Causes of the Regional Variability in Observed Sea Level,Sea Surface Temperature and Ocean Colour Over the Period 1993–2011

We analyse the regional variability in observed sea surface height (SSH), sea surface temperature (SST) and ocean colour (OC) from the ESA Climate Change Initiative datasets over the period 1993–2011. The analysis focuses on the signature of the ocean large-scale climate fluctuations driven by the atmospheric forcing and do not address the mesoscale variability. We use the ECCO version 4 ocean reanalysis to unravel the role of ocean transport and surface buoyancy fluxes in the observed SSH, SST and OC variability. We show that the SSH regional variability is dominated by the steric effect (except at high latitude) and is mainly shaped by ocean heat transport divergences with some contributions from the surface heat fluxes forcing that can be significant regionally (confirming earlier results). This is in contrast with the SST regional variability, which is the result of the compensation of surface heat fluxes by ocean heat transport in the mixed layer and arises from small departures around this background balance. Bringing together the results of SSH and SST analyses, we show that SSH and SST bear some common variability. This is because both SSH and SST variability show significant contributions from the surface heat fluxes forcing. It is evidenced by the high correlation between SST and buoyancy-forced SSH almost everywhere in the ocean except at high latitude. OC, which is determined by phytoplankton biomass, is governed by the availability of light and nutrients that essentially depend on climate fluctuations. For this reason, OC shows significant correlation with SST and SSH. We show that the correlation with SST displays the same pattern as the correlation with SSH with a negative correlation in the tropics and subtropics and a positive correlation at high latitude. We discuss the reasons for this pattern.     

Simulating Stable Isotope Ratios in Plumes of Groundwater Pollutants with BIOSCREEN‐AT‐ISO

BIOSCREEN is a well‐known simple tool for evaluating the transport of dissolved contaminants in groundwater, ideal for rapid screening and teaching. This work extends the BIOSCREEN model for the calculation of stable isotope ratios in contaminants. A three‐dimensional exact solution of the reactive transport from a patch source, accounting for fractionation by first‐order decay and/or sorption, is used. The results match those from a previously published isotope model but are much simpler to obtain. Two different isotopes may be computed, and dual isotope plots can be viewed. The dual isotope assessment is a rapidly emerging new approach for identifying process mechanisms in aquifers. Furthermore, deviations of isotope ratios at specific reactive positions with respect to “bulk” ratios in the whole compound can be simulated. This model is named BIOSCREEN‐AT‐ISO and will be downloadable from the journal homepage.     

Electric and magnetic components of ballooning perturbations in the magnetotail plasma sheet before breakup

Using data from THEMIS spacecraft we investigated transverse to the magnetic field mutually perpendicular electric and magnetic components of ballooning type perturbations with periods 60–240 s, which are observed in the magnetospheric plasma sheet during the period preceding substorm onset. With applying Hilbert transform, we analyzed the phase relations between them. It is shown that the perturbations are dominated by radial electric and azimuthal magnetic (that is, toroidal) components which are usually in phase or out-of-phase. Along with them, approximately 2.5 times less intense azimuthal electric and radial magnetic components are present, which are more often phase-shifted by π/2. It is concluded that the observed perturbations are not a simple consequence of the development of plasma sheet ballooning instability, leading to the growth of strongly elongated along the magnetotail ballooning structures. It is pointed out that this conclusion is confirmed by simultaneous ground-based observations of magnetically conjugate auroral structures.     

Reconstructions of the heliospheric modulation potential and Wolf numbers based on the content of the <Superscript>14</Superscript>C isotope in tree rings during the Maunder and Spörer minimums

Data on variations in the content of the 14C cosmogenic isotope in tree rings and the Earth’s atmosphere (Δ¹⁴C) make it possible to study the behavior of solar activity (SA) in previous centuries and millenniums. The latter is related to the fact that SA temporal variations result in a change in the IMF (Interplanetary Magnetic Field) parameters and, as a consequence, in the galactic cosmic ray (GCR) flux, under the action of which the ¹⁴C isotope is produced in the Earth’s atmosphere. This makes it possible to study SA history based on data on the ¹⁴C isotope content in tree rings. However, in this case we have several difficulties related to climate change. Climate changes result in carbon redistribution between natural reservoirs, which is reflected in radiocarbon data and results in solar signal distortion. The effect of variations in the global temperature and carbon dioxide concentration on the reconstruction of the heliospheric modulation potential and Wolf numbers from the late 14th century to the early 19th century is considered. It has been shown that the radiocarbon data do not make it possible to conclude that SA during the Maunder minimum was extremely low as compared to SA during the Dalton minimum.     

The geochemistry of steam hydrothermal occurrences in the Koshelev volcanic massif,southern Kamchatka

New data are presented on the geochemistry of thermal waters in the Koshelev volcanic massif in southern Kamchatka. We discuss the conditions for the generation of thermal waters, possible variants of thermal and deep-seated material supply for the Koshelev hydrothermal system, and propose a conceptual model for the system.     

The instability of an electron beam with a finite radius in a boundless plasma

Within the framework of a linear theory, the instability of an electron beam with a finite radius in a cold magnetised boundless plasma is considered. It is shown that a finite beam dimension influences the generation of quasi-potential waves in two aspects: the perpendicular wave number is quantised so that the frequencies of the waves are subjected to strong selection; a new kind of instability appears due to wave energy losses by emission into surrounding space. Growth rate dependence of wave numbers and frequencies is investigated for typical parameters of experiments with electron beams in space.     

Mudstone lithogeochemistry and formation conditions of Vendian deposits in the Shkapovo-Shikhan Basin

Variation of geochemical modules and indices in mudstones from the Upper Vendian Kairovo and Shkapovo groups of the Shkapovo-Shikhan Basin provides the comprehensive information on changes in maturity of the fine aluminosiliciclastic material delivered in the basin, characterizes the redox environment in bottom water, and makes it possible to reconstruct the rock composition in provenance and its evolution through time. The generally moderate maturity of the fine terrigenous clastic material suggests that a nearly semiarid-semihumid climate dominated in paleodrainage area throughout the Late Vendian. It has been established that reducing environment did not exist in bottom water of the central Shkapovo-Shikhan Basin throughout the Late Vendian. Intermediate rocks prevailed in the paleodrainage area. More silicic rocks could occur only in the early Staropetrovo and late Salikhovo times. Data points of mudstones from the Kairovo and Shkapovo Groups plotted on the Cr-Ni, Co-V, Co/Hf-Ce/Cr, La-Th, and La/Sm-Sc/Th diagrams indicate that both Archean and more mature Paleoproterozoic crustal blocks existed in different proportions in the Late Vendian within source areas.     

Statistical analysis for the hydrogeological evaluation of the fracture networks in hard rocks

The hydrogeological effectiveness of fracture sets is determined and evaluated by the fuzzy c-mean and hierarchical clustering. These cluster analyses combine the geological spatial attributes and the hydraulic relevant attributes of fractures. Based on the results of the clustering the fracture set volumes are estimated.