Topographic change and numerically modelled near surface wind flow in a bowl blowout     

Thomas A.G. Smyth  Patrick A. Hesp  Ian J. Walker  Thad Wasklewicz  Paul A. Gares  Alexander B. Smith 《地球表面变化过程与地形》2019,44(10):1988-1999

A number of studies have measured and numerically modelled near surface wind velocity over a range of aeolian landforms and made suppositions about topographic change and landform evolution. However, the precise measurement and correlation of flow dynamics and resulting topographic change have not yet been fully realized. Here, using repeated high-resolution terrestrial laser scanning and numerical flow modelling within a bowl blowout, we statistically analyse the relationship between wind speed, vertical wind velocity, turbulent kinetic energy and topographic change over a 33-day period. Topographic results showed that erosion and deposition occurred in distinct regions within the blowout. Deposition occurred in the upwind third of the deflation basin, where wind flow became separated and velocity and turbulent kinetic energy decreased, and erosion occurred in the downwind third of the deflation basin, where wind flow reattached and aligned with incident wind direction. Statistical analysis of wind flow and topographic change indicated that wind speed had a strong correlation with overall topographic change and that vertical wind velocity (including both positive and negative) displayed a strong correlation with negative topographic change (erosion). Only weak or very weak correlations exist for wind flow parameters and positive topographic change (accretion). This study demonstrates that wind flow modelling using average incident wind conditions can be utilized successfully to identify regions of overall change and erosion for a complex aeolian landform, but not to identify and predict regions where solely accretion will occur. © 2019 John Wiley & Sons, Ltd.  相似文献   

Atmospheric river orientation determines flood occurrence     

Helen V. Griffith  Andrew J. Wade  David A. Lavers  Glenn Watts 《水文研究》2020,34(23):4547-4555

Atmospheric Rivers (ARs) have been linked to many of the largest recorded UK winter floods. These large-scale features can be 500–800 km in width but produce markedly different flood responses in adjacent catchments. Here we combine meteorological and hydrological data to examine why two impermeable catchments on the west coast of Britain respond differently to landfalling ARs. This is important to help better understand flood generation associated with ARs and improve flood forecasting and climate-change impact assessment. Analysis of 32 years of a newly available ERA5 high-resolution atmospheric reanalysis and corresponding 15-min river flow data show that the most impactful ARs arise through a combination of the orientation and magnitude of their water vapour flux. At the Dyfi catchment, AR orientations of between 238–258° result in the strongest hydrological responses, whereas at the Teifi the range is 224–243°. We believe this differential flood response is the result of catchment orientation and topography enhancing or suppressing orographic rainfall totals, even in relatively low-relief coastal catchments. Further to the AR orientation, ARs must have an average water vapour flux of 400–450 kg m⁻¹ s⁻¹ across their lifetime. Understanding the preferential properties of impactful ARs at catchments allows for the linking of large-scale synoptic features, such as ARs, directly to winter flood impacts. These results using two test catchments suggest a novel approach to flood forecasts through the inclusion of AR activity.  相似文献   

An archaeology of natural places     

William H. Walker 《Geoarchaeology》2004,19(5):503-505

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Origin and age of metal veins in Canyon Diablo graphite nodules     

Connor D. Hilton  Richard D. Ash  Philip M. Piccoli  David A. Kring  Timothy J. McCoy  Richard J. Walker 《Meteoritics & planetary science》2020,55(4):771-780

Previous studies attributed the origin of metal veins penetrating graphite nodules in the Canyon Diablo IAB main group iron meteorite to condensation from vapor or melting of host metal. Abundances of 16 siderophile elements measured in kamacite within vein and host meteorite are most consistent with an origin by melting of the host metal followed by fractional crystallization of the liquid. The presence of the veins within graphite nodules may be explained by impact, as peak shock temperatures, and thus the most likely areas to undergo metal melting are at metal–graphite interfaces. The origin of the veins is constrained by Re‐Os chronometry to have occurred early (>4 Ga) in solar system history.  相似文献   

Hybrid Neoliberalism: Implications for Sustainable Development     

Claudia Baldwin  Graham Marshall  Helen Ross  Jim Cavaye  Janet Stephenson  Lyn Carter 《社会与自然资源》2019,32(5):566-587

Neoliberalism is frequently blamed for challenges in achieving sustainable development; consequently some also question if sustainability is still a useful concept. Neoliberal influence on natural resource management has evolved over the last 30?years to a hybrid form that seeks to compensate for its negative social and environmental externalities. Through review of literature and critical analysis of three case studies of resource development in Australia and New Zealand, we argue that, in spite of modifications under hybrid approaches, neoliberalism still tests achievement of sustainability goals, due to privileging industry and shifting risk and costs to future generations, through inadequate regulation, neglect of public consultation, lack of transparency, and weak impact assessment. We suggest that while neoliberal approaches bring both benefits and disadvantages, sustainability principles must continue to be kept at the forefront of legislation, regulation and management.  相似文献   

Effects of the suspension feeding mussel Mytilus trossulus on a brackish water macroalgal and associated invertebrate community     

Jonne Kotta  Kristjan Herkül  Ilmar Kotta  Helen Orav-Kotta  & Velda Lauringson 《Marine Ecology》2009,30(S1):56-64

The importance of suspension-feeding mussels is particularly apparent in benthic communities; however, the role of this feeding strategy on the development of macroalgal and associated invertebrate communities is in general poorly known. The effect of suspension-feeding mussels Mytilus trossulus on benthic communities was studied in an in situ factorial field experiment in the Northern Baltic Sea over one ice-free season. The experiment was performed under different regimes of wave exposure (low and moderate) and on different sedimentary habitats (soft bottom with high organic content, soft bottom with low organic content, and hard bottom). In general the presence of mussels was associated with increased biomass of filamentous algae, herbivores and deposit feeders and decreased biomass of charophytes. The effect of M. trossulus interacted with the effect of exposure and substrate. Stronger responses were observed in moderately exposed than in sheltered areas. The presence of M. trossulus affected charophytes and deposit feeders on sand with low content of organic matter and filamentous algae on pebbles but not on other substrate types. The magnitude of the effects varied between months. The results suggest that (i) even in dynamic coastal systems the biodeposits and excretions of mussels are at least partly assimilated locally and are not flushed away to the open sea, (ii) the accumulation of faecal material induced elevated growth of deposit feeders, (iii) mussels enhanced the growth of ephemeral macroalgae and reduced the growth of perennial macroalgae, and (iv) together with increasing benthic primary production, mussels indirectly increase the production of herbivores.  相似文献   

Comparison of benthic and pelagic suspension feeding in shallow water habitats of the Northeastern Baltic Sea   总被引：1，自引：0，他引：1  

Velda Lauringson  Jonne Kotta  Helen Orav-Kotta  Ilmar Kotta  Kristjan Herkül  & Arno Põllumäe 《Marine Ecology》2009,30(S1):43-55

Combining field experiments with the biomass distribution data of dominant suspension feeders we compared the benthic and pelagic suspension feeding rates in shallow non-tidal brackish water coastal habitats. We found that pelagic grazing exceeded benthic grazing in almost all cases, on average from 14 to 4819 times depending on the site. Benthic grazing rates were related to site-specific environmental parameters and showed no relationship with water chlorophyl a (Chl a ) content, whereas pelagic grazing rates varied both spatially and temporally and were related to water Chl a content. Our results indicate that in several shallow coastal habitats, pelagic suspension feeding substantially exceeds benthic suspension feeding. This suggests that pelagic recycling is higher than the amounts of energy redirected from pelagic to benthic food webs by benthic suspension feeders. These results increase our knowledge of the energy flows in coastal ecosystems.  相似文献   

Selecting MPAs to conserve groundfish biodiversity: the consequences of failing to account for catchability in survey trawls     

Fraser  Helen M.; Greenstreet  S. P. R.; Piet  Gerjan J. 《ICES Journal of Marine Science》2009,66(1):82-89

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Using MPAs to address regional-scale ecological objectives in the North Sea: modelling the effects of fishing effort displacement   总被引：1，自引：0，他引：1  

Greenstreet  Simon P. R.; Fraser  Helen M.; Piet  Gerjan J. 《ICES Journal of Marine Science》2009,66(1):90-100

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From green spaces to vital places: connection and expression in urban greening     

Lisa de Kleyn  Laura Mumaw  Helen Corney 《The Australian geographer》2020,51(2):205-219

ABSTRACT

Urban greening, the improvement or increase of green spaces in cities, has purported environmental, individual, social and cultural benefits. The extent and qualities of urban green spaces, and our opportunities to engage with them, reflect and shape human responses to those spaces. Planning scholars recognise the traditional role and obligation of planning to help reduce social problems and see the potential for the public to be leaders in defining responses. However, use of technical, scientific and economic approaches by urban land managers can limit recognition of diverse connections to urban green and advance narrow conceptions of nature. We sample people’s responses to different forms of urban green and greening in three case studies from Melbourne, Australia. We show that modern connections and expressions are personal, social and dynamic. Human experiences are embedded in nature and connections develop from interactions with and about nature, in formal and informal spaces. Diverse connections prompt responses to nature, and actions affecting nature itself. Accordingly, we propose ways to develop more receptive, responsive, inclusive and connected forms of urban greening. These include recognising diverse connections and expressions, encouraging dynamic relationships with nature, and providing varied ways of engaging with urban green spaces that foster stewardship.  相似文献