Hydrodynamics and sediment dynamics in the German Bight. A focus on observations and numerical modelling in the East Frisian Wadden Sea

This work deals with analysis of hydrographic observations and results of numerical simulations. The data base includes acoustic Doppler current profilers (ADCP) observations, continuous measurements on data stations and satellite data originating from the medium resolution imaging spectrometer (MERIS) onboard the European Space Agency (ESA) satellite ENVISAT with a spatial resolution of 300 m. Numerical simulations use nested models with horizontal resolutions ranging from 1 km in the German Bight to 200 m in the East Frisian Wadden Sea coupled with a suspended matter transport model. Modern satellite observations have now a comparable horizontal resolution with high-resolution numerical model of the entire area of the East Frisian Wadden Sea allowing to describe and validate new and so far unknown patterns of sediment distribution. The two data sets are consistent and reveal an oscillatory behaviour of sediment pools to the north of the back-barrier basins and clear propagation patterns of tidally driven suspended particulate matter outflow into the North Sea. The good agreement between observations and simulations is convincing evidence that the model simulates the basic dynamics and sediment transport processes, which motivates its further use in hindcasting, as well as in the initial steps towards forecasting circulation and sediment dynamics in the coastal zone.     

Snow loads on wire mesh and cable net rockfall slope protection systems

Snow load on mesh systems is complicated by many factors. This paper presents field instrumentation data on snow load variation with temperature, snowfall and snow depth on a mesh system. It was found that snow load pattern on mesh systems changed with temperature even without variation in snow depth. It reached its maximum value when the temperature rose just above freezing to melt the interface. The field data was used to formulate appropriate snow load models for the various conditions of temperature in the field. The snow load models were used to study the performance of a number of mesh systems in North America and estimate the interface friction that was prevalent for the different surface conditions.     

When hazard avoidance is not an option: lessons learned from monitoring the postdisaster Oso landslide,USA

On 22 March 2014, a massive, catastrophic landslide occurred near Oso, Washington, USA, sweeping more than 1 km across the adjacent valley flats and killing 43 people. For the following 5 weeks, hundreds of workers engaged in an exhaustive search, rescue, and recovery effort directly in the landslide runout path. These workers could not avoid the risks posed by additional large-scale slope collapses. In an effort to ensure worker safety, multiple agencies cooperated to swiftly deploy a monitoring and alerting system consisting of sensors, automated data processing and web-based display, along with defined communication protocols and clear calls to action for emergency management and search personnel. Guided by the principle that an accelerating landslide poses a greater threat than a steadily moving or stationary mass, the system was designed to detect ground motion and vibration using complementary monitoring techniques. Near real-time information was provided by continuous GPS, seismometers/geophones, and extensometers. This information was augmented by repeat-assessment techniques such as terrestrial and aerial laser scanning and time-lapse photography. Fortunately, no major additional landsliding occurred. However, we did detect small headscarp failures as well as slow movement of the remaining landslide mass with the monitoring system. This was an exceptional response situation and the lessons learned are applicable to other landslide disaster crises. They underscore the need for cogent landslide expertise and ready-to-deploy monitoring equipment, the value of using redundant monitoring techniques with distinct goals, the benefit of clearly defined communication protocols, and the importance of continued research into forecasting landslide behavior to allow timely warning.

     

Further comments concerning “geographic” and “economic” economic geography

This article considers whether the growing theoretical and methodological diversity or pluralistic nature of economic geography contributes to its lack of engagement outside the discipline and academy. Although we are enthusiastic about the vibrancy this pluralism brings, we also speculate that it contributes to the discipline's tendency to fall short of significantly impacting key debates in the social sciences. In particular, we consider the disciplinary challenges to influencing mainstream debates over financialization and the recent financial crisis and the recurring lament that economic geography “misses the boat” by failing to significantly impact key scholarly and policy issues. Specifically, we suggest that methodological and theoretical diversity, local contextualization, and relational analysis, all of which we support as vital to the discipline, make it difficult to isolate a disciplinary core. We conclude that pluralism produces a vibrant discipline with unique explanatory power but that it also has important impacts on the design, execution, and influence of geographers’ research outside the discipline.     

INFLUENCE OF ENSO ON MAXIMUM,MINIMUM, AND MEAN TEMPERATURES IN THE SOUTHEAST UNITED STATES

The El Niño/Southern Oscillation (ENSO) phenomenon, in both its warm and cold states, has a pronounced influence on mean monthly temperature and precipitation in Southeast United States, particularly along the Gulf of Mexico coast. This paper examines the influence of ENSO warm and cold events on the average monthly maximum and minimum as well as mean temperatures at 88 stations across the Southeast during 1931–1994. Composite time series for the 24-month period from July prior to a warm- or cold-event year (year -1) to June following a warm- or cold-event year (year +1) are examined. In the months with the largest mean temperature departures, January and February of years +0 and +1, maximum and minimum temperature departures are of the same sign as the mean temperature departure. However, in much of the region south of Virginia, the maximum and minimum temperature departures are of opposite sign during the autumn of year +0 and spring of year +1. The role of cloud cover is examined in relation to the temperature response to ENSO. A decreased diurnal temperature range during the autumn of year +0 to the spring of year +1 occurred during warm events and is believed to be associated with increased cloud cover caused by an enhanced subtropical jet stream. [Key words: ENSO, temperature, cloud cover, Southeast United States.]     

Geochemical effects of oxidation products and framboidal pyrite oxidation in acid mine drainage prediction techniques

Acid mine drainage predictive testwork associated with the Australian Mineral Industries Research Association (AMIRA) P387A Project: Prediction and Kinetic Control of Acid Mine Drainage (AMD) has critically examined static acid assessment and kinetic information from acid–base accounting techniques, including net acid production potential (NAPP), net acid generation (NAG) and column leach tests. This paper compares results on two waste rock samples that were obtained from the Kaltim Prima Coal mine (KPC) containing significant quantities of fine-grained framboidal pyrite. In agreement with other research, the authors' results indicated that framboidal pyrite is more reactive than euhedral forms due to the greater specific surface area of framboidal pyrite. This is evidenced by optical microscopy of reacted samples. Importantly, the results showed that NAPP testing is biased by the rapid acid generating oxidation of framboidal pyrite prior to, and during the acid neutralisation capacity (ANC) test. This can result in negative ANC values for samples containing significant framboidal pyrite (often “corrected” to zero kg H₂SO₄/t) when significant ANC is actually present in the sample. NAG testing using H₂O₂ indicated that samples containing a significant quantity of framboidal pyrite can result in the catalytic decomposition of the H₂O₂ prior to complete oxidation of the sulfide minerals present, requiring sequential addition of H₂O₂ for completion. A benefit of the NAG test, however, is that it assesses the net acid generation capacity of the sample without bias towards acid generation as is observed using NAPP methods. The kinetic NAG test also gives information on the reaction sequence of framboidal and euhedral pyrite. Periodic (kinetic) analysis of sub-samples from column leach tests indicated rapid oxidation of the framboidal pyrite compared to the euhedral pyrite, which was correlated with the greater framboidal pyrite surface area.Calculations to determine the sulfide/sulfate acidity derived from the oxidation of framboidal pyrite prior to; and during the ANC test have been developed to provide a better indication of the actual ANC (ANC_Actual) of the sample. Paste pH values of <pH 4–5 may be one suitable trigger mechanism for the implementation of this new method. This has led to an improved NAPP estimation of total acid production. Together with NAG and column leach testing this improved methodology has resulted in accurate AMD characterisation of samples containing acidic oxidation products and framboidal pyrite.     

Monitoring overburden layer changes and fault movements from time-lapse seismic data on the Valhall Field

A method developed by Røste et al. , which discriminates between layer thickness and velocity changes, is tested on pre-stack time-lapse seismic ocean bottom cable (OBC) data from the Valhall Field. A key parameter in this discrimination process is the dilation factor, α, which is the relative velocity change divided by the relative thickness change within a given layer. The high quality and good repeatability of the OBC data enables us to estimate α with a reasonable accuracy for α-values between 0 and −5. For α-values below −5, complementary information, like for instance geomechanics is required. For the top reservoir horizon we estimate a maximum subsidence of 0.50 m ± 0.29 m and a corresponding velocity decrease for the sequence from the seabed to the top reservoir of 2.0 m s⁻¹± 0.40 m s⁻¹.
Time-lapse distortion patterns with characteristic time-shift versus offset signatures are observed. The positions and vertical extents of the distortion zones are determined from ray path considerations and modelling. The distortion zones correlate with buried faults, indicating that a (time-lapse) distortion zone might be produced by a localized slip in a fault zone. We present an extended method which allows for vertical (in addition to lateral) variations in the relative thickness and velocity changes. This method can be viewed as a simplified version of time-lapse tomography, but involving fewer unknown parameters, giving more stability to the estimated changes in thickness and velocity. Using this technique, we are able to estimate α for positions with localized time-lapse distortions.     

Turbulent flux observations and modelling over a shallow lake and a wet grassland in the Nam Co basin,Tibetan Plateau

The Tibetan Plateau plays an important role in the global water cycle and is strongly influenced by climate change. While energy and matter fluxes have been more intensely studied over land surfaces, a large proportion of lakes have either been neglected or parameterised with simple bulk approaches. Therefore, turbulent fluxes were measured over wet grassland and a shallow lake with a single eddy-covariance complex at the shoreline in the Nam Co basin in summer 2009. Footprint analysis was used to split observations according to the underlying surface, and two sophisticated surface models were utilised to derive gap-free time series. Results were then compared with observations and simulations from a nearby eddy-covariance station over dry grassland, yielding pronounced differences. Observations and footprint integrated simulations compared well, even for situations with flux contributions including grassland and lake. The accessibility problem for EC measurements on lakes can be overcome by combining standard meteorological measurements at the shoreline with model simulations, only requiring representative estimates of lake surface temperature.