High‐frequency water quality monitoring in an urban catchment: hydrochemical dynamics,primary production and implications for the Water Framework Directive

This paper describes the hydrochemistry of a lowland, urbanised river‐system, The Cut in England, using in situ sub‐daily sampling. The Cut receives effluent discharges from four major sewage treatment works serving around 190 000 people. These discharges consist largely of treated water, originally abstracted from the River Thames and returned via the water supply network, substantially increasing the natural flow. The hourly water quality data were supplemented by weekly manual sampling with laboratory analysis to check the hourly data and measure further determinands. Mean phosphorus and nitrate concentrations were very high, breaching standards set by EU legislation. Although 56% of the catchment area is agricultural, the hydrochemical dynamics were significantly impacted by effluent discharges which accounted for approximately 50% of the annual P catchment input loads and, on average, 59% of river flow at the monitoring point. Diurnal dissolved oxygen data demonstrated high in‐stream productivity. From a comparison of high frequency and conventional monitoring data, it is inferred that much of the primary production was dominated by benthic algae, largely diatoms. Despite the high productivity and nutrient concentrations, the river water did not become anoxic, and major phytoplankton blooms were not observed. The strong diurnal and annual variation observed showed that assessments of water quality made under the Water Framework Directive (WFD) are sensitive to the time and season of sampling. It is recommended that specific sampling time windows be specified for each determinand, and that WFD targets should be applied in combination to help identify periods of greatest ecological risk. © 2015 The Authors. Hydrological Processes published by John Wiley & Sons Ltd.     

Discovering environmental data: metadatabases,network information resource tools and the GENIE system

Abstract

The existence of global computer networks in conjunction with various computer based tools offers the GIS community the possibility of identifying existing spatial data in a faster and more complete way. Using such tools could help the GIS community reduce the high costs of data collection. This paper focuses on the discovery of environmental data using metadatabases and network information resource tools and includes comments on some of the limitations of these computer based tools. The article will conclude by describing how the system developed by the GENIE project attempts to overcome some of these limitations.     

Fisheries mismanagement

We analysed the extent to which European politicians have adhered to scientific recommendations on annual total allowable catches (TACs) from 1987 to 2011, covering most of the period of the Common Fisheries Policy (CFP). For the 11 stocks examined, TACs were set higher than scientific recommendations in 68% of decisions. Politically-adjusted TACs averaged 33% above scientifically recommended levels. There was no evidence that the 2002 reform of the CFP improved decision-making, as was claimed at the time. We modelled the effects of such politically-driven decision-making on stock sustainability. Our results suggest that political adjustment of scientific recommendations dramatically increases the probability of a stock collapsing within 40 years.In 2012 European fisheries policy will undergo a once-a-decade reform. Ten years ago radical reforms were promised but the changes failed to improve sustainability. It is likely that the 2012 reform will be similarly ineffective unless decision-making is changed so that catch allocations are based on science rather than politics.     

A verification framework for interannual-to-decadal predictions experiments

Decadal predictions have a high profile in the climate science community and beyond, yet very little is known about their skill. Nor is there any agreed protocol for estimating their skill. This paper proposes a sound and coordinated framework for verification of decadal hindcast experiments. The framework is illustrated for decadal hindcasts tailored to meet the requirements and specifications of CMIP5 (Coupled Model Intercomparison Project phase 5). The chosen metrics address key questions about the information content in initialized decadal hindcasts. These questions are: (1) Do the initial conditions in the hindcasts lead to more accurate predictions of the climate, compared to un-initialized climate change projections? and (2) Is the prediction model’s ensemble spread an appropriate representation of forecast uncertainty on average? The first question is addressed through deterministic metrics that compare the initialized and uninitialized hindcasts. The second question is addressed through a probabilistic metric applied to the initialized hindcasts and comparing different ways to ascribe forecast uncertainty. Verification is advocated at smoothed regional scales that can illuminate broad areas of predictability, as well as at the grid scale, since many users of the decadal prediction experiments who feed the climate data into applications or decision models will use the data at grid scale, or downscale it to even higher resolution. An overall statement on skill of CMIP5 decadal hindcasts is not the aim of this paper. The results presented are only illustrative of the framework, which would enable such studies. However, broad conclusions that are beginning to emerge from the CMIP5 results include (1) Most predictability at the interannual-to-decadal scale, relative to climatological averages, comes from external forcing, particularly for temperature; (2) though moderate, additional skill is added by the initial conditions over what is imparted by external forcing alone; however, the impact of initialization may result in overall worse predictions in some regions than provided by uninitialized climate change projections; (3) limited hindcast records and the dearth of climate-quality observational data impede our ability to quantify expected skill as well as model biases; and (4) as is common to seasonal-to-interannual model predictions, the spread of the ensemble members is not necessarily a good representation of forecast uncertainty. The authors recommend that this framework be adopted to serve as a starting point to compare prediction quality across prediction systems. The framework can provide a baseline against which future improvements can be quantified. The framework also provides guidance on the use of these model predictions, which differ in fundamental ways from the climate change projections that much of the community has become familiar with, including adjustment of mean and conditional biases, and consideration of how to best approach forecast uncertainty.     

A Review of High-Performance Computational Strategies for Modeling and Imaging of Electromagnetic Induction Data

Many geoscientific applications exploit electrostatic and electromagnetic fields to interrogate and map subsurface electrical resistivity—an important geophysical attribute for characterizing mineral, energy, and water resources. In complex three-dimensional geologies, where many of these resources remain to be found, resistivity mapping requires large-scale modeling and imaging capabilities, as well as the ability to treat significant data volumes, which can easily overwhelm single-core and modest multicore computing hardware. To treat such problems requires large-scale parallel computational resources, necessary for reducing the time to solution to a time frame acceptable to the exploration process. The recognition that significant parallel computing processes must be brought to bear on these problems gives rise to choices that must be made in parallel computing hardware and software. In this review, some of these choices are presented, along with the resulting trade-offs. We also discuss future trends in high-performance computing and the anticipated impact on electromagnetic (EM) geophysics. Topics discussed in this review article include a survey of parallel computing platforms, graphics processing units to multicore CPUs with a fast interconnect, along with effective parallel solvers and associated solver libraries effective for inductive EM modeling and imaging.     

Volcanism in the Sumisu Rift, I. Major element, volatile, and stable isotope geochemistry

A bimodal volcanic suite with KAr ages of 0.05–1.40 Ma was collected from the Sumisu Rift using alvin. These rocks are contemporaneous with island arc tholeiite lavas of the Izu-Ogasawara arc 20 km to the east, and provide a present day example of volcanism associated with arc rifting and back-arc basin initiation. Major element geochemistry of the basalts is most similar to that of basalts found in other, more mature back-arc basins, which indicates that back-arc basins need not begin their magmatic evolution with lavas bearing strong arc signatures.Volatile concentrations distinguish Sumisu Rift basalts from island arc basalts and MORB. H₂O contents, which are at least four times greater than in MORB, suppress plagioclase crystallization. This suppression results in a more mafic fractionating assemblage, which prevents Al₂O₃ depletion and delays the initiation of Fe₂O_3^(tot) and TiO₂ enrichment. However, unlike arc basalts,Fe^3+/ΣFe ratios are only slightly higher than in MORB and are insufficient to cause magnetite saturation early enough to suppress Fe₂O_3^(tot) and TiO₂ enrichment. Thus, major element trends are more similar to those of MORB than arcs.H₂O, CO₂ and S are undersaturated relative to pure phase solubility curves, indicating exsolution of an H₂O-rich mixed gas phase. HighH₂O/S, highδD, and low (MORB-like)δ³⁴S ratios are considered primary and distinctive of the back-arc basin setting.     

Holocene excursions of the Northwest European geoid

Computer-assisted analyses of more than 600 radiocarbon-dated sea-level indicators from northwestern Europe, concentrated around the North Sea margin, indicate that vertical crustal movements are more important that eustatic sea-level change in determining the locus of Holocene shoreline positions through time. For the past 14,000 radiocarbon years, the divergence of sea-level data for the northwest European sectors exceeds the maximum estimated sea-level rise by a factor of two or more. Projecting these data to a single meridian demonstrates the remarkable variety of vertical crustal movement in northwestern Europe.Accumulating radiocarbon-dated sea-level indicators into millennial cohorts, we generate isobase maps which begin to specify areas of notable vertical crustal mobility. These isobase maps appear to confirm that eustatic sea-level rise is subordinate to postglacial geoidal excursions in determining the locus of contemporary northwestern European shorelines.