Geochemistry and evolution of the fuego volcanic complex, Guatemala     

Craig A Chesner  William I Rose Jr. 《Journal of Volcanology and Geothermal Research》1984,21(1-2)

Four closely spaced vents along a fissure make up the Fuego and Acatenango volcanic centers in western Guatemala. The Fuego complex is composed of the Fuego and Meseta vents, but historic activity has consisted exclusively of high-Al₂O₃ basalts from the Fuego vent. The Meseta vent is inactive and deeply exposed. Prehistoric lavas from Fuego and Meseta are generally more silicic than historic Fuego lavas, but all the rocks form a single coherent geochemical variation pattern. Major element chemistry of these rocks is consistent with plagioclase, olivine, augite, and magnetite (POAM) fractionating from high-Al₂O₃ basalt. Separate batches of magma can be recognized from trace-element data throughout the history of the Fuego complex. This suggests that closed-system, POAM fractionation of distinct magma bodies occurs at Fuego. Trace-element data requires that deep fractionation of olivine, clinopyroxene, and perhaps magnetite from primary olivine tholeiite occurs before arrival of new magma into the shallow (8–16 km) magma chamber at Fuego. Migration of activity from Meseta to Fuego along the fissure is correlated with the change towards more mafic compositions at Fuego. The shift of the vents may have resulted in shorter repose periods and less time for fractionation before eruption. A minimum age of 17,000 years was required to build the Fuego complex.The andesitic rocks from the adjacent, larger composite volcanoes of Acatenango and Agua have higher incompatible element concentrations, different incompatible element ratios, and lower CaO, Na₂O, and Al₂O₃ contents than Fuego's lavas. We believe the magmatic evolution of Acatenango and Agua is much more complex than Fuego.  相似文献   

Sedimentary macrofossil records reveal ecological change in English lakes: implications for conservation     

Helen Bennion  Carl D. Sayer  Stewart J. Clarke  Thomas A. Davidson  Neil L. Rose  Ben Goldsmith  Ruth Rawcliffe  Amy Burgess  Gina Clarke  Simon Turner  Emma Wiik 《Journal of Paleolimnology》2018,60(2):329-348

Aquatic macrophytes play a key role in providing habitat, refuge and food for a range of biota in shallow lakes. However, many shallow lakes have experienced declines in macrophyte vegetation in recent decades, principally due to eutrophication. As changes in macrophyte composition and abundance can affect overall ecological structure and function of a lake, an assessment of the timing and nature of such changes is crucial to our understanding of the wider lake ecosystem. In the typical absence of historical plant records, the macro-remains of macrophytes preserved in lake sediments can be used to assess long-term changes in aquatic vegetation. We generated recent (150–200 years) plant macrofossil records for six English lakes subject to conservation protection to define past macrophyte communities, assess trajectories of ecological change and consider the implications of our findings for conservation targets and strategies. The data for all six lakes reveal a diverse submerged macrophyte community, with charophytes as a key component, in the early part of the sedimentary records. The stratigraphies indicate considerable change to the aquatic vegetation over the last two centuries with a general shift towards species more typically associated with eutrophic conditions. A common feature is the decline in abundance of low-growing charophytes and an increase in tall canopy-forming angiosperms such as fine-leaved Potamogeton species, Zannichellia palustris and Callitriche species. We hypothesise, based on findings from long-term datasets and palaeoecological records from enriched shallow lakes where plants are now absent, that the observed shifts provide a warning to managers that the lakes are on a pathway to complete macrophyte loss such that nutrient load reduction is urgently needed. It is the sound understanding of present-day plant ecology that affords such reliable interpretation of the fossil data which, in turn, provide valuable context for current conservation decisions.  相似文献   

Trade-offs between mitigation costs and temperature change     

Geoffrey Blanford  James Merrick  Richard Richels  Steven Rose 《Climatic change》2014,123(3-4):527-541

This paper uses the MERGE integrated assessment model to identify the least-cost mitigation strategy for achieving a range of climate policies. Mitigation is measured in terms of GDP foregone. This is not a benefit-cost analysis. No attempt is made to calculate the reduction in damages brought about by a particular policy. Assumptions are varied regarding the availability of energy-producing and energy-using technologies. We find pathways with substantial reductions in temperature change, with the cost of reductions varying significantly, depending on policy and technology assumptions. The set of scenarios elucidates the potential energy system transformation demands that could be placed on society. We find that policy that allows for “overshoot” of a radiative forcing target during the century results in lower costs, but also a higher temperature at the end of the century. We explore the implications of the costs and availability of key mitigation technologies, including carbon capture and storage (CCS), bioenergy, and their combination, known as BECS, as well as nuclear and energy efficiency. The role of “negative emissions” via BECS in particular is examined. Finally, we demonstrate the implications of nationally adopted emissions timetables based on articulated goals as a counterpoint to a global stabilization approach.  相似文献   

Non-Kyoto radiative forcing in long-run greenhouse gas emissions and climate change scenarios     

Steven K. Rose  Richard Richels  Steve Smith  Keywan Riahi  Jessica Strefler  Detlef P. van Vuuren 《Climatic change》2014,123(3-4):511-525

Climate policies must consider radiative forcing from Kyoto greenhouse gases, as well as other forcing constituents, such as aerosols and tropospheric ozone that result from air pollutants. Non-Kyoto forcing constituents contribute negative, as well as positive forcing, and overall increases in total forcing result in increases in global average temperature. Non-Kyoto forcing modeling is a relatively new component of climate management scenarios. This paper describes and assesses current non-Kyoto radiative forcing modeling within five integrated assessment models. The study finds negative forcing from aerosols masking (offsetting) approximately 25 % of positive forcing in the near-term in reference non-climate policy projections. However, masking is projected to decline rapidly to 5–10 % by 2100 with increasing Kyoto emissions and assumed reductions in air pollution—with the later declining to as much as 50 % and 80 % below today’s levels by 2050 and 2100 respectively. Together they imply declining importance of non-Kyoto forcing over time. There are however significant uncertainties and large differences across models in projected non-Kyoto emissions and forcing. A look into the modeling reveals differences in base conditions, relationships between Kyoto and non-Kyoto emissions, pollution control assumptions, and other fundamental modeling. In addition, under climate policy scenarios, we find air pollution and resulting non-Kyoto forcing reduced to levels below those produced by air pollution policies alone—e.g., China sulfur emissions fall an additional 45–85 % by 2050. None of the models actively manage non-Kyoto forcing for climate implications. Nonetheless, non-Kyoto forcing may be influencing mitigation results, including allowable carbon dioxide emissions, and further evaluation is merited.  相似文献   

Evaluating rainfall patterns using physics scheme ensembles from a regional atmospheric model   总被引：2，自引：0，他引：2  

Fei Ji  Marie Ekström  Jason P. Evans  Jin Teng 《Theoretical and Applied Climatology》2014,115(1-2):297-304

This study evaluated the ability of Weather Research and Forecasting (WRF) multi-physics ensembles to simulate storm systems known as East Coast Lows (ECLs). ECLs are intense low-pressure systems that develop off the eastern coast of Australia. These systems can cause significant damage to the region. On the other hand, the systems are also beneficial as they generate the majority of high inflow to coastal reservoirs. It is the common interest of both hazard control and water management to correctly capture the ECL features in modeling, in particular, to reproduce the observed spatial rainfall patterns. We simulated eight ECL events using WRF with 36 model configurations, each comprising physics scheme combinations of two planetary boundary layer (pbl), two cumulus (cu), three microphysics (mp), and three radiation (ra) schemes. The performance of each physics scheme combination and the ensembles of multiple physics scheme combinations were evaluated separately. Results show that using the ensemble average gives higher skill than the median performer within the ensemble. More importantly, choosing a composite average of the better performing pbl and cu schemes can substantially improve the representation of high rainfall both spatially and quantitatively.  相似文献   

Sediments of Lake Vens (SW European Alps,France) record large-magnitude earthquake events     

Jade Petersen  Bruno Wilhelm  Marie Revel  Yann Rolland  Christian Crouzet  Fabien Arnaud  Elodie Brisset  Eric Chaumillon  Olivier Magand 《Journal of Paleolimnology》2014,51(3):343-355

We studied sediment cores from Lake Vens (2,327 m asl), in the Tinée Valley of the SW Alps, to test the paleoseismic archive potential of the lake sediments in this particularly earthquake-sensitive area. The historical earthquake catalogue shows that moderate to strong earthquakes, with intensities of IX–X, have impacted the Southern Alps during the last millennium. Sedimentological (X-ray images, grain size distribution) and geochemical (major elements and organic matter) analyses show that Lake Vens sediments consist of a terrigenous, silty material (minerals and organic matter) sourced from the watershed and diatom frustules. A combination of X-ray images, grain-size distribution, major elements and magnetic properties shows the presence of six homogenite-type deposits interbedded in the sedimentary background. These sedimentological features are ascribed to sediment reworking and grain sorting caused by earthquake-generated seiches. The presence of microfaults that cross-cut the sediment supports the hypothesis of seismic deposits in this system. A preliminary sediment chronology is provided by ²¹⁰Pb measurement and AMS ¹⁴C ages. According to the chronology, the most recent homogenite events are attributable to damaging historic earthquakes in AD 1887 (Ligure) and 1564 (Roquebillière). Hence, the Lake Vens sediment recorded large-magnitude earthquakes in the region and permits a preliminary estimate of recurrence time for such events of ~400 years.  相似文献   

Internal and forced variability along a section between Greenland and Portugal in the CLIPPER Atlantic model     

Anne Marie Treguier  Claire Gourcuff  Pascale Lherminier  Herle Mercier  Bernard Barnier  Gurvan Madec  Jean-Marc Molines  Thierry Penduff  Lars Czeschel  Claus Böning 《Ocean Dynamics》2006,56(5-6):568-580

Numerical models are used to estimate the meridional overturning and transports along the paths of two hydrographic cruises, carried out in 1997 and 2002 from Greenland to Portugal. We have examined the influence of the different paths of the two cruises and found that it could explain 0.4 to 2 Sv of difference in overturning (the precise value is model-dependent). Models show a decrease in the overturning circulation between 1997 and 2002, with different amplitudes. The CLIPPER ATL6 model reproduces well the observed weakening of the overturning in density coordinates between the cruises; in the model, the change is due to the combination of interannual and high-frequency forcing and internal variability associated with eddies and meanders. Examination of the -coordinate overturning reveals model–data discrepancies: the vertical structure in the models does not change as much as the observed one. The East Greenland current variability is mainly wind-forced in the ATL6 model, while fluctuations due to eddies and instabilities explain a large part of the North Atlantic Current variability. The time-residual transport of dense water and heat due to eddy correlations between currents and properties is small across this section, which is normal to the direction of the main current.  相似文献   

Discussion of ‘Oceanographic and eustatic control of carbonate platform evolution and sequence stratigraphy on the Cretaceous (Valanginian–Campanian) passive margin,northern Gulf of Mexico’ by Phelps et al. (2014), Sedimentology, 61, 461–496          下载免费PDF全文

Peter R. Rose 《Sedimentology》2017,64(3):854-857

Errors in Phelps et al. ( 2014 ) arise from: (i) inclusion of the East Texas Basin and basin‐flank formations in a regional stratigraphic transect purported to represent the San Marcos Arch (axis of the Comanche Platform, central and south Texas); and (ii) revision of Edwards Group strata (Person Formation) that ignores well‐documented studies in the subsurface and adjacent outcrops in the Balcones fault zone and Edwards Plateau. Consequently, the Upper Albian Composite Sequence 104–101 of Phelps et al. ( 2014 ) should be revised from one cycle to three and the upper boundary of the Albian Supersequence should be elevated to 99·6 Ma.  相似文献   

Unpacking the complex nature of cooperative interactions: case studies of Israeli–Palestinian environmental cooperation in the greater Bethlehem area     

Kyra Marie Reynolds 《GeoJournal》2017,82(4):701-719

In the last few decades, a growing number of theorists have suggested that the natural environment can be a platform for promoting cooperation between former adversaries and can perhaps contribute to peacebuilding. However, environmental cooperation has not lived up to these claims. In many cases, such cooperation has largely been ineffective and/or inequitable. Therefore, there is a growing awareness that we cannot be overly optimistic at the first signs of ‘cooperation’. It is argued that this reality results from the great complexity inherent in cooperative interactions. This paper explores the nature of such cooperation in two Israeli–Palestinian case studies. The Israeli–Palestinian conflict is one of the longest-running protracted conflicts in the modern era and is currently characterised by a political stalemate. However, there is also a willingness by some at the local level to cooperate. Therefore Israel/Palestine provides an ideal case study. The findings of the paper illuminate the complex nature of environmental cooperation and reveal that even with the presence of good intentions, cooperation at the subnational level is impacted by the broader socio-political structures and contexts within which it is embedded. In these case studies, this is negatively affecting both the nature and scale of the processes and outcomes. Ultimately, these factors are making such interactions limited, unstable and/or prone to collapse. The paper concludes that only by conducting in-depth multi-tiered and context-specific analyses of cooperative processes and subsequently finding ways to overcome the identified barriers can we move towards more successful environmental cooperation.  相似文献   

Preliminary study on the preservation of giant clam (Tridacnidae) shells from the Balobok Rockshelter archaeological site,south Philippines     

Marie Grace Pamela G. Faylona  Claire E. Lazareth  Anne‐Marie Smah  Sandrine Caquineau  Hugues Boucher  Wilfredo P. Ronquillo 《Geoarchaeology》2011,26(6):888-901

Tridacnidae shells, a valuable archive of past environments, are common in the Balobok Rockshelter archaeological site on Sanga‐Sanga Island in the south Philippines. This site was occupied during the mid‐Holocene (ca. 5000–8800 ¹⁴C yr B.P.), a period of Neolithic cultural expansion in the Philippines. This paper focuses on the preservation of two shell specimens, Hippopus hippopus and Tridacna maxima, unearthed from two mid‐Holocene layers within the rockshelter. The shells' mineralogy and microstructure (prismatic and crossed‐lamellar) were studied using micro‐Fourier transform infrared spectroscopy and scanning electron microscopy to determine if the samples were suitable as paleoenvironmental records. Both shells are still aragonitic but aragonite crystals of both microstructure types are partly dissolved. This dissolution, characteristic of meteoric water alteration, precludes their utility in paleoenvironmental geochemical studies. Nevertheless, these shells are abundant in archaeological sites in the region and may be better preserved in other depositional contexts; more studies on Philippine Tridacnidae shell diagenesis are needed. © 2011 Wiley Periodicals, Inc.  相似文献