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111.
Properties of suspended sediment in the estuarine turbidity maximum of the highly turbid Humber Estuary system, UK 总被引:1,自引:0,他引:1
Measurements are presented of the properties of suspended particulate matter (SPM) in the estuarine turbidity maximum (ETM) of the upper Humber and Ouse estuaries during transient, relatively low freshwater inflow conditions of September 1995. Very high concentrations of near-bed SPM (more than 100 g l−1) were observed in the low-salinity (less than 1), upper reaches. SPM within the ETM consisted largely of fine sediment (silt and clay) that existed as microfloc and macrofloc aggregates and individual particles. Primary sediment particles were very fine grained, and typically, about 20–30% was clay-sized at high water. The clay mineralogy was dominated by chlorite and illite. There was a pronounced increase in particle size in the tidal river, up-estuary of the ETM. The mean specific surface area (SSA) of near-bed SPM within the ETM was 22 m2 g−1 on a spring tide and 24 m2 g−1 on a neap tide. A tidal cycle of measurements within a near-bed, high concentration SPM layer during a very small neap tide gave a mean SSA of 26 m2 g−1. The percentage of silt and clay in surficial bed sediments along the main channel of the estuary varied strongly. The relatively low silt and clay percentage of surficial bed sediments (about 10–35%) within the ETM’s region of highest near-bed SPM concentrations and their low SSA values were in marked contrast to the overlying SPM. The loss on ignition (LOI) of near-bed SPM in the turbid reaches of the estuary was about 10%, compared with about 12% for surface SPM and more than 40% in the very low turbidity waters up-estuary of the ETM. Settling velocities of Humber–Ouse SPM, sampled in situ and measured using a settling column, maximized at 1.5 mm s−1 and exhibited hindered settling at higher SPM concentrations. 相似文献
112.
M. J. Grosskopf R. P. Drake C. C. Kuranz A. R. Miles J. F. Hansen T. Plewa N. Hearn D. Arnett J. C. Wheeler 《Astrophysics and Space Science》2009,322(1-4):57-63
The National Ignition Facility (NIF) will soon provide experiments with far more than ten times the energy than has been previously available on laser facilities. In the context of supernova-relevant hydrodynamics, this will enable experiments in which hydrodynamic instabilities develop from multiple, coupled interfaces in a diverging explosion. This paper discusses the design of such blast-wave-driven explosions in which the relative masses of the layers are scaled to those within the star. It reports scaling simulations with CALE to model the global dynamics of such an experiment. CALE is a hybrid, Arbitrary Lagrangian-Eulerian code. The simulations probed the instability growth and multi-interface interactions in mass-scaled systems using different materials. The simulations assist in the target design process and in developing an experiment that can be diagnosed. 相似文献
113.
Ulyana A. Dyudina Andrew P. Ingersoll Carolyn C. Porco William Kurth Anthony Del Genio Joseph Ferrier 《Icarus》2007,190(2):545-555
We report on Cassini Imaging Science Subsystem (ISS) data correlated with Radio and Plasma Wave Science (RPWS) observations, which indicate lightning on Saturn. A rare bright cloud erupt at ∼35° South planetocentric latitude when radio emissions (Saturn Electrostatic Discharges, or SEDs) occur. The cloud consisting of few consecutive eruptions typically lasts for several weeks, and then both the cloud and the SEDs disappear. They may reappear again after several months or may stay inactive for a year. Possibly, all the clouds are produced by the same atmospheric disturbance which drifts West at 0.45 °/day. As of March 2007, four such correlated visible and radio storms have been observed since Cassini Saturn Orbit Insertion (July 2004). In all four cases the SEDs are periodic with roughly Saturn's rotation rate (h10m39), and show correlated phase relative to the times when the clouds are seen on the spacecraft-facing side of the planet, as had been shown for the 2004 storms in [Porco, C.C., and 34 colleagues, 2005. Science 307, 1243-1247]. The 2000-km-scale storm clouds erupt to unusually high altitudes and then slowly fade at high altitudes and spread at low altitudes. The onset time of individual eruptions is less than a day during which time the SEDs reach their maximum rates. This suggests vigorous atmospheric updrafts accompanied by strong precipitation and lightning. Unlike lightning on Earth and Jupiter, where considerable lightning activity is known to exist, only one latitude on Saturn has produced lightning strong enough to be detected during the two and a half years of Cassini observations. This may partly be a detection issue. 相似文献
114.
Randall J. Schaetzl Helen Enander Michael D. Luehmann David P. Lusch Carolyn Fish Michael Bigsby 《自然地理学》2013,34(1):2-39
Abstract We present a new physiographic map of Michigan, that is also available interactively, online. Only four, small-scale physiographic maps of Michigan had been previously published. Our mapping project made use of a wide variety of spatial data, in a GIS environment, to visualize and delineate the physical landscape in more detail than has been done previously. We also examined many of the unit boundaries in the field, using a GIS running on a GPS-enabled laptop. Unlike previous physiographic maps, the online version of the map enables users to query the criteria used to define each of the 224 boundaries of its 10 major and 91 minor physiographic units. The interactive nature of the online version of the map is a unique enhancement to physiographic maps and mapping. Our study also provides data on the number and types of criteria used to define each of the 224 unit boundaries within the map. Most of our unit boundaries are based on data derived from 10-m raster elevation data and NRCS soils data, e.g., relief, soil wetness, escarpments, landscape fabric, and parent material characteristics. Data gleaned from NRCS SSURGO county-scale soil maps were a strength of the project. [Key words: Michigan, physiography, landforms, soils, GIS, mapping] 相似文献
115.
Carolyn W. Burns 《新西兰海洋与淡水研究杂志》2013,47(1):149-150
Calamoecia lucasi was found with Boeckella propinqua in the Kaihoka Lakes, Nelson, and Boeckella hamata with Boeckella triarticulata in Lake Elterwater, Marlborough. These are the first records of C. lucasi in the South Island, New Zealand, and of B. hamata co‐occurring with B. triarticulata. 相似文献
116.
117.
Differences between males and females in the morphology of the fifth legs were found in stage IV copepodites of Boeckella hamata and in stage V cope‐podites of B. hamata, B. propinqua, B. dilatata, B. triarticulata, and Calamoecia lucasi. There were also sexual differences in overall body size. In B. hamata, B. triarticulata, and B. dilatata, the differences were sufficiently obvious for stage V copepodites to be sexed at low magnifications. The diagnostic features of all stages are described. 相似文献
118.
Extensive areas of methane-derived authigenic carbonate (MDAC) have been mapped in the Irish Sea. In the Irish Sector, 23
seabed mounds associated with the Codling Fault Zone were identified by multi-beam echo sounder mapping. Inspection by ROV-mounted
video showed that these mounds are rocky features rising 5–10 m above the normal seabed; sampling showed that they are comprised
of quartz grains bound together by carbonate cement, probably MDAC. Two separate locations have been mapped in the UK Sector.
At Texel 11, seabed mounds and a 6–8 m high cliff were mapped geophysically (MBES, SSS and seismic profiler surveys). Video
surveys showed that both the mounds and the cliff are rocky reefs colonised by a prolific fauna. Samples proved to be carbonate-cemented
sediments, and carbon isotope analysis (δ13C −41 to −46% PDB) showed that the cement was MDAC. Similar surveys of the Holden’s Reefs area proved the presence of similar
rocky reefs which are also cemented by MDAC. The total area covered by these two MDAC occurrences is estimated to be >500,000 m2. These MDAC occurrences are comparable in nature and formation to the ‘bubbling reefs’ of the Kattegat. As the bubbling reefs
are “seabed features formed by leaking gas”, one of the marine habitats identified by the European Commission’s Habitats Directive
as being sensitive and worthy of protection, it is suggested that the Irish Sea carbonate reefs should also be considered
as special habitats. 相似文献
119.
No-take marine protected areas (MPAs), where all fishing is prohibited, have been shown to provide benefits that include greater productivity of fish stocks due to increased densities, average sizes, and reproductive output. A critical component of this success is the effective management of MPAs to ensure that only those activities deemed permissible, are allowed to occur. As of 2008, 161 MPAs had been designated on the Pacific coast of Canada by federal, provincial or municipal authorities. The objective of this study was to discover how many of these MPAs are intended to provide full protection to habitats and species from commercial fishing and whether management measures were put in place to actualize this conservation intent. The comprehensive spatial dataset was built illustrating commercial fisheries closures and this was overlaid with MPA locations in a GIS. The majority of MPAs were designated as IUCN Strict Nature Reserve (Type Ia), Wilderness Area (Type Ib), and National Park (Type II) marine reserves, which are intended to be free from exploitation. It was found that 160 of the 161 MPAs are open to some commercial harvesting within their bounds. One small municipal MPA and portions of three other MPAs are not open to commercial harvesting. The incongruence between management intent and fisheries permitted suggests a management failure between designation of MPAs and implementation of fisheries management regulations. 相似文献
120.
Steady convective exchange flows down slopes 总被引:2,自引:0,他引:2
Jeff J. Sturman Carolyn E. Oldham Greg N. Ivey 《Aquatic Sciences - Research Across Boundaries》1999,61(3):260-278