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91.
D. C. Mason I. J. Davenport R. A. Flather C. Gurney G. J. Robinson J. A. Smith 《Estuarine, Coastal and Shelf Science》2001,53(6):759
A sensitivity analysis of the waterline method of constructing a Digital Elevation Model (DEM) of an intertidal zone using remote sensing and hydrodynamic modelling is described. Variation in vertical height accuracy as a function of beach slope is investigated using a set of nine ERS Synthetic Aperture Radar (SAR) images of the Humber/Wash area on the English east coast acquired between 1992 and 1994. Waterlines from these images are heighted using a hydrodynamic tide-surge model and interpolated using block kriging. On 1:500 slope beaches, an average block height estimation standard deviation of 18–22 cm is achieved. This rises to 27 cm on 1:100 slope beaches, and 32 cm on 1:30 slope beaches. The average heighting error at different slopes is decomposed into components due to waterline heighting error, inadequate sensor resolution and interpolation inaccuracy. It is shown that, at 1:500 slope, waterline heighting error and interpolation inaccuracy are the main error sources, whilst at 1:30 slope, errors due to inadequate sensor resolution become dominant. The ability of the technique to generate intertidal DEMs for almost the entire coastal zone in a complete ERS SAR scene covering 100×100 km is demonstrated. 相似文献
92.
ABSTRACT Environmental sustainability and the long-term wellbeing of Māori (the indigenous people of New Zealand) are interdependent and degradation of landscapes risks the progressive degradation of Māori wellbeing. The present study developed an analysis framework based on Ki Uta Ki Tai (holistic-mountains to the sea- management philosophy advocated by Ngāi Tahu) for exploring relationships between landcover and Māori values to enable predictions of cultural values through space and time. We used this framework to predict how two Māori values (Overall Health and Cultural Land Use) have been altered as a result of landcover change between 2001–2012 in three Canterbury catchments. The area of native vegetation declined while exotic pasture increased between 2001–2012, and there were corresponding declines in both cultural health scores. These results suggest that the change in landcover has reduced the ability of the landscape to support Māori values. This framework for assessing changes in Māori values with respect to changing environmental conditions may identify opportunities for Māori to better engage in land use management decisions. 相似文献
93.
94.
This study presents the results of the decoupling of a free-roll decay test by wavelet transforms. A free-roll decay test was performed to determine the coefficients of damping terms in equations of motion. No motion of the model was restricted during the experiment. A slight yaw motion was found while the model was in the free-roll decay motion. It was necessary to extract a pure roll motion from the experimental data. Wavelet transforms were applied to the signals to extract the pure roll motion. The results were compared to those found through the Fourier transform. Discrete wavelet transforms were able to efficiently decouple the test signals, while the continuous wavelet transform and the Fourier transform could not. 相似文献
95.
Julian Augley Mark Huxham Teresa F. Fernandes Alastair R. Lyndon Sarah Bury 《Estuarine, Coastal and Shelf Science》2007,72(4):648-656
The stable carbon isotope ratios (δ13C) of the organic fraction of intertidal sediments in the Forth Estuary and the Firth of Forth, Scotland, were measured to determine if terrestrially derived carbon was present in the estuarine sediments. It was hypothesised that differences in the inputs from marine vs. terrestrial sources to the organic carbon of estuarine and marine sediments, as well as differences in ambient seawater stable oxygen isotope (δ18O) ratios between the estuary and the Outer Firth, would allow the use of these two stable isotopes as habitat markers for juvenile plaice (Pleuronectes platessa), to allow determination of nursery habitats. Muddy and sandy sediments from the estuary and sandy sediments from the Outer Firth were sampled and δ13C measured. Juvenile plaice were caught at two estuarine sites and at two Outer Firth sites and otoliths were removed for δ13C and δ18O analysis. The sandy sediments in the estuary showed a strong gradient of δ13C enrichment with distance down the estuary, while the muddy sediments showed a much shallower gradient. δ13C and δ18O measured in the carbonate of juvenile plaice otoliths showed no clear difference between otoliths of fish caught at one of the estuarine sites and at the two Outer Firth sites. However, the isotope ratios of both carbon and oxygen in plaice otoliths from the other estuarine site showed the expected trend of depletion in the heavier isotopes. While the measurements recorded here did not conclusively distinguish between otoliths from juveniles caught in the estuarine site and those caught in the other three sites, they show that stable isotopes have potential to distinguish between estuarine habitats with terrestrial carbon inputs, and coastal marine habitats with predominantly marine carbon inputs. 相似文献
96.
The seismic expression of a salt-filled channel which cuts across the Mid North Sea High in Quadrant 37 is described, with features interpreted as being produced by salt-edge dissolution forming both eastern and western margins of the channel. The apparent half-graben nature of the channel is shown to be only superficial, and due to complex faulting associated with, but not defining, its western margin. The shallower faulting here is a Mesozoic to early Tertiary growth fault related to local dissolution of Zechstein salt. The dissolution effect appears in turn to have been localized by the presence of a deeper fault that was already downthrown to the east in Zechstein times, when it seems to have limited the eastward progradation of Zechstein shelf carbonates and anhydrites, and had probably ceased to move significantly before the onset of the Late Cimmerian erosional phase. The origin of this arcuate fault is tentatively ascribed to subsidence around a granite batholith. Zechstein salt originally spread some distance to the east and west of the channel; it was dissolved from the edges inwards, mainly before the Late Cretaceous, giving rise to a thicker Mesozoic sequence on parts of the flanks of the channel than in the middle. Besides providing an interesting structural case history, the features described have implications regarding Zechstein sedimentation, reservoir potential, the tectonic history of the North Sea, and the nature of the Mid North Sea High itself. 相似文献
97.
在建筑工程中,现浇钢筋混凝土楼板出现裂缝的情况较多,这已成为影响住宅工程质量的一大通病。对其产生裂缝的原因进行了分析,并结合工程实际,就预防和综合治理提出了较全面的对策。 相似文献
98.
《Journal of Oceanography》2007,63(6):983-994
A mesoscale iron-enrichment study (SEEDS II) was carried out in the western subarctic Pacific in the summer of 2004. The iron
patch was traced for 26 days, which included observations of the development and the decline of the bloom by mapping with
sulfur hexafluoride. The experiment was conducted at almost the same location and the same season as SEEDS (previous iron-enrichment
experiment). However, the results were very different between SEEDS and SEEDS II. A high accumulation of phytoplankton biomass
(∼18 mg chl m−3) was characteristic of SEEDS. In contrast, in SEEDS II, the surface chlorophyll-a accumulation was lower, 0.8 to 2.48 mg m−3, with no prominent diatom bloom. Photosynthetic competence in terms of F
v/F
m for the total phytoplankton community in the surface waters increased after the iron enrichments and returned to the ambient
level by day 20. These results suggest that the photosynthetic physiology of the phytoplankton assemblage was improved by
the iron enrichments and returned to an iron-stressed condition during the declining phase of the bloom. Pico-phytoplankton
(<2 μm) became dominant in the chlorophyll-a size distribution after the bloom. We observed a nitrate drawdown of 3.8 μM in the patch (day 21), but there was no difference in silicic acid concentration between inside and outside the patch. Mesozooplankton
(copepod) biomass was three to five times higher during the bloom-development phase in SEEDS II than in SEEDS. The copepod
biomass increased exponentially. The grazing rate estimation indicates that the copepod grazing prevented the formation of
an extensive diatom bloom, which was observed in SEEDS, and led to the change to a pico-phytoplankton dominated community
towards the end of the experiment. 相似文献
99.
Atsushi Kaneda Hidetaka Takeoka Eiji Nagaura Yoshitsugu Koizumi 《Journal of Oceanography》2002,58(4):547-556
A cold-water intrusion, called a “bottom intrusion”, occurs in the lower layer of the Bungo Channel in Japan. It is an intrusion
from the shelf slope region of the Pacific Ocean margin in the south of the channel. In order to reveal the fundamental characteristics
of the bottom intrusion, we conducted long-term observations of water temperature at the surface and bottom layers of the
channel and 15-day current observations at the bottom of the shelf-break region. The long-term water temperature data indicated
that the bottom intrusion occurs repeatedly between early summer and late autumn, and its reiteration between early and mid-summer
causes a local minimum of water temperature in the lower layer in mid-summer. Moreover, the data revealed that most of the
bottom intrusions occurred in neap tidal periods. The current meter recorded a bottom intrusion with a speed of approximately
15 cm⋅s−1. The current meter also revealed that the intruded cold water slowly retreated back to the shelf slope region after the intrusion.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
100.
In-Seong Han Koichiro Kamio Takeshi Matsuno Atsuyoshi Manda Atsuhiko Isobe 《Journal of Oceanography》2001,57(2):235-249
Relation between internal waves with short time scale and density distribution near the shelf break in the East China Sea is studied utilizing moored current meters, thermometers and conductivity-temperature-depth (CTD) casts. A well developed pycnocline was frequently observed around 150–200 m depth near the shelf break accompanied with the development of internal waves with short time scale. During the cruise in May 1998, the intensified internal wave motion with short time scale and the distinct offshore flow were observed just below the lower pycnocline, which shoaled and extended above the shelf area. It is suggested that vertical mixing generated by amplified internal waves would produce cross-shelf ageostophic density current around the pycnocline. During the cruise in May 1999, on the other hand, the lower pycnocline was located offshore below the shelf break, and the internal wave motion was amplified just above the lower pycnocline. In this case, the offshore flow should be generated above the lower pycnocline, but vertical profiles of current velocity were not obtained because acoustic Doppler current profiler (ADCP) data were not available around the lower pycnocline. 相似文献