Miracle-dz/UniFAR-FTUs huggingface dataset:
Evidence of Suess solar-cycle bursts in subtropical Holocene speleothem δ18O records

Several studies indicate that changes in solar activity may have driven Holocene subtropical monsoon variability on decadal and centennial timescales, but the strength and nature of this link remains debated. In this study, we combine a recent mapping of the Holocene solar-cycle activity with four subtropical speleothem δ18O records, which allows a strong test of the link between solar activity, monsoon activity (or intensity), and the hydrological cycle. This is possible because the speleothem δ18O records mainly reflect changes in local rainfall composition, which is controlled by changes in total moisture loss along the atmospheric transport path and monsoon intensity. We find that the spectral density distributions of the speleothem records exhibit particularly significant ~210 yr cyclicities that tend to coincide in time with the three Suess solar-cycle bursts, i.e. intervals around 1850–3200 BP, 4500–5700 BP, and 7750–8850 BP when the ~210 yr solar cycle was particularly strong. The speleothems from Dongge Cave (China) and Sofular Cave (Turkey) appear to have recorded all three Suess bursts, whereas the speleothems from Heshang Cave (China) and Pink Panther Cave (southwestern USA) only recorded the first and last Suess bursts, and the middle Suess burst, respectively. The temporal relationship between the Suess solar cycle and particularly significant 210 yr oscillations in the speleothem δ18O records therefore supports the notion that solar variability played a significant role in driving centennial-scale changes in the hydrological cycle in the subtropics during the Holocene.
Calculated phase equilibria involving chemical potentials to investigate the textural evolution of metamorphic rocks

Evolving pressure–temperature conditions during metamorphism drive changes in the stable mineral assemblage, mineral proportions and mineral compositions in rocks. These changes are achieved via the diffusion of components between minerals, fluid and melt, the driving force for diffusion being the gradients in chemical potential of the components developed spatially within the rock. This study utilises recent developments in the software thermocalc to investigate quantitatively chemical potential relationships in rocks, with the phases involved being (solid) solutions. Phase diagrams with chemical potentials as axes are used to understand better the spatial rearrangement of components during the metamorphic evolution of rocks and the metamorphic textures that result. In contrast to qualitative chemical potential diagrams, quantitative diagrams can be contoured for mineral composition, allowing consideration of chemical zoning in minerals. Furthermore, the amount of material required to diffuse to equalise chemical potentials can be calculated. We start by demonstrating the approach via an example of retrograde corona development in an ultra‐high‐temperature granulite. Whereas the use of chemical potentials to consider the retrograde development of corona textures is well known, they are also significant in considering the prograde history. The role of chemical potentials in prograde metamorphic textural evolution is highlighted in consideration of the consumption and growth of aluminosilicates during the kyanite‐to‐sillimanite reaction, and the growth of garnet porphyroblasts.
Lower hybrid cavities in the inner magnetosphere

We present observations of lower hybrid cavities from altitudes above 10,000 km, using data from Viking and Cluster satellites. Lower hybrid cavities (LHCs) are narrow (ion gyroradius scale) density depletions with enhanced amplitude of waves in the lower hybrid frequency range, previously reported below 1750 km altitude by the Freja satellite and several sounding rockets. Detailed analysis of a Cluster event shows the same kind of rotating wave structure as previously observed on sounding rockets, with a change of sense of rotation at the lower hybrid frequency. The scale size of the structures are of the same order as the ion gyro radius, in similarity with the ionospheric observations. There are too few Cluster events yet to enable any occurrence statistics, but the distribution of the Viking LHCs are consistent with Freja results from the topside ionosphere.
Indian Ocean‐monsoon coupled interactions and impending monsoon droughts

Monsoon droughts over the Indian subcontinent emanate from failures in the seasonal (June–September) monsoon rains. While prolonged dry‐spells (“monsoon‐breaks”) pervade on sub‐seasonal/intra‐seasonal time‐scales, the underlying causes for these long‐lasting anomalies remain elusive. Based on analyses of a suite of observed data sets, we report an ocean‐atmosphere dynamical coupling on intra‐seasonal time‐scales, in the tropical Indian Ocean, which is pivotal in forcing extended monsoon‐breaks and causing droughts over the subcontinent. This coupling involves a feedback between the monsoonal flow and thermocline depth in the Equatorial Eastern Indian Ocean (EEIO), in which an anomaly of the summer monsoon circulation induces downwelling and maintains a higher‐than‐normal heat‐content. The near‐equatorial anomalies induce strong and sustained suppression of monsoon rainfall over the subcontinent. It is concluded that the intra‐seasonal evolution of the ocean‐monsoon coupled system is a vital key to unlocking the dynamics of monsoon droughts.
Submarine melting of the 1985 Jakobshavn Isbræ floating tongue and the triggering of the current retreat

[1] Photogrammetric reanalysis of 1985 aerial photos has revealed substantial submarine melting of the floating ice tongue of Jakobshavn Isbrae, west Greenland. The thickness of the floating tongue determined from hydrostatic equilibrium tapers from ∼940 m near the grounding zone to ∼600 m near the terminus. Feature tracking on orthophotos shows speeds on the July 1985 ice tongue to be nearly constant (∼18.5 m d−1), indicating negligible dynamic thinning. The thinning of the ice tongue is mostly due to submarine melting with average rates of 228 ± 49 m yr−1 (0.62 ± 0.13 m d−1) between the summers of 1984 and 1985. The cause of the high melt rate is the circulation of warm seawater (thermal forcing of up to 4.2°C) beneath the tongue with convection driven by the substantial discharge of subglacial freshwater from the grounding zone. We believe that this buoyancy-driven convection is responsible for a deep channel incised into the sole of the floating tongue. A dramatic thinning, retreat, and speedup began in 1998 and continues today. The timing of the change is coincident with a 1.1°C warming of deep ocean waters entering the fjord after 1997. Assuming a linear relationship between thermal forcing and submarine melt rate, average melt rates should have increased by ∼25% (∼57 m yr−1), sufficient to destabilize the ice tongue and initiate the ice thinning and the retreat that followed.
Physical, dielectric, and C band microwave scattering properties of first‐year sea ice during advanced melt

[1] This paper investigates the influence of solar heating and intermittent cloud cover on the physical and dielectric properties of naturally snow-free, warm (>−2°), first-year sea ice (FYI) in the southeastern margin of the Beaufort Sea during advanced melt. A simple three-layer physical model describing the surface is introduced and copolarized C band microwave signatures are simulated using a multilayer scattering model forced with four sets of measured surface parameters. Modeled backscatter signatures are compared to coincident surface-based C band scatterometer signatures in order to elucidate the signature controlling properties of the ice. Results show that 50 MHz impedance probe dielectric measurements of desalinated upper ice layers exhibit statistically significant diurnal variations due to the link between solar forcing and the availability of free water in brine-free upper ice layers. Enhanced downwelling longwave radiation to the surface from low-level stratus clouds is positively linearly associated (r = 0.709) with volumetric moisture mv detected in upper ice layers. Model results show that desalinated upper ice layers contribute volume scattering from smooth, snow-free FYI under the observed surface mv range. Sustained cloud-free periods result in the formation of a 0.5–2.5 cm granular surface layer, composed of 5.2 mm ice grains, which enhances backscatter under relatively dry conditions. Sensitivity analyses show that layer thickness plays a significant role in scattering due to the increased number density of inclusions which act as discrete scatterers, and sufficient energy may penetrate to, and scatter from, the saline columnar ice layer under relatively dry conditions only (mv < 2%).
Investigation of Hydrological Variability in West Africa Using Land Surface Models

Abstract The availability of freshwater is a particularly important issue in Africa where large portions of the continent are arid or semiarid and climate is highly variable. Sustainable water resource management requires the assessment of hydrological variability in response to nature climate fluctuation. In this study, a land surface model, the Integrated Biosphere Simulator (IBIS), and a hydrological routing model, the Hydrological Routing Algorithm (HYDRA), are used to investigate the hydrological variability in two large basins, the Lake Chad basin (LCB) and the Niger River basin (NRB), located in West Africa, over the period from 1950 to 1995. The IBIS land surface hydrological module was calibrated and validated for arid and semiarid Africa, and major enhancements were made to the module, including the development of a dynamic root water–extraction formulation, the incorporation of a Green–Ampt infiltration parameterization, and modification to the prescribed root distribution, the runoff module, a.
Long‐range prediction of the onset and end of the rainy season in the West African Sahel

Using upper-wind data for three stations across the West African Sahel, simple empirical schemes for predicting the onset and cessation of the rainy season for more than 2 months ahead are presented. Agriculturally reliable rainfall commences about 70 days after the first sudden changes in wind direction from westerly to easterly at the 400 hPa level and above. These sudden changes signal the withdrawal of the subtropical (westerly) jet, thus leading to the establishment of the African easterly jet at the 700 hPa level. Cessation of rainfall occurs about 80 days after the destruction, at the peak of the rainy season, of the mid-tropospheric (700–400 hPa) vertical wind shear. A method for estimating the length of the rainy or growing season also is proposed.
Threshold behavior in a fissured granitic catchment in southern China: 2. Modeling and uncertainty analysis

In general, preferential flow occurring in forest catchments cannot be reasonably described using classical partial differential equations. As a result, linear or nonlinear reservoir models are widely used in hillslope and catchment hydrology. Currently, few studies have simulated the hydrological threshold behavior that has been observed in many experimental catchments. In this study, five models with different structures were constructed using linear reservoir method to explore the inherent mechanisms of threshold behavior and to analyze the uncertainty of model structure in threshold simulations. According to the model results, the average bedrock depression storage over the study catchment (0.99 km2), which can be represented using the height of the lowest lateral outlet from the reservoir bottom (h1), was 1.5–5.1 mm. Substantial movable water percolated into the fissure bedrock and was discharged into the streamflow as base flow after storm events, illustrating why the slope of the linear relationships between the total event precipitation plus the antecedent soil moisture index (P + ASI) and the event quick flow depth above the rising threshold was less than one. Streamflow was simulated effectively by all five models with (h1 > 0) or without (h1 = 0) bedrock depression storage; however, different ratios of annual infiltration into bedrock to annual interflow discharged to the stream were obtained by models with h1 > 0 (2.5–2.8) and h1 = 0 (1.8–1.9). Namely, the calculated infiltration into bedrock was larger by models with h1 > 0 than that by models with h1 = 0. At the storm event scale, the simulated total bedrock flow was larger than the interflow for models with h1 > 0 by a ratio of 1:0.7, whereas for models with h1 = 0 the ratio was ∼1:1.5.
Role of inertial instability in the West African monsoon jump

The West African monsoon jump is a sudden shift in the latitude of the West African precipitation maximum from the Guinean coast near 4°N into Sahel near 12°N in late June or early July. An examination of reanalyses and observations indicates that the Sahel rainy season develops smoothly and the monsoon jump occurs because of an abrupt decrease in Guinean coast rainfall. We show that this abrupt end of the coastal rainy season occurs when inertial instability develops over the region, 1 month later than it develops in the vicinity of the marine Atlantic Intertropical Convergence Zone. The reason for this delay is the presence of the African easterly jet, which places strong negative meridional zonal wind gradients over the coast to preserve the inertially stable environment. When the African easterly jet moves farther north due to the seasonal solar forcing, these gradients weaken and then reverse to satisfy the threshold condition for inertial instability; the rapid end of the Guinean coast rainy season follows. The northward movement and intensity of the African easterly jet are controlled by the seasonal development of strong meridional land surface temperature gradients and are independent of the formation of the Atlantic cold tongue. This explanation for the West African monsoon jump relates the phenomenon to the shape and location of the African continent, including the low‐latitude position of the Guinean coast and the large expanse of the continent to the north.
Caracterización hidrológica de una laguna costera de Baja California Sur, México

From April 1997 to September 1998 ten samplings were carried out in Ensenada de La Paz in order to analize the spatial and seasonal variation of some physical and chemical parameters, and their association. Temperature and salinity showed differences at temperate season (April, May and June) and warm season (July, August and September). Average and standard deviation in the temperate season were 23.55±1.35°C, while in the warm were 30.25±0.95°C. In temperate season is frecuently found salinity greater than 37 ups, while in the warm season is less than 37 ups. Because of the high spatial variability it is not possible to use tipical average values for the rest of the parameters. However, during the temperate season low clorophyll values and high seston were registered, that could indicated that suspended matter is inorganic. Meanwhile, the last months of the warm season showed high clorophyll and high values of seston, wich could possibly be an indicator of ligth attenuation dueto organic matter (phytoplankton). Three groups were identified from statistical analysis (p<0.05). These groups represent the mouth, northern and southeastern areas in the lagoon. The parameters that explained the majority of the variance were temperature, salinity, chlorophyll a, seston, water transparency and, to a lesser degre, the nutrients. In order to understand and manage coastal lagoons the seasonal characterization first, and the aplication of simulation models later, under different tide conditions, are basic.
Resolution and Reliability of the α-spectrometric 230Th/234U Method for Age Determination

最近のウランおよびトリウム同位体分析への質量分析計技術の導入は,230Th/234U年代測定法の精密化とともに,必要試料の大幅減量や適用範囲の14C法による測定年代域への拡張も可能にした. 一方,従来のαスペクトル法でも,測定機器類の計数効率や安定性の向上と,試料の放射化学的処理法の改良によって,測定誤差がTIMS法の4～5倍にまで改善された. 今では,最終間氷期最盛期相当の測定値(約125ka)の誤差が,95.5%の確率を意味する2σの統計誤差で表示しても,TIMS230Th/234U法では約1ka(1%),αスペクトル法でもおおよそ5ka(4%)と,以前に比べ格段に小さくなった. しかし,そのような年代値を,みかけ上誤差が小さいからというだけで,そのまま信用することはできない. 本論では,真に信頼できる年代値を得るには,最良の試料を用いることが不可欠であるという立場から,試料が230Th/234U法固有の前提条件と必要条件を満たすことを検証するための方法を提示し,さらに230Th/234U法の信頼性を高めるための方策を論じた.
The Role of Sea Ice Thickness Distribution in the Arctic Sea Ice Potential Predictability: A Diagnostic Approach with a Coupled GCM

AbstractThe intrinsic seasonal predictability of Arctic sea ice is investigated in a 400-yr-long preindustrial simulation performed with the Centre National de Recherches Meteorologiques Coupled Global Climate Model, version 3.3 (CNRM-CM3.3). The skill of several predictors of the pan-Arctic sea ice area was quantified: the sea ice area itself, the pan-Arctic sea ice volume, and some areal predictors built from the subgrid ice thickness distribution (ITD). Sea ice area provides a potential predictability of about 3 months, which is consistent with previous studies using model and observation data. Sea ice volume predictive skill for winter sea ice area prediction is weak. Nevertheless, there is a higher potential to predict the September ice area with the June volume anomaly than with the June area anomaly. Using ITD-based predictors, two “regimes” of predictability were highlighted. The first one, a “persistence regime,” applies to winter/early spring sea ice seasonal predictability. The winter sea ice c.
THE BENEFITS AND NEGATIVE IMPACTS OF BIOMASS CROPS ON RESOURCE PROTECTION

To identify existing knowledge and knowledge gaps on the benefits and negative impacts of biomass crops on resource protection. The study focuses on enabling land to be targeted for biomass crops and on identifying practices that are sustainable to resource management. This will provide supporting evidence for Natural England and the Forestry Commission to decide on suitable land for energy grant aids.
Tilting of active folds and drainage asymmetry on the Manawatu anticlines, New Zealand: a preliminary investigation

The apparent southward tilting of five anticlines in the Manawatu, North Island, New Zealand, is investigated using two drainage basin analysis techniques: the transverse topographic symmetry factor (T) and the asymmetry factor (AF). The techniques are used to determine whether westward‐flowing trunk streams on the gentle western limbs of five anticlines are migrating southwards across their drainage basins, concomitant with down‐tilting of the fold axes. While results show potential for the techniques to be applied in such a tectonic setting, our findings are inconclusive. This could be due to the incipient nature of the folds (c. 0·5 Ma in age), and it would seem more appropriate to apply the techniques in concert with detailed field analyses of river migration patterns. Copyright © 2008 John Wiley & Sons, Ltd.
Nutrient cycling in the Indian sector of the Southern Ocean over the last 50,000 years

Most high‐southern latitude records of carbon and nitrogen isotopic ratios and elemental ratios are from the Antarctic and Polar Front zones, thus hindering a comprehensive view of nutrient cycling in the Southern Ocean. We present, for the first time, two records from the Subantarctic Zone and the southern Subtropical Zone of the Indian Ocean. These records provide a latitudinal transect covering the main oceanographic systems of the Southern Ocean. Carbon and nitrogen content of the diatom‐bound organic matter increases during the last glacial in the Antarctic and Subantarctic zones but does not show a clear climate‐related signal in the Subtropical Zone. Comparison of these records with sea‐surface temperatures reconstructed at the core locations and record of dust deposition over Antarctica suggests that eolian iron input possibly switched diatom physiology toward higher carbon to silica and nitrogen to silica uptake and storage south of the Subantarctic Front due to the dependency of photosynthesis on iron concentration levels. Conversely, the northernmost core was too remote from any iron source over the last 50,000 years. Antarctic diatoms therefore have the sole potential to change the nutrient content of the waters escaping from the Southern Ocean, hence providing partial support to the silicic leakage hypothesis as a potential cause of lower glacial atmospheric CO2.
Taxonomía y sistemática de Stipa Sect. Stipa L. (POACEAE) y grupos afines

El genero Stipa L. es un complicado grupo de gramineas, cuya caracterizacion y limites taxonomicos siguen siendo fuente de controversia. Fue descrito por Linnaeus (1753), quien utilizo las palabras de origen griego “Stupe” o “Stuppeion” (plumosa o fibrosa) en referencia probablemente a la arista plumosa de algunas especies (Stipa pennata L.), cuya vistosidad hace que sean cultivadas como plantas ornamentales. Tambien se baraja la hipotesis de que Linnaeus (1753) se refiriese a las hojas fibrosas de algunas de estas plantas (S. tenacissima L.). El trabajo que aqui presentamos se limita a las especies de la sect. Stipa s. str. , que se caracterizan por la arista bigeniculada, con la seta plumosa (pelos mayores de 3,5 mm), ovario con dos estilos y comprende 14 especies distribuidas por Europa, NW de Africa y Asia. A este grupo se ha anadido otras dos secciones: Smirnovia Tzvelev (13 especies distribuidas por Asia) caracterizado por tener la arista unigeniculada o bigeniculada, con la seta plumosa (pelos mayores de 3 mm), ligulas de las hojas basales cortas, ovario con dos estilos y Subsmirnovia Tzvelev (1 especie del W de Asia), caracterizado por tener la arista unigeniculada, con la seta plumosa, ligulas muy largas y ovario con dos estilos. Ambas secciones muestran una similitud morfologica con la seccion Stipa y por lo que su estudio se hacia necesario para reforzar las conclusiones sobre dicha seccion. El objetivo principal es presentar una revision taxonomica de las tres secciones, basadas principalmente en el estudio morfologico y anatomico de material de herbario procedente de toda el area de distribucion. Se emplean en la medida de lo posible analisis morfometricos, univariantes y multivariantes para clarificar las relaciones taxonomicas de las especies y sus taxones infraespecificos. Se ha estudiado el valor discriminatorio de los caracteres empleados tradicionalmente y se han buscado nuevos caracteres. De este modo se ha elaborado una propuesta taxonomica para las secciones Smirnovia, Stipa y Submirnovia, con nuevas claves dicotomicas, descripciones detalladas, sinonimia, tipificaciones, mapas de distribucion e ilustraciones de cada taxon.