Anthropogenic influences on shoreline and nearshore evolution in the San Francisco Bay coastal system   总被引：1，自引：0，他引：1  

Kate L. Dallas  Patrick L. Barnard 《Estuarine, Coastal and Shelf Science》2011

Analysis of four historical bathymetric surveys over a 132-year period has revealed significant changes to the morphology of the San Francisco Bar, an ebb-tidal delta at the mouth of San Francisco Bay estuary. From 1873 to 2005 the San Francisco Bar vertically-eroded an average of 80 cm over a 125 km² area, which equates to a total volume loss of 100 ± 52 million m³ of fine- to coarse-grained sand. Comparison of the surveys indicates the entire ebb-tidal delta contracted radially, with the crest moving landward an average of 1 km. Long-term erosion of the ebb-tidal delta is hypothesized to be due to a reduction in the tidal prism of San Francisco Bay and a decrease in coastal sediment supply, both as a result of anthropogenic activities. Prior research indicates that the tidal prism of the estuary was reduced by 9% from filling, diking, and sedimentation. Compilation of historical records dating back to 1900 reveals that a minimum of 200 million m³ of sediment has been permanently removed from the San Francisco Bay coastal system through dredging, aggregate mining, and borrow pit mining. Of this total, ∼54 million m³ of sand-sized or coarser sediment was removed from central San Francisco Bay. With grain sizes comparable to the ebb-tidal delta, and its direct connection to the bay mouth, removal of sediments from central San Francisco Bay may limit the sand supply to the delta and open coast beaches.  相似文献   

加拿大海王星:科学、运行、管理     

王克林  Kate Moran 《地球科学进展》2013,28(5):521-528

加拿大海王星是世界最大的海底缆接科学观测网,于2009年开始运行.它连接了位于不同水深和不同海洋地质环境的大批观测仪器,把数据连续不断地通过互联网传给科学家和大众.海王星的建立是为了推动地震过程和大地构造、海底地下流体、海洋生物与气候变化、深海生态系统、工程和信息科学等五大科学命题的研究.为最大程度地推动国际合作,加速科学发展步伐,它的系统使用完全开放,数据全部免费公开,这在科学史上前所未见.这种全方位、全开放的复杂庞大的科研系统需要高超的管理方法和优良的学术环境.  相似文献   

Interpreting What is Rural and Urban for Western U.S. Counties     

Kate A. Berry  Nancy L. Markee  Nanci Fowler  Gary R. Giewat 《The Professional geographer》2000,52(1):93-105

The paper examines how rural and urban are interpreted and applied to counties in eleven states in the western United States. After reviewing various conceptual approaches, we turn to a three‐part analysis of county commissioners' perceptions and census data to identify characteristics associated with urban‐ness and rurality. The analysis involves comparing qualitative and quantitative survey and interview data, using a multiple regression analysis to correlate census variables with commissioners' perceptions of their home counties, and using cluster analysis techniques on census variables to identify patterns and unevenness in rurality and urbanness. Three characteristics mentioned by the widest range of commissioners and found to be statistically significant in the regression analysis were population concentration, total population, and the agricultural land base. Population concentration, in particular, was identified most frequently by interviewees as the single most important variable in characterizing an urban county and had the most meaningful contribution to predicting commissioners' perceptions of their home counties in the regression analysis. The cluster analysis identified five county types: largest urban centers, growing regional hubs, high growth rural, dispersed rural, and stable rural agriculture. These county types were widely distributed, reflecting the spatial unevenness of macroscale processes operating across eleven western states.  相似文献   

Information infrastructure for Australia’s Integrated Marine Observing System     

Marton G. Hidas  Roger Proctor  Natalia Atkins  Julian Atkinson  Laurent Besnard  Peter Blain  Philip Bohm  Jon Burgess  Kim Finney  Dan Fruehauf  Guillaume Galibert  Xavier Hoenner  Jacqui Hope  Craig Jones  Sebastien Mancini  Benedicte Pasquer  David Nahodil  Kate Reid  Katherine Tattersall 《Earth Science Informatics》2016,9(4):525-534

Australia’s Integrated Marine Observing System (IMOS, imos.org.au) is research infrastructure to establish an enduring observing program for Australian oceanic waters and shelf seas. The observations cover physical, biological, and chemical variables to address themes of multi-decadal ocean change, climate variability and weather extremes, boundary currents and inter-basin flows, continental shelf processes and ecosystem responses.IMOS observations are collected by national facilities based on various platform types and operated by partner institutions around the country. In this paper we describe the infrastructure and workflows developed to manage and distribute the data to the public. We highlight the existing standards and open-source software we have adopted, and the contributions we have made. To demonstrate the value of this infrastructure we provide some illustrations of use and uptake.All IMOS data are freely and openly available to the public via the Ocean Portal (https://imos.aodn.org.au). All IMOS-developed software is open-source and accessible at https://github.com/aodn.  相似文献   

Storm Surges in the Strait of Georgia Simulated with a Regional Model     

Nancy Soontiens  Susan E. Allen  Doug Latornell  Kate Le Souëf  Idalia Machuca  Jean-Philippe Paquin 《大气与海洋》2016,54(1):1-21

The Strait of Georgia is a large, semi-enclosed body of water between Vancouver Island and the mainland of British Columbia connected to the Pacific Ocean via Juan de Fuca Strait at the south and Johnstone Strait at the north. During the winter months, coastal communities along the Strait of Georgia are at risk of flooding caused by storm surges, a natural hazard that can occur when a strong storm coincides with high tide. This investigation produces storm surge hindcasts using a three-dimensional numerical ocean model for the Strait of Georgia and the surrounding bodies of water (Juan de Fuca Strait, Puget Sound, and Johnstone Strait) collectively known as the Salish Sea. The numerical model employs the Nucleus for European Modelling of the Ocean architecture in a regional configuration. The model is evaluated through comparisons of tidal elevation harmonics and storm surge with observations. Important forcing factors contributing to storm surges are assessed. It is shown that surges entering the domain from the Pacific Ocean make the most significant contribution to surge amplitude within the Strait of Georgia. Comparisons between simulations and high-resolution and low-resolution atmospheric forcing further emphasize that remote forcing is the dominant factor in surge amplitudes in this region. In addition, local wind patterns caused a slight increase in surge amplitude on the mainland side of the Strait of Georgia compared with Vancouver Island coastal areas during a major wind storm on 15 December 2006. Generally, surge amplitudes are found to be greater within the Strait of Georgia than in Juan de Fuca Strait.  相似文献   

Voice Under Scrutiny: Feminist Methods,Anticolonial Responses,and New Methodological Tools     

Kate Coddington 《The Professional geographer》2017,69(2):314-320

“Giving voice” to participants has been an important element of qualitative feminist research projects in geography. In this article, I explore scholarship that has questioned qualitative research's reliance on voice, arguing that implicit connections between voice, authenticity, and empowerment are beginning to be unpacked, particularly by scholars engaged in anticolonial work. I draw on anticolonial scholarship to build on and extend feminist debates centered on voice and participation. Feminist attention to voice must be situated within the colonial frameworks and histories of social science research. Scholarship focused on ongoing settler colonial relationships highlights methods both for cautiously proceeding with and consciously refusing incorporating voice within qualitative research. I draw on anticolonial approaches to frame research decisions, voice, and the ethical and methodological dilemmas of its use.  相似文献   

Formation of a regional image through geography textbooks: The case of north-west Bohemia     

Silvie R. Kučerová  Zdeněk Kučera  Kateřina Novotná 《Norsk geografisk tidsskrift. Norwegian journal of geography》2018,72(3):176-195

The purpose of the article is to examine the ways in which regional geography textbooks are used in elementary education, using north-west Bohemia as a case study. The authors analysed 18 textbooks published since the beginning of the 20th century, in two steps: (1) the construction of geographical names frequency maps indicating which parts of the case region are accentuated or suppressed in individual textbooks, and (2) a qualitative analysis of the textbooks’ content. The study revealed that a complex image of north-west Bohemia in interwar period in Czechoslovakia and in the period of accession to the European Union is presented in the textbooks. The textbooks published during communist era are imbued with the adoration of local industries, whereas those published later, in the period of political and socio-economic transformation, accentuate the risks of excessive environmental exploitation. At any time since the beginning of the 20th century, the places and regions that represent the values preferred by the governing ideology are emphasized within the studied textbooks. Thus, the geography textbooks, that reflect the society-wide discourse, disseminate not only knowledge but also dominant values. In this way, a desired image of reality is created that legitimates the aims and stances of those in power.  相似文献   

A long‐term vegetation history of the Mojave–Colorado desert ecotone at Joshua Tree National Park     

Camille A. Holmgren  Julio L. Betancourt  Kate A. Rylander 《第四纪科学杂志》2010,25(2):222-236

Thirty‐eight dated packrat middens were collected from upper desert (930–1357 m) elevations within Joshua Tree National Park near the ecotone between the Mojave Desert and Colorado Desert, providing a 30 ka record of vegetation change with remarkably even coverage for the last 15 ka. This record indicates that vegetation was relatively stable, which may reflect the lack of invasion by extralocal species during the late glacial and the early establishment and persistence of many desert scrub elements. Many of the species found in the modern vegetation assemblages were present by the early Holocene, as indicated by increasing Sørenson's Similarity Index values. C₄ grasses and summer‐flowering annuals arrived later at Joshua Tree National Park in the early Holocene, suggesting a delayed onset of warm‐season monsoonal precipitation compared to other Sonoran Desert and Chihuahuan Desert localities to the east, where summer rains and C₄ grasses persisted through the last glacial–interglacial cycle. This would suggest that contemporary flow of monsoonal moisture into eastern California is secondary to the core processes of the North American Monsoon, which remained intact throughout the late Quaternary. In the Holocene, northward displacement of the jet stream, in both summer and winter, allowed migration of the subtropical ridge as far north as southern Idaho and the advection of monsoonal moisture both westward into eastern California and northward into the southern Great Basin and Colorado Plateau. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   

Avoiding deforestation in Panamanian protected areas: An analysis of protection effectiveness and implications for reducing emissions from deforestation and forest degradation     

Jordan S. Oestreicher  Karina Benessaiah  Maria C. Ruiz-Jaen  Sean Sloan  Kate Turner  Johanne Pelletier  Bruno Guay  Kathryn E. Clark  Dominique G. Roche  Manfred Meiners  Catherine Potvin 《Global Environmental Change》2009,19(2):279-291

Reducing greenhouse gas emissions from deforestation and forest degradation (REDD) is likely to be central to a post-Kyoto climate change mitigation agreement. As such, identifying conditions and factors that will shape the success or failure of a reduced deforestation scheme will provide important insights for policy planning. Given that protected areas (PAs) are a cornerstone in forest conservation, we draw on interviews and secondary data to analyze the effects of available PA resources, governance ability, the level of community involvement, and provincial deforestation rates on land-cover change in nine PAs in Panama. Our results illustrate that coupling surveillance measures with greater funding and strong governance are paramount to reducing deforestation. Alone, however, these factors are insufficient for forest protection. We argue that conservation approaches that complement effective surveillance with community participation and equitable benefit sharing will address the wider issues of leakage and permanence.  相似文献   

Lateglacial ice-cap dynamics in NW Scotland: evidence from the fjords of the Summer Isles region     

Martyn S. Stoker  Tom Bradwell  John A. Howe  Ian P. Wilkinson  Kate McIntyre 《Quaternary Science Reviews》2009,28(27-28):3161-3184

The seaboard of western Scotland is a classic fjord landscape formed by glaciation over at least the last 0.5 Ma. We examine the glacial geology preserved in the fjords (or sea lochs) of the Summer Isles region of NW Scotland using high-resolution seismic data, multibeam swath bathymetry, seabed sediment cores, digital terrain models, aerial photographs, and field investigations. Detailed analyses include seismic facies and lithofacies interpretations; sedimentological and palaeoenvironmental analyses; and radiocarbon dating of selected microfauna. Our results indicate that the Pleistocene sediments of the Summer Isles region, on- and offshore, can be subdivided into several lithostratigraphic formations on the basis of seismic character, geomorphology and sedimentology. These are: subglacial tills; ice-distal and glacimarine facies; ice-proximal and ice-contact facies; moraine assemblages; and Holocene basin fill. The submarine landscape is also notable for its large-scale mass-movement events – the result of glaciodynamic, paraglacial or seismotectonic processes. Radiocarbon dating of marine shells indicate that deglaciation of this part of NW Scotland was ongoing between 14 and 13 ka BP – during the Lateglacial Interstadial (Greenland Interstadial 1) – consistent with cosmogenic surface-exposure ages from previous studies. A sequence of numerous seafloor moraine ridges charts oscillatory retreat of the last ice sheet from a buoyant calving margin in The Minch to a firmly grounded margin amongst the Summer Isles in the early part of Lateglacial Interstadial (GI-1) (pre-14 ka BP). Subsequent, punctuated, frontal retreat of the ice mass occurred in the following ～1000 years, during which time ice-cap outlet glaciers became topographically confined and restricted to the fjords. A late-stage readvance of glaciers into the inner fjords occurred soon after 13 ka BP, which calls into question the accepted limits of ice extent during the Younger Dryas Stadial (Greenland Stadial 1). We examine the wider implications of our chronostratigraphic model, discussing the implications for British Ice Sheet deglaciation, Lateglacial climate change, and the style and rates of fjord sedimentation.  相似文献