Zooplankton in Bays of the Novaya Zemlya Archipelago: Composition,Distribution, and Role in Phytoplankton Grazing and Biosedimentation

Oceanology - The zooplankton community in two bays of the eastern coast of the Novaya Zemlya archipelago (Blagopoluchiya Bay and Tsivolki Bay) has been studied for the first time. Copepods of the...     

Large-Eddy Simulation of Flow and Pollutant Transport in Urban Street Canyons with Ground Heating

Our study employed large-eddy simulation (LES) based on a one-equation subgrid-scale model to investigate the flow field and pollutant dispersion characteristics inside urban street canyons. Unstable thermal stratification was produced by heating the ground of the street canyon. Using the Boussinesq approximation, thermal buoyancy forces were taken into account in both the Navier–Stokes equations and the transport equation for subgrid-scale turbulent kinetic energy (TKE). The LESs were validated against experimental data obtained in wind-tunnel studies before the model was applied to study the detailed turbulence, temperature, and pollutant dispersion characteristics in the street canyon of aspect ratio 1. The effects of different Richardson numbers (Ri) were investigated. The ground heating significantly enhanced mean flow, turbulence, and pollutant flux inside the street canyon, but weakened the shear at the roof level. The mean flow was observed to be no longer isolated from the free stream and fresh air could be entrained into the street canyon at the roof-level leeward corner. Weighed against higher temperature, the ground heating facilitated pollutant removal from the street canyon.     

Climate and the equilibrium state of land surface hydrology parameterizations

For given climatic rates of precipitation and potential evaporation, the land surface hydrology parameterizations of atmospheric general circulation models will maintain soil-water storage conditions that balance the moisture input and output. The surface relative soil saturation for such climatic conditions serves as a measure of the land surface parameterization state under a given forcing. The equilibrium value of this variable for alternate parameterizations of land surface hydrology are determined as a function of climate and the sensitivity of the surface to shifts and changes in climatic forcing are estimated.     

Concentrations and composition of aerosols and particulate matter in surface waters along the transatlantic section

Along the transatlantic section from Ushuaia to Gdańsk (March 26–May 7, 2015; cruise 47 of R/V Akademik Ioffe), data were obtained on the concentrations of aerosols in the near-water layer of the atmosphere and of particulate matter in surface waters, as well as of organic compounds within the considered matter (C_org, chlorophyll a, lipids, and hydrocarbons). The concentrations of aerosols amounted to 1237–111 739 particles/L for the fraction of 0.3–1 μm and to 0.02–34.4 μg/m²/day for the matter collected by means of the network procedure. The distribution of aerosols is affected by circumcontinental zoning and by the fluxes from arid areas of African deserts. The maximum concentration of the treated compounds were found in the river–sea frontal area (the runoff of the Colorado River, Argentina), as well as when nearing the coasts, especially in the English Channel.     

Privacy and spatial pattern preservation in masked GPS trajectory data

Personal trajectory data are increasingly collected for a variety of academic and recreational pursuits. As access to location data widens and locations are linked to other information repositories, individuals become increasingly vulnerable to identification. The quality and precision of spatially linked attributes are essential to accurate analysis; yet, there is a trade-off between privacy and geographic data resolution. Obfuscation of point data, or masking, is a solution that aims to protect privacy and maximize preservation of spatial pattern. Trajectory data, with multiple locations recorded for an entity over time, is a strong personal identifier. This study explores the balance between privacy and spatial pattern resulting from two methods of obfuscation for personal GPS data: grid masking and random perturbation. These methods are applied to travel survey GPS data in the greater metropolitan regions of Chicago and Atlanta. The rate of pattern correlation between the original and masked data sets declines as the distance thresholds for masking increase. Grid masking at the 250-m threshold preserves route anonymity better than other methods and distance thresholds tested, but preserves spatial pattern least. This study also finds via linear regression that median trip speed and road density are significant predictors of trip anonymity.     

First find of kutnohorite in modern sediments of the South Caspian basin

High-manganese kutnohorite was found in the surface layer of bottom sediments of the South Caspian basin by the method of X-ray diffraction for the first time. Bottom sediments were collected by a multicorer during the 39th voyage of R/V Rift in 2012. Study of the samples by a complex of methods (X-ray diffraction, scanning electron microscopy, atomic absorption, and analysis of the carbon isotope composition) allowed us to attribute kutnohorite to autigenic minerals of the early stage of diagenesis.     

Sources of Minor and Rare-Earth Elements in Hydrothermal Edifices of Near-Continental Rifts with Sedimentary Cover: Evidence from the Guaymas Basin,Southern Trough

The mineralogy and geochemistry of a fragment of an active hydrothermal edifice from the Hydrothermal Hill of the Southern Trough valley of the Guaymas Basin in the Gulf of California were studied. The sample was collected from a depth of 1995 m by the Pisces manned submersible on cruise 12 of the R/V Akademik Mstislav Keldysh, Institute of Oceanology, Russian Academy of Sciences. The fragment and the edifice itself consists of two accrete pipes: ore (pyrrhotite) and barren (carbonate) combined in a single edifice by an outer barite–opal zone. The ore edifice is located in the rift zone of the Guaymas Basin with a thick sedimentary cover and is depleted in metals in comparison with ores from rift zones of the open ocean, which are not blocked by sedimentary deposits. This is explained by loss of metals at the boundary between hot sills and sedimentary rocks and by the processes of interaction of hydrothermal solutions with sedimentary deposits. The sedimentary series faciitates long-term preservation of endogenous heat and the ore formation process. Ore edifices of the Guaymas Basin are mostly composed of pyrrhotite, have a specific set of major elements, microelements and REEs, and contain naphthenic hydrocarbons. They may be search signs of hidden polymetallic deposits, considered to be the roots of ore occurrences localized under the surface of the bottom in young active rifts with high spreading and sedimentation rates, i.e., in near-continental areas of rifts of the humid zone with avalanche sedimentation.     

Dynamics of the transition region

In this review, we consider the problem of the apparent redshifts of the UV lines in the transition region and review the basic observations made over the last decades, especially the observations of the last few years from satellite observatories. Moreover, we revise the most popular theoretical explanations for the motions in the transition region. This review is a contribution to the understanding of the physical processes in this important layer of the solar atmosphere and it points out the pending problems.     

Mapping recharge from space: roadmap to meeting the grand challenge

Fields of diffuse recharge flux play pivotal roles in: (1) linking surface and subsurface hydrologic systems, (2) controlling the biogeochemistry of terrestrial systems, and (3) determining the sustainability of well withdrawals from aquifers. This hydrologic flux is intimately related to the distribution and functioning of vegetation cover and type. In turn, it also plays a significant role in the distribution of vegetation. Until now, recharge has been mostly estimated as residual of either surface or subsurface water balance. In situ instruments for measurement of this quantity are difficult to implement and maintain. Long-term and spatially explicit (mapped) monitoring of recharge flux have been elusive goals. A review is presented of the possible spaceborne and airborne remote sensing and data interpretation techniques that may address the grand challenge of recharge mapping on large scales. The approaches rely on microwave remote sensing in order to measure land surface states in the presence of atmosphere and vegetation cover that attenuate and disturb the signal as it travels from the surface to the sensor. The emphasis is on radar systems that also have beneficial ground spatial resolution characteristics. Finally, examples of two candidate space-borne systems are presented as feasible approaches to the required measurements.     

Estimating secondary production and benthic consumption in monitoring studies: A case study of the impacts of dredged material disposal in Galveston Bay, Texas

We examined the effects of dredged material disposal on benthic macroinvertebrates in Galveston Bay, Texas, USA, while investigating the utility of estimating secondary production with estimation methods that have less rigorous data requirements than most classical techniques. Production estimates were compared to estimates of benthic consumption by blue crabs, shrimp, and epibenthic fish. There was no evidence that dredged material disposal had a detrimental impact on benthic production; however, production was low throughout the entire bay the year following dredged material disposal, which may have obscured an assessment of the impact of disposal. In fact, disposal sites yielded both the highest production estimates and species richness in both the upper and lower bay areas 2 yr after disposal. Of the five estimation methods used, two that incorporated environmental parameters (temperature and depth) yielded similar and moderate results, ranging from 1.1 g ash-free dry weight m² yr¹ to 26.9 g ash-free dry weight (AFDW) m^?2 yr^?1 over the 4 yr studied. Daily food ration estimates applied to fishery-independent trawl-survey data yielded overall benthic consumption estimates ranging from 1.1 g AFDW m^?2 to 1.7 g AFDW m^?2. A second method of estimating consumption, which used transfer efficiency estimates and annual fisheries statistics produced slightly lower benthic consumption estimates (0.72–1.13 g AFDW m^?2). The average consumption estimate exceeded benthic production in the upper bay in one of the 4 yr for which benthic production was estimated. In years with high benthic production, the estimated benthic food requirement of epibenthic predators was roughly 10–15% of benthic production. Variation in annual benthic production estimates was two to three times greater than the variation in consumption estimates.