Quantifying urban land cover change between 2001 and 2006 in the Gulf of Mexico region

We estimated urbanization rates (2001–2006) in the Gulf of Mexico region using the National Land Cover Database (NLCD) 2001 and 2006 impervious surface products. An improved method was used to update the NLCD impervious surface product in 2006 and associated land cover transition between 2001 and 2006. Our estimation reveals that impervious surface increased 416 km² with a growth rate of 5.8% between 2001 and 2006. Approximately 1110.1 km² of non-urban lands were converted into urban land, resulting in a 3.2% increase in the region. Hay/pasture, woody wetland, and evergreen forest represented the three most common land cover classes that transitioned to urban. Among these land cover transitions, more than 50% of the urbanization occurred within 50 km of the coast. Our analysis shows that the close-to-coast land cover transition trend, especially within 10 km off the coast, potentially imposes substantial long-term impacts on regional landscape and ecological conditions.     

The degradation characteristics of microbial biomass in soil

Soil microbial biomass is a primary source of soil organic carbon (SOC) and therefore plays a fundamental role in carbon and nitrogen cycling. However, little is known about the fate and transformations of microbial biomass in soil. Here we employ HR-MAS NMR spectroscopy to monitor ¹³C and ¹⁵N labeled soil microbial biomass and leachate degradation over time. As expected, there is a rapid loss of carbohydrate structures. However, diffusion edited HR-MAS NMR data reveals that macromolecular carbohydrates are more resistant to degradation and are found in the leachate. Aromatic components survive as dissolved species in the leachate while aliphatic components persist in both the biomass and leachate. Dissolved protein and peptidoglycan accumulate in the leachate and recalcitrant amide nitrogen and lipoprotein persists in both the degraded biomass and leachate. Cross-peaks that appear in ¹H-¹⁵N HR-MAS NMR spectra after degradation suggest that specific peptides are either selectively preserved or used for the synthesis of unknown structures. The overall degradation pathways reported here are similar to that of decomposing plant material degraded under similar conditions suggesting that the difference between recalcitrant carbon from different sources is negligible after decomposition.     

Three-phase numerical model of water migration in partially frozen geological media: model formulation,validation, and applications

Water in the subsurface of the Earth’s cold regions—and possibly the subsurface of Mars—resides in the liquid, vapor, and ice phases. However, relatively few simulations addressing full three-phase, nonisothermal water dynamics in below-freezing porous media have been undertaken. This paper presents a nonisothermal, three-phase approach to modeling water migration in partially frozen porous media. Conservation equations for water (as ice, liquid, and vapor) and a single gas species (in the gas phase and dissolved in water) are coupled to a heat transport equation and solved by a finite-volume method with fully implicit time stepping. Particular attention is given to the method of spatial differencing when the pore space is partially filled with ice. The numerical model is able to reproduce freezing-induced water redistribution observed in laboratory experiments. Simulations of Earth permafrost dynamics and of the formation and evolution of a planetary-scale cryosphere on Mars demonstrate the new capabilities.     

Global photometric properties of Asteroid (4) Vesta observed with Dawn Framing Camera

Dawn spacecraft orbited Vesta for more than one year and collected a huge volume of multispectral, high-resolution data in the visible wavelengths with the Framing Camera. We present a detailed disk-integrated and disk-resolved photometric analysis using the Framing Camera images with the Minnaert model and the Hapke model, and report our results about the global photometric properties of Vesta. The photometric properties of Vesta show weak or no dependence on wavelengths, except for the albedo. At 554 nm, the global average geometric albedo of Vesta is 0.38 ± 0.04, and the Bond albedo range is 0.20 ± 0.02. The bolometric Bond albedo is 0.18 ± 0.01. The phase function of Vesta is similar to those of S-type asteroids. Vesta’s surface shows a single-peaked albedo distribution with a full-width-half-max ∼17% relative to the global average. This width is much smaller than the full range of albedos (from ∼0.55× to >2× global average) in localized bright and dark areas of a few tens of km in sizes, and is probably a consequence of significant regolith mixing on the global scale. Rheasilvia basin is ∼10% brighter than the global average. The phase reddening of Vesta measured from Dawn Framing Camera images is comparable or slightly stronger than that of Eros as measured by the Near Earth Asteroid Rendezvous mission, but weaker than previous measurements based on ground-based observations of Vesta and laboratory measurements of HED meteorites. The photometric behaviors of Vesta are best described by the Hapke model and the Akimov disk-function, when compared with the Minnaert model, Lommel–Seeliger model, and Lommel–Seeliger–Lambertian model. The traditional approach for photometric correction is validated for Vesta for >99% of its surface where reflectance is within ±30% of global average.     

Time–space continuity of daily maps of fractional snow cover and albedo from MODIS

Using reflectance values from the seven MODIS “land” bands with 250 or 500 m resolution, along with a corresponding cloud product, we estimate the fraction of each 500 m pixel that snow covers, along with the albedo of that snow. The daily products have data gaps and errors because of cloud cover and sensor viewing geometry. Rather than make users interpolate and filter these patchy daily maps without completely understanding the retrieval algorithm and instrument properties, we use the daily time series to improve the estimate of the measured snow properties for a particular day. We use a combination of noise filtering, snow/cloud discrimination, and interpolation and smoothing to produce our best estimate of the daily snow cover and albedo. We consider two modes: one is the “predictive” mode, whereby we estimate the snow-covered area and albedo on that day using only the data up to that day; the other is the “retrospective” mode, whereby we reconstruct the history of the snow properties for a previous period.     

The arsenic source term for an in-pit uranium mine tailings facility and its long-term impact on the regional groundwater

Detailed field sampling and analyses and laboratory-based diffusion-cell experiments were used in conjunction with 3-D reactive transport modeling (MODFLOW and MT3D99) to quantify the fate and long-term (10 ka) transport of As in the Rabbit Lake In-pit Tailings Management Facility (RLITMF), northern Saskatchewan, Canada. The RLITMF (300 m × 425 m × 90 m thick) was engineered to ensure solute transport within the RLITMF is dominated by diffusion. Concentrations of As in the tailings pore fluids ranged from 0.24 to 140 mg/L (n = 43). Arsenic speciation analyses indicate 90% of this arsenic exists as As⁵⁺. This observation is supported by pH–Eh measurements of pore fluids (n = 135). Geochemical analyses yielded a strong inverse correlation between the Fe/As molar ratio in the tailings solids and the corresponding concentration of dissolved As, which is attributed to the adsorption of As to secondary 2-line ferrihydrite present in the tailings. Diffusion-cell testing yielded values for the effective diffusion coefficient, sorption coefficient, and effective porosity of As in the tailings of 4.5 × 10⁻¹⁰ m²/s, 2–4 cm³/g and 0.36, respectively. Reactive transport simulations using the field and laboratory data show adsorption of As to the tailings and diffusive transport of dissolved As in the tailings should reduce the source term concentration of As to between 40% and 70% of the initial concentrations over the 10 ka simulation period. Based on these simulations, the As concentrations in the regional groundwater, 50 m down gradient of the tailings facility, should be maintained at background concentrations of 0.001 mg/L over the 10 ka period. These findings suggest the engineered in-pit disposal of U mine tailings can provide long-term protection for the local groundwater regime from As contamination.     

A fresh look at discordant redshift galaxies in compact groups

We reexamine the statistics of discordant redshift galaxies in compact groups. We find that 43 out of 100 groups in the Hickson catalog contain at least one discordant redshift galaxy. We show that, despite the prevailing impression, all previous attempts have failed to explain this large number of discordant redshift galaxies. The order of magnitude excess survives all of our attempts to refine the sample.     

Assessment and Assimilation of FY-3 Humidity Sounders and Imager in the UK Met Office Global Model

China's Feng Yun 3(FY-3) polar orbiting satellites are set to become an important source of observational data for numerical weather prediction(NWP),atmospheric reanalyses,and climate monitoring studies over the next two decades.As part of the Climate Science for Service Partnership China(CSSP China) program,FY-3 B Microwave Humidity Sounder 1(MWHS-1) and FY-3 C MWHS-2 observations have been thoroughly assessed and prepared for operational assimilation.This represents the first time observations from China's polar orbiting satellites have been used in the UK's global NWP model.Since 2016,continuous data quality monitoring has shown occasional bias changes found to be correlated to changes in the energy supply scheme regulating the platform heating system and other transient anomalies.Nonetheless,MWHS-1 and MWHS-2 significantly contribute to the 24-h forecast error reduction by 0.3% and 0.6%,respectively,and the combination of both instruments is shown to improve the fit to the model background of independent sounders by up to 1%.The observations from the Microwave Radiation Imager(MWRI) also are a potentially significant source of benefits for NWP models,but a solar-dependent bias observed in the instrument half-orbits has prevented their assimilation.This paper presents the bases of a correction scheme developed at the Met Office for the purpose of a future assimilation of MWRI data.     

Evidence for long-term instability in the Storegga Slide region off western Norway

Shallow-seismic surveys around the Storegga Slide off western Norway have allowed greater understanding of the development of this part of the European margin. The northern flank of the scarp is formed of seismically well-layered, hemipelagic and distal-glaciomarine deposits in which a variety of luid-escape structures, probably due to gas, are locally abundant. There is evidence of slides that substantially pre-date the earliest slide previously recognized. Surveying on the North Sea Fan to the southwest of the Storegga Slide shows the markedly different nature of the autochthonous sediments on the southern flank of the Storegga Slide; there is a predominance of glacigenic debris flows in the upper part of the sequence, lesser maximum slopes, and an apparent absence of interstitial gas and/or hydrates. This contrast has had considerable effect on slope stability and has influenced the position of the southwestern Storegga Slide boundary. The North Sea Fan succession includes at least three major buried slides, termed the Vigra, Møre and Tampen slides, all of which substantially pre-date the Storegga event and probably pre-date predominantly glacigenic margin sedimentation. Post-late Weichselian slope failure is locally significant. The region has a long, but as yet chronologically poorly defined history of instability in which seismic triggering is considered to have been important.