Sustainable livelihoods approaches to inform government‐local partnerships and decision‐making in vulnerable environments

Sustainable livelihoods approaches used in international development are applied to a vulnerable New Zealand catchment. The Waiapu Catchment has a high proportion of indigenous residents, and is one of the most remote and deprived areas in the country. Linear and centralised approaches to indigenous development have failed to bring about desired changes. We identify “capitals” (social, human/political, physical, natural, financial and cultural) present in the catchment. From this assessment, we propose capital‐based holistic approaches to bring about community‐led change. The assessment and resulting approaches can be used in other vulnerable environments around the world.     

Hydrogeology of a coal-seam gas exploration area, southeastern British Columbia, Canada: Part 2. Modeling potential hydrogeological impacts associated with depressurizing

A three-dimensional, finite-element flow model was used to assess the hydrogeological effects of depressurizing coalbeds lying in the Weary Creek exploration block, Elk River valley, southeastern British Columbia, Canada. The simulation results permit, at an early stage, assessment of the environmental and economic implications of how the flow system may respond to depressurization. Estimated reservoir conditions for the coal-seam gas targets lying within the Upper Jurassic–Lower Cretaceous Mist Mountain Formation indicate that the coalbeds must be depressurized by up to 350 m to attain the critical gas desorption pressure. The simulations suggest that depressurizing has little effect on groundwater flux to the Elk River. Simulated water production for three depressurizing wells operating under steady-state, single-phase flow for initial reservoir conditions of 13 and 16.5 cm³/g is 645 m³/d (4,057 barrels/d) and 355 m³/d (2,233 barrels/d), respectively. Groundwaters collected from monitoring wells have relatively low salinity, ranging from about 250–1,300 mg/L. The groundwater is supersaturated with respect to Ca–Mg–Fe carbonates (calcite, dolomite, and siderite) and Al-bearing silicates, including kaolinite and illite. Dissolved trace-metal concentrations are low; only Fe, Cd, Cr, and Zn exceed Canadian water-quality guidelines for aquatic life. Groundwaters were devoid of the more soluble monocyclic aromatic organic compounds, including benzene, toluene, ethylbenzene, and polycyclic aromatic compounds, including naphthalene. Electronic Publication     

Direct calculation of thermodynamic properties of the barite/celestite solid solution from molecular principles

 Thermodynamic properties of the barite–celestite solid solution were calculated using molecular principles. Cation–cation (Ba–Ba, Sr–Sr, and Ba–Sr) interaction energies were derived from a number of random and ordered cation distributions which were energy-optimized using force potentials as incorporated in the program package GULP. With these interaction energies, diagrams for the enthalpy and free energy of mixing could be computed for the entire range of the solid solution between the barite and celestite end members and for a number of annealing temperatures. These thermodynamic data show that the solid solution is nonideal. The system has a tendency for Ba²⁺ and Sr²⁺ cations to order onto alternating layers ||(100). However, this ordering scheme is thermodynamically only relevant for annealing temperatures below approximately 500 K and systems that are kinetically inhibited during crystal growth. For sufficiently long annealing times at room temperature, the solid solution tends to exsolve with barite–celestite interfaces ||(100). The cell parameters a and c were calculated to have almost linear behavior for the whole solid solution, suggesting close to ideal behavior according to Vegard's law. In contrast, b tends to deviate positively from linearity, in agreement with experimental values. Received: 6 April 1999 / Revised, accepted: 29 September 1999     

Dendrochronology and lichenometry: colonization, growth rates and dating of geomorphological events on the east side of the North Patagonian Icefield, Chile

This paper highlights the importance for dating accuracy of initial studies of delay before colonization for both trees and lichens and tree age below core height, particularly in recently deglaciated terrain where colonization and growth rates may vary widely due to differences in micro-environment. It demonstrates, for the first time, how dendrochronology and lichenometry can be used together in an assessment of each other's colonization and growth rates, and then cross-correlated to provide a supportive dating framework. The method described for estimating tree age below core height is also new. The results show that on the east side of the North Patagonian Icefield in the Arco and Colonia valleys, Nothofagus age below a core height of 112 cm can vary from 5 to 41 years and delay before colonization may range from a maximum of 22 years near water to a minimum of 93 years on the exposed flanks of the Arenales and Colonia Glaciers. Tree age plus colonization delay supplied a maximum growth rate of 4.7 mm/year for the lichen Placopsis perrugosa and lichen colonization is estimated to take from 2.5 to approximately 13 years. A minimum lichenometric date of 1883 was estimated for an ice-formed trimline at the junction of the Arenales and Colonia glaciers and a maximum dendrochronological date of 1881 for a water-formed trimline in the Arco valley. Tree and lichen ages around the valley suggest that a glacial outburst drained the 1881 high level lake releasing approximately 265 million cubic metres of water. Repeated flooding, with a minimum of 38 high lake levels, is suggested by horizontal sediment lines on the Arco valley walls and moraine flanks. Dating confirmed diminishing flood levels with a last minor flood in 1963. The wider significance of the work is that it should produce more accurate dating of recent glacier fluctuations around the North Patagonia Icefield, an area where dated reference surfaces are extremely scarce.     

Simulated changes in the relationship between tropical ocean temperatures and the western African monsoon during the mid-Holocene

Results from nine coupled ocean-atmosphere simulations have been used to investigate changes in the relationship between the variability of monsoon precipitation over western Africa and tropical sea surface temperatures (SSTs) between the mid-Holocene and the present day. Although the influence of tropical SSTs on the African monsoon is generally overestimated in the control simulations, the models reproduce aspects of the observed modes of variability. Thus, most models reproduce the observed negative correlation between western Sahelian precipitation and SST anomalies in the eastern tropical Pacific, and many of them capture the positive correlation between SST anomalies in the eastern tropical Atlantic and precipitation over the Guinea coastal region. Although the response of individual model to the change in orbital forcing between 6 ka and present differs somewhat, eight of the models show that the strength of the teleconnection between SSTs in the eastern tropical Pacific and Sahelian precipitation is weaker in the mid-Holocene. Some of the models imply that this weakening was associated with a shift towards longer time periods (from 3–5 years in the control simulations toward 4–10 years in the mid-Holocene simulations). The simulated reduction in the teleconnection between eastern tropical Pacific SSTs and Sahelian precipitation appears to be primarily related to a reduction in the atmospheric circulation bridge between the Pacific and West Africa but, depending on the model, other mechanisms such as increased importance of other modes of tropical ocean variability or increased local recycling of monsoonal precipitation can also play a role.     

A multi-model analysis of the role of the ocean on the African and Indian monsoon during the mid-Holocene

We investigate the role of the ocean feedback on the climate in response to insolation forcing during the mid-Holocene (6,000 year BP) using results from seven coupled ocean–atmosphere general circulation models. We examine how the dipole in late summer sea-surface temperature (SST) anomalies in the tropical Atlantic increases the length of the African monsoon, how this dipole structure is created and maintained, and how the late summer SST warming in the northwest Indian Ocean affects the monsoon retreat in this sector. Similar mechanisms are found in all of the models, including a strong wind evaporation feedback and changes in the mixed layer depth that enhance the insolation forcing, as well as increased Ekman transport in the Atlantic that sharpens the Atlantic dipole pattern. We also consider changes in interannual variability over West Africa and the Indian Ocean. The teleconnection between variations in SST and Sahelian precipitation favor a larger impact of the Atlantic dipole mode in this region. In the Indian Ocean, the strengthening of the Indian dipole structure in autumn has a damping effect on the Indian dipole mode at the interannual time scale.     

Mid-Holocene monsoons: a multi-model analysis of the inter-hemispheric differences in the responses to orbital forcing and ocean feedbacks

The response of monsoon circulation in the northern and southern hemisphere to 6?ka orbital forcing has been examined in 17 atmospheric general circulation models and 11 coupled ocean–atmosphere general circulation models. The atmospheric response to increased summer insolation at 6?ka in the northern subtropics strengthens the northern-hemisphere summer monsoons and leads to increased monsoonal precipitation in western North America, northern Africa and China; ocean feedbacks amplify this response and lead to further increase in monsoon precipitation in these three regions. The atmospheric response to reduced summer insolation at 6?ka in the southern subtropics weakens the southern-hemisphere summer monsoons and leads to decreased monsoonal precipitation in northern South America, southern Africa and northern Australia; ocean feedbacks weaken this response so that the decrease in rainfall is smaller than might otherwise be expected. The role of the ocean in monsoonal circulation in other regions is more complex. There is no discernable impact of orbital forcing in the monsoon region of North America in the atmosphere-only simulations but a strong increase in precipitation in the ocean–atmosphere simulations. In contrast, there is a strong atmospheric response to orbital forcing over northern India but ocean feedback reduces the strength of the change in the monsoon although it still remains stronger than today. Although there are differences in magnitude and exact location of regional precipitation changes from model to model, the same basic mechanisms are involved in the oceanic modulation of the response to orbital forcing and this gives rise to a robust ensemble response for each of the monsoon systems. Comparison of simulated and reconstructed changes in regional climate suggest that the coupled ocean–atmosphere simulations produce more realistic changes in the northern-hemisphere monsoons than atmosphere-only simulations, though they underestimate the observed changes in precipitation in all regions. Evaluation of the southern-hemisphere monsoons is limited by lack of quantitative reconstructions, but suggest that model skill in simulating these monsoons is limited.     

Helium isotopes provide no evidence for deep mantle involvement in widespread Cenozoic volcanism across Central Asia

Small-volume alkali basaltic volcanism has occurred intermittently for the past + 30 My across a vast area of thick continental crust from southern Siberia, through Mongolia to northeast China. With a lack of evidence for Basin-and-Range-type crustal extension or rifting, models to explain the widely dispersed, yet long-lived, volcanism tend to favour involvement of one or more mantle plume(s). We examine the range of ³He/⁴He isotope values in olivine phenocrysts from basalts, and their entrained mantle xenoliths, from Hamar Daban in southern Siberia, and Hangai in central Mongolia, in order to examine whether upwelling lower mantle appears to be present beneath central Asia and thus test the validity of the plume model for this region. Our results show that the maximum ³He/⁴He value for the Siberian basalts is 8.12 ± 0.2R_a, and the maximum value for Mongolian basalts is 9.5 ± 0.5R_a. These values suggest that there is no significant contribution from a high ³He/⁴He primordial component that would strongly argue a lower mantle source. Overlap with commonly reported values for MORB leads us to propose that the source of the magmatism derives from the shallow asthenosphere. Alternative models to a deeply sourced mantle plume that may be able to explain the magmatism include: a shallow thermal anomaly confined to the upper mantle but either fed laterally or caused by thermal blanketing of the large Asian landmass; replacement or delamination of the lowermost lithosphere in response to tectonic stresses; or large-scale mantle disturbance or overturn caused by a protracted history of subduction beneath central Asia that ended regionally with the Jurassic closure of the Mongol-Okhotsk Ocean, but continues further afield with the present Indo-Asia collision.     

Effect of geochemical conditions on fate of organic compounds in groundwater

In situ microcosms were successfully used to study the degradation of a range of organic compounds in two pristine aquifers, one aerobic (Vejen) and one anaerobic (Villa Farm). Degradation and sorption behavior in the laboratory column microcosms packed with Villa Farm sediment was very similar to that in the in situ microcosms. However, when the columns were packed with quartz and equilibrated with aerated Villa Farm groundwater, behavior mirrored that at Vejen, indicating that oxygen rather than sediment or groundwater composition was the critical parameter. The aromatic and polyaromatic compounds (benzene, toluene,o-xylene, naphthalene) degraded under aerobic conditions only. The organochlorine compounds (trichloroethylene, tetrachloroethylene, 1,1,1-trichloroethane, 1,4-dichlorobenzene and 1,2-dichlorobenzene) showed little or no sign of degradation either aerobically or anaerobically. Interpretation of the data was complicated by strong sorption to the Villa Farm sediment but tetrachloromethane, nitrobenzene, ando-nitrophenol appeared to degrade under anaerobic conditions only. Phenol degraded rapidly under both sets of conditions.