Quantifying the spatio-temporal patterns of settlement growth in a metropolitan region of Ghana

Retrospective understanding of the magnitude and pace of urban expansion is necessary for effective growth management in metropolitan regions. The objective of this paper is to quantify the spatial–temporal patterns of urban expansion in the Greater Kumasi Sub-Region (GKSR)—a functional region comprising eight administrative districts in Ghana, West Africa. The analysis is based on Landsat remote sensing images from 1986, 2001 and 2014 which were classified using supervised maximum likelihood algorithm in ERDAS IMAGINE. We computed three complementary growth indexes namely; Average Annual Urban Expansion Rate, Urban Expansion Intensity Index (UEII) and Urban Expansion Differentiation Index to estimate the amount and intensity of expansion over the 28-year period. Overall, urban expansion in the GKSR has been occurring at an average annual rate of 5.6 %. Consequently, the sub-region’s built-up land increased by 313 km² from 88 km² in 1986 to 400 km² in 2014. The analysis further show that about 72 % of the total built-up land increase occurred in the last 13 years alone, with UEII value of 0.605 indicating a moderate intensity of urban expansion. Moreover, the metropolitan-core of the sub-region, being the focal point of urban development and the historical origins of expansion, accounted for more than half of the total built-up land increase over the 28-year period. Over the last decade and half however, urban expansion has spilled into the neighbouring peripheral districts, with the highest intensity and fastest rate of expansion occurring in districts located north and north east of the sub-regional core. We recommend a comprehensive regional growth management strategy grounded in effective strategic partnerships among the respective administrative districts to curb unsustainable urban expansion.     

Stress tensor and focal mechanisms in the Dead Sea basin

We use the recorded seismicity, confined to the Dead Sea basin and its boundaries, by the Dead Sea Integrated Research (DESIRE) portable seismic network and the Israel and Jordan permanent seismic networks for studying the mechanisms of earthquakes in the Dead Sea basin. The observed seismicity in the Dead Sea basin is divided into nine regions according to the spatial distribution of the earthquakes and the known tectonic features. The large number of recording stations and the adequate station distribution allowed the reliable determinations of 494 earthquake focal mechanisms. For each region, based on the inversion of the observed polarities of the earthquakes, we determine the focal mechanisms and the associated stress tensor. For 159 earthquakes, out of the 494 focal mechanisms, we could determine compatible fault planes. On the eastern side, the focal mechanisms are mainly strike-slip mechanism with nodal planes in the N-S and E-W directions. The azimuths of the stress axes are well constrained presenting minimal variability in the inversion of the data, which is in agreement with the Eastern Boundary fault on the east side of the Dead Sea basin and what we had expected from the regional geodynamics. However, larger variabilities of the azimuthal and dip angles are observed on the western side of the basin. Due to the wider range of azimuths of the fault planes, we observe the switching of σ₁ and σ₂ or the switching of σ₂ and σ₃ as major horizontal stress directions. This observed switching of stress axes allows having dip-slip and normal mechanisms in a region that is dominated by strike-slip motion.     

Wave-induced drift of large floating sheets

In this article we study the wave-induced drift of large, flexible shallow floating objects, referred to as sheets. When surface waves propagate through a sheet, they provide a mean stress on the sheet, resulting in a mean drift. In response, the sheet generates an Ekman current. The drift velocity of the sheet is determined by (i) the wave-induced stress, (ii) the viscous stress due to the Ekman current, and (iii) the Coriolis force. The sheet velocity and the current beneath the sheet are determined for constant and depth-varying eddy viscosities.     

The Basic Formal Ontology as a Reference Framework for Modeling the Evolution of Administrative Units

In information systems, ontologies promise advantages such as enhanced interoperability, knowledge sharing, and integration of data sources. In this article, we show that the upper ontology Basic Formal Ontology can facilitate the modeling of an evolution of administrative units. This is demonstrated by creating a spatiotemporal ontology for the administrative units of Switzerland. The ontology tackles the problem that the geometric data is typically captured by taking snapshots at regular intervals while the thematic data is continually updated. The ontology presented merges time‐stamped geometries with a formally described history of administrative units, allowing for complex spatiotemporal queries neither standard approach would support. The resulting populated knowledge base was evaluated against a set of spatiotemporal test queries. The evaluation showed that this knowledge base supports a wide range of queries on the evolution of the administrative units of Switzerland between 1960 and 2010.     

Geochemical evidence of the 8.2 ka event and other Holocene environmental changes recorded in paleolagoon sediments,southeastern Brazil

The paleoclimatic record of Juréia Paleolagoon, coastal southeastern Brazil, includes cyclic and gradual changes with different intensities and frequencies through geological time, and it is controlled by astronomical, geophysical, and geological phenomena. These variations are not due to one single cause, but they result from the interaction of several factors, which act at different temporal and spatial scales. Here, we describe paleoenvironmental evidence regarding climatic and sea level changes from the last 9400 cal yr BP at the Juréia Paleolagoon — one of the main groups of protected South Atlantic ecosystems. Geochemical evidences were used to identify anomalies from multi-proxy analyses of a paleolagoon sediment core. The anomalies of centennial scale were correlated to climate and transgression–regression cycles from the Holocene period. Decadal scale anomalous oscillations in the Quaternary paleolagoon sediments occur between 9400 and 7500 cal yr BP, correlated with long- and short-term natural events, which generated high sedimentation rates, mainly between 8385 and 8375 cal yr BP (10 cm/yr). Our results suggest that a modern-day short-duration North Atlantic climatic event, such as the 8.2 ka event, could affect the environmental equilibrium in South America and intensify the South American Summer Monsoon.     

Anthropogenic and lithogenic sources of lead in Lower Silesia (Southwest Poland): An isotope study of soils,basement rocks and anthropogenic materials

To discriminate possible anthropogenic and lithogenic sources of Pb in Lower Silesia (SW Poland), the Pb isotope composition was investigated in a spectrum of rocks and anthropogenic materials as well as within 10 soil profiles. Silicate rocks in Lower Silesia have ²⁰⁶Pb/²⁰⁷Pb ratios that vary from 1.17 for serpentinites to 1.38 for gneisses, and this variability is reflected in the isotope composition of the mineral soil horizons. The Pb isotope composition of coals, ores and anthropogenic materials (slags and fly ashes) is rather uniform, with ²⁰⁶Pb/²⁰⁷Pb ratios ranging from 1.17 to 1.18. Similar ratios were observed in ore and coal samples from Upper Silesia. The O soil horizons also have uniform ²⁰⁶Pb/²⁰⁷Pb ratios of 1.17–1.18 and the heterogeneity of the ²⁰⁶Pb/²⁰⁷Pb ratios increases with depth in the soil profiles. Five soils, with varying Pb concentrations, analysed far from contamination centres, show consistent, approximately 2-fold enrichment in Pb concentration from the C to A horizons, which is consistent with natural re-distribution of Pb within the profiles. The increase in the Pb concentration is accompanied by a decrease in ²⁰⁶Pb/²⁰⁷Pb ratios, also attributed to natural Pb isotope fractionation. Four soil profiles from industrial areas show variable enrichments in Pb concentrations and these are attributed to anthropogenic input from air-borne pollutants or even slag particles at smelting sites. The implication is that a lithogenic Pb source can deviate from the basement rock composition, and detailed isotope characteristics of the geological background and natural enrichments in soils are often needed to determine the lithogenic/anthropogenic proportions of Pb in soils.     

Genetic geochemical model for mining affected groundwaters of the Lusatian post-mining district

Using groundwater quality data from the Lusatian post-mining district a hydrogeochemical model is derived for the evolution of mining affected groundwaters in pyrite-rich dumps which consist mainly of silicates and variable amounts of calcite. Pyrite oxidation paralleled by buffer processes leads to gypsum saturation in a significant portion of the water. Gypsum precipitation controls SO₄ and Ca concentrations in groundwaters above an ionic strength (I) of 60 mM. It has been found that there is always a clear relationship between I, SO₄ and Ca concentrations. In particular, there is a tendency that Ca concentrations decrease with increase in ionic strength above I = 60 mM and a striking rareness of samples with SO₄ concentrations between 20 and 30 mM above an ionic strength of 100 mM. These observations are explained by a genetic model. This model also explains the observed relationship between the c(Fe)/c(SO₄)-ratio, the ionic strength, and the observed pH-values. Based on the field data and supported by geochemical equilibrium calculations, it is shown that silicate weathering along with calcite dissolution must be a significant buffering process at least in some areas.     

The stability of the MOC as diagnosed from model projections for pre-industrial, present and future climates

The stability of the Atlantic meridional overturning circulation (MOC) is investigated for various climate scenario runs, using data from the CMIP3 archive of coupled atmosphere-ocean models. Apart from atmospheric feedbacks, the sign of the salt flux into the Atlantic basin that is carried by the MOC determines whether the MOC is in the single or multiple equilibria regime. This salt advection feedback is analyzed by diagnosing the freshwater and salt budgets for the combined Atlantic and Arctic basins. Consistent with the finding that almost all coupled climate models recover from hosing experiments, it is found that most models feature a negative salt advection feedback in their pre-industrial climate: freshwater perturbations are damped by this feedback, excluding the existence of a stable off-state for the MOC. All models feature enhanced evaporation over the Atlantic basin in future climates, but for a moderate increase in radiative forcing (B1 and 2 CO₂ scenarios), there is a decrease of the fresh water flux carried by the MOC into the Atlantic (the deficit is made up by increased fresh water transport by the gyre circulation). In this forcing regime the salt advection feedback becomes less negative: for three models from an ensemble of eight it is positive in a 2 CO₂ climate, while two models feature a positive feedback in the pre-industrial climate. For even warmer climates (A1B-equilibrium and 4 CO₂) the salt feedback becomes more negative (damping) again. It is shown that the decrease in northward fresh water transport at 34°S by the MOC (in B1-equilibrium and 2 CO₂) is due to a reduction of the inflow of intermediate waters relative to thermocline waters, associated with a robust shoaling of the MOC in future, warmer climates. In A1B and 4 CO₂ climates northward freshwater transport increases again. The MOC keeps shoaling, but both intermediate and thermocline water masses freshen.     

Growth, condition and energy stores of Arctic grayling fry inhabiting natural and artificial constructed Arctic tundra streams

Juvenile north-temperate and Arctic fishes are faced with trade-offs between energy allocation to growth and energy storage (primarily lipids) prior to over-wintering. We determined classical morphometric (fork length, body weight and condition factor) and biochemical (whole body triglycerides, muscle RNA/DNA ratio, muscle proteins) measures of growth and condition in individual young-of-the-year (YOY) Arctic grayling (Thymallus arcticus). Grayling were collected just prior to over-wintering in late August (approximately 50 days after swim-up) from two natural streams and five locations within a 3.4 km long artificial stream constructed as a fish habitat compensation project and diversion channel for the diamond mining industry in Northwest Territories, Canada (64°45′N). Fork lengths, body weights and whole body triglyceride levels in grayling collected from all sites along the artificial stream were significantly lower than fish collected from one of the natural streams. Condition factor (weight-at-length) was not different among grayling collected from natural and artificial streams. Muscle proteins were lower in grayling collected from four sites along the artificial stream compared to the natural streams. In contrast, muscle RNA/DNA ratios were greater in grayling collected from two sites in the artificial stream compared to natural streams. There were no consistent differences in any variable among grayling collected at the five artificial stream sites or among grayling collected from the two natural streams. The higher RNA/DNA ratios and lower fork lengths, whole body triglycerides and muscle proteins in grayling inhabiting the artificial stream are consistent with energy still being primarily allocated to growth in these fish at this late stage of summer. Individuals that are both larger and possess greater energy storage in the form of triglycerides are more likely to survive the long over-wintering period at this latitude. Our results suggest that YOY grayling using the artificial stream as nursery habitat will likely face increased over-winter mortality, thus raising concerns over the use of fish presence, spawning and rearing as criteria for the initial success of artificial streams as habitat compensation measures in Arctic tundra regions. Further research is needed to determine the potential consequences of reduced size and energy storage in juvenile fishes in order to assess the viability of stream fish habitat compensation and restoration projects associated with industrial development in Arctic tundra regions.