Water level variations in the Neuse and Pamlico Estuaries,North Carolina due to local and remote forcing

Water level time series records from the Neuse and Pamlico River Estuaries were statistically compared to local and distant wind field data, water level records within the Pamlico Sound and also coastal ocean sites to determine the relative contribution of each time series to water levels in the Neuse and Pamlico Estuaries. The objectives of this study were to examine these time series data using various statistical methods (i.e. autoregressive, empirical orthogonal function analysis (EOF), exploratory data analysis (EDA)) to determine short- and long-time-scale variability, and to develop predictive statistical models that can be used to estimate past water level fluctuations in both the Neuse Estuary (NE) and Pamlico Estuary (PE). Short- and long-time-scale similarities were observed in all time series of estuarine, Pamlico Sound and subtidal coastal ocean water level and wind component data, due to events (nor'easters, fronts and tropical systems) and seasonality. Empirical orthogonal function analyses revealed a strong coastal ocean and wind field contribution to water level in the NE and PE. Approximately 95% of the variation was captured in the first two EOF components for water level data from the NE, sound and coastal ocean, and 70% for the PE, sound and coastal ocean. Spectral density plots revealed strong diurnal signals in both wind and water level data, and a strong cross correlation and coherency between the NE water level and the North/South wind component. There was good agreement between data and predictions using autoregressive statistical models for the NE (R² = 0.92) and PE (R² = 0.76). These methods also revealed significant autoregressive lags for the NE (days 1 and 3) and for the PE (days 1, 2 and 3). Significant departures from predictions are attributed to local meteorological and hydrological events. The autoregressive techniques showed significant predictive improvement over ordinary least squares methods. The results are considered within the context of providing long time-scale hindcast data for the two estuaries, and the importance of these data for multidisciplinary researchers and managers.     

Circulation and dispersion in a cancellate coast: The rivers,bays and estuaries of central Maine

The glacially carved central coast of Maine is incised by river systems with interconnecting channels, offshore-trending submarine ridges, and narrow passages between nearshore islands and headlands. The tidal range exceeds 3 m, leading to complex and vigorous circulation patterns with strong flows in narrow channels, near river mouths, and between islands. The spongiform coastal morphology allows enhanced exchange between offshore waters, estuaries and internecine bays, resulting in rapid dispersal of nutrients, larvae and contaminants throughout the region. A fine-grid numerical circulation model has been used to examine the influences of the tides, river flows and winds on the dispersion of lobster larvae and pollutants in the nearshore and riverine environment. This paper describes the model application, presents a few salient features of the circulation patterns, and examines some implications for the coastal environment. For example, under realistic tides and variable southwest summer winds, about 80% of neutral near-surface particles introduced near the offshore islands (a proxy for stage IV lobster larvae from offshore sources) remain within a few km of the islands over a two-week period. On the other hand, a persistent, periodic sea breeze can remove more than two-thirds of the particles from the domain over the same period. Tidal mixing disperses pollutants entering the upper Kennebec River to the offshore and through internecine passages in about one week.     

Temperature evolution in the presence of anisotropic stresses

In a recent paper by Das et al. (Astrophys. Space Sci. 361:99, 2016) it was shown that the sign of the anisotropy parameter plays a pivotal role in determining the time of formation of the horizon of a collapsing radiating star. Spurred on by this observation we investigate the impact of the (an)isotropy featured in the (Das et al. in Astrophys. Space Sci. 361:99, 2016) collapsing model on the temperature profiles of the evolving system. We show that the temperature within the stellar interior is increased as the anisotropy in the pressure grows. Relaxational effects due to heat dissipation within the core further enhances the temperature at each interior point of the stellar distribution.     

Time distributions in satellite constellation design

The aim of the time distribution methodology presented in this paper is to generate constellations whose satellites share a set of relative trajectories in a given time, and maintain that property over time without orbit corrections. The model takes into account a series of orbital perturbations such as the gravitational potential of the Earth, the atmospheric drag, the Sun and the Moon as disturbing third bodies and the solar radiation pressure. These perturbations are included in the design process of the constellation. Moreover, the whole methodology allows to design constellations with multiple relative trajectories that can be distributed in a minimum number of inertial orbits.     

Micromorphological characteristics of glacimarine sediments: implications for distinguishing genetic processes of massive diamicts

Glacimarine diamicts are produced by diverse processes, and genetic differentiation is often problematic using macro-sedimentological criteria alone. Micromorphology offers a potentially helpful tool in such investigations. Macroscopically massive diamict samples of known glacimarine origin, from the Polar North Atlantic, Antarctica and north Irish Sea, were prepared for micromorphological analysis to (1) identify microstructures unique to different modes of sedimentation and (2) interpret genetic processes from those structures. The samples comprised examples of debris-flow, iceberg-turbate and suspension settling deposits from late Quaternary glacier-influenced marine environments: tidewater glacier, sub- or pro-ice shelf and continental slopes in front of ice stream termini. Results show two significant features of debris-flow sediments: a bimodal grain fabric of near-horizontal and -vertical grains, and laminated clay and silt coatings on sand and pebble grains. Coatings are best developed in sediments with finer grain-size distributions and in debris-flow sediments which have had relatively long run-out distances on trough-mouth fans, suggesting continuous rotation of grains in a buoyant, turbulent aqueous environment. This is significant because it precludes debris-flow delivery by plug flow. The micromorphology of iceberg turbate has not been described previously. It contains structures similar to those described in tills, so that unambiguous identification of these sediments seems unlikely based on micromorphological criteria alone. Suspension sediments range from fine-grained massive diamicts containing microfossils to more heterogeneous coarser sediments characterised by abrupt textural variations, from ice-distal and ice-proximal glacimarine environments respectively. The ice-proximal sediments contain fine vertical lineations marking the trajectories of dropstones through wet matrix. These dropstone tracks have not been reported in previous studies.     

Melt density and the average composition of basalt

Densities of residual liquids produced by low pressure fractionation of olivine-rich melts pass through a minimum when pyroxene and plagioclase joint the crystallization sequence. The observation that erupted basalt compositions cluster around the degree of fractionation from picritic liquids corresponding to the density minimum in the liquid line of descent may thus suggest that the earth's crust imposes a density filter on the liquids that pass through it, favoring the eruption of the light liquids at the density minimum over the eruption of denser more fractionated and less fractionated liquids.