Symplectic integrators for long-term integrations in celestial mechanics

We discuss the use of symplectic integration algorithms in long-term integrations in the field of celestial mechanics. The methods' advantages and disadvantages (with respect to more common integration methods) are discussed. The numerical performance of the algorithms is evaluated using the 2-body and circular restricted 3-body problems. Symplectic integration methods have the advantages of linear phase error growth in the 2-body problem (unlike most other methods), good conservation of the integrals of the motion, good performance for moderately eccentric orbits, and ease of use. Its disadvantages include a relatively large number of force evaluations and an inability to continuously vary the step size.     

Assessment of perfluorinated compounds (PFCs) in plasma of bottlenose dolphins from two southeast US estuarine areas: relationship with age, sex and geographic locations

Plasma PFCs were measured in 157 bottlenose dolphins (Tursiops truncatus) sampled from two US southeast Atlantic sites (Charleston (CHS), SC and Indian River Lagoon (IRL), FL) during 2003-2005. ∑PFCs, perfluoroalkyl carboxylates (∑PFCAs), perfluoroalkyl sulfonates (∑PFSAs) and individual compounds were significantly higher in CHS dolphins for all age/sex categories compared to IRL dolphins. Highest ∑PFCs concentrations occurred in CHS juvenile dolphins (2340 ng/g w.w.); significantly higher than found in adults (1570 ng/g w.w. males; 1330 ng/g w.w. females). ∑PFCAs were much greater in CHS dolphins (≈ 21%) compared to IRL dolphins (≈ 7%); ∑PFSAs were 79% in CHS dolphins versus 93% in IRL dolphins. PFOS, the dominant compound, averaged 72% and 84%, respectively, in CHS and IRL dolphins. Decreasing PFC levels occurred with age on the bioaccumulation of PFCs in both sites. These observations suggest PFC accumulation in these two dolphin populations are influenced by site-specific exposures with significantly higher levels in CHS dolphins.     

Spatial and Temporal Variability in Estuary Habitat Use by American Alligators

Estuarine habitat occupied by Alligator mississippiensis, a primarily freshwater species, is spatially and temporally heterogeneous largely due to a salinity gradient that fluctuates. Using long-term night light survey data, we examined seasonal patterns in alligators’ habitat use by size classes in midstream and downstream estuary zones of Shark River, Everglades National Park, in southern Florida. We observed predominantly large-sized alligators (total length?≥?1.75 m); observations of alligators in the small size classes (0.5 m?≤?total length?<?1.25 m) were rare especially in the higher-salinity downstream zone. The density of alligators in the downstream zone was lower than that of the midstream zone during the dry season when salinity increases due to reduced precipitation. Conversely, the density of the large size alligators was higher in the downstream zone than in the midstream zone during the wet season, likely because of reduced salinity. We also found a significant declining trend over time in the number of alligators in the dry season, which coincides with the reported decline in alligator relative density in southern Florida freshwater wetlands. Our results indicated high adaptability of alligators to the fluctuating habitat conditions. Use of estuaries by alligators is likely driven in part by physiology and possibly by reproductive cycle, and our results supported their opportunistic use of estuary habitat and ontogenetic niche shifts.     

Simultaneous calibration of surface flow and baseflow simulations: a revisit of the SWAT model calibration framework

Accurate analysis of water flow pathways from rainfall to streams is critical for simulating water use, climate change impact, and contaminants transport. In this study, we developed a new scheme to simultaneously calibrate surface flow (SF) and baseflow (BF) simulations of soil and water assessment tool (SWAT) by combing evolutionary multi‐objective optimization (EMO) and BF separation techniques. The application of this scheme demonstrated pronounced trade‐off of SWAT's performance on SF and BF simulations. The simulated major water fluxes and storages variables (e.g. soil moisture, evapotranspiration, and groundwater) using the multiple parameters from EMO span wide ranges. Uncertainty analysis was conducted by Bayesian model averaging of the Pareto optimal solutions. The 90% confidence interval (CI) estimated using all streamflows substantially overestimate the uncertainty of low flows on BF days while underestimating the uncertainty of high flows on SF days. Despite using statistical criteria calculated based on streamflow for model selection, it is important to conduct diagnostic analysis of the agreement of SWAT behaviour and actual watershed dynamics. The new calibration technique can serve as a useful tool to explore the trade‐off between SF and BF simulations and provide candidates for further diagnostic assessment and model identification. Copyright © 2011 John Wiley & Sons, Ltd.     

Extent and magnitude of copper contamination in marinas of the San Diego region, California, USA

Marinas are areas of special water quality concern because of the potential for pollutant accumulation within their protected waters. Perhaps the largest contaminant source to marinas is antifouling paints that leach copper to prevent the growth of encrusting organisms on vessel bottoms. Very little monitoring of marinas is typically conducted despite the potential environmental risk, particularly in the San Diego region of California, USA where as many as 17,000 recreational vessels are berthed. The objective of this study was twofold: (1) determine the extent and magnitude of dissolved copper concentrations in marinas throughout the San Diego region, and (2) determine if elevated copper concentrations in marinas of the San Diego region are resulting in adverse biological impacts. A probabilistic study design was used to sample water column copper concentrations and toxicity (using Mytilus galloprovincialis) at 30 stations. Results indicated that exceedence of state water quality objectives was widespread (86% of marina area), but that toxicity was much less prevalent (21% of marina area). Toxicity identification evaluations (TIEs) conducted at the most toxic sites indicated that toxicity was largely due to trace metals, most likely copper. Toxicity was reduced using TIE treatments that chelated trace metals such as cation exchange column, ethylenediaminetetraacetic acid (EDTA), and sodium thiosulfate (STS). Moreover, increasing dissolved copper concentrations correlated with increasing toxicity and these copper concentrations were high enough to account for virtually all of the observed toxicity.     

Real-time measurement of volcanic SO2 emissions: validation of a new UV correlation spectrometer (FLYSPEC)

A miniaturized, lightweight and low-cost UV correlation spectrometer, the FLYSPEC, has been developed as an alternative for the COSPEC, which has long been the mainstay for monitoring volcanic sulfur dioxide fluxes. Field experiments have been conducted with the FLYSPEC at diverse volcanic systems, including Masaya (Nicaragua), Poás (Costa Rica), Stromboli, Etna and Vulcano (Italy), Villarica (Chile) and Kilauea (USA). We present here those validation measurements that were made simultaneously with COSPEC at Kilauea between March 2002 and February 2003. These experiments, with source emission rates that ranged from 95 to 1,560 t d⁻¹, showed statistically identical results from both instruments. SO₂ path-concentrations ranged from 0 to >1,000 ppm-m with average correlation coefficients greater than r ²=0.946. The small size and low cost create the opportunity for FLYSPEC to be used in novel deployment modes that have the potential to revolutionize the manner in which volcanic and industrial monitoring is performed.     

The influence of groundwater abstraction on interpreting climate controls and extreme recharge events from well hydrographs in semi-arid South Africa

There is a scarcity of long-term groundwater hydrographs from sub-Saharan Africa to investigate groundwater sustainability, processes and controls. This paper presents an analysis of 21 hydrographs from semi-arid South Africa. Hydrographs from 1980 to 2000 were converted to standardised groundwater level indices and rationalised into four types (C1–C4) using hierarchical cluster analysis. Mean hydrographs for each type were cross-correlated with standardised precipitation and streamflow indices. Relationships with the El Niño–Southern Oscillation (ENSO) were also investigated. The four hydrograph types show a transition of autocorrelation over increasing timescales and increasingly subdued responses to rainfall. Type C1 strongly relates to rainfall, responding in most years, whereas C4 notably responds to only a single extreme event in 2000 and has limited relationship with rainfall. Types C2, C3 and C4 have stronger statistical relationships with standardised streamflow than standardised rainfall. C3 and C4 changes are significantly (p <?0.05) correlated to the mean wet season ENSO anomaly, indicating a tendency for substantial or minimal recharge to occur during extreme negative and positive ENSO years, respectively. The range of different hydrograph types, sometimes within only a few kilometres of each other, appears to be a result of abstraction interference and cannot be confidently attributed to variations in climate or hydrogeological setting. It is possible that high groundwater abstraction near C3/C4 sites masks frequent small-scale recharge events observed at C1/C2 sites, resulting in extreme events associated with negative ENSO years being more visible in the time series.

     

Using UAV acquired photography and structure from motion techniques for studying glacier landforms: application to the glacial flutes at Isfallsglaciären

Glacier and ice sheet retreat exposes freshly deglaciated terrain which often contains small‐scale fragile geomorphological features which could provide insight into subglacial or submarginal processes. Subaerial exposure results in potentially rapid landscape modification or even disappearance of the minor‐relief landforms as wind, weather, water and vegetation impact on the newly exposed surface. Ongoing retreat of many ice masses means there is a growing opportunity to obtain high resolution geospatial data from glacier forelands to aid in the understanding of recent subglacial and submarginal processes. Here we used an unmanned aerial vehicle to capture close‐range aerial photography of the foreland of Isfallsglaciären, a small polythermal glacier situated in Swedish Lapland. An orthophoto and a digital elevation model with ~2 cm horizontal resolution were created from this photography using structure from motion software. These geospatial data was used to create a geomorphological map of the foreland, documenting moraines, fans, channels and flutes. The unprecedented resolution of the data enabled us to derive morphological metrics (length, width and relief) of the smallest flutes, which is not possible with other data products normally used for glacial landform metrics mapping. The map and flute metrics compare well with previous studies, highlighting the potential of this technique for rapidly documenting glacier foreland geomorphology at an unprecedented scale and resolution. The vast majority of flutes were found to have an associated stoss‐side boulder, with the remainder having a likely explanation for boulder absence (burial or erosion). Furthermore, the size of this boulder was found to strongly correlate with the width and relief of the lee‐side flute. This is consistent with the lee‐side cavity infill model of flute formation. Whether this model is applicable to all flutes, or multiple mechanisms are required, awaits further study. © 2016 The Authors. Earth Surface Processes and Landforms published by John Wiley & Sons Ltd.     

A lunar rock of deep crustal origin: sample 76535

Lunar sample 76535 is a coarse-grained troctolitic granulite exhibiting a texture indicative of long annealing times. It is composed of homogeneous crystals of plagioclase (58 per cent, An₉₆), olivine (37 per cent, Fo₈₈) and bronzite (4 per cent, En₈₆).Chromian spinel-bronzite-diopside (Wo₄₆En₅₀Fs₄) symplectic intergrowths commonly occur along olivine-plagioclase boundaries and as tiny inclusions within olivine grains. These symplectites apparently formed by a reaction of the type:

$\text{OI + An + Chromite → Opx + Cpx + Al-Mg-chromite}$

. The reaction is related to the experimentally determined reaction

$\text{OI + An = Opx + Cpx + Sp}$

of Kushiro and Yoder (1966). The enstatite content of the diopside coexisting with the bronzite indicates equilibration at about 1000°C. Thermodynamic calculations for 1000°C indicate that the symplectites formed at a minimum pressure of about 0.6 kb. Low alumina contents of the pyroxenes indicate equilibration near this minimum pressure.Clusters of the same assemblage found in the symplectic intergrowths, but containing accessory metal, troilite, Ca-phosphates, baddeleyite, plagioclase and/or K-feldspar occur sporadically throughout the rock. These apparent late stage products crystallized in the low temperature-high pressure region discussed above.Phase relations of co-existing metal phases indicate that the rock cooled at a few tens of degrees/my, corresponding to depths of 10–20 km below the lunar surface, in agreement with the above pressure estimate.We infer that 76535 represents an original cumulate deposited at a depth between about 10 and 30 km. The last liquid crystallized in the relatively high pressure-low temperature field opx + cpx + Al-Mg-chromite. Cooling was extremely slow and accompanied by extensive chemical and textural re-equilibration. Reaction to form the symplectites occurred during the late stages of re-equilibration.     

Population structure and reproductive characteristics of the gulf pipefish,Syngnathus scovelli, in Mobile Bay, Alabama

The gulf pipefish,Syngnathus scovelli, is the dominant syngnathid found in coastal regions of the Gulf of Mexico and is the only species in this region known to occur in both freshwater and saltwater habitats. Relatively little is known about the population and reproductive cycles ofS. scovelli, particularly for those found in low salinity environments. The focus of the current study was to collect population structure and reproductive data forS. scovelli from a low salinity habitat, Meaher Park, located at the mouth of Mobile Bay, Alabama. Sampling was conducted twice a month from January 2003 to January 2004. Environmental parameters, as well as population and reproductive parameters, were collected. Water temperature was the primary abiotic factor associated with both the appearance ofS. scovelli and their breeding cycle. Based on gonadosomatic (GSI) and brood pouch somatic indices (BPSI), females and males were reproductively active throughout the summer. Peaks in male GSI and BPSI were consistent with the subsequent appearance of a large number of juveniles in early fall. These event coincided with the higher temperatures seen during late summer and early fall. Sex ratios (male : female 1 : 1.64) and operational sex ratios (1 : 4.09) indicated that this was a female biased population. Although there was no difference in the average size of males and females in this population, the largest individuals collected were female. The female-biased sex ratio supports previous genetic analyses suggesting thatS. scovelli exhibits true sex-role reversal and that operational sex ratios are a reliable indicator of the intensity of mating competition and sex roles.