Are peatlands in different states with respect to their thermodynamic behaviour? A simple test of peatland energy and entropy budgets     

Fred Worrall  Ross Morrison  Chris Evans  Joerg Kaduk  Susan Page  Alex Cumming  Mark Rayment  Nicholas Kettridge 《水文研究》2021,35(12):e14431

Whilst all ecosystems must obey the second law of thermodynamics, these physical bounds and controls on ecosystem evolution and development are largely ignored across the ecohydrological literature. To unravel the importance of these underlying restraints on ecosystem form and function, and their power to inform our scientific understanding, we have calculated the entropy budget of a range of peat ecosystems. We hypothesize that less disturbed peatlands are ‘near equilibrium’ with respect to the second law of thermodynamics and thus respond to change by minimizing entropy production. This ‘near equilibrium’ state is best achieved by limiting evaporative losses. Alternatively, peatlands ‘far-from-equilibrium’ respond to a change in energy inputs by maximizing entropy production which is best achieved by increasing evapotranspiration. To test these alternatives this study examined the energy balance time series from seven peatlands across a disturbance gradient. We estimate the entropy budgets for each and determine how a change in net radiation (ΔR_n) was transferred to a change in latent heat flux (ΔλE). The study showed that: (i) The transfer of net radiation to latent heat differed significantly between peatlands. One group transferred up to 64% of the change in net radiation to a change in latent heat flux, while the second transferred as little as 27%. (ii) Sites that transferred the most energy to latent heat flux were those that produced the greatest entropy. The study shows that an ecosystem could be ‘near equilibrium’ rather than ‘far from equilibrium’.  相似文献   

A serious flooding event in Nigeria in 2012 with specific focus on Benue State: a brief review     

Susan Agada  N. Nirupama 《Natural Hazards》2015,77(2):1405-1414

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A sea surface height control dam at the Strait of Gibraltar     

Jim Gower 《Natural Hazards》2015,78(3):2109-2120

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HPToday: retrospective and prospective          下载免费PDF全文

Jim Buttle 《水文研究》2015,29(15):3441-3442

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Sensitivity of a hydraulic model to channel erosion uncertainty during extreme flooding          下载免费PDF全文

Jefferson S. Wong  Jim E. Freer  Paul D. Bates  David A. Sear  Elisabeth M. Stephens 《水文研究》2015,29(2):261-279

Recent research into flood modelling has primarily concentrated on the simulation of inundation flow without considering the influences of channel morphology. River channels are often represented by a simplified geometry that is implicitly assumed to remain unchanged during flood simulations. However, field evidence demonstrates that significant morphological changes can occur during floods to mobilize the boundary sediments. Despite this, the effect of channel morphology on model results has been largely unexplored. To address this issue, the impact of channel cross‐section geometry and channel long‐profile variability on flood dynamics is examined using an ensemble of a 1D–2D hydraulic model (LISFLOOD‐FP) of the ~1 : 2000 year recurrence interval floods in Cockermouth, UK, within an uncertainty framework. A series of simulated scenarios of channel erosional changes were constructed on the basis of a simple velocity‐based model of critical entrainment. A Monte‐Carlo simulation framework was used to quantify the effects of this channel morphology together with variations in the channel and floodplain roughness coefficients, grain size characteristics and critical shear stress on measures of flood inundation. The results showed that the bed elevation modifications generated by the simplistic equations reflected an approximation of the observed patterns of spatial erosion that enveloped observed erosion depths. The effect of uncertainty on channel long‐profile variability only affected the local flood dynamics and did not significantly affect the friction sensitivity and flood inundation mapping. The results imply that hydraulic models generally do not need to account for within event morphodynamic changes of the type and magnitude of event modelled, as these have a negligible impact that is smaller than other uncertainties, e.g. boundary conditions. Instead, morphodynamic change needs to happen over a series of events to become large enough to change the hydrodynamics of floods in supply limited gravel‐bed rivers such as the one used in this research. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

The need for national deep decarbonization pathways for effective climate policy     

Chris Bataille  Henri Waisman  Michel Colombier  Laura Segafredo  Jim Williams  Frank Jotzo 《Climate Policy》2016,16(4):S7-S26

Constraining global average temperatures to 2 °C above pre-industrial levels will probably require global energy system emissions to be halved by 2050 and complete decarbonization by 2100. In the nationally orientated climate policy framework codified under the Paris Agreement, each nation must decide the scale and method of their emissions reduction contribution while remaining consistent with the global carbon budget. This policy process will require engagement amongst a wide range of stakeholders who have very different visions for the physical implementation of deep decarbonization. The Deep Decarbonization Pathways Project (DDPP) has developed a methodology, building on the energy, climate and economics literature, to structure these debates based on the following principles: country-scale analysis to capture specific physical, economic and political circumstances to maximize policy relevance, a long-term perspective to harmonize short-term decisions with the long-term objective and detailed sectoral analysis with transparent representation of emissions drivers through a common accounting framework or ‘dashboard’. These principles are operationalized in the creation of deep decarbonization pathways (DDPs), which involve technically detailed, sector-by-sector maps of each country’s decarbonization transition, backcasting feasible pathways from 2050 end points. This article shows how the sixteen DDPP country teams, covering 74% of global energy system emissions, used this method to collectively restrain emissions to a level consistent with the 2 °C target while maintaining development aspirations and reflecting national circumstances, mainly through efficiency, decarbonization of energy carriers (e.g. electricity, hydrogen, biofuels and synthetic gas) and switching to these carriers. The cross-cutting analysis of country scenarios reveals important enabling conditions for the transformation, pertaining to technology research and development, investment, trade and global and national policies.

Policy relevance

In the nation-focused global climate policy framework codified in the Paris Agreement, the purpose of the DDPP and DDPs is to provide a common method by which global and national governments, business, civil society and researchers in each country can communicate, compare and debate differing concrete visions for deep decarbonization in order to underpin the necessary societal and political consensus to design and implement short-term policy packages that are consistent with long-term global decarbonization.  相似文献   

Distribution and Characteristics of Dinosaur Eggs in China     

HAO Ziguo  FEI Hongcai  HAO Qingqing  LIU Lian  Susan Turner 《《地质学报》英文版》2016,90(1):370-375

正China is one of the most prolific countries for dinosaur material in the world,from skeletons to footprints and eggs.At present,China has documented more than 160kinds of dinosaur,35 genera and 39 ichnospecies of dinosaur footprints,and 17 genera and 44 oospecies of dinosaur eggs.The dinosaur eggs in China are mainly distributed in Xinjiang,Inner Mongolia,Ningxia,Gansu,  相似文献   

Spatial and temporal constraints on regional-scale groundwater flow in the Pampa del Tamarugal Basin,Atacama Desert,Chile   总被引：1，自引：0，他引：1  

Richard S. Jayne  Ryan M. Pollyea  Justin P. Dodd  Elizabeth J. Olson  Susan K. Swanson 《Hydrogeology Journal》2016,24(8):1921-1937

Aquifers within the Pampa del Tamarugal Basin (Atacama Desert, northern Chile) are the sole source of water for the coastal city of Iquique and the economically important mining industry. Despite this, the regional groundwater system remains poorly understood. Although it is widely accepted that aquifer recharge originates as precipitation in the Altiplano and Andean Cordillera to the east, there remains debate on whether recharge is driven primarily by near-surface groundwater flow in response to periodic flood events or by basal groundwater flux through deep-seated basin fractures. In addressing this debate, the present study quantifies spatial and temporal variability in regional-scale groundwater flow paths at 20.5°S latitude by combining a two-dimensional model of groundwater and heat flow with field observations and δ¹⁸O isotope values in surface water and groundwater. Results suggest that both previously proposed aquifer recharge mechanisms are likely influencing aquifers within the Pampa del Tamarugal Basin; however, each mechanism is operating on different spatial and temporal scales. Storm-driven flood events in the Altiplano readily transmit groundwater to the eastern Pampa del Tamarugal Basin through near-surface groundwater flow on short time scales, e.g., 10⁰–10¹ years, but these effects are likely isolated to aquifers in the eastern third of the basin. In addition, this study illustrates a physical mechanism for groundwater originating in the eastern highlands to recharge aquifers and salars in the western Pampa del Tamarugal Basin over timescales of 10⁴–10⁵ years.  相似文献   

Estuarine Habitat and Demographic Factors Affect Juvenile Chinook (<Emphasis Type="Italic">Oncorhynchus tshawytscha</Emphasis>) Growth Variability in a Large Freshwater Tidal Estuary     

Pascale?A.?L.?GoertlerEmail author  Charles?A.?Simenstad  Daniel?L.?Bottom  Susan?Hinton  Lia?Stamatiou 《Estuaries and Coasts》2016,39(2):542-559

Estuarine rearing has been shown to enhance within watershed biocomplexity and support growth and survival for juvenile salmon (Oncorhynchus sp.). However, less is known about how growth varies across different types of wetland habitats and what explains this variability in growth. We focused on the estuarine habitat use of Columbia River Chinook salmon (Oncorhynchus tshawytscha), which are listed under the Endangered Species Act. We employed a generalized linear model (GLM) to test three hypotheses: (1) juvenile Chinook growth was best explained by temporal factors, (2) habitat, or (3) demographic characteristics, such as stock of origin. This study examined estuarine growth rate, incorporating otolith microstructure, individual assignment to stock of origin, GIS habitat mapping, and diet composition along ~130 km of the upper Columbia River estuary. Juvenile Chinook grew on average 0.23 mm/day in the freshwater tidal estuary. When compared to other studies in the basin our growth estimates from the freshwater tidal estuary were similar to estimates in the brackish estuary, but ~4 times slower than those in the plume and upstream reservoirs. However, previous survival studies elucidated a possible tradeoff between growth and survival in the Columbia River basin. Our GLM analysis found that variation in growth was best explained by habitat and an interaction between fork length and month of capture. Juvenile Chinook salmon captured in backwater channel habitats and later in the summer (mid-summer and late summer/fall subyearlings) grew faster than salmon from other habitats and time periods. These findings present a unique example of the complexity of understanding the influences of the many processes that generate variation in growth rate for juvenile anadromous fish inhabiting estuaries.  相似文献   

Emerging Asias: Transnational Forces,Developmental States,and “Asian Values”     

Jim Glassman 《The Professional geographer》2016,68(2):322-329

Discussions of East Asian developmental states and Asian values discourse have been deformed by national-territorial frameworks that limit scholars' ability to highlight transnational phenomena. Such limits can be overcome by adopting a “Pacificist” perspective, one that highlights the transnational collaborative efforts of Pacific ruling class members, from both Asia and the United States. Such a Pacificist approach has the virtue of highlighting phenomena of transnational class formation that help account for the emergence of both developmental states in East Asia and Asian values discourse, and it also suggested the importance of attending to other kinds of emerging actors in Asian development politics, such as labor and democracy movements.  相似文献