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121.
Stephen M. Chiswell John R. Zeldis Mark G. Hadfield Matthew H. Pinkerton 《新西兰海洋与淡水研究杂志》2013,47(4):465-489
We present the results of a combined observational and numerical study to investigate cool plumes of nutrient-rich upwelled water that emanate near the Kahurangi Shoals and extend into Greater Cook Strait. Surface temperature and chlorophyll are mapped using satellite observations to produce surface climatologies, to validate a numerical simulation and to show the utility of using spatial temperature differences as a measure of upwelling. We find upwelling near the Kahurangi Shoals is strongly wind-driven in the weather band. Upwelling occurs at all times of the year, but its surface signature is only visible in summer months. The upwelled nutrient-rich water supports increased primary production compared to surrounding waters, particularly in summer when the water column is more stratified and surrounding surface waters are presumably nutrient depleted. 相似文献
122.
123.
George O. Marmorino Geoffrey B. Smith Jakov V. Toporkov Mark A. Sletten Dragana Perkovic Stephen J. Frasier 《Deep Sea Research Part I: Oceanographic Research Papers》2009,56(3):435-441
Airborne infrared and synthetic aperture radar imagery collected over the Gulf Stream are used to examine the surface patterns of small-scale thermal convection and wind-driven Langmuir circulation. These patterns have a thermal contrast of ~0.25 °C, which is roughly an order of magnitude larger than predicted by large-eddy simulations but consistent with the effect on surface temperature of surfactant accumulations induced by mixed-layer eddies. 相似文献
124.
Limonitic oncoliths from the Bajocian of Europe, widely known as ‘snuff-boxes’, grew by accretion of bundles of laminae on one side, followed by overturning and accretion of laminae on the other side. A diverse hard-substrate encrusting fauna grew interleaved with the ferruginous laminations. The palaeoecological preferences of this fauna indicate that its growth, and hence the accumulation of the laminations, took place on the gloomy undersides of the oncoliths. This upsidedown growth is supported by characteristics of the lamination bundles themselves, and by the predominant present-day orientations of the snuff-boxes. The abundance of the associated fauna and the lack of carbonate-dissolving macroborers cutting the laminae suggest an original ferric composition. Precipitation was probably under the control of non-photosynthetic microorganisms that inhabited the microenvironments represented by the oncoliths' lower surfaces. 相似文献
125.
126.
Takaaki Noguchi Tomoki Nakamura Kyoko Okudaira Hajime Yano Seiji Sugita Mark J. Burchell 《Meteoritics & planetary science》2007,42(3):357-372
Abstract— Outside the Earth's atmosphere, silica aerogel is one of the best materials to capture finegrained extraterrestrial particles in impacts at hypervelocities. Because silica aerogel is a superior insulator, captured grains are inevitably influenced by frictional heat. Therefore, we performed laboratory simulations of hypervelocity capture by using light‐gas guns to impact into aerogels finegrained powders of serpentine, cronstedtite, and Murchison CM2 meteorite. The samples were shot at >6 km s?1 similar to the flyby speed at comet P/Wild‐2 in the Stardust mission. We investigated mineralogical changes of each captured particle by using synchrotron radiation X‐ray diffraction (SR‐XRD), transmission electron microscope (TEM), and field emission scanning electron microscope (FE‐SEM). SR‐XRD of each grain showed that the majority of the bulk grains keep their original mineralogy. In particular, SR‐XRD and TEM investigations clearly exemplified the presence of tochilinite whose decomposition temperature is about 300 °C in the interior of the captured Murchison powder. However, TEM study of these grains also revealed that all the samples experienced melting and vesiculation on the surface. The cronstedtite and the Murchison meteorite powder show remarkable fracturing, disaggregation, melting, and vesiculation. Steep thermal gradients, about 2500 °C/μm were estimated near the surface of the grains (<2 μm thick) by TEM observation. Our data suggests that the interior of >4 μm across residual grains containing abundant materials that inhibit temperature rise would have not experienced >300 °C at the center. 相似文献
127.
Joshua Kurek Les C. Cwynar Thomas A. Ager Mark B. Abbott Mary E. Edwards 《Quaternary Science Reviews》2009,28(9-10):799-811
Fossil Chironomidae assemblages (with a few Chaoboridae and Ceratopogonidae) from Zagoskin and Burial Lakes in western Alaska provide quantitative reconstructions of mean July air temperatures for periods of the late-middle Wisconsin (~39,000–34,000 cal yr B.P.) to the present. Inferred temperatures are compared with previously analyzed pollen data from each site summarized here by indirect ordination. Paleotemperature trends reveal substantial differences in the timing of climatic warming following the late Wisconsin at each site, although chronological uncertainty exists. Zagoskin Lake shows early warming beginning at about 21,000 cal yr B.P., whereas warming at Burial Lake begins ~4000 years later. Summer climates during the last glacial maximum (LGM) were on average ~3.5 °C below the modern temperatures at each site. Major shifts in vegetation occurred from ~19,000 to 10,000 cal yr B.P. at Zagoskin Lake and from ~17,000 to 10,000 cal yr B.P. at Burial Lake. Vegetation shifts followed climatic warming, when temperatures neared modern values. Both sites provide evidence of an early postglacial thermal maximum at ~12,300 cal yr B.P. These chironomid records, combined with other insect-based climatic reconstructions from Beringia, indicate that during the LGM: (1) greater continentality likely influenced regions adjacent to the Bering Land Bridge and (2) summer climates were, at times, not dominated by severe cold. 相似文献
128.
Benjamin Poulter Rebecca L. Feldman Mark M. Brinson Benjamin P. Horton Michael K. Orbach Samuel H. Pearsall Enrique Reyes Stanley R. Riggs John C. Whitehead 《Ocean & Coastal Management》2009,52(3-4):147-153
Coastal areas are among the world's most vulnerable landscapes to impacts related to climate change, including inundation from sea-level rise (SLR), increased exposure to shoreline erosion, and greater frequency and intensity of storms. The status of research on the physical, ecological, and socio-economic effects of vulnerability to SLR and progress toward planning for its consequences varies from region to region worldwide. Here, we synthesize the results of three decades of SLR research and the development of coastal management policies in North Carolina, USA. We identify the major factors responsible for opening new policy ‘windows’ that address SLR, including how stakeholders have developed an increased understanding of the risks, the extent of public dialogue about potential response strategies, and advances in political receptivity to policy change. Research and policy progress in North Carolina continue to provide a model for other regions to help guide and evaluate the development of coastal policies. 相似文献
129.
Mark F. Forst 《Ocean & Coastal Management》2009,52(6):294-306
The primary role of the Integrated Coastal Zone Management model was to arbitrate conflicts between stakeholders in a living and natural resource environment characterized by a common property and open access doctrine. A chronology of events describes how the development and acceptance of an ecosystems approach policy began to converge and coincide with the spread and development of Integrated Coastal Zone Management. Those organizations that gave representation to the conservation ethic became internationally recognized as surrogate natural resource ‘users’, the interests of which possessed commonality with all stakeholder interests in general. The tenants of conservation policy were therefore largely employed to decide the merits of disputes over ocean and coastal resources.In the 1990s, scientists created a forum to debate, better define, and institutionalize a sound basis for ecosystem management theory and practice. Protocols were developed that embedded science in living and natural resources planning and management. These protocols were shaped and adopted to serve an evermore contemporary Integrated Coastal Zone Management model. Improvements in methodology include the use of adaptive management, ecological modeling and monitoring, appropriate temporal and spatial scales, salient indicators, and stakeholder participation. This contemporary approach is dependent upon recognizing the benefits inherent in utilizing instruments capable of managing resources on a holistic level.Bioregional planning and zoning accommodate the successful management of resources on this level. It is a direct outcome of the convergence of Integrated Coastal Zone Management and the ecosystems approach. Bioregional zoning schemes are capable of traversing the private property and common property doctrines that define the respective terrestrial and aquatic environments of the coastal zone.A comparative case study of the Great Barrier Reef Marine Park and the Belize Marine Protected Area Program is included as an annex, the analysis of which is predicated upon the principles espoused in the literature. 相似文献
130.
Mark Cropper Silvia Zane Roberto Turolla Luca Zampieri Matteo Chieregato Jeremy Drake Aldo Treves 《Astrophysics and Space Science》2007,308(1-4):161-166
We report XMM-Newton observations of the isolated neutron star RBS1774 and confirm its membership as an XDINS. The X-ray spectrum is best fit
with an absorbed blackbody with temperature kT=101 eV and absorption edge at 0.7 keV. No power law component is required. An absorption feature in the RGS data at 0.4 keV
is not evident in the EPIC data, but it is not possible to resolve this inconsistency. The star is not seen in the UV OM data
to m
AB
∼21. There is a sinusoidal variation in the X-ray flux at a period of 9.437 s with an amplitude of 4%. The age as determined
from cooling and magnetic field decay arguments is 105–106 yr for a neutron star mass of 1.35–1.5 M⊙.
相似文献