Theoretical calculation of equilibrium Mg isotope fractionation between silicate melt and its vapor

Isotope fractionation during the evaporation of silicate melt and condensation of vapor has been widely used to explain various isotope signals observed in lunar soils, cosmic spherules, calcium–aluminum-rich inclusions, and bulk compositions of planetary materials. During evaporation and condensation, the equilibrium isotope fractionation factor (α) between high-temperature silicate melt and vapor is a fundamental parameter that can constrain the melt’s isotopic compositions. However, equilibrium α is difficult to calibrate experimentally. Here we used Mg as an example and calculated equilibrium Mg isotope fractionation in MgSiO₃ and Mg₂SiO₄ melt–vapor systems based on first-principles molecular dynamics and the high-temperature approximation of the Bigeleisen–Mayer equation. We found that, at 2500 K, δ²⁵Mg values in the MgSiO₃ and Mg₂SiO₄ melts were 0.141?±?0.004 and 0.143?±?0.003‰ more positive than in their respective vapors. The corresponding δ²⁶Mg values were 0.270?±?0.008 and 0.274?±?0.006‰ more positive than in vapors, respectively. The general \(\alpha - T\) equations describing the equilibrium Mg α in MgSiO₃ and Mg₂SiO₄ melt–vapor systems were: \(\alpha_{{{\text{Mg}}\left( {\text{l}} \right) - {\text{Mg}}\left( {\text{g}} \right)}} = 1 + \frac{{5.264 \times 10^{5} }}{{T^{2} }}\left( {\frac{1}{m} - \frac{1}{{m^{\prime}}}} \right)\) and \(\alpha_{{{\text{Mg}}\left( {\text{l}} \right) - {\text{Mg}}\left( {\text{g}} \right)}} = 1 + \frac{{5.340 \times 10^{5} }}{{T^{2} }}\left( {\frac{1}{m} - \frac{1}{{m^{\prime}}}} \right)\), respectively, where m is the mass of light isotope ²⁴Mg and m′ is the mass of the heavier isotope, ²⁵Mg or ²⁶Mg. These results offer a necessary parameter for mechanistic understanding of Mg isotope fractionation during evaporation and condensation that commonly occurs during the early stages of planetary formation and evolution.     

Long-Term Changes in the Extreme Significant Wave Heights on the Western North Pacific: Impacts of Tropical Cyclone Activity and ENSO

Seasonal extreme wave statistics were reproduced by using the 25-km-grid global wave model of WAVEWATCH-III. The results showed that the simulated wave dataset for the present climate (1979-2009) was similar to Climate Forecast System Reanalysis (CFSR) wave data. Statistics such as the root mean squared error (RMSE) and correlation coefficient (CC) over the western North Pacific (WNP) basin were 0.5 m and 0.69 over the analysis domain. The largest trends and standard deviation were around the southern coast of Japan and western edge of the WNP. Linear regression analysis was employed to identify the relationship between the leading principal components (PCs) of significant wave heights (SWHs) in the peak season of July to September and sea surface temperature (SST) anomalies in the equatorial Pacific. The results indicated that the inter-annual variability of SWH can be associated with the El Niño-Southern Oscillation in the peak season. The CC between the first PC of the SWH and anomalies in the Nino 3.4 SST index was also significant at a 99% confidence level. Significant variations in the SWH are affected by tropical cyclones (TCs) caused by increased SST anomalies. The genesis and development of simulated TCs can be important to the variation in SWHs for the WNP in the peak season. Therefore, we can project the variability of SWHs through TC activity based on changes in SST conditions for the equatorial Pacific in the future.     

Sensitivity of Tropical Cyclone Intensity and Structure to Planetary Boundary Layer Parameterization

The advanced weather research and forecasting model is used to investigate the influence of planetary boundary layer (PBL) processes on intensity and structure of the storm Phailin (2013). Five simulations are conducted with five PBL schemes; Yonsei University (YSU), Mellor?Yamada?Nakanishi?Niino order2.5 (MYNN2), Assymetric Convective Model2 (ACM2), Medium Range Forecast (MRF), and Bougeault and Lacarrere (BouLac). The simulation duration includes the pre???intensification and rapid intensification phase of Phailin before landfall. Results indicate that during the pre???intensification phase, storm’s track and intensity are not much sensitivity to PBL but structural changes are noted. A significant sensitivity of track and intensity to PBL parameterizations are found during rapid intensification phase. BouLac and MRF produced two extremes with 39 hPa intense and 16 km compact storm for BouLac than MRF. Further analysis reveals an outward movement of air parcel just above the boundary layer which causes spin-down for YSU and MYNN2. BouLac is associated with stronger eddy diffusivity and moisture fluxes within the boundary layer and stronger cyclonic vorticity just above the boundary layer than other experiments. Stronger cyclonic vorticity above the boundary layer in BouLac favors intense updraft, facilitating more moisture transport from the boundary layer to upper layers aiding stronger secondary circulation and robustly intensifying the storm. A relatively deeper and drier inflow layer associated with weaker cyclonic vorticity just above the boundary layer reduces the moisture transport and weaken the secondary circulation for MRF than others.     

Characteristics and regional classification of the copepod community in Ariake Bay with note on comparison with 3 decades ago

Ariake Bay, Kyushu Island, has recently exhibited environmental degradation in the form of red tides and anoxic bottom water. To determine the characteristics and regional classification of the copepod community, zooplankton surveys were made throughout the bay in three cruises each in October 2004, January 2005 and March 2009 by vertical tows of a 0.1-mm-mesh plankton net. Oithona davisae was the most abundant in January and March, and Microsetella norvegica in October. Cluster analysis revealed that the copepod community from each cruise was generally separated into the inner to eastern-middle region and the western-middle to mouth region. A SIMPER analysis revealed that dissimilarity between the groups and similarity within each group were mainly due to the dominant species, but the similarities within the outer-region group in January and March were mostly contributed by Paracalanus parvus s.l. A non-metric multidimensional scaling with bubble plots of environmental variables and a BIOENV analysis showed that transparency was more different between the two groups than temperature and salinity. As compared with two similarly sized, eutrophic bays (Tokyo and Osaka Bays), Ariake Bay differs from Tokyo Bay in the dominance of M. norvegica and from Osaka Bay in the high abundance of O. davisae even in the colder season. The dominant species and the regional classification of the copepod community in the bay were similar to those in the studies in the 1970s, suggesting that the copepod community has not notably changed during the last 3 decades.     

A model for simulating the response of runoff from the mountainous watersheds of inland river basins in the arid area of northwest China to climatic changes

The subaerial tidal sand area in the northern Jiangsu Province (Subei), stretching from Dongtai towards east with a fan shape, is an early developing stage of radial sand ridges distributed in the South Yellow Sea. Since 5000–6000 a BP, after the Holocene transgression maximum in the northern Jiangsu Province, subaqueous tidal sand bodies were exposed and changed into land gradually. The environmental magnetism analysis shows that subaerial tidal sand strata are formed by the convergent-divergent paleo-tidal current field. The sediment source of tidal sand strata came early from the Changjiang River and late from the Yellow River. Sea floor erosion by tidal currents also served as an important sand source. Drilling cores and ground-penetrating profile show that there exists no probability of sand supplying directly by a large river through the apical area of tidal sand ridges either on land or in the sea. Fluvial deposits supplied the tidal sand bodies by alongshore transportation, which corresponds to the conclusions obtained by the analyses of provenance and paleocurrent field. Project supported by the National Natural Science Foundation of China (Grant Nos. 43236120 and 49676288).     

Environmental Factors Contributing to the Development and Demise of a Toxic Dinoflagellate (<Emphasis Type="Italic">Karlodinium veneficum</Emphasis>) Bloom in a Shallow,Eutrophic, Lagoonal Estuary

A dense bloom of the ichthyotoxic dinoflagellate Karlodinium veneficum was discovered in the Neuse River Estuary, North Carolina, on 19 October 2006 and was associated with four subsequent fish kills. Microscopic, photopigment, DNA, and toxicological techniques confirmed bloom identity and toxicity. High-resolution spatio-temporal data from ship-board and fixed automated sampling stations provided a unique opportunity to investigate the environmental conditions that initiated, maintained, and terminated the K. veneficum bloom. Bloom initiation and growth were favored by high nutrient availability and reduced dispersal during the period of declining riverine discharge after Tropical Storm Ernesto. K. veneficum out-competed other co-occurring dinoflagellates, perhaps because of the production of karlotoxins that are known to act as grazing deterrents and to facilitate mixotrophic feeding. Once the bloom was established, small-scale hydrodynamic processes, coupled with vertical migration, concentrated cells along a frontal convergence to high densities (>200,000 cells per milliliter). By 26 October 2006, wind mixing and possible nutrient stress disrupted the bloom. Release of cell-bound toxins during the bloom collapse likely accounted for the associated fish kill events where fish were reported as exhibiting typical symptoms of karlotoxin poisoning. The dynamics of this bloom underscore the tight control of harmful algal blooms by meteorological forcing, hydrology, and sediment nutrient input in this shallow lagoonal estuary.     

Chemistry of snow and lake water in Antarctic region

Surface snow and lake water samples were collected at different locations around Indian station at Antarctica, Maitri, during December 2004–March 2005 and December 2006–March 2007. Samples were analyzed for major chemical ions. It is found that average pH value of snow is 6.1. Average pH value of lake water with low chemical content is 6.2 and of lake water with high chemical content is 6.5. The Na⁺ and Cl^? are the most abundantly occurring ions at Antarctica. Considerable amount of SO ₄ ^2? is also found in the surface snow and the lake water which is attributed to the oxidation of DMS produced by marine phytoplankton. Neutralization of acidic components of snow is mainly done by NH ₄ ⁺ and Mg²⁺. The Mg²⁺, Ca²⁺ and K⁺ are nearly equally effective in neutralizing the acidic components in lake water. The NH ₄ ⁺ and SO ₄ ^2? occur over the Antarctica region mostly in the form of (NH₄)₂SO₄.     

Application on Floor Water Inrush Evaluation Based on AHP Variation Coefficient Method with GIS

The prediction and prevention of floor water inrush is directly related to the safety of the coal mine production. The previous evaluation method of floor water inrush was more one-sided and lacked main control factors related to mining conditions. In order to evaluate the floor water inrush more accurately, under the project background of geological data of Wanglou coal mine, stope width, mining depth, fault scale index, water pressure, water abundance and thickness of aquifer were selected as main controlling factors of floor water inrush. Combined with the subjective weight analytical hierarchy process and the objective weight variation coefficient method, the weight coefficients corresponding to the main controlling factors were obtained respectively. The thematic map of the risk assessment of coal seam floor water inrush was drawn by combining the constructed comprehensive weight vulnerability index model and geographic information system. The results show that: ① according to the actual geological data of mine, two fault related factors were removed. And stope width and mining depth were increased as the main controlling factors to evaluate floor water inrush. It is easier to compare and calculate the weight of evaluation factors. ② The constructed comprehensive weight vulnerability index model can comprehensively evaluate the risk of floor water inrush. And the results of the evaluation are more accurate. ③ The related thematic maps can directly reflect the risk of floor water inrush, which is of guiding significance for the prediction and prevention of coal seam floor water inrush.     

Influence of internal decadal variability on the summer rainfall in Eastern China as simulated by CCSM4

The combined impact of the Pacific Decadal Oscillation(PDO) and Atlantic Multidecadal Oscillation(AMO) on the summer rainfall in eastern China was investigated using CCSM4. The strongest signals occur with the combination of a positive PDO and a negative AMO(+PDO- AMO), as well as a negative PDO and a positive AMO(-PDO + AMO). For the +PDO- AMO set, significant positive rainfall anomalies occur over the lower reaches of the Yangtze River valley(YR),when the East Asian summer monsoon becomes weaker, while the East Asian westerly jet stream becomes stronger, and ascending motion over the YR becomes enhanced due to the jet-related secondary circulation. Contrary anomalies occur over East Asia for the-PDO + AMO set. The influence of these two combinations of PDO and AMO on the summer rainfall in eastern China can also be observed in the two interdecadal rainfall changes in eastern China in the late 1970 s and late 1990 s.     

Changes in Habitat Availability for Multiple Life Stages of Diamondback Terrapins (<Emphasis Type="Italic">Malaclemys terrapin</Emphasis>) in Chesapeake Bay in Response to Sea Level Rise

Global sea level rise (SLR) will significantly alter coastal landscapes through inundation and erosion of low-lying areas. Animals that display area fidelity and rely on fringing coastal habitats during multiple life stages, such as diamondback terrapins (Malaclemys terrapin Schoepff 1793), are likely to be particularly vulnerable to SLR-induced changes. We used a combination of empirical nest survey data and results from a regional SLR model to explore the long-term availability of known nesting locations and the modeled availability of fringing coastal habitats under multiple SLR scenarios for diamondback terrapin in the MD portion of Chesapeake Bay and the MD coastal bays. All SLR scenarios projected the rapid inundation of historically used nesting locations of diamondback terrapins with 25%–55% loss within the next 10 years and over 80% loss by the end of the century. Model trajectories of habitat losses or gains depended on habitat type and location. A key foraging habitat, brackish marsh, was projected to decline 6%–94%, with projections varying spatially and among scenarios. Despite predicted losses of extant beach habitats, future gains in beach habitat due to erosion and overwash were projected to reach 40%–600%. These results demonstrate the potential vulnerability of diamondback terrapins to SLR in Chesapeake Bay and underscore the possibility of compounding negative effects of SLR on animals whose habitat requirements differ among life stages. More broadly, this study highlights the vulnerability of species dependent on fringing coastal habitats and emphasizes the need for a long-term perspective for coastal development in the face of SLR.