Miracle-dz/UniFAR-FTUs huggingface dataset:
Rethinking geochemical feature of the Afar and Kenya mantle plumes and geodynamic implications

[1] We discuss the spatial and temporal variation in the geochemistry of mantle sources which were sampled by the Eocene to Quaternary mafic magmas in the vicinity of the Afar and Kenya plume upwelling zones, East Africa. Despite the contributions of lithospheric and crustal sources, carefully screened Eocene to Quaternary mafic lavas display wide range of Sr-Nd-Pb isotopic and incompatible trace elemental compositions that can be attributed to significant intraplume heterogeneity. The geochemical variations reflect the involvement of at least four mantle plume components as sources for the northeastern Africa magmatism: (1) isotopically depleted but trace element-enriched component; (2) component characterized by radiogenic Pb isotope signatures (HIMU? ); (3) enriched mantle-like component; and (4) high-3He/4He-type (as HT2-type basalts) plume component. The first component disappears in the Miocene-Quaternary magmatism, and the second component is hardly recognized after the eruption of Miocene basalt in southern Ethiopia. Plume-unrelated depleted asthenosphere starts to involve at a nascent stage of seafloor spreading centers in the Red Sea and Gulf of Aden. The other two-plume components have persisted from the late Eocene to present, but their proportions have changed through time and space. We propose a model of multiple impingements of plumelets within the broad upwelling zone connected to the African Superplume in the lower mantle beneath southern Africa. The plumelet contains a matrix of high-3He/4He-type component with blobs, streaks, or ribbons of other components.
Temporally integrated estimate of the Indonesian throughflow using tritium

Because of the high interannual and seasonal variability, transports from the various methods used to estimate the Indonesian throughflow encompass a large range of values. Here, we estimate a temporally integrated transport for the throughflow from comparison of the tritium water column inventory on both sides of the throughflow. Our approach is based on the simple idea that tritium, with a radioactive decay half‐life of 12.32 yr, is well suited to infer the transit time (and consequently the mass flow) of the waters through the Indonesian archipelago. We show that the tritium budget implies a flow of 8.6 ± 4 Sv, corresponding to a transit time of 10.5 yr. This result, which represents an average over seasons and several ENSO and non‐ENSO periods, shows that repeated tritium measurements on both sides of the Indonesian Seas could provide a useful method for monitoring the long‐term evolution of the throughflow.
Geochemistry of kimberlites from the Nakyn field, Siberia: Evidence for unique source composition

Two newly discovered kimberlite pipes in the Nakyn field, Siberia yield Rb-Sr isochron ages of ca. 364 Ma, similar to emplacement ages of other major diamond-bearing pipes on the Siberian platform. Unlike any other Siberian kimberlites, however, the rocks from the Nakyn field show some similarities to South African group II (micaceous) kimberlites in their mineralogy and chemical compositions. Several key geochemical ratios (TiO 2 /K 2 O, 0.43; Nb/Zr, 0.4) in the Nakyn kimberlites are the same as for group II, whereas others such as Ba/Nb (0.95) and Ni/MgO (45.2) are intermediate between groups I and II, and La/Nb (0.58) ratios are similar to group I kimberlites. The Nakyn kimberlites are unique in having concentrations of incompatible elements two to three times lower than kimberlites from any cratonic area worldwide, coupled with higher Sm/Nd (0.21) and Lu/Hf (0.06) and lower La/Yb (25.8). Ranges of initial Sr and Nd isotope composition are very narrow in the Nakyn kimberlites, at ϵ Nd (t) +0.9 to −0.7 and 87 Sr/ 86 Sr(t) 0.7059–0.7068. These compositions are closer to group I than to group II kimberlites, but they require a source with higher Rb/Sr and lower Sm/Nd ratios than Group I kimberlites from both Siberia and South Africa. The trace element and isotope signatures of the Nakyn kimberlites appear to indicate a specific source located within the lithospheric mantle, distinct from that of other Siberian kimberlites.
Circumpolar thinning of Arctic sea ice following the 2007 record ice extent minimum

September 2007 marked a record minimum in sea ice extent. While there have been many studies published recently describing the minimum and its causes, little is known about how the ice thickness has changed in the run up to, and following, the summer of 2007. Using satellite radar altimetry data, covering the Arctic Ocean up to 81.5° North, we show that the average winter sea ice thickness anomaly, after the melt season of 2007, was 0.26 m below the 2002/2003 to 2007/2008 average. More strikingly, the Western Arctic anomaly was 0.49 m below the six‐year mean in the winter of 2007/2008. These results show no evidence of short‐term preconditioning through ice thinning between 2002 and 2007 but show that, after the record minimum ice extent in 2007, the average ice thickness was reduced, particularly in the Western Arctic.
Bulk heat transfer coefficient in the ice–upper ocean system in the ice melt season derived from concentration–temperature relationship

[1] The bulk heat transfer coefficient in the ice–upper ocean system (Kb) in the ice melt season is estimated by a new method at 18 areas that cover much of the Antarctic seasonal ice zone. The method is based on a model in which ice melting is caused only by heat input through open water and is treated in a bulk fashion in the ice–upper ocean system. Kb is estimated by fitting a convergent curve derived from the model to an observed ice concentration–temperature plot (CT-plot). Estimated Kb is 1.15 ± 0.72 × 10−4 m s−1 on average. If Kb can be expressed by the product of the heat transfer coefficient (ch) and the friction velocity (uτ), ch is 0.0113 ± 0.0055. This value is about two times larger than that estimated at the ice bottom. The relationship between Kb and the geostrophic wind speed (Uw), which is roughly proportional to uτ, shows a significant positive correlation, as expected. Further, Kb seems more likely to be proportional to the square or cube of Uw rather than a linear relationship. Since Kb estimated from our method is associated with ice melting in a bulk fashion in the ice–upper ocean system, this relationship likely indicates both the mixing process of heat in the upper ocean (proportional to uτ3) and the local heat transfer process at the ice–ocean interface (proportional to uτ).
Metal‐rich concretions on the roots of salt marsh plants: Mechanism and rate of formation

The roots of the vascular plant Spartina maritima, growing in the saltmarshes of the Tagus Estuary, Portugal, are surrounded by tubular concretions whose diameter can reach >0.2 cm. Concretions are also found scattered within the sediment matrix in and below the root zone. The concretions comprise 4% (DW) of the sediment and contain 11.7 ± 1.6% iron compared to 4.9 ± 0.3% iron in the sediment in which they are found. They are formed by the precipitation of iron oxides in the pores between the sediment grains; this has filled about one‐sixth of the originally available pore space. To produce the concretions, the plants have extracted 0.25% Fe from the anoxic bulk sediment and concentrated it into the oxidized microenvironment surrounding each root. A mass‐balance model using cylindrical geometry shows that the observed concretion density can be produced by a network of roots with 1‐cm spacing. The space between the roots limits the amount of Fe that is available to a given root and thus determines the size of the individual concretion. Field observations and mathematical modeling show that plants can produce concretions on their roots in the space of a few weeks. The rhizoconcretions are 5–10 times enriched in Cd, Cu, Pb, and Zn with respect to the sediment surrounding them, and the smaller diameter concretions are more enriched than the larger ones. The preferential enrichment of the smaller diameter concretions, which was not observed for Fe and Mn, is independent of depth in the sediment for Cd and Cu; however, for Zn and Pb, the preferential enrichment is most pronounced within the upper trace metal‐contaminated sediment layer. The rhizoconcretions have acquired their load of metals via diffusion from the surrounding sediment. In the case of Fe and Mn, the concentration gradient that drives the diffusion is maintained by the precipitation of insoluble oxides. In the case of Cd, Cu, Zn, and Pb, the mechanism that maintains a concentration gradient toward the surface of the root is not know, but our data show that S. maritima is capable of mobilizing trace metals dispersed in reducing anoxic estuarine sediment and concentrating them into the distinct oxidized microenvironments that surround the roots.
Distribution of Fine Roots of Ponderosa Pine and Douglas-Fir in a Central Idaho Forest

This study describes soil horizon depth and fine root distribution in cores collected at two distances from the boles of Douglas-fir and ponderosa pine trees at a study site in a central Idaho forest. Concentration and content of fine roots extracted from soil cores were compared among species, soil horizons, tree size, and distance from bole. Approximately 80% of litter and humus samples contained no fine roots. The highest fine root content and concentrations of fine roots occurred in deep mineral soil for both species (1.24 g and 2.82 g/l for Douglas-fir and 0.98 g and 2.24 g/l for ponderosa pine, respectively). No statistically significant differences were found in fine root content or concentration between species in any of the four soil horizons. Tree size was not a significant factor in fine root distribution in this study. Significant variables were horizon, distance from bole, and interactions among tree size, location of sample, and soil horizon. This study, which was part of a larger US Forest Service study to develop a predictive model of postfire tree mortality, provides baseline information that may be useful in predicting postfire damage to fine roots.
A Paradigm Shift in Hydrology: Storage Thresholds Across Scales Influence Catchment Runoff Generation

A paradigm shift is occurring in the science surrounding runoff generation processes. Results of recent field investigations in landscapes and during periods previously unobservable are shaping new ideas on how runoff is generated and transferred from the hillslope to the catchment outlet. The previous paradigm saw runoff generation and contributing area variability as a continuum. The new paradigm is based not on continual storage satisfaction and runoff generation but threshold-mediated, connectivity-controlled processes dictated by heterogeneity in the catchment. This review focuses on the body of literature summarizing research on storage, storage thresholds and runoff generation, particularly over the last several years during which this paradigm shift has occurred. Storage thresholds that control the release of water exist at scales as small as the soil matrix and as large as the catchment. Hysteresis in storage‐runoff relationships at all scales manifest because of these thresholds. Because storage thresholds at a range of scales have now been recognized as important, connectivity has become an important concept crucial to understanding how water is transferred through a catchment. This new paradigm requires basins to be instrumented within the context of a water budget investigation, with measurements taken within key catchment units, in order to be successful. New model approaches that incorporate connectivity are required to address the findings of field hydrologists. These steps are crucial if our community wishes to adopt the holisitic view of the catchment necessary to answer the questions posed to us by the society.
Simulations of Indonesian rainfall with a hierarchy of climate models

This dissertation describes the analysis of the monthly, seasonal and interannual rainfall variabilities over the Maritime Continent and describes the potentials and limits of a wide range of climate models in simulating these variabilities. The study analyzes the simulated rainfall variability from two global reanalyses, an atmospheric general circulation model (AGCM), an atmospheric regional climate model (RCM) and an ocean general circulation model (OGCM). The two reanalyses and the AGCM output is available at T42 and T106 resolutions, while the RCM resolves 0.5◦ and 1/6◦. The study explores the uncoupled as well as the coupled mode of RCM and OGCM and focuses mainly on the period 1979 to 1993. With a regionalization method introduced in this study, the Maritime Continent is divided into three distinct climate regions, the south monsoonal, the northwest semi-monsoonal and the Molucca anti-monsoonal region. All three regions show different responses to monsoon and El Niño/Southern Oscillation (ENSO). Two important rainfall variabilities ranging from monthly to interannualy time scale are the annual monsoon cycle and the irregular ENSO. The monsoon regulates local SST variability via ocean circulation, which in turn influences heat content of the upper ocean and eventually local rainfall. The study points to remote ENSO influences through SST forcing. Indeed, there is a local ocean circulation mechanism that drives the ENSO impact on Indonesian rainfall. The rainfall climate of this region is potentially predictable on monthly and seasonal scales but only for limited and specific periods and regions. Despite such a potential, the study shows a consistent predictability barrier in spring as an intrinsic character of the Indonesian rainfall and a challenge to climate modeling in the region, because it limits model applications. The barrier is found by all models and at different resolutions. The RCM and the OGCM have been especially tailored to the region and they produce realistic results. The global atmospheric model produces the large scale system well and the nested regional model shows a local phenomenon obscured in the global. A coupled atmosphere/ocean regional model shows improved dynamics through a better sea-air interaction and ocean/atmosphere feedback. However, also the uncoupled ocean and atmosphere models, separately, produce realistic results of rainfall and ocean variability albeit with some drawbacks. The quality of the RCM simulations is confined, in most cases, to the quality of the prescribed boundary forcings.
Dynamics of channel bifurcations in noncohesive sediments

Braided rivers produce flow confluences and divergences (diffluences) in roughly equal numbers, but braided river research has focused mainly on confluences. Divergences, however, are of equal importance dynamically: they are sites of formation of central bars and the development of flow divisions that can steer the flow toward one part of the braided network or another. In a series of experiments on flow in isolated, well‐defined bifurcations, we found that although a central bar always develops, the divided flow may continue to flow on both sides of the bar (“stable” bifurcation) or may eventually be forced entirely to one side of the bar or the other (“unstable” bifurcation). We found that an unstable bifurcation forms when the flow field is characterized by both a low Shields stress and a nonuniform incoming flow. We also found that divergences with erodible banks tend to an equilibrium configuration that depends mainly on the widening ratio of the channel.
Volume and area changes of the Milne Ice Shelf, Ellesmere Island, Nunavut, Canada, since 1950

[1] Ground penetrating radar (GPR) surveys of the 205 km2Milne Ice Shelf conducted in 2008 and 2009 are compared with radio echo sounding (RES) data from 1981 to provide the first direct measurements of thinning for any northern Ellesmere Island ice shelf. Our results show an average thinning for the ice shelf as a whole of 8.1 ± 2.8 m, with a maximum of >30 m, over this 28-year period. Direct-line comparisons along a 7.5 km transect near the front of ice shelf indicate a mean thinning of 2.63 ± 2.47 m over the same period. Reductions in areal extent (29%, 82 ± 8.4 km2: 1950–2009) and volume (13%, 1.5 ± 0.73 km3 water equivalent (w.e.): 1981–2008/2009) indicate that the Milne Ice Shelf has been in a state of negative mass balance for at least the last 59 years. A comparison of mean annual specific mass balance measurements with the nearby Ward Hunt Ice Shelf (WHIS) suggests that basal melt is a key contributor to Milne Ice Shelf thinning. Glacier inflow to the ice shelf has also reduced markedly over the past 28 years. The transition of ice shelf ice to lake ice was the most important source of mass loss. A 28.5 km2 epishelf lake now exists on the landward side of the ice shelf. Given these recent changes, disintegration of the Milne Ice Shelf will almost certainly continue in the future.
Mercado Integrado Latinoamericano (MILA): análisis de correlación y diversificación de los portafolios de acciones de los tres países miembros en el período 2007-2012

En este trabajo se analizan los factores en comun de los mercados accionarios de los paises pertenecientes al Mercado Integrado Latinoamericano, MILA: Chile, Colombia y Peru, con el fin de explorar la existencia de una posible integracion financiera que afecte los beneficios de diversificacion para los inversionistas. Para ello, se investigan los rendimientos historicos diarios de las 15 acciones mas negociadas en cada uno de ellos, en el periodo de enero de 2009 a junio de 2012, sobre los cuales se realizan dos evaluaciones: primero, se obtiene el portafolio optimo en cada pais y otro del mercado en conjunto; y segundo, mediante un analisis de componentes principales en cada pais, se determinan el numero de factores de riesgo compartidos y la incidencia de cada pais en su variacion. Encontramos una alta correlacion entre los activos de los paises, lo cual evidencia una integracion financiera que repercute en que los beneficios de una diversificacion de portafolios para un inversionista se minimicen. Se espera continuar con la aplicacion de metodologias novedosas relacionadas con los mercados integrados teniendo en cuenta variables fundamentales que incidan en los resultados.
Stress-dependent behavior of saturated clay

A program of K0-consolidated undrained triaxial compression tests have been performed in order to investigate the effects of consolidation stress level on the compression and shear behavior of resedimented Boston blue clay (RBBC). Specimens were consolidated to maximum vertical effective stresses in the range 0.15 – 10 MPa and tested at three overconsolidation ratios, OCR = 1, 2, and 4. The results show that the virgin compression curves are essentially linear in e-logσ’v space over the consolidation stress range. However, the normally consolidated K0 stress ratio increases with the level of consolidation stress. The stress-strain-strength properties measured in undrained shear are significantly affected by the consolidation stress level at each OCR and show indications of non-normalizable behavior. At high pressures, the undrained shear stressstrain behavior becomes more ductile, requiring larger strains to mobilize peak resistance and exhibiting less post-peak strain softening. The undrained strength ratio (su/σ’vc) is not uniquely controlled by OCR as suggested by SHANSEP equation, but consistently decreases with increasing consolidation effective stress. There is notable reduction in the stiffness ratio (Eu/σ’vc) with stress level, and significant decrease in the large strain friction angle.
Dynamic Panel Data Analysis of the Impacts of Climate Change on Agricultural Production in Japan

This study empirically identifies the impact of global-warming-induced climate change on Japan’s agricultural production using panel data. First, we constructed panel data; combining time-series data from 1995 to 2006 for a cross-section of eight regions in Japan. Next, we conducted a static panel data analysis, using a function for agricultural products incorporating labor and three weather variables (temperature, solar radiation, and precipitation.) From the estimation results of the production function, we selected the production function with the aforementioned labor and weather variables and found that the rising temperatures and precipitation and falling solar radiation caused by climate change have reduced the rice production, while rising temperatures and precipitation have reduced the vegetable and potato production in Japan. Second, we conducted dynamic panel data analysis, using a production function for agricultural products incorporating labor, a one-period lagged output, and the same three weather variables. Based on the estimation results of the dynamic panel data model, we selected the production function for agricultural products using only the labor and three weather variables and found the same results for both the rice production and vegetable and potato production in Japan. Based on the estimated results of the static and dynamic-panel data models for variable mean annual temperature, which serves as a proxy for climate change, we concluded that an increase of 1°C in mean annual temperature would reduce rice production by 5.8% in the short term and 3.9% in the long term, and vegetables and potatoes productions by 5.0% and 8.6% in the short term and long term, respectively.
MODULUS REDUCTION AND DAMPING CURVES FOR SAND OF SOUTH-EAST COAST OF INDIA

Adequate information on dynamic soil properties, especially strain dependent shear modulus (G) and damping ratio (ξ) for each soil layer are the essential input data for seismic ground response analysis and soil-structure interaction studies. In the present study, the shear modulus and damping ratio of sand are estimated for a wide range of strains based on undrained strain-controlled cyclic triaxial tests. The bender elements are also utilized in the cyclic triaxial test to estimate the low strain shear modulus. For this purpose, the soil samples are taken from a nuclear power plant site located at the south-east coastal region of India. Based on the experimental results, an empirical expression is developed to calculate the maximum shear modulus, Gmax as function of void ratio and effective confining stress. Predictive relationships are also developed for estimating normalized shear modulus and damping ratio curves for the sand. The predictive relationships are based on the hyperbolic model and cyclic triaxial test results. The developed modulus reduction and damping ratio curves from the predictive relationships are compared with the previously available curves in the literature.
First observation of the overshoot effect for polar mesosphere winter echoes during radiowave electron temperature modulation

Polar mesosphere winter echoes (PMWE), observed with the EISCAT VHF radar located near Tromsø, Norway on October 24, 2006, were modulated using the EISCAT Heating facility. The heater was turned on for 20 s and then off for 160 s. The experiment confirmed previous results that when the heater was switched on, the PMWE power dropped significantly compared to the undisturbed level measured before heating. The experiment showed for the first time that, after the heater was switched off, the PMWE strength overshot the value that it had before heating. By using data from 6 heating cycles we find that the overshoot effect is about 50% of the pre‐heating value, which is rather weak compared to 3–5 times for PMSE. No, or little recovery of PMWE strength during heating periods was observed. This may indicate the presence of very small dust particles, such as meteoric smoke particles.