Regional Climatic Fluctuations Research Articles

Isotope features (δ13С, δ18О) of continental carbonates from Permian and Triassic boundary deposits Northeast of Russian plate: paleoclimatic and biotic causes, chemostratigraphy

The carbon and oxygen isotopic composition were determined in pedogenic, sedimentary and organogenic carbonates of continental deposits of the Upper Permian (Vyatkian stage) and lower Triassic (Induan stage) of the northeastern part of the Moscow Syneclise. It is assumed that variations in 18О (18.0 29.1 SMOW) and 13С (-8.8 0.7 PDB) values in them could be associated with both regional climate fluctuations and perturbation of the global carbon cycle at the Permian and Triassic boundary. The decrease in 18О values in the pedogenic carbonates of the roof sequence of the Vyatkian stage, apparently, was due to the cooling in the northeast of the Pangea supercontinent. The negative excursion of 13С values at this stratigraphic level is correlated with a similar excursion found in the Paleo-and Neotetis marine carbonates and corresponds to the Late Permian biotic event.

Зрошення — головний елемент сучасних агротехнологій в умовах Південного Степу України

The purpose. To justify scientifically directions of application of irrigation in modern crop production technologies in rainless conditions of South Steppe of Ukraine. Methods. Analysis, synthesis, generalization. Results. In conditions of climate fluctuation it is necessary to use in irrigation farming of Ukraine the intensive crop production technologies based on use of innovative methods with optimization of different methods of showering and regimes of irrigation, fertilizer systems, treatment and protection of plants. Structure of sown area and crop rotations on irrigated lands of Ukraine for intelligent use of irrigated lands and avoidance of negative impact of external factors of natural and anthropogenic character is offered. Methodological and methodical approaches are developed on the basis of integral criterion of irrigated lands for their intelligent use, avoidance of degradation processes, protection and reproduction of fertility. Resources saving techniques are improved of cultivation of different crops on biological properties with observance of project normative expenditures worked out by scientists of Institute of irrigation farming and other scientific institutes of NAAS. Scientific approaches on state-private partnership in guidance system of water resources are developed, and instruments of state support and regulation of entrepreneurial business in the field of irrigation farming are specified. Conclusions. The major on immediate prospects will be problems of decreasing all sorts of resource losses by irrigation and other elements of agrotechnologies in conditions of regional climate fluctuations. For this purpose it is necessary to develop new scientific approaches on application of innovative techniques of artificial irrigation on the basis of minimization of discharge of water, energy, work and means, setting of irrigation water, fertilizers, pesticides and biological preparations, taking into account location of root system of crops for determination of optimum doses of watering, use of solar energy for alternative power supplies and so forth.

Isotope Characteristics (δ13C, δ18O) of Continental Carbonates from Permian‒Triassic Rocks in the Northeastern Russian Plate: Paleoclimatic and Biotic Reasons and Chemostratigraphy

Carbon and oxygen isotope compositions were determined in the pedogenic, sedimentary, and organogenic carbonates from Upper Permian (Vyatkian Stage) and Lower Triassic (Induan Stage) continental rocks in the northeastern Moscow Syneclise. Variations of δ18O (18.0 to 29.1‰ SMOW) and δ13C (‒8.8 to 0.7‰ PDB) in them could be provoked both by regional climatic fluctuations and by perturbation of the global carbon cycle at the Permian‒Triassic boundary. Decrease of δ18O in pedogenic carbonates at the top of the Vyatkian Stage was likely caused by cooling on the northeastern side of Pangea. The negative excursion of δ13C values at this stratigraphic level correlates with the analogous excursion recorded in marine carbonates of the Paleo- and Neotethys and corresponds to the end-Permian biotic event.

Вплив змін клімату на розвиток рослинництва в умовах Західного регіону

The purpose. To determine parameters of climate fluctuations in region for 1945–2018 and their influence on development and efficiency of branch of plant growing. Methods. Field, laboratory-analytical and mathematical-statistical (applied according to available techniques). Results. Results of weather observations of Rivne center of hydrometeorology for 1945–2018 were analyzed. It is noted that the threshold of the average annual air temperature (7°C) was exceeded in 1988 –1992. On the average for 1988–2017 it exceeded the norm on 1,2°C, in 2018 — on 1,8°C. The sums of effective temperatures were above 5 and 10°C during 1971–2018 and had grown accordingly on 30,8 and 52,8%. Mid-annual rainfall amount in 2013–2017 matched to norm (569 mm), and in 2018 was less than the norm on 29%. It was established that practically at equal rainfall amount stores of productive moisture under winter wheat in 0–100 cm soil layer in June-July 2013–2018 were twice less than in 1985–1990. It was established that at the similar depth of precipitation, productive moisture reserves at winter wheat cultivation in 0–100 cm soil layer of in June-July 2013–2018 were twice as low as in 1985–1990. Improvement of heat supply of the territory contributed to increase in the share of corn, soybeans and sunflower in the structure of crops from 4% in 2000 to 52,3% in 2018. As a result of implementation of modern technologies and improvement of temperature regimen in 2010–2018, the yield of winter wheat increased from 2,9 to 4,5 t/hectare, grain corn — from 4,9 to 8,2, soybeans — from 1,4 to 2,7, winter rape — from 2,3 to 3,2, and sunflower — from 1,9 to 2,4 t/hectare. Conclusions. Due to the progressive global climate changes, the heat supply of Western Forest-Steppe and Western Polissia improved significantly. That led to domination in the structure of crops sowing area of the region of warm-weather crops (grain corn, soybean and sunflower). And also in combination with the use of modern cultivation technologies, that ensured rapid increase in the yield of all agricultural crops.

The Effects of Anthropogenic Land Use Changes on Climate in China Driven by Global Socioeconomic and Emission Scenarios

AbstractThe land surface, which interacts with lower atmosphere, is subject to substantial amounts of human activities. It results in regional climate fluctuations and must be assessed with a combination of future socioeconomic and emission policies to improve regional resilience and responsive efficiency on global mitigation and adaptation. Spatial heterogeneity in regional climate induced by land use changes of future global socioeconomic and emission scenarios is explored. Comparisons are carried out among both historical and future land use‐induced regional meteorological changes to investigate various climatic roles of land use conversions in China. The underlying changes in the surface albedo, leaf area index, energy exchange, and water balances are also examined. It is found that the increase of the summer temperature and the diurnal temperature range are the largest under the fifth Shared Socioeconomic Pathway characterized by more intensive urbanization. While temperature increase from urbanization and deforestation can be offset by cooling from vegetation evaporation increase under the extreme Representative Concentration Pathway (RCP) 8.5, which has no climate mitigation policies and high greenhouse gas concentration. In addition, RCP4.5 scenario would cause an average temperature increase of 1.41°C by 2050 at an annual rate of 0.028°C in China. The global climatic forcing warms the entire region and enhances precipitation intensity, and these effects are more substantial than those by regional land use changes, showing a strong background influence. Our research reveals the future climatic responses to regional anthropogenic land use changes under various scenarios and policies and provides ways to downscale global mitigation impacts into regional insights.

Predicting attenuation of salinized surface- and groundwater-resources from legacy energy development in the Prairie Pothole Region

Oil and gas (energy) development in the Williston Basin, which partly underlies the Prairie Pothole Region in central North America, has helped meet U.S. energy demand for decades. Historical handling and disposal practices of saline wastewater co-produced during energy development resulted in salinization of surface and groundwater at numerous legacy energy sites. Thirty years of monitoring (1988–2018) at Goose Lake, which has been producing since the 1960s, documents long-term spatial and temporal changes in water quality from legacy energy development. Surface water quality was highly variable and decoupled from changes in groundwater quality, likely due to annual and regional climatic fluctuations. Therefore, changes in surface water-quality were not considered a reliable indicator of subsurface chloride migration. However, chloride concentrations in monitoring wells near wastewater sources exhibited systematic temporal reductions allowing for estimates of the time required for natural attenuation of groundwater to U.S. Environmental Protection Agency acute and chronic chloride toxicity benchmarks and a local background level. Point attenuation rates differed based on sediment type (outwash vs till) and yielded a range of predicted years when water-quality targets will be reached: acute – 2045 to 2113; chronic – 2069 to 2160; background – 2126 to 2275. Bulk attenuation rates from four separate years of data were used to calculate the distances chloride could migrate downgradient from the largest wastewater source. Potential distances of downgradient migration before dilution to water-quality targets decreased from 1989 to 2018: acute – 949 to 673 m; chronic – 1220 to 922 m; background – 1878 to 1525 m. Several downgradient wetlands are within these distances and will continue to receive saline contaminated groundwater for years. While these results demonstrate chloride attenuation at a legacy energy site, they also highlight the persistence of saline wastewater contamination and the need to mitigate future spills to prevent long-term salinization from energy development.

Exploring the Sensitivity of Subtropical Stand Aboveground Productivity to Local and Regional Climate Signals in South China

Subtropical forest productivity is significantly affected by both natural disturbances (local and regional climate changes) and anthropogenic activities (harvesting and planting). Monthly measures of forest aboveground productivity from natural forests (primary and secondary forests) and plantations (mixed and single-species forests) were developed to explore the sensitivity of subtropical mountain productivity to the fluctuating characteristics of climate change in South China, spanning the 35-year period from 1981 to 2015. Statistical analysis showed that climate regulation differed across different forest types. The monthly average maximum temperature, precipitation, and streamflow were positively correlated with primary and mixed-forest aboveground net primary productivity (ANPP) and its components: Wood productivity (WP) and canopy productivity (CP). However, the monthly average maximum temperature, precipitation, and streamflow were negatively correlated with secondary and single-species forest ANPP and its components. The number of dry days and minimum temperature were positively associated with secondary and single-species forest productivity, but inversely associated with primary and mixed forest productivity. The multivariate ENSO (EI Niño-Southern Oscillation) index (MEI), computed based on sea level pressure, surface temperature, surface air temperature, and cloudiness over the tropical Pacific Ocean, was significantly correlated with local monthly maximum and minimum temperatures (Tmax and Tmin), precipitation (PRE), streamflow (FLO), and the number of dry days (DD), as well as the monthly means of primary and mixed forest aboveground productivity. In particular, the mean maximum temperature increased by 2.5, 0.9, 6.5, and 0.9 °C, and the total forest aboveground productivity decreased by an average of 5.7%, 3.0%, 2.4%, and 7.8% in response to the increased extreme high temperatures and drought events during the 1986/1988, 1997/1998, 2006/2007, and 2009/2010 EI Niño periods, respectively. Subsequently, the total aboveground productivity values increased by an average of 1.1%, 3.0%, 0.3%, and 8.6% because of lagged effects after the wet La Niña periods. The main conclusions of this study demonstrated that the influence of local and regional climatic fluctuations on subtropical forest productivity significantly differed across different forests, and community position and plant diversity differences among different forest types may prevent the uniform response of subtropical mountain aboveground productivity to regional climate anomalies. Therefore, these findings may be useful for forecasting climate-induced variation in forest aboveground productivity as well as for selecting tree species for planting in reforestation practices.

Interpreting the effect of regional climate fluctuations on Quercus robur L. trees under a temperate continental climate (southern Romania)

Interpreting the effect of regional climate fluctuations on Quercus robur L. trees under a temperate continental climate (southern Romania)

Effects of local and regional climatic fluctuations on dengue outbreaks in southern Taiwan.

BackgroundSouthern Taiwan has been a hotspot for dengue fever transmission since 1998. During 2014 and 2015, Taiwan experienced unprecedented dengue outbreaks and the causes are poorly understood. This study aims to investigate the influence of regional and local climate conditions on the incidence of dengue fever in Taiwan, as well as to develop a climate-based model for future forecasting.Methodology/Principle findingsHistorical time-series data on dengue outbreaks in southern Taiwan from 1998 to 2015 were investigated. Local climate variables were analyzed using a distributed lag non-linear model (DLNM), and the model of best fit was used to predict dengue incidence between 2013 and 2015. The cross-wavelet coherence approach was used to evaluate the regional El Niño Southern Oscillation (ENSO) and Indian Ocean Dipole (IOD) effects on dengue incidence and local climate variables. The DLNM results highlighted the important non-linear and lag effects of minimum temperature and precipitation. Minimum temperature above 23°C or below 17°C can increase dengue incidence rate with lag effects of 10 to 15 weeks. Moderate to high precipitation can increase dengue incidence rates with a lag of 10 or 20 weeks. The model of best fit successfully predicted dengue transmission between 2013 and 2015. The prediction accuracy ranged from 0.7 to 0.9, depending on the number of weeks ahead of the prediction. ENSO and IOD were associated with nonstationary inter-annual patterns of dengue transmission. IOD had a greater impact on the seasonality of local climate conditions.Conclusions/SignificanceOur findings suggest that dengue transmission can be affected by regional and local climatic fluctuations in southern Taiwan. The climate-based model developed in this study can provide important information for dengue early warning systems in Taiwan. Local climate conditions might be influenced by ENSO and IOD, to result in unusual dengue outbreaks.

Freshwater Contributions and Nitrogen Sources in a South Texas Estuarine Ecosystem: a Time-Integrated Perspective from Stable Isotopic Ratios in the Eastern Oyster (Crassostrea virginica)

Freshwater inflows to Texas estuaries vary widely due to regional climate fluctuations and are being substantially altered by human activities. The natural abundance stable isotope ratios of carbon and nitrogen in oyster adductor muscle were used to acquire a time-integrated view of freshwater and nitrogen contributions to the Mission-Aransas National Estuarine Research Reserve in South Texas. The study objective was to determine the influence of inputs from the San Antonio and Guadalupe rivers, which deliver approximately 1.6 km3 of water to the mid-Texas coastal region annually. A transect of sampling stations extending from the head of San Antonio Bay (northeast of the Reserve boundary) to the Aransas Pass ship channel (roughly 70 km to the southwest) was visited multiple times between 2009 and 2011. Carbon isotopic values increased from approximately −25 to −17‰ while δ15N values decreased from approximately +16 to +10‰ between the bay and ship channel. This range of carbon isotope values translates into time-integrated freshwater fractions as high as 0.8 (1 = 100% fresh) at the most inland sampling station to freshwater fractions around zero approaching the Gulf of Mexico. Contributions from the San Antonio and Guadalupe rivers to waters of the reserve vary between wet and dry years, but overall, the data suggest that these rivers are persistent and substantial sources of fresh water and nitrogen to the reserve. This study emphasizes the importance of connectivity and lateral exchanges among bays/lagoons when considering potential sources of fresh water and nitrogen that control ecosystem structure and function.

Climate variability and lake ecosystem responses in western Scandinavia (Norway) during the last Millennium

This paper provides a high-resolution temperature reconstruction for the last Millennium from Lake Atnsjøen, SE Norway (61°52′31″N, 10°10′37″E). The sedimentary record reveals strong influence of the large-scale global climate patterns on the local climate in southern part of Eastern Norway. We reconstructed mean July air temperature using Chironomidae-based transfer function and fossil Chironomidae assemblages. The reconstruction was supported by a selection of climate-sensitive geochemical and paleoecological sedimentary proxies of terrestrial and aquatic origin, including Cladocera, pollen and macrofossils. Presented results revealed that summer temperatures were 1–2°C warmer than the mean Millennial temperatures during the 11th, 13th, 15th and 20th centuries and 1–2°C lower during the 12th, 14th, 17th–18th centuries. A persistent cold period, the Little Ice Age (LIA), occurred between 1550 and 1800CE, was interrupted by a short warming at 1650CE. The recognized regional climate fluctuations during the last Millennium affected the lake and its catchment, of which the strongest impact was caused by the LIA cooling. During the LIA the catchment vegetation was impacted by climate deterioration and the lake productivity reached its lowest level during the last Millennium. The current temperature reconstruction is in agreement with a previous continental scale temperature reconstruction for Europe. From obtained results it emerges that during the LIA the climate of western Scandinavia has been dictated by the atmospheric patterns originating from the North Atlantic.

Impacts of regional climatic fluctuations on radial growth of Siberian and Scots pine at Mukhrino mire (central-western Siberia)

Ring width (TRW) chronologies from Siberian (Pinus sibirica) and Scots (Pinus sylvestris) pine trees were sampled at Mukhrino – a large mire complex in central-western Siberia – to evaluate the impacts of hydroclimatic variability on tree growth over the last three centuries. For this purpose, we compared climate-growth correlation profiles from trees growing on peat soils with those growing on adjacent mineral soils. Tree growth at both peat and mineral soils was positively correlated to air temperature during the vegetation period. This finding can be explained by (i) the positive influence of temperature on plant physiological processes (i.e. growth control) during the growing season and (ii) the indirect impact of air temperatures on water table fluctuations. We observe also a strong link between TRW and the winter Palmer Drought Severity Index (PDSI), especially in Siberian pine, reflecting the isolating effect of snow and limited freezing damage in roots. Significant negative relations were, by contrast, observed between bog TRW chronologies and hydroclimatic indices during spring and summer; they are considered an expression of the negative impacts of high water levels and moist peat soils on root development. Some unusually old bog pines – exhibiting >500 growth rings – apparently colonized the site at the beginning of the Little Ice Age, and therefore seem to confirm that (i) peat conditions may have been drier in Siberia than in most other regions of western Europe during this period. At the same time, the bog trees also point to (ii) their strong dependence on surface conditions.

Millennial-scale Asian summer monsoon variations in South China since the last deglaciation

Characterizing spatiotemporal variability of the Asian summer monsoon (ASM) is critical for full understanding of its behavior, dynamics, and future impacts. The present knowledge about ASM variations since the last glaciation in South China largely relies on several precisely-dated speleothem stable oxygen isotope (δ18O) records. Although these speleothem δ18O signals provide useful evidence for regional past environmental changes, their validity for denoting ASM intensity remains a great controversy. The Huguangyan Maar Lake (HML) provides one of the most complete archives of environmental and climatic changes in the tropical–subtropical South and East Asia since the last glaciation. Here we document a continuous centennial- to millennial-scale ASM record over the past 16 ky BP from the high-sedimentation-rate HML sediments. In contrast with the low-amplitude variations of Chinese speleothem-derived δ18O signals and the Chinese loess-based monsoon precipitation proxy indexes, our multi-proxy records reveal a pattern of high-amplitude regional climatic fluctuations, including fine-scale oscillations during the Bølling–Allerød warming, the 8.2 ka cooling event, and an abrupt climate shift from 6.5–5.9 ka. The existence of Bond-like cold/dry events indicates a distinct influence of the North Atlantic circulation on low-latitude monsoon changes. The broad comparability between the HML paleo-proxies, Chinese speleothem δ18O records, and the northern hemisphere summer insolation throughout the Holocene, suggests that solar insolation exerts a profound influence on ASM changes. These findings reinforce a model of combined insolation and glacial forcing of the ASM.

Climate Change and Fluctuations in the Karelian-Kola Region

In this work we consider the regularities of changes of climate and assessed the potential impact of these changes on some of the characteristics of the hydrological regime and biota water bodies of the North of the European territory of Russia from temperate latitudes to the Arctic. Within the annual course, variation of monthly air temperature values is irregular for different seasons, with most intensive warming in January and March. In summer, variations in air temperature are multidirectional. Variations in the thermal regime led, in its turn, to later ice cover formation and earlier ice-breakup resulted in the longer ice-free period. Data analysis revealed variations in the course of precipitation of warm and cold periods. Under distinguished increase of precipitation sums, a total number of days with precipitation was revealed to be equal to or lower than its climatic norm. The total precipitation amount increase occurred due to increasing frequency of rainfalls of 10 mm and more. In winter, the snow cover height exceeded the climatic norm. As the increase of annual sums of precipitation is compensated by a rise of evapotranspiration, any trend in the total river inflow into Lake Onego is absent.

Influence of regional rainfall and Atlantic sea surface temperature on tree-ring growth of Poincianella pyramidalis, semiarid forest from Brazil

A tree-ring width chronology was developed from samples of thirteen Poincianella pyramidalis trees from the Caatinga semiarid region of northeastern Brazil, where the climate is characterized by marked seasonality in precipitation levels. Although a thin continuous marginal parenchyma band represents the limit of seasonal xylem production, and in spite of the presence of false rings, cross-dating is possible. In this sense, an interseries correlation of 0.572 was found indicating a considerable degree of consistency in the variability found among trees. Precipitation between January and July has a direct influence on growth, while a five month dry season interrupts the active division of cambial cells. A significant positive correlation was also found between sea surface temperatures (SSTs) in the tropical Atlantic and tree growth, but with a lag of six months. As the rainfall regime of northeastern Brazil presents a great deal of inter-annual variability due to fluctuations in global factors such as the SSTs of the tropical Atlantic and the intertropical convergence zone, the close relationship observed between P. pyramidalis tree growth and regional climate fluctuations appears as a logical plant-environment interaction that can be used as a reliable parameter for dendroecological inferences on tree growth dynamics and the reconstructions of past droughts in the Caatinga region.

Transgressive stratigraphic record and possible oscillations of late Pleistocene Lake Bonneville, Northern Hogup Mountains, Utah, U.S.A.

Abstract Distinct, mappable facies changes make the stratigraphic record of the shorezone of late Pleistocene Lake Bonneville the most robust indicator for past lake level oscillations. Unfortunately, clear stratigraphic evidence of transgressive and regressive deposits has been generally lacking. New stratigraphic and chronological data within the lacustrine shorezone sediments of the Hogup Mountains of northwestern Utah provide some of the best evidence yet for oscillations within the overall transgressive phase of the lake. This study documents two previously unknown oscillations, hereby named the Lower Hogup (~ 22 cal ka) and Upper Hogup (~ 20.6 cal ka) oscillations and provides further evidence for the previously proposed U2 oscillation (~ 21.3 cal ka). The study suggests that the water level of the lake changed dramatically (up to 25% of the lake’s total volume) during the transgressive phase (~ 30–15 cal ka). With the additional oscillations documented in this study, there are seven proposed oscillatory events during the transgressive phase of the lake. These events likely correlate to rapid but short term regional climatic fluctuations during the broader climatic trends of the Last Glacial Maximum. However, it is still unknown what specific climatic drivers are causing these oscillations and if these events can be correlated to other global climatic events.

Reciprocal Changes In Foreset To Bottomset Facies In A Gilbert-Type Delta: Response To Short-Term Changes In Base Level

Abstract Results of a detailed sedimentological study of the mid-Pleistocene Gilbert-type Ilias delta at the southern coast of the Corinth Rift, Greece, are reported. The study indicates that the development of a turbidite-dominated facies assemblage (TFA) of delta foreset deposits is associated with an oblique delta-brink geometry, which signifies a deficit of delta-front accommodation due to the falling or stable base level. A debrite-dominated assemblage (DFA) of foreset deposits forms when the base level is rising and the delta-brink geometry becomes sigmoidal, signifying an increase in delta-front accommodation. The comparison of coeval foreset and toeset to bottomset deposits in the delta indicates a reverse pattern of reciprocal changes in facies assemblages, with the foreset TFA deposits corresponding to delta-foot DFA deposits, and with the foreset DFA deposits corresponding to delta-foot TFA deposits. This reciprocal alternation of TFA and DFA facies assemblages is attributed to changes in the delta-front accommodation driven by short-term base-level changes, with a degree of “noise” in the facies record due to the system autogenic variability and regional climatic fluctuations. The study sheds a new light on the changing pattern of subaqueous sediment dispersal in Gilbert-type deltaic systems in response to base-level changes. It also indicates a new possibility for the recognition of a hidden record of such changes in other similar ancient deltas on the basis of their detailed facies analysis.

Late Quaternary fluvial terrace evolution in the main southern Amazonian tributary

Late Quaternary sedimentary deposits from Amazonian lowlands are important geological archives for understanding the origin, evolution and controls of the largest fluvial drainage basin on Earth. Climate has been most often claimed as the main factor affecting river evolution in this region. An increasing volume of publications have also highlighted tectonics as a relevant control. This work investigates the late Quaternary evolution of the Madeira River, the biggest southern tributary of the Amazonas Basin and a major waterway in South America, with the goal of discussing the factor with highest potential of influence on its development in space and time. The approach consisted of carrying out a detailed morphological, sedimentological and chronological characterization of terrace deposits. Three terraces were recognized, which record sandy/pebbly channel, muddy channel/oxbow lake, point bar, floodplain, as well as crevasse channel, crevasse splay and levee deposits. The topographically highest terrace T1 formed in the time interval before 43,500 and 31,696–32,913calyrs BP, the intermediate terrace T2 between 25,338–26,056 and 14,129–14,967calyrs BP, and the lowest terrace T3 between 12,881–13,245 and 3158–3367calyrs BP. These terraces are the testimony of successive downcutting and sediment aggradation. Episodes of terrace erosion and deposition cannot be fully accommodated within the framework of fluctuating river base level tied to Late Pleistocene–Holocene global or regional climate fluctuations. Changes in tectonic subsidence rates might have played an important role in the equilibrium state of this particular fluvial system.

Archaeomagnetism at Ebla (Tell Mardikh, Syria). New data on geomagnetic field intensity variations in the Near East during the Bronze Age

Thanks to systematic excavations conducted at Tell Mardikh/Ebla (Syria) during more than 40 years, we collected eleven groups of Bronze Age ceramic fragments defining a series of seven time intervals dated to between ∼2300 BC and ∼1400 BC. Archaeointensity experiments were performed using the Triaxe protocol that takes into account both anisotropy thermoremanent magnetization and cooling rate effects. The results, complemented by three other data previously obtained from Ebla, allow the recovery of geomagnetic field intensity variations over nearly 1000 years characterized by a V-shape, with a distinct relative intensity minimum around the 18th century BC. They also permit to constrain the occurrence of an intensity maximum between ∼2300 and ∼2000 BC. Together with other archaeointensity data obtained from Syrian, Levantine and Anatolian regions, the results from Ebla help to make emerging a coherent pattern of geomagnetic field intensity variations in the Near East over the entire Bronze period. This evolution was marked by distinct intensity maxima at ∼2600–2500 BC, ∼2300–2000 BC, ∼1550–1350 BC and at the very beginning of the first millennium BC (Iron Age), the latter showing a much higher magnitude than the three older ones. We discuss the fact that the detected geomagnetic field intensity maxima could be associated with the occurrence of archaeomagnetic jerks that appear synchronous, within age uncertainties, with significant regional climatic fluctuations.

Long-Term Fluctuations in Circalunar Beach Aggregations of the Box Jellyfish Alatina moseri in Hawaii, with Links to Environmental Variability

The box jellyfish Alatina moseri forms monthly aggregations at Waikiki Beach 8–12 days after each full moon, posing a recurrent hazard to swimmers due to painful stings. We present an analysis of long-term (14 years: Jan 1998– Dec 2011) changes in box jellyfish abundance at Waikiki Beach. We tested the relationship of beach counts to climate and biogeochemical variables over time in the North Pacific Sub-tropical Gyre (NPSG). Generalized Additive Models (GAM), Change-Point Analysis (CPA), and General Regression Models (GRM) were used to characterize patterns in box jellyfish arrival at Waikiki Beach 8–12 days following 173 consecutive full moons. Variation in box jellyfish abundance lacked seasonality, but exhibited dramatic differences among months and among years, and followed an oscillating pattern with significant periods of increase (1998–2001; 2006–2011) and decrease (2001–2006). Of three climatic and 12 biogeochemical variables examined, box jellyfish showed a strong, positive relationship with primary production, >2 mm zooplankton biomass, and the North Pacific Gyre Oscillation (NPGO) index. It is clear that that the moon cycle plays a key role in synchronizing timing of the arrival of Alatina moseri medusae to shore. We propose that bottom-up processes, likely initiated by inter-annual regional climatic fluctuations influence primary production, secondary production, and ultimately regulate food availability, and are therefore important in controlling the inter-annual changes in box jellyfish abundance observed at Waikiki Beach.