The groundwater–land-surface–atmosphere connection: Soil moisture effects on the atmospheric boundary layer in fully-coupled simulations

This study combines a variably-saturated groundwater flow model and a mesoscale atmospheric model to examine the effects of soil moisture heterogeneity on atmospheric boundary layer processes. This parallel, integrated model can simulate spatial variations in land-surface forcing driven by three-dimensional (3D) atmospheric and subsurface components. The development of atmospheric flow is studied in a series of idealized test cases with different initial soil moisture distributions generated by an offline spin-up procedure or interpolated from a coarse-resolution dataset. These test cases are performed with both the fully-coupled model (which includes 3D groundwater flow and surface water routing) and the uncoupled atmospheric model. The effects of the different soil moisture initializations and lateral subsurface and surface water flow are seen in the differences in atmospheric evolution over a 36-h period. The fully-coupled model maintains a realistic topographically-driven soil moisture distribution, while the uncoupled atmospheric model does not. Furthermore, the coupled model shows spatial and temporal correlations between surface and lower atmospheric variables and water table depth. These correlations are particularly strong during times when the land-surface temperatures trigger shifts in wind behavior, such as during early morning surface heating.     

First order approximation of Broadband Directional Albedo with High Resolution Quickbird Imagery: a case study for arid urban areas

Albedo is a key forcing parameter controlling the planetary radiative energy budget and its partitioning between the surface and the atmosphere. Characterizing and developing high resolution albedo for an urban environment in arid regions is important because of the high urbanization rate in these regions and because of the high land-cover heterogeneity within urban settings. Using a Monte Carlo simulation of a multi-variable regression, we (a) correlate directional solar reflectance (albedo) ground measurements from Phoenix, AZ, with four narrowband reflectance data from QuickBird, and (b) developed a new set of coefficients for converting QuickBird narrowband reflectances to albedo. The albedo models were then applied to a second image over Las Vegas, NV, to assess their feasibility and accuracy. Two wavebands, visible-near infrared (VNIR) and total shortwave albedo, were evaluated for two reflectance models: surface and top-of-atmosphere. Results show that it is possible to accurately estimate directional albedo from high resolution imagery, specifically QuickBird, with the most accurate result from an atmospherically corrected VNIR model. The methodology presented in this paper could thus be applied in other urban areas to obtain a first order estimation of albedo. The new set of coefficients can be applied as first order albedo estimate by researchers, urban planners, developers and city managers interested in the influence of high-resolution albedo on a myriad of urban ecosystem processes.     

Barium content of marine sediments near drilling sites: A potential pollutant indicator

Barite is commonly used as a weighting agent in oil- and gas-well drilling mixture; therefore, the distribution pattern of barium in marine sediments near drilling sites may provide an indicator of anthropogenic chemical contamination from these operations. Present average content of barium in benthic sediments from the Southern California Bight was determined to be 637 ppm, with a range from 43 to 1899 ppm, and that of the mainland and the channel island intertidal sediments averaged 879 and 388 ppm, respectively.     

Dynamic finite strip analysis of surface foundations

The finite strip method is used to study the dynamic response of surface strip foundations. This method is simple to use and versatile. The two-dimensional problem is effectively reduced to an equivalent one-dimensional problem. The choice of trigonometric series for the displacement functions results in the uncoupling of the terms of the series and a significant reduction in the semi-bandwidth of the complex set of equations, making the method well suited to small computers. Non-homogeneous soil profiles are treated as a matter of course. The finite strip solutions are shown to be in general agreement with other theoretical methods of analysis.     

Tepee-shaped agglutinated microbialites: an example from a Famennian carbonate platform on the Lennard Shelf, northern Canning Basin, Western Australia

Distinctive, metre‐scale antiformal structures are well developed in a Famennian carbonate platform in the Chedda Cliffs area of the Lennard Shelf reef complexes. The structures are distinguished by chevron‐shaped crests and thickened cores and contain abundant non‐skeletal allochems (ooids/pisoids, peloids and intraclasts) of silt to pebble size and variably developed laminations and fenestrae. The internal morphology and pervasive occurrence of fenestral clotted and wavy laminated fabrics suggest that these structures are microbial mounds composed of agglutinated stromatolites and thrombolites. Microbial fabrics most probably originated through sediment trapping and binding by microbial mats with early lithification involving microbial calcification and cementation of trapped sediment. The facies and stratigraphic context of the mounds support a shallow subtidal, transitional backreef to reef‐flat setting; however, alone these mounds do not provide unequivocal environmental information. Other large antiformal structures in Famennian platforms on the Lennard Shelf, previously described as tepee structures, show morphological similarities to the Chedda Cliffs mounds, which suggests that these other structures may also be microbial mounds. The presence of microbial mounds in platform successions further highlights the importance of microbial communities in the Lennard Shelf reef complexes.     

Community-level destruction of hard corals by the sea urchin Diadema setosum

Sea urchins are common herbivores and bioeroders of coral ecosystems, but rarely have they been reported as corallivores. We determined the spatial pattern of hard coral damage due to corallivory and bioerosion by the sea urchin Diadema setosum Leske in Hong Kong waters. Coral damage was common at the northeastern sites, with 23.7 – 90.3% colonies being either collapsed or severely damaged with >25% tissue loss. Many genera of corals were impacted by the sea urchin but the damage was most obvious for the structure forming genus Platygyra. The percentage of severely damaged and collapsed coral had significant positive correlation with the abundance of D. setosum, which ranged from 0.01 to 5.2 individuals per coral head or 0.1 – 21.1 individuals m⁻² across the study sites. Remedial management actions such as sea urchin removal are urgently needed to save these fringing coral communities.     

The impact of coastal urbanization on the structure of phytobenthic communities in southern Brazil

The anthropogenic pressures on coastal areas represent important factors affecting local, regional, and even global patterns of distribution and abundance of benthic organisms. This report undertakes a comparative analysis of the community structure of rocky shore intertidal phytobenthos in both pristine like environments (PLE) and urbanized environments (UBE) in southern Brazil, characterizing variations on different spatial scales. Multivariate analysis of variance indicated that the PLE is characterized by a larger number of taxa and an increased occurrence of Rhodophyta species in relation to UBE. In contrast, UBE were dominated by opportunistic algae, such as Cladophora and Ulva spp. Significance tests further indicated higher species richness and Shannon-Wiener diversity on the PLE in relation to UBE. Here we provide data showing the magnitude of seaweed biodiversity loss and discuss direct and indirect consequences of unplanned urbanization on these communities.     

Spin state of ferric iron in MgSiO3 perovskite and its effect on elastic properties

Recent studies have indicated that a significant amount of iron in MgSiO₃ perovskite (Pv) is Fe³⁺ (Fe³⁺/ΣFe = 10–60%) due to crystal chemistry effects at high pressure (P) and that Fe³⁺ is more likely than Fe²⁺ to undergo a high-spin (HS) to low-spin (LS) transition in Pv in the mantle. We have measured synchrotron Mössbauer spectroscopy (SMS), X-ray emission spectroscopy (XES), and X-ray diffraction (XRD) of Pv with all iron in Fe³⁺ in the laser-heated diamond-anvil cell to over 100 GPa. Fe³⁺ increases the anisotropy of the Pv unit cell, whereas Fe²⁺ decreases it. In Pv synthesized above 50 GPa, Fe³⁺ enters into both the dodecahedral (A) and octahedral (B) sites approximately equally, suggesting charge coupled substitution. Combining SMS and XES, we found that the LS population in the B site gradually increases with pressure up to 50–60 GPa where all Fe³⁺ in the B site becomes LS, while Fe³⁺ in the A site remains HS to at least 136 GPa. Fe³⁺ makes Pv more compressible than Mg-endmember below 50 GPa because of the gradual spin transition in the B site together with lattice compression. The completion of the spin transition at 50–60 GPa increases bulk modulus with no associated change in density. This elasticity change can be a useful seismic probe for investigating compositional heterogeneities associated with Fe³⁺.