Latitudinal Sections Research Articles

Оценка химического состава сапропелей различных месторождений

Complex chemical composition and wide mining opportunities determine the use of sapropels and sapropel-based products in various sectors of national economy. The fullest potential of sapropel is revealed in agriculture, where it is used as fertilizer, a component of soils, raw materials for humic preparations production etc. The aim was to study the sapropels’ suitability for the production of humic fertilizers. Using validated methods we analyze chemical composition of sapropel sediments from 4 freshwater lakes located within the latitudinal section of 53–56° N in the temperate climate. Microbiological parameters of all studied samples are within the normal range. Dry matter content in the range of 46.1–51.3% corresponds to the normative indicators. The mass fraction of organic matter varies in the range of 31.8–39.9% DM. This allows classifying all samples as organo-clay, and determines the possibility of their use for soils of light granulometric composition. The relatively high content of humic (18.3–22.9% DM) and fulvic acids (3.7–6.4% DM) makes it possible to use the studied sapropel samples for the manufacture of humic preparations (especially, a sapropel sample of the lake Chervonoe, Belarus). Low P and K content (0.24–0.36% DM and 0.32–0.42% DM, respectively) can negatively affect the efficiency of fertilizers from these sapropel species; this can be avoided by mixing sapropel with manure or enrichment with mineral fertilizers. Indicators of heavy metal (Cu, Mn, Zn, Co, Pb and Cd) content in all studied samples meet the safety requirements. Samples from deeper layers of the Rusaki Lake (Altai Territory) and the Beloe Lake (Novosibirsk Region) refer to the 1st class of suitability, the rest (according to a number of indicators) – to the 2nd class. The content of trace elements in the studied sapropels is within the established norms and makes it possible to use them for replenishing the deficit of trace elements in soils. In general, all the studied samples can be used as environmentally friendly organomineral fertilizers, as well as production of humic preparations to increase in the biological and energy capacity of agrocenoses and to reproduce the soil fertility.

Betholletia excelsa Fruit: Unveiling Toughening Mechanisms and Biomimetic Potential for Advanced Materials.

Dry fruits and nutshells are biological capsules of outstanding toughness and strength with biomimetic potential to boost fiber-reinforced composites and protective structures. The strategies behind the Betholletia excelsa fruit mechanical performance were investigated with C-ring and compression tests. This last test was monitored with shearography and simulated with a finite element model. Microtomography and digital and scanning electron microscopy evaluated crack development. The fruit geometry, the preferential orientation of fibers involved in foam-like sclereid cells, promoted anisotropic properties but efficient energy dissipating mechanisms in different directions. For instance, the mesocarp cut parallel to its latitudinal section sustained higher forces (26.0 ± 2.8 kN) and showed higher deformation and slower crack propagation. The main toughening mechanisms are fiber deflection and fiber bridging and pullout, observed when fiber bundles are orthogonal to the crack path. Additionally, the debonding of fiber bundles oriented parallel to the crack path and intercellular cracks through sclereid and fiber cells created a tortuous path.

Latitudinal responses of the ionosphere over South America during HILDCAA intervals: Case studies

Aspects regarding the influence of High-Intensity Long-Duration Continuous Auroral Electrojet Activity (HILDCAA) intervals on ionospheric dynamics have been objecting to increasing interest in the last years. Notwithstanding, some key interconnections between the HILDCAA intervals impacts on the ionosphere over distinct latitudes, according to the solar cycle phase, remain to require further investigation. In this work, the F2 layer peak height and its critical frequency (hmF2 and foF2, respectively) from Digisonde data obtained over São Luís (2.60° S; 44.21° W), Cachoeira Paulista (22.70° S; 44.98° W), and Port Stanley (51.60° S, 57.9° W), were evaluated to unravel more details of the ionospheric responses to four HILDCAA intervals as case studies. Those are equatorial, low, and mid-latitude stations, respectively, and the main results over them presented a similar trend in terms of solar cycle dependence, with the greater impact on the ionospheric density along with solar maximum conditions, despite the higher frequency of HILDCAA occurrences in the descending and minimum phases. The variation of hmF2 due to HILDCAA effects in comparison to quiet time is about 20% in equatorial and mid-latitudes, while over the low latitude station the hmF2 ranges positively up to 40%. These results enhance our understanding of the HILDCAAs magnitude degree both regarding its solar cycle occurrence, and its effects in different ionospheric latitudinal sections.

Algae, polyporales fungi and insects – xylophages of the Smolny Island natual reserve (Khanty-Mansi Autonomous Okrug, Russia)

Smolny Island is a specially protected natural area of regional importance aimed to preserve a unique natural ecosystem of typical floodplain landscapes of the latitudinal section of the Ob River. The purpose of this research is to obtain primary data on the species composition and state of algological, polyporale communities and insects-xylophages of the Smolny Island natural reserve. The standard algological, mycological and entomological research methods were used. The original studies results for several components of the ecosystem are presented for the first time. The composition, structure, occurrence of freshwater algae, forest, polyporale communities and forest insects pests were investigated. The freshwater algocenoses of the island have a typical regional composition, in summer there is a tendency to cenosis characteristic of the region's swamps (diatom-euglena viridis type) in autumn there's diatom, with low occurrence of species. An increased saprobity of the studied waters was detected. In total, 12 insects xylophages species of the Agaricomycetes class were found in forest communities (coniferous, floodplain, small-leaved cenosis), with the richest species community in the test plot of small-leaved forest and the least variety in the coniferous one. No great risk for the development of a mass insects-xylophages area in the test plots was revealed, but the constant monitoring of the forest stock of the Smolny Island natural reserve is necessary to prevent the development of invasions and preserve the biodiversity of the island. The research results can be recommended as special diagnostic methods for tracking the diversity and condition of island communities.

Синтаксономия ксеропетрофитной растительности Южного Урала: союз Elytrigion pruiniferae all. nov.

Синтаксономия ксеропетрофитной растительности Южного Урала: союз Elytrigion pruiniferae all. nov.

Speed structure of the mantle of the border of the Eastern European and West European platforms

This work is devoted to studying the velocity structure of the mantle of the border area of the East European and West European platforms in the crust separated by the Teiserre-Tornquist zone. The mantle under the territory of Poland and Western Ukraine is being investigated. The work uses a three-dimensional P-velocity model of the mantle, constructed using the Taylor approximation method developed by V. S. Geyko. The method’s advantages are independent of the initial approximation (reference model) and the best approximation of nonlinearity. In this area, the exploration depth is 2500 km south of 50 °NL and 1700 km north of 50 °NL. A detailed analysis of horizontal sections of a 3D P-velocity model of the mantle up to a depth of 850 km with a step of 50 km has been carried out. The change in the spatial distribution of the zero seismic velocity boundary is analyzed throughout the depths. This boundary separates the high-velocity upper mantle of the East European Platform and the low-velocity upper mantle of the West European Platform. At the depths of the transition zone of the upper mantle, this boundary separates the low-velocity upper mantle of the East European platform and the high-velocity upper mantle of the West European platform (in this geosphere, a velocity inversion has occurred with respect to the upper mantle). In latitudinal sections, two inclined layers are distinguished. One of them is associated with the upper mantle under the DDV and reaches the mantle under the Carpathians, where it begins to plunge into the high-velocity transition zone of the upper mantle. The second layer is associated with the mantle under the northwestern end of the Baltic syneclise, which extends to the mantle under the Presudet monocline, where it also plunges into the high-velocity transition zone of the upper mantle. In longitudinal sections, inclined layers are distinguished, extending from the mantle under the South Scandinavian megablock of the Baltic Shield to the mantle under the Bohemian massif and the Carpathians, where they plunge into the high-velocity transition zone of the upper mantle. In the study area, three super-deep fluids were identified, characterized by increased stratification of the medium (alternation of higher and lower velocities). The first includes the well-known oil and gas fields of the Central European oil and gas basin (Pomorie and Presudet monocline (Poland)). The second is associated with oil and gas fields of the North Ciscarpathian oil and gas basin (southeastern Poland) and the Carpathian oil and gas basin (Western Ukraine). The extracted super-deep fluid in the mantle of the Baltic Sea corresponds to both the Gdansk Gulf of the Baltic Sea and the Kaliningrad fields (southeast of the Baltic Sea).

Correlation Analysis of High-Throughput Fruit Phenomics and Biochemical Profiles in Native Peppers (Capsicum spp.) from the Primary Center of Diversification

The main goal of this work was to investigate the relationship between the fruit morphology and biochemical composition of peppers (Capsicum spp.). For that purpose, one hundred native varieties from the Andean region, where the genus Capsicum has its origin, were analysed for different phytochemical compounds. In addition, pepper fruits were assessed with the highly precise phenomics tool Tomato Analyzer. The collection showed a broad variability which was more evident within the C. annuum group. On average, C. frutescens accessions displayed the highest levels of solid soluble content, pH, polyphenols and antioxidant activity. The Tomato Analyzer descriptors under the categories of size, shape index, and latitudinal section, mostly contributed to the variance among Capsicum groups. C. annuum hold the larger fruits, whereas C. frutescens comprised fruits of smaller sizes. The correlation analysis revealed that biochemical traits were negatively correlated with the fruit parameters related to size, suggesting that huger fruits contain lower amounts of chemical metabolites. The multivariate approximations demonstrated that Andean peppers assorted according to morphometric and colorimetric characteristics, but independently of their species or geographical origin. Groups of valuable native varieties carrying promising traits were identified.

Отложения среднего неоплейстоцена в нижнем течении р. Печоры

The results of lithological studies of Quaternary deposits in the coastal outcrops of the valley of the lower course of the river are presented. Pechora. In the latitudinal section of the Pechora, two horizons of boulder loams (moraines) and underlying horizons, dividing or overlapping the moraine strata, are exposed to intermoraine sediments of fluvial genesis. Based on the results of lithological studies of textural, granulometric and mineralogical features of fine earth of deposits and petrographic composition of coarse material, it was concluded that material was supplied during the formation of moraines from different terrigenous-mineralogical provinces. The formation of the lower Pechora (Dnieper) moraine is associated with the North-Eastern feeding province, and the upper Moscow (Vychegda) moraine, with the North-West Fennoscandian center of glaciation. The glacial genesis of boulder loams has been confirmed.

Dissolved neodymium and hafnium isotopes and rare earth elements in the Congo River Plume: Tracing and quantifying continental inputs into the southeast Atlantic

The Congo River is the second largest river by discharge in the world and a major source of element inputs into the South Atlantic Ocean. Yet, the element fluxes and transport mechanisms across and beyond its estuary and their impacts on the marine distribution and cycling of many major and trace elements are not well understood. We present the first combined dissolved neodymium (Nd) and hafnium (Hf) isotope and rare earth element (REE) concentration distributions following the Congo River plume along its flow path off the West African coast and along a connected offshore latitudinal section at 3°S. The Congo River freshwater itself is characterized by extraordinarily high Nd and Hf concentrations of up to 4000 pmol/kg and 54 pmol/kg, and by Nd (εNd) and Hf (εHf) isotope compositions that range between −15.6 and −16.4 and between 0.35 and −1.4, respectively. Our near- and offshore data indicate that at salinities above 23 conservative mixing of Congo-derived Nd and Hf concentrations and isotopic signatures with ambient surface seawater occurs for at least 1000 km to the northwest of the river mouth. This demonstrates a large spatial extent of the influence of the Congo plume on trace metal distributions in the eastern south Atlantic surface waters. A comparison between dissolved Nd and Hf fluxes from the Congo River and the shelf zone estimated based on radium isotope compositions indicate that release from Congo-derived particulate phases likely balances strong estuarine REE and Hf removal in the low salinity zone. The combined riverine and shelf zone flux for Nd is almost twice as high as that estimated for the Amazon River, despite that the Amazon discharge is about five times higher than that of the Congo River. Even the offshore Nd flux estimated for the 3 °S transect based on radium isotope compositions still corresponds to ∼40% of the Congo-shelf-zone flux and reaches 150 ± 50 Mg/year for Nd. Moreover, intermediate waters below the plume are strongly affected by exchange with particulate inputs from the Congo River given that Nd isotope signatures are inconsistent with values expected from large-scale water mass mixing and instead support unradiogenic Nd release either from sinking or deposited Congo-derived detrital material. Deep and bottom water isotopic signatures are also slightly affected by interaction with particles and benthic Nd release.

Oceanographic conditions and diversity of sea stars (Echinodermata: Asteroidea) in the Gulf of California, México.

Species richness is one of the best indicators of biodiversity. However, there are few investigations on concordance of diversity patterns and environmental settings for marine regions. The objectives of this study were to correlate species richness of shallow water (< 200 m deep) sea stars with key oceanographic factors in the Gulf of California, México, and to predict species richness of Asteroidea using multiple regressions. In these analyses the Gulf was divided into nine sections of one degree in latitude (from 23-31 degrees N), at each section we recorded: continental shelf area (at 100 and 200 m depth), temperature mean and range at three depth levels (0, 60 and 120 m), thermocline depth, surface nutrient concentrations (nitrates, phosphates and silicates), surface photosynthetic pigment concentration, and integrated productivity. Sea star species richness at each latitudinal section was estimated from literature data, new collections and museum records. Species were assigned to one of the following feeding guilds: predators of small mobile invertebrates (I), detritivores (D), predators of colonial organisms (C), generalist carnivores (G), and planktivores (P). There are 47 shallow water asteroid species in the Gulf of California (16 I, 15 D, eight C, six G, one P and one not assigned). Total species richness and guild species richness showed strong latitudinal attenuation patterns and were higher in the southernmost Gulf, an area characterized by a narrow shelf, high temperature, and low nutrient concentrations. Species diversity for each guild was correlated to a set of oceanographic parameters: temperature, nitrate concentration, and integrated productivity were linked to richness in must cases. We detected that nutrients and surface pigments always presented negative relationships with species richness, indicating that productive environments limit asteroid diversity in the study area. Finally, the postulated regression models to estimate species richness from oceanographic data were significant and highly precise. We conclude that species richness of Asteroidea in the Gulf of California is related to oceanographic conditions and can be estimated from regional oceanographic information.

Phytochemical Assessment of Native Ecuadorian Peppers (Capsicum spp.) and Correlation Analysis to Fruit Phenomics.

In this work, the impact of pepper (Capsicum spp.) fruits morphology on their composition for health-promoting compounds was investigated. For that purpose, pepper accessions from Ecuador, one of the hotspots in Capsicum’s origin, were analyzed for ascorbic acid, polyphenols, capsaicinoids, and prevention of cholesterol oxidation. Plant and fruit phenomics were assessed with conventional descriptors and Tomato Analyzer digital traits. Significant differences among accessions and species revealed a large diversity within the collection. The Capsicum frutescens group displayed the highest levels of capsaicinoids, whereas the polyphenols shortly varied among the five domesticated species. Capsicum pubescens exhibited the lowest content of ascorbic acid. The conventional descriptors describing the magnitude of plants and fruits, as well as digital attributes under the categories of size, shape index, and latitudinal section, mostly explained the variance among Capsicum groups. Correlation test revealed that phytochemical components were negatively correlated with the morphometric fruit attributes, suggesting that huge fruits contained lower amounts of nutraceutical compounds. Multivariate analysis showed that parameters related to fruit size, shape, and nutraceutical composition primarily contribute to the arrangement of pepper accessions. Such results suggested that those traits have been subjected to higher selection pressures imposed by humans.

Meridional Mass Transport of Bottom Water in the South Atlantic

Estimates of the meridional mass transport of Antarctic Bottom Water, calculated using the coupled ocean-atmosphere Earth System Model on the basis of the original data assimilation method are presented. For assimilation, we use data of the latitudinal CTD sections of temperature and salinity of the WOCE international experiment in 1991–1995. Estimates of the current velocities of Antarctic Bottom Water with the assimilation of observational data are given. We used the author’s data-assimilation method, which was previously referred to as the generalized Kalman Filter (GKF) method. In this particular case, it coincides with the classical Kalman method (EnKF). We also present the estimates of mass transport based on a standard geostrophic dynamic scheme. It is shown that model calculations with data assimilation are qualitatively the same and are quantitatively close to the estimates of the geostrophic flow transport based on the dynamic method.

Mesocarp of Brazil nut (Bertholletia excelsa) as inspiration for new impact resistant materials

Aiming to produce bioinspired impact and puncture resistant materials, the mesocarp of the Brazil nut (Bertholletia excelsa) was characterized. The mesocarp composition was investigated by chemical extraction and its microstructure was analyzed by optical microscopy and microtomography (microCT). A compression test evaluated the force needed to open the mesocarp shell. Shore D hardness testing and nanoindentation measured the local mechanical properties at different length scales. Brazil nut mesocarp has a higher content of lignin (56%) than other nutshells and is mainly composed of sclereids and fibers cells arranged together and not in separated layers as usually found in nature. The mesocarp has an internal and external layer with fibers oriented from peduncle to opercular opening and a middle layer where entangled fibers are latitudinally oriented. To open a Brazil nut mesocarp, compression forces of 10 079 ± 1460 N (parallel to latitudinal section) and 14 785 ± 4050 N (perpendicular to latitudinal section) are needed. Such forces are higher than the forces needed to open most nutshells, if fracture force is normalized by shell thickness. The Shore D hardness test showed that hardness is uniform in the mesocarp, although it is higher in the center of the thickness than close to the inner or outer surface. The cell wall of fibers has a higher reduced modulus than the cell wall of sclereids although they have a similar hardness. These microstructural and mechanical results indicate that Brazil nutshell has great potential as a source for bioinspiration and motivates further studies.

Circulation patterns in the Gulf of Finland from daily to seasonal timescales

We studied circulation patterns in the Gulf of Finland (GoF), an estuary-like sub-basin of the Baltic Sea. Circulation patterns in the GoF are complex and vary from season to season and year to year. Estuarine circulation in the gulf is heavily modified by many factors, such as wind forcing, topography and geostrophic effects. Based on a 7-year run of the NEMO 3D hydrodynamic model with a 500 m horizontal resolution, we analysed seasonal changes of mean circulation patterns. We found that there were clear seasonal differences in the circulation patterns in the GoF. Features that moved or changed direction from season to season were damped or hidden in the averages. To further study these differences, we also carried out a self-organising map (SOM) analysis of currents for several latitudinal sections. The results of the SOM analysis emphasised the estuary-like nature of the GoF. Circulation changed rapidly from normal estuarine circulation to reverse estuarine circulation. The dominant southwesterly winds supported the reversal of the estuarine circulation. Both normal and reversed estuarine circulation were roughly as common in our data. The SOM analysis also demonstrated how the long-term cyclonic mean circulation field and the average salinity field emerged from the interaction of normal and reversed estuarine circulation.

Coral reefs of the Red Sea — Challenges and potential solutions

The Red Sea is a unique body of water, hosting some of the most productive and diverse coral reefs. Human populations along coasts of the Red Sea were initially sparse due to the hot and arid climate surrounding it, but this is changing with improved desalination techniques, accessible energy, and increased economic interest in coastal areas. In addition to increasing pressure on reefs from coastal development, global drivers, primarily ocean acidification and seawater warming, are threatening coral reefs of the region. While reefs in southern sections of the Red Sea live near or above their maximum temperature tolerance and have experienced bleaching events in the recent past, coral reefs in northern sections are considered a coral reef refugia from global warming and acidification, at least for the coming decades. Such differential sensitivities along the latitudinal gradient of the Red Sea require differential solutions and management. In an effort to identify the appropriate solutions to conserve and maintain resilience of these reefs along a latitudinal gradient, we used a SWOT analysis (strengths/weaknesses/opportunities/threats) to frame the present situation and to propose policy solutions as useful planning procedures. We highlight the need for immediate action to secure the northern sections of the Red Sea as a coral reef climate change refuge by management and removal of local stressors. There is a need to strengthen the scientific knowledge base for proper management and to encourage regional collaboration on environmental issues. Based on scientific data, solutions such as marine protected areas, fishing regulation, and reef restoration approaches were ranked for five distinct latitudinal sections in the Red Sea and levels of interventions are recommended.

Сравнительная характеристика песчаных пород уфимского яруса в Соликамской впадине

The results of study of sands rocks of the Ufimian Stage in the wells cross-sections of the Solikamsk depression allowed determining evolution of their composition expressed in the change from predominantly oligomictic quartz partially with fragments of rock to polymictic greywacke presented mostly by the fragments of volcanic rock. This change may be resulted from successive erosion from external to internal zone of the Uralian orogen or shifting the base level of erosion eastward. Facial analysis of rock allowed identifying that the sedimentation initially occurred in the lagoon conditions following the shallow-water and deltaic (Solikamsk time), and continental lake and river (Sheshminskiy time) conditions. The obtained results allowed restoring paleogeographic and tectonic conditions of sedimentation. In the latitudinal section of the Solikamskaya depression, a regular variation of sand material from the east (Uralian orogenic belt) to the sea basin (westward) was revealed, and the deposits were associated with channel and fan deltaic facies. Overlying continental lacustrine, alluvial, and proluvial sediments, are widely developed only at the southwestern part of the basin.

Variations in the structural and functional diversity of zooplankton over vertical and horizontal environmental gradients en route to the Arctic Ocean through the Fram Strait.

A multi-scale approach was used to evaluate which spatial gradient of environmental variability is the most important in structuring zooplankton diversity in the West Spitsbergen Current (WSC). The WSC is the main conveyor of warm and biologically rich Atlantic water to the Arctic Ocean through the Fram Strait. The data set included 85 stratified vertical zooplankton samples (obtained from depths up to 1000 metres) covering two latitudinal sections (76°30’N and 79°N) located across the multi-path WSC system. The results indicate that the most important environmental variables shaping the zooplankton structural and functional diversity and standing stock variability are those associated with depth, whereas variables acting in the horizontal dimension are of lesser importance. Multivariate analysis of the zooplankton assemblages, together with different univariate descriptors of zooplankton diversity, clearly illustrated the segregation of zooplankton taxa in the vertical plane. The epipelagic zone (upper 200 m) hosted plentiful, Oithona similis-dominated assemblages with a high proportion of filter-feeding zooplankton. Although total zooplankton abundance declined in the mesopelagic zone (200–1000 m), zooplankton assemblages in that zone were more diverse and more evenly distributed, with high contributions from both herbivorous and carnivorous taxa. The vertical distribution of integrated biomass (mg DW m-2) indicated that the total zooplankton biomass in the epipelagic and mesopelagic zones was comparable. Environmental gradients acting in the horizontal plane, such as the ones associated with different ice cover and timing of the spring bloom, were reflected in the latitudinal variability in protist community structure and probably caused differences in succession in the zooplankton community. High abundances of Calanus finmarchicus in the WSC core branch suggest the existence of mechanisms advantageous for higher productivity or/and responsible for physical concentration of zooplankton. Our results indicate that regional hydrography plays a primary role in shaping zooplankton variability in the WSC on the way to the Arctic Ocean, with additional effects caused by biological factors related to seasonality in pelagic ecosystem development, resulting in regional differences in food availability or biological production between the continental slope and the deep ocean regions.

Deep sequencing of amplified Prasinovirus and host green algal genes from an Indian Ocean transect reveals interacting trophic dependencies and new genotypes.

High-throughput sequencing of Prasinovirus DNA polymerase and host green algal (Mamiellophyceae) ribosomal RNA genes was used to analyse the diversity and distribution of these taxa over a ∼10 000 km latitudinal section of the Indian Ocean. New viral and host groups were identified among the different trophic conditions observed, and highlighted that although unknown prasinoviruses are diverse, the cosmopolitan algal genera Bathycoccus, Micromonas and Ostreococcus represent a large proportion of the host diversity. While Prasinovirus communities were correlated to both the geography and the environment, host communities were not, perhaps because the genetic marker used lacked sufficient resolution. Nevertheless, analysis of single environmental variables showed that eutrophic conditions strongly influence the distributions of both hosts and viruses. Moreover, these communities were not correlated, in their composition or specific richness. These observations could result from antagonistic dynamics, such as that illustrated in a prey-predator model, and/or because hosts might be under a complex set of selective pressures. Both of these reasons must be considered to interpret environmental surveys of viruses and hosts, because covariation does not always imply interaction.

Development and analysis of 3D ionosphere modeling using base functions and GPS data over Iran

In this study, a 3D-model of the electron density has been performed using the global positing system (GPS) measurements over Iran. 2D spherical harmonic functions and empirical orthogonal functions are used as base functions to model the horizontal and the vertical content of the electron density, respectively. The ionosonde data in Tehran (φ = 35.7382°, λ = 51.3851°) has been used for choosing an optimum value for the regularization parameter. To apply the method for constructing a 3D-image of the electron density, GPS measurements of the Iranian permanent GPS network (at 3-day in 2007) have been used. The instability of solution has been numerically analyzed and the Tikhonov method has been used for regularizing the solution. To come up with an optimum regularization parameter, the relative error in electron density profile computed from ionosonde measurements and their 3D model are minimized. The modeling region is between 24° to 40°N and 44° to 64°W. The result of 3D-Model has been compared to that of the international reference ionosphere model 2012 (IRI-2012). The data analysis shows that the latitudinal section of ionosphere electron density from 3D technique supports the expected time and height variations in ionosphere electron density. Moreover, these findings show that the height of maximum electron density is changed during the day and night and confirms the efficiency of multi-layer models in comparison to single-layer models. This method could recover 64–99 % of the ionosphere electron density.

Reconstructing the upper water column thermal structure in the Atlantic Ocean

The thermal structure of the upper ocean (0–1000 m) is set by surface heat fluxes, shallow wind‐driven circulation, and the deeper thermohaline circulation. Its long‐term variability can be reconstructed using deep‐dwelling planktonic foraminifera that record subsurface conditions. Here we used six species (Neogloboquadrina dutertrei, Globorotalia tumida, Globorotalia inflata, Globorotalia truncatulinoides, Globorotalia hirsuta, and Globorotalia crassaformis) from 66 core tops along a meridional transect spanning the mid‐Atlantic (42°N to 25°S) to develop a method for reconstructing past thermocline conditions. We estimated the calcification depths from δ18O measurements and the Mg/Ca‐temperature relationships for each species. This systematic strategy over this large latitudinal section reveals distinct populations with different Mg/Ca‐temperature relationships for G. inflata, G. truncatulinoides, and G. hirsuta in different areas. The calcification depths do not differ among the different populations, except for G. hirsuta, where the northern population calcifies much shallower than the southern population. N. dutertrei and G. tumida show a remarkably constant calcification depth independent of oceanographic conditions. The deepest dweller, G. crassaformis, apparently calcifies in the oxygen‐depleted zone, where it may find refuge from predators and abundant aggregated matter to feed on. We found a good match between its calcification depth and the 3.2 ml/l oxygen level. The results of this multispecies, multiproxy study can now be applied down‐core to facilitate the reconstruction of open‐ocean thermocline changes in the past.