtze River (inclusive) at the decadal to multi-decadal time scale (10- to 50-yr) after 1750, as well as for north China on the 10- to 30-year range in the eighteenth century. The FDI is less coherent with the ENSO index for other regions of China. The results of the present study may add to our understanding of the connections between long-term changes of annual precipitation and large-scale oscillations in the coupled ocean–atmosphere system, and provide a scientific basis for developing policies to adapt to future changes in water abundance.

Formalizing Trust in Historical Weather Data

Abstract Historical instrumental weather observations are vital to understanding past, present, and future climate variability and change. However, the quantity of historical weather observations to be rescued globally far exceeds the resources available to do the rescuing. Which observations should be prioritized? Here we formalize guidelines help make decisions on rescuing historical data. Rather than wait until resource-intensive digitization is done to assess the data’s value, insights can be gleaned from the context in which the observations were made and the history of the observers. Further insights can be gained from the transcription platforms used and the transcribers involved in the data rescue process, without which even the best historical observations can be mishandled. We use the concept of trust to help integrate and formalize the guidelines across the life cycle of data rescue, from the original observation source to the transcribed data element. Five cases of citizen science-based historical data rescue, two from Canada and three from Australia, guide us in constructing a trust checklist. The checklist assembles information from the original observers and their observations to the current transcribers and transcription approaches they use. Nineteen elements are generated to help future data rescue projects answer the question of whether resources should be devoted to rescuing historical meteorological material under consideration. Significance Statement Historical weather observations, such as ships’ logs and weather diaries, help us to understand our past, present, and future climate. More observations are waiting to be rescued than there are resources. Only after they have been rescued—transcribed—can the records be indexed, searched, and analyzed. Given the vast task, citizen scientists are often recruited to transcribe past weather records. Various tools, including software platforms, help volunteers transcribe these handwritten records. We provide guidance on choosing observations to rescue. This guidance is novel because it emphasizes trust throughout the data rescue process: trust in who the observers were and how the observations were made, trust in who the current transcribers are, and trust in the software tools that are used for transcription.

Forecasting of disaster floods in Dniester valley

In recent years, two catastrophic floods have occurred in the Carpathian region and in Podillya: one on July 23–28, 2008, and the other on June 20–24, 2020. Both caused enormous damage to the environment and the population, which was widely reported in the media. To be prepared for natural disasters, you need to learn to predict them, that is, to know in what area they occur, what will be the height of the rise of water and when it will happen. From this triad, the first two components have already learned to predict, but the third has not yet. The article considers the possibility of a weather forecast, which was confirmed during the flood of June 20–24, 2020. O.M. Adamenko and D.O. Zorin plotted global climate change over the period of the Earth's history from its birth 4.567 billion years ago to the present. It turned out that the warm and cold periods alternated periodically, from the Galactic Year (225–250 million years), of which there were 19, to the current 11 summer cycles of solar activity. A total of 13 orders of cycles were identified, which interfere in the form of sinusoids, determining the periodicity of geological events. Geotectonic epochs of the 2nd order (50–70 million years) are superimposed on the cyclicity of the 1st order – galactic years – these are Karelian, Baikal, Caledonian, Hercynian, Pacific and Alpine tectonic-magmatic epochs, which are divided into parts of the 3rd (30–40 million years) and 4th (10–15 million) orders. The following cycles – 5 (3–5 million years), 6 (150–140 thousand years) and 7 (10–20 thousand years) are associated with a large Cenozoic cooling, which ended with the Quaternary glaciation. 8 (1–4 thousand years) and 9 (500–600 years) cycles reflect changes in warming and cooling in the quarter. And then the analysis of events is reconstructed on the basis of archaeological and chronicle data: from the beginning of our era to the XII century. Warming of the IX cycle continued – a small climatic optimum and a small ice age (XIII – XVII centuries). Since the XIX century modern warming began with clear 33-year fluctuations of the X cycle. Since 1881, instrumental observations have appeared at meteorological stations and hydro posts. XI (20–15–11 years), XII (5–6 years) and XIII (3–4 years) cycles appeared. Against the background of 33 annual fluctuations in the global climate, 11 annual cycles and catastrophic floods of 1911, 1927, 1941, 1955, 1969, 1980, 1988, 2002, 2008 appeared, and the catastrophic flood of 2020 predicted by O.M. Adamenko and D.O. Zorin. Thus, it is possible to learn to predict the time of the next catastrophic flood.

Monitoring and irrigation regime formation when growing crops using the "Irrigation Online" system

The paper analyzes the results of the implementation of an information and analytical irrigation management system “Irrigation Online” that enables to quickly generate and provide the users with the information about the current and projected state of soil moisture. A set of soil survey works was performed including the analysis of available information on soil reclamation conditions and irrigated land use; visual soil survey with the identification of points for detailed soil survey; soil sampling and laboratory studies on particle size distribution, hydrophysical soil properties and formation of input data for irrigation management. The configured system of instrumental monitoring observations on moisture supply, current meteorological parameters, and actual irrigation terms and rates allows predicting more accurately irrigation terms and rates in the reference fields as well as making their daily correction. The method of point information dissemination on irrigation arrays using remote sensing data was developed. In the course of research satellite image data and plant reflectivity by the NDVI and NDWI indices along with their variability and spatial heterogeneity using the ArcGIS geoinformation system were analyzed. The use of remote sensing data expands the capabilities of the system in terms of data dissemination on the timing and irrigation rates in the fields, which are out of monitoring observations. The results of the use of the operational irrigation management system in production conditions are given. The achieved results were demonstrated while cultivating corn for grain and sunflower. It was proved that by applying the system “Irrigation Online" and keeping moisture supply in the optimal range the highest possible crop yield can be achieved in production conditions.

Current trends in the distribution of ice deposit fields on the territory of Ukraine during 1991-2020 regarding 1981-2010

The presented article is devoted to the study of modern trends in the spread of ice deposits on the territory of Ukraine in the last thirty years of 1991-2020 (new climate standard) relative to the period 1981-2010. recommended by WMO. The conducted research is related to the research work on the study of climate change carried out at the UkrSMI. Question status. Despite certain achievements in the study of the distribution of ice-frost deposits in the territory of Ukraine in the past, the task of determining the existing trends and subsequent changes in their distribution under the influence of climate change remains unresolved. The purpose of the study was to determine the current state and features of the distribution of the field of ice deposits on the territory of Ukraine with the identification of centers of increase and decrease in the average amount of such deposits, as well as trends relative to another observation period. Materials and methods. Data of actual instrumental observations of ice deposits at all meteorological stations of Ukraine for two periods 1991-2020 and 1981-2010 were used for processing. The main research methods were physical-statistical with the determination of the normalized values of the number of cases of such deposits and cartographic with the visualization of the results. The information obtained is not only informative, since it reflects the current trends in the distribution of one of the types of ice-frost deposits, which are adverse weather phenomena, but also allows you to plan the work of weather-dependent industries in more detail, ensuring their uninterrupted operation. Main results. It has been established that most of the deviations of the average number of ice cases for the study period relative to the period of 1981-2010. were insignificant, but in some areas during the cold season, especially in winter, they reached higher values. values. It has been established that in January and December there is a predominance of positive deviations of the average number of ice cases in Ukraine. Most of the centers of positive deviations are based on the territory of the western region from Volyn. Rivne and Zhytomyr regions to the Carpathians, as well as in the north of the Chernihiv and Sumy regions, as well as in a number of central regions from Vinnitsa to Poltava and Dnepropetrovsk regions. Also, noticeable foci of such deviations are observed in the north and east of the Kharkiv region, as well as in the north of the Luhansk region. They are noticeable in the south of the country. In February and March, foci of negative deviations were most often encountered. The most pronounced of them were observed in the western region in the territory from the Zhytomyr region to the Carpathian region, as well as in some central regions. In February, a focus of positive deposits was discovered in the north of the Chernihiv region. In April-October, the field of ice deposits for 1991-2020. compared to 1981-2010 practically did not change. In November, an increase in the number and spatial distribution of positive deviations of the average amount of ice deposits was revealed. They were mainly distributed in the central regions from Vinnitsa to the Poltava and Dnepropetrovsk regions, as well as in the east of the Kharkiv region and the north of the Luhansk region.

Assessment of safe exploitability of undermined objects of the Underground Ore Mining Department of the Mine Management of the PJSC “ArcelorMittal Kryvyi Rih”

The article is devoted to monitoring surface displacement and the condition of monitored objects. The object of research is the process of displacement of the earth’s surface and the state of protected objects of the “United” deposit of the mine department for underground mining of ores of PJSC “ArcelorMittal Kryvyi Rih”. The displacement process is monitored based on long-lasting instrumental observations to determine surface deformations and assess the safety of exploitation of the monitored objects within the mining allotment. The study findings enable ascertaining that in the southern and central parts of the minefield, the displacement process has stopped, but in the northern part, it is still developing, and mining will have no impact on the technological objects of the Mine Management in the next two years. Over the recent two years, actual subsidence rates in the railway area have not exceeded 2.7 mm/month, and they are significantly lower than the permissible values (100 mm/month). The road sections shifting and the base for the removal of the road continue to develop. Mining operations at the deposit “Obiednanyi” have no hazardous impact on the “Schistose Rocks” natural geological reserve, the settlement of Karnavatka and the cemetery “Zakhidne”. Displacement on road and road base sections is in progress. In the vicinity of the settlement of Zhukivka, the maximum relative deformations (3.2 mm/m) are still much lower than the permissible one (6 mm/m), and they will not reach their maximum permissible values in the nearest two three years. In the last year, deformation rates decreased and reached the 2018 figure. Therefore, all the monitored objects within the mining allotment can be safely exploited.

Identifying Hydro‐Sensitive Coral δ18O Records for Improved High‐Resolution Temperature and Salinity Reconstructions

AbstractStable oxygen isotopic ratios in corals (δ18Ocoral) are commonly utilized to reconstruct climate variability beyond the limit of instrumental observations. These measurements provide constraints on past seawater temperature, due to the thermodynamics of isotopic fractionation, but also past salinity, as both salinity and seawater δ18O (δ18Osw) are similarly affected by precipitation/evaporation, advection, and other processes. We use historical observations, isotope‐enabled model simulations, and the PAGES Iso2k database to assess the potential of δ18Ocoral to provide information on past salinity. Using ‘‘pseudocorals’’ to represent δ18Ocoral as a function of observed or simulated temperature and salinity/δ18Osw, we find that δ18Osw contributes up to 89% of δ18Ocoral variability in the Western Pacific Warm Pool. Although uncertainty in the δ18Osw‐salinity relationship influences the inferred salinity variability, corals from these sites could provide valuable δ18Osw reconstructions. Coordinated in situ monitoring of salinity and δ18Osw is vital for improving estimates of hydroclimatic change.

Assessing the intercolony δ18O proxy calibration in a coral microatoll and its implication for ENSO reconstruction in the northern South China Sea

Massive Porites corals are widely used for paleoclimate reconstruction, however the potential of Porites coral microatoll δ18O as high-resolution archive of paleoclimate has only been recognized recently, and the systematic chemistry-climate relationship has yet to be well characterized in the western Pacific. In this study, we examined the reproducibility of microatoll δ18O records against two adjacent Porites corals from the Xisha Islands in the northern South China Sea (SCS) and evaluated the reliability of microatoll δ18O as a proxy for reconstructing regional climate and El Niño-Southern Oscillation (ENSO) variability. The seasonal to interannual variability in microatoll δ18O was primarily controlled by local sea surface temperature (SST), while the δ18O signal might be suppressed by sea surface salinity (SSS) variations on interannual timescale. Despite the overlapping coral δ18O records exhibited similar patterns of variability, the mean values were consistently offset by ~0.2‰ and the sensitivity of δ18O proxy to climate also varied across different coral colonies. The microatoll δ18O exhibited relatively high proxy-SST sensitivities and amplitude of the seasonal variabilities. These results suggested that intercolony δ18O variability was a significant source of uncertainty in coral-based paleoclimate reconstructions. Microatoll δ18O anomaly appeared to serve as a sensitive and relatively reliable proxy for ENSO variability, although the imprints of weak-to-moderate ENSO events could not be fully captured due to the complex relationship between the East Asian Monsoon and ENSO, as well as the local seawater salinity changes. This study further strengthened the evidence for microatoll as an alternate climate archive in the SCS and highlighted its potential in helping resolve poorly understood paleoclimate before instrumental observations.