Predicting the effects of shade on water temperature in small streams

A computer model for stream water temperature was developed, and tested in a small pasture stream near Hamilton, New Zealand. The model quantifies shading by riparian vegetation, hillsides, and stream banks using three coefficients: canopy angle, topography angle, and canopy shade factor. Shade was measured directly and found to vary significantly along the channel. Using the maximum measured shade, a close match was achieved between observed and predicted daily maximum and minimum water and bed sediment temperature. Model predictions of incoming and outgoing long‐wave radiation flux closely matched measurements, but there were unexplained discrepancies in short‐wave radiation flux. Model predictions indicate that moderate shade levels (c. 70%) may be sufficient in temperate climates to restore headwater pasture stream temperatures to 20°C, an estimate of the thermal tolerance for sensitive invertebrates.     

Coleoptera and microbe biomass in Antarctic Dry Valley paleosols adjacent to the Inland Ice: Implications for Mars

Bulk paleosol samples collected from a Middle to Early Miocene moraine in the New Mountain area of the Dry Valleys, Antarctica, yielded Coleoptera exoskeletons and occasional endoskeletons showing considerable diagenetic effects along with several species of bacteria, all lodged in a dry-frozen but salt-rich horizon at shallow depth to the land surface. The till is at the older end of a chronologic sequence of glacial deposits, thought to have been deposited before the transition from wet-based to cold-based ice (～15 Ma), and hence, entirely weathered in contact with the subaerial atmosphere. It is possible, though not absolutely verifiable, that the skeletons date from this early stage of emplacement having undergone modifications whenever light snowmelt occurred or salt concentrations lowered the freezing temperature to maintain water as liquid. Correlation of the Coleoptera species with cultured bacteria in the sample and the likelihood of co-habitation with Beauveria bassiani found in two adjacent, although younger paleosols, leads to new questions about the antiquity of the Coleoptera and the source of N and glucose from chitinase derived from the insects. The skeletons in the 831 section may date close to the oldest preserved chitin (Oligocene) yet found on Earth. While harsh Martian conditions make it seemingly intolerable for complex, multicellular organisms such as insects to exist in the near-surface and subaerially, life within similar cold, dry paleosol microenvironments (Cryosols) of Antarctica point to life potential for the Red Planet, especially when considering the relatively diverse microbe (bacteria and fungi) population.     

Dynamic Rupture in a 3-D Particle-based Simulation of a Rough Planar Fault

An appreciation of the physical mechanisms which cause observed seismicity complexity is fundamental to the understanding of the temporal behaviour of faults and single slip events. Numerical simulation of fault slip can provide insights into fault processes by allowing exploration of parameter spaces which influence microscopic and macroscopic physics of processes which may lead towards an answer to those questions. Particle-based models such as the Lattice Solid Model have been used previously for the simulation of stick-slip dynamics of faults, although mainly in two dimensions. Recent increases in the power of computers and the ability to use the power of parallel computer systems have made it possible to extend particle-based fault simulations to three dimensions. In this paper a particle-based numerical model of a rough planar fault embedded between two elastic blocks in three dimensions is presented. A very simple friction law without any rate dependency and no spatial heterogeneity in the intrinsic coefficient of friction is used in the model. To simulate earthquake dynamics the model is sheared in a direction parallel to the fault plane with a constant velocity at the driving edges. Spontaneous slip occurs on the fault when the shear stress is large enough to overcome the frictional forces on the fault. Slip events with a wide range of event sizes are observed. Investigation of the temporal evolution and spatial distribution of slip during each event shows a high degree of variability between the events. In some of the larger events highly complex slip patterns are observed.     

Carbon sequestration and environmental effects of afforestation with Pinus radiata D. Don in the Western Cape, South Africa

A three-step methodology to assess the carbon sequestration and the environmental impact of afforestation projects in the framework of the Flexible Mechanisms of the Kyoto Protocol (Joint Implementation and Clean Development Mechanism) was developed and tested using a dataset collected from the Jonkershoek forest plantation, Western Cape, South Africa, which was established with Pinus radiata in former native fynbos vegetation and indigenous forest. The impact of a change in land use was evaluated for a multifunctional, a production and a non-conversion scenario. First, the carbon balance was modelled with GORCAM and was expressed as (1) C sequestration in tC ha⁻¹ year⁻¹ in soil, litter, and living biomass according to the rules of the first commitment period of the Kyoto Protocol, and (2) CO₂ emission reductions in tC ha⁻¹ year⁻¹, which includes carbon sequestered in the above-mentioned pools and additionally in wood products, as well as emission reductions due to fossil fuel substitution. To estimate forest growth, three data sources were used: (1) inventory data, (2) growth simulation with a process-based model, and (3) yield tables. Second, the effects of land use change were assessed for different project scenarios using a method related to Life Cycle Assessment (LCA). The method uses 17 quantitative indicators to describe the impact of project activities on water, soil, vegetation cover and biodiversity. Indicator scores were calculated by comparing indicator values with reference values, estimated for the climax vegetation. The climax vegetation is the site-specific ecosystem phase with the highest exergy content and the highest exergy flow dissipation capacity. Third, the land use impact per functional unit of 1 tC sequestered was calculated by combining the results of step 1 and step 2. The average baselines to obtain carbon additionality are 476 tC ha⁻¹ for indigenous forest and 32 tC ha⁻¹ for fynbos. Results show that the influence of the growth assessment method on the magnitude of C sequestration and hence on the environmental impact per functional unit is large. When growth rate is assessed with the mechanistic model and with the yield table, it is overestimated in the early years and underestimated in the long term. The main conclusion of the scenario analysis is that the production forest scenario causes higher impacts per functional unit than the multifunctional scenario, but with the latter being less efficient in avoiding CO₂ emissions. The proposed method to assess impacts on diverse components of the ecosystem is able to estimate the general tendency of the adverse and positive effects of each scenario. However, some indicators, more specifically about biodiversity and water balance, could be improved or reinterpreted in light of specific local data about threat to biodiversity and water status.     

Design formulations for supplemental viscous dampers to highway bridges

Design formulas for supplemental viscous dampers to building structures are readily available in FEMA provisions and MCEER research reports. However, for the design of supplemental viscous dampers corresponding to a desired system damping ratio of highway bridges, there exist, if any, few design guidelines. This is particularly true if the bridge components such as elastomeric bearings, piers and abutment possess different damping ratios, stiffnesses, and lumped masses. In this paper, the design formulas for supplemental viscous dampers to highway bridges have been derived based on the concept of ‘composite damping ratio’. The design formulas can be used to determine the damping coefficients of the dampers corresponding to a desired system damping ratio of the bridge in which different component damping ratios may be assumed for the elastomeric bearings, piers and abutments. The proposed design formulas are numerically validated by comparing the seismic responses of a three‐span bridge equipped with viscous dampers with those of the same bridge without viscous dampers but with an assigned inherent system damping ratio equal to the target system damping ratio. Copyright © 2005 John Wiley & Sons, Ltd.     

Velocity structure and properties of the lunar crust

Lunar seismic data from three Apollo seismometers are interpreted to determine the structure of the Moon's interior to a depth of about 100 km. The travel times and amplitudes ofP arrivals from Saturn IV B and LM impacts are interpreted in terms of a compressional velocity profile. The most outstanding feature of the model is that, in the Fra Mauro region of Oceanus Procellarum, the Moon has a 65 km thick layered crust. Other features of the model are: (i) rapid increase of velocity near the surface due to pressure effects on dry rocks, (ii) a discontinuity at a depth of about 25 km, (iii) near constant velocity (6.8 km/s) between 25 and 65 km deep, (iv) a major discontinuity at 65 km marking the base of the lunar crust, and (v) very high velocity (about 9 km/s) in the lunar mantle below the crust. Velocities in the upper layer of the crust match those of lunar basalts while those in the lower layer fall in the range of terrestrial gabbroic and anorthositic rocks.Lamant-Doherty Geological Observatory Contribution No. 1768.     

Shallow lunar structure determined from the passive seismic experiment

Data relevant to the shallow structure of the Moon obtained at the Apollo seismic stations are compared with previously published results of the active seismic experiments. It is concluded that the lunar surface is covered by a layer of low seismic velocity (V _p ? 100 m s^?1), which appears to be equivalent to the lunar regolith defined previously by geological observations. This layer is underlain by a zone of distinctly higher seismic velocity at all of the Apollo landing sites. The regolith thicknesses at the Apollo 11, 12, and 15 sites are estimated from the shear-wave resonance to be 4.4, 3.7, and 4.4 m, respectively. These thicknesses and those determined at the other Apollo sites by the active seismic experiments appear to be correlated with the age determinations and the abundances of extralunar components at the sites.     

Evidence that biological activity affects Ocean Bottom Seismograph recordings

Brief and impulsive signals of uncertain origin appear regularly on records from Ocean Bottom Seismographs (OBS) of several institutions. These signals have been recorded on nearly all deployments of the Texas OBS, including sites at depths greater than 7000 m. At some sites, they account for over 90% of the events recorded. They are of short duration (usually 0.5–4.0 s) and have a characteristic frequency (usually in the range of 4–18 Hz) that differs from site to site. When networks of OBS instruments are deployed, the signals are not recorded simultaneously by different instruments. Neither the frequency content nor the distribution of durations of these signals is similar to what is observed for known earthquake events.We present evidence suggesting that the signals are of biological origin, perhaps caused by animals touching the OBS units. (1) The distribution of these signals on instruments deployed at depths shallower than 1000 m shows a 24 h periodicity, while there is a 24 h periodic pattern on instruments deployed at sites deeper than 1000 m (where there is no visible light). (2) The frequency of occurrence of signals is similar to the vertical distribution of biomass in the oceans, i.e., they appear most frequently on OBS instruments deployed at very shallow depths. (3) Biological material has been found attached to several OBS units upon recovery.University of Texas Institute for Geophysics contribution number 468.     

Geomorphological characteristics of slope failures in northeast Viti Levu island,Fiji, triggered by Tropical Cyclone Winston in February 2016

The highways circumnavigating Viti Levu play a pivotal role in Fiji's socioeconomic development, and are a crucial link to transport aid during disasters. Slope failures triggered by heavy rainfall and tropical cyclones have led to considerable damage and fatalities along Viti Levu's main roads in the past. Knowledge of slope instability mechanisms is key for the successful identification and management of slope failure hazards, however, there is a paucity of such information for Fiji's main roads. Severe Tropical Cyclone (STC) Winston was the strongest cyclone on record to make landfall in Fiji and affected the Fiji Islands from the early hours of 20 February until 3 am, 21 February, 2016. We present a field reconnaissance examining the characteristics and mechanisms of slope failures induced by STC Winston along a 35 km stretch of the northern part of the Viti Levu's ring road, “Kings Road”. Approximately 61 distinct shallow, small‐scale slope failures were identified most of which were of a complex type and included earth and debris slides (planar and rotational) with a minor flow component. The trigger for the slope failures was the ~258 mm of rainfall in 24 hours after 30‐days of antecedent rainfall totalling 482 mm. This caused rapid increases in porewater pressures, especially at the contact of residual soils and the underlying weathered basement rock. Evidence of recurring slips along Kings Road indicates that contemporary slope instability is likely caused by elevated porewater pressure during high intensity rainfall events in clay‐dominated soils.     

Influence of Hydrological Regime in Determining the Response of Macroalgal Blooms to Nutrient Loading in Two Irish Estuaries

Eutrophication and the development of persistent opportunistic macroalgal blooms are recognised as one of the main detrimental effects of increased anthropogenic pressures on estuarine and coastal systems. This study aimed to highlight the interplay between pressures and controlling physical factors on ecosystem functioning. The hypothesis that hydrological regime can control the growth of opportunistic macroalgae was tested with the study of two Irish estuaries, the Argideen and the Blackwater, with similar nutrient loading sources but divergent hydrological regimes. Seasonal monitoring data was initially examination, while the application of a pre-existing box model allowed a further analysis of the influence of residence time and nutrient load modifications on macroalgal growth. Seasonal oscillations in monitored river flow rates altered nutrient transfer from the catchments to the estuaries in both cases, as is shown through differences between winter and summer nutrient concentrations. In the Argideen, however, the relative contribution of phosphorus (P) from adjacent marine waters was high due to the shorter residence times and greater influx of marine water into the estuary. Modelling studies showed that in the Argideen Estuary, P load reduction would have potentially minimal impact on macroalgal growth due to the shorter residence time which increased the influx of P from marine sources. Nitrogen (N) load reduction of 60 % had a significant, albeit limited, impact on macroalgae and was insufficient in achieving the environmental objectives for this waterbody. For the more river-dominated Blackwater Estuary, modelled reductions in P resulted in a considerable decrease in biomass. Any further P decreases would accentuate the existing disparity in estuarine N:P ratios with possible repercussions for N transport to the coastal system. Hence, the hydrological complexity of estuarine systems demonstrated dictates that a portfolio of separate, but complimentary, management approaches may be required to address eutrophication in these estuaries.