A warm-season comparison of WRF coupled to the CLM4.0, Noah-MP,and Bucket hydrology land surface schemes over the central USA

In climate modeling studies, there is a need to choose a suitable land surface model (LSM) while adhering to available resources. In this study, the viability of three LSM options (Community Land Model version 4.0 [CLM4.0], Noah-MP, and the five-layer thermal diffusion [Bucket] scheme) in the Weather Research and Forecasting model version 3.6 (WRF3.6) was examined for the warm season in a domain centered on the central USA. Model output was compared to Parameter-elevation Relationships on Independent Slopes Model (PRISM) data, a gridded observational dataset including mean monthly temperature and total monthly precipitation. Model output temperature, precipitation, latent heat (LH) flux, sensible heat (SH) flux, and soil water content (SWC) were compared to observations from sites in the Central and Southern Great Plains region. An overall warm bias was found in CLM4.0 and Noah-MP, with a cool bias of larger magnitude in the Bucket model. These three LSMs produced similar patterns of wet and dry biases. Model output of SWC and LH/SH fluxes were compared to observations, and did not show a consistent bias. Both sophisticated LSMs appear to be viable options for simulating the effects of land use change in the central USA.     

Different Asian Monsoon Rainfall Responses to Idealized Orography Sensitivity Experiments in the HadGEM3-GA6 and FGOALS-FAMIL Global Climate Models

Recent work has shown the dominance of the Himalaya in supporting the Indian summer monsoon(ISM),perhaps by surface sensible heating along its southern slope and by mechanical blocking acting to separate moist tropical flow from drier midlatitude air.Previous studies have also shown that Indian summer rainfall is largely unaffected in sensitivity experiments that remove only the Tibetan Plateau.However,given the large biases in simulating the monsoon in CMIP5 models,such results may be model dependent.This study investigates the impact of orographic forcing from the Tibetan Plateau,Himalaya and Iranian Plateau on the ISM and East Asian summer monsoon(EASM) in the UK Met Office's Had GEM3-GA6 and China's Institute of Atmospheric Physics FGOALS-FAMIL global climate models.The models chosen feature oppositesigned biases in their simulation of the ISM rainfall and circulation climatology.The changes to ISM and EASM circulation across the sensitivity experiments are similar in both models and consistent with previous studies.However,considerable differences exist in the rainfall responses over India and China,and in the detailed aspects such as onset and retreat dates.In particular,the models show opposing changes in Indian monsoon rainfall when the Himalaya and Tibetan Plateau orography are removed.Our results show that a multi-model approach,as suggested in the forthcoming Global Monsoon Model Intercomparison Project(GMMIP) associated with CMIP6,is needed to clarify the impact of orographic forcing on the Asian monsoon and to fully understand the implications of model systematic error.     

Alignment between nationally determined contributions and the sustainable development goals for West Africa

The UN Sustainable Development Goals (SDGs) and the 2015 Paris Agreement are two of the most important policy frameworks of the twenty-first century. However, the alignment of national commitments linked to them has not yet been analysed for West African states. Such analyses are vital to avoid perverse outcomes if states assess targets and develop SDG implementation plans, and Nationally Determined Contributions (NDC) under the Paris Agreement, without integrated planning and cross-sectoral alignment. This article provides a situation analysis guided by the following questions: (a) Which priority sectors are mentioned in relation to adaptation and mitigation in West African NDCs? (b) Are the NDCs of West African states well aligned with the SDGs? (c) What are the co-benefits of NDCs in contributing towards the SDGs? and (d) How are West African states planning to finance actions in their NDCs? The study uses iterative content analysis to explore key themes for adaptation and mitigation within NDCs of 11 West African states and their alignment to selected SDGs. A national multi-stakeholder workshop was held in Ghana to examine the co-benefits of the NDCs in contributing towards the SDGs and their implementation challenges. Results show that agriculture and energy are priority sectors where NDCs have pledged significant commitments. The analysis displays good alignment between mitigation and adaptation actions proposed in NDCs and the SDGs. These represent opportunities that can be harnessed through integration into national sectoral policies. However, cross-sectoral discussions in Ghana identify significant challenges relating to institutional capacity, a lack of coordination among institutions and agencies, and insufficient resources in moving towards integrated implementation of national planning priorities to address successfully both NDC priorities and the SDGs.

Key policy insights

• Positive alignments between West African NDCs and SDGs present opportunities for mutual benefits that can advance national development via a more climate resilient pathway.

• NDCs of West African states can provide mutual benefits across the water–energy–food nexus, such as through climate-smart agriculture and low carbon energy technologies.

• Ghanaian multi-sectoral insights show the need to empower national coordinating bodies to overcome misalignments across different sectors.

     

Speleothem stable isotope records interpreted within a multi-proxy framework and implications for New Zealand palaeoclimate reconstruction

A primary step in the interpretation of speleothem stable isotope records (¹⁸O/¹⁶O and ¹³C/¹²C) is to conduct a comparison with other local palaeoclimate proxies. Here, two new master speleothem δ¹⁸O and δ¹³C records (one from eastern North Island, and the other from western/southern South Island, New Zealand) are evaluated against independent precipitation and temperature proxy information to assess their palaeoclimate reconstruction potential. This comparison also resulted in a serendipitous opportunity to reconstruct past circulation using climate regime classification [Lorrey, A.M., Fowler, A.M., Salinger, J., 2007a. Regional climate regime classification as a qualitative tool for interpreting multi-proxy palaeoclimate data spatial patterns: a New Zealand case study. Palaeo-3, in press], specifically because these two regional climate districts are hyper-sensitive to westerly circulation changes, and in many cases, exhibit contrasting climate character in response to circulation anomalies.For both the western South Island and the eastern North Island master speleothem δ¹³C records, variations tracked changes in relative regional precipitation. The δ¹⁸O master speleothem record for both regions varied with temperature change. Both records contain strong regional climate signals that suggest they have good value for palaeoclimate reconstruction. The ensuing attempt at a multi-proxy reconstruction of regional climate regimes from the compiled proxies indicates past circulation in the New Zealand sector has varied considerably during the past four millennia. Centennial-scale circulation changes for the past 4000 years are evident, and are analogous to modern Blocking, Zonal and Trough regime types [Kidson J. W., 2000. An analysis of New Zealand synoptic types and their use in defining weather regimes. International Journal of Climatology 20, 299–316] that characterise changes in present-day (prevailing) westerly circulation. This palaeoclimate reconstruction indicates modern regional climate regime classification can be extended at least as far back as the temporal coverage of the records presented here, and it can likely be improved on with better dating control and the addition of new records with higher resolution. It is also anticipated that future work will expand to include more proxy data from across New Zealand to improve the clarity of past climate regime occurrence for the Late Holocene.     

Thermodynamic and kinetic control on anaerobic oxidation of methane in marine sediments

The free energy yield of microbial respiration reactions in anaerobic marine sediments must be sufficient to be conserved as biologically usable energy in the form of ATP. Anaerobic oxidation of methane (AOM) coupled to sulfate reduction (SRR) has a very low standard free energy yield of ΔG^° = −33 kJ mol⁻¹, but the in situ energy yield strongly depends on the concentrations of substrates and products in the pore water of the sediment. In this work ΔG for the AOM-SRR process was calculated from the pore water concentrations of methane, sulfate, sulfide, and dissolved inorganic carbon (DIC) in sediment cores from different sites of the European continental margin in order to determine the influence of thermodynamic regulation on the activity and distribution of microorganisms mediating AOM-SRR. In the zone of methane and sulfate coexistence, the methane-sulfate transition zone (SMTZ), the energy yield was rarely less than −20 kJ mol⁻¹ and was mostly rather constant throughout this zone. The kinetic drive was highest at the lower part of the SMTZ, matching the occurrence of maximum AOM rates. The results show that the location of maximum AOM rates is determined by a combination of thermodynamic and kinetic drive, whereas the rate activity mainly depends on kinetic regulation.     

Sulfur isotope biogeochemistry of the Proterozoic McArthur Basin

Previous geochemical and biomarker studies of the late Paleo-Mesoproterozoic propose a stratified world, with strongly reducing (possibly sulfidic) deep-ocean conditions overlain by an oxygenated surface-ocean and atmosphere. To investigate such a scenario, we look to the structure of the biogeochemical sulfur cycle. We present sulfur (³²S, ³³S, ³⁴S, and ³⁶S in sulfides) isotope data from the McArthur Basin (Barney Creek, Reward, Velkerri, and McMinn formations) that allows for a direct evaluation of the surface biosphere. We are interested in investigating the types of information that can be gained by including ³³S and ³⁶S. When the ³⁴S/³²S fractionations are small, the inclusion of ³³S and ³⁶S provides little additional information, but does provide ancillary evidence for relative isotopic homogeneity (with the internal consistency of ³³S/³²S and ³⁶S/³²S). When the ³⁴S/³²S fractionations are large, direct information about the fractionation mechanisms can be obtained, with the potential to distinguish the biological from abiological processes. For example, the reconstruction of the Roper Group suggests that seawater sulfate concentrations were high enough to buffer against spatial heterogeneities. Overall, our findings agree with previously proposed redox structure of the Proterozoic ocean, highlight contributions from the oxidative sulfur cycle, and outline a new tool for interpreting the state of the surface sulfur cycle.     

Effect of divalent cations on the kinetics of Fe(III) complexation by organic ligands in natural waters

We have investigated the kinetics of Fe(III) complexation by several organic ligands including fulvic acid, citrate and ethylenediaminetetraacetic acid (EDTA). Particular attention was given to examination of the effect of competitive divalent cations (Me: Ca²⁺ and Mg²⁺) at concentrations typical of seawater on the complexation rate. All experiments were conducted in 0.5 M NaCl solution buffered with 2 mM bicarbonate at pH 8.0 in the absence and presence of Me (25 μM-250 mM). The rate constants of complex formation determined by using the competitive ligand (5-sulfosalicylic acid) method combined with visible spectrophotometry ranged from 3.3 × 10⁴ to 3.2 × 10⁶ M⁻¹ s⁻¹. The mechanism of complexation was then examined based on a kinetic model. When EDTA was used as a ligand, Me at concentrations comparable to the ligand markedly retarded the rate of iron complex formation due to the predominance of an adjunctive pathway (where iron-ligand complex is formed via direct association of iron to Me-ligand complex). In contrast, the competing effect of Me on iron complexation by citrate and fulvic acid was observed only when the Me concentration was in excess of the ligand by more than a factor of 10-1000. The kinetic model suggests that iron complexation by fulvic acid occurs predominantly via a disjunctive pathway (where iron complexation by ligand occurs after dissociation of Me from Me-ligand complex) at concentrations of divalent cations and natural organic matter typical of natural waters including seawater and freshwater.     

The credibility of volunteered geographic information

The proliferation of information sources as a result of networked computers and other interconnected devices has prompted significant changes in the amount, availability, and nature of geographic information. Among the more significant changes is the increasing amount of readily available volunteered geographic information. Although volunteered information has fundamentally enhanced geographic data, it has also prompted concerns with regard to its quality, reliability, and overall value. This essay situates these concerns as issues of information and source credibility by (a) examining the information environment fostering collective information contribution, (b) exploring the environment of information abundance, examining credibility and related notions within this environment, and leveraging extant research findings to understand user-generated geographic information, (c) articulating strategies to discern the credibility of volunteered geographic information (VGI), including relevant tools useful in this endeavor, and (d) outlining specific research questions germane to VGI and credibility.     

Early diagenetic vivianite [Fe3(PO4)2 · 8H2O] in a contaminated freshwater sediment and insights into zinc uptake: A μ-EXAFS, μ-XANES and Raman study

The sediments in the Salford Quays, a heavily-modified urban water body, contain high levels of organic matter, Fe, Zn and nutrients as a result of past contaminant inputs. Vivianite [Fe₃(PO₄)₂ · 8H₂O] has been observed to have precipitated within these sediments during early diagenesis as a result of the release of Fe and P to porewaters. These mineral grains are small (<100 μm) and micron-scale analysis techniques (SEM, electron microprobe, μ-EXAFS, μ-XANES and Raman) have been applied in this study to obtain information upon the structure of this vivianite and the nature of Zn uptake in the mineral. Petrographic observations, and elemental, X-ray diffraction and Raman spectroscopic analysis confirms the presence of vivianite. EXAFS model fitting of the FeK-edge spectra for individual vivianite grains produces Fe–O and Fe–P co-ordination numbers and bond lengths consistent with previous structural studies of vivianite (4O atoms at 1.99–2.05 Å; 2P atoms at 3.17–3.25 Å). One analysed grain displays evidence of a significant Fe³⁺ component, which is interpreted to have resulted from oxidation during sample handling and/or analysis. EXAFS modelling of the Zn K-edge data, together with linear combination XANES fitting of model compounds, indicates that Zn may be incorporated into the crystal structure of vivianite (4O atoms at 1.97 Å; 2P atoms at 3.17 Å). Low levels of Zn sulphate or Zn-sorbed goethite are also indicated from linear combination XANES fitting and to a limited extent, the EXAFS fitting, the origin of which may either be an oxidation artifact or the inclusion of Zn sulphate into the vivianite grains during precipitation. This study confirms that early diagenetic vivianite may act as a sink for Zn, and potentially other contaminants (e.g. As) during its formation and, therefore, forms an important component of metal cycling in contaminated sediments and waters. Furthermore, for the case of Zn, the EXAFS fits for Zn phosphate suggest this uptake is structural and not via surface adsorption.     

Contamination,risk, and heterogeneity: on the effectiveness of aquifer remediation

The effectiveness of aquifer remediation is typically expressed in terms of a reduction in contaminant concentrations relative to a regulated maximum contaminant level (MCL), and is usually confirmed by sparse monitoring data and/or simple model calculations. Here, the effectiveness of remediation is re-examined from a more thorough risk-based perspective that goes beyond the traditional MCL concept. A methodology is employed to evaluate the health risk to individuals exposed to contaminated household water that is produced from groundwater. This approach explicitly accounts for differences in risk arising from variability in individual physiology and water use, the uncertainty in estimating chemical carcinogenesis for different individuals, and the uncertainties and variability in contaminant concentrations within groundwater as affected by transport through heterogeneous geologic media. A hypothetical contamination scenario is developed as a case study in a saturated, alluvial aquifer underlying an actual Superfund site. A baseline (unremediated) human exposure and health risk scenario, as induced by contaminated groundwater pumped from this site, is predicted and compared with a similar estimate based upon pump-and-treat exposure intervention. The predicted reduction in risk in the remediation scenario is not an equitable one—that is, it is not uniform to all individuals within a population and varies according to the level of uncertainty in prediction. The importance of understanding the detailed hydrogeologic connections that are established in the heterogeneous geologic regime between the contaminated source, municipal receptors, and remediation wells, and its relationship to this uncertainty is demonstrated. Using two alternative pumping rates, we develop cost-benefit curves based upon reduced exposure and risk to different individuals within the population, under the presence of uncertainty.