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51.
Salinity changes in the World Ocean since 1950 in relation to changing surface freshwater fluxes 总被引:1,自引:0,他引:1
Nikolaos Skliris Robert Marsh Simon A. Josey Simon A. Good Chunlei Liu Richard P. Allan 《Climate Dynamics》2014,43(3-4):709-736
Global hydrographic and air–sea freshwater flux datasets are used to investigate ocean salinity changes over 1950–2010 in relation to surface freshwater flux. On multi-decadal timescales, surface salinity increases (decreases) in evaporation (precipitation) dominated regions, the Atlantic–Pacific salinity contrast increases, and the upper thermocline salinity maximum increases while the salinity minimum of intermediate waters decreases. Potential trends in E–P are examined for 1950–2010 (using two reanalyses) and 1979–2010 (using four reanalyses and two blended products). Large differences in the 1950–2010 E–P trend patterns are evident in several regions, particularly the North Atlantic. For 1979–2010 some coherency in the spatial change patterns is evident but there is still a large spread in trend magnitude and sign between the six E–P products. However, a robust pattern of increased E–P in the southern hemisphere subtropical gyres is seen in all products. There is also some evidence in the tropical Pacific for a link between the spatial change patterns of salinity and E–P associated with ENSO. The water cycle amplification rate over specific regions is subsequently inferred from the observed 3-D salinity change field using a salt conservation equation in variable isopycnal volumes, implicitly accounting for the migration of isopycnal surfaces. Inferred global changes of E–P over 1950–2010 amount to an increase of 1 ± 0.6 % in net evaporation across the subtropics and an increase of 4.2 ± 2 % in net precipitation across subpolar latitudes. Amplification rates are approximately doubled over 1979–2010, consistent with accelerated broad-scale warming but also coincident with much improved salinity sampling over the latter period. 相似文献
52.
Reconnaissance level geomorphological observations in the northern part of Evia (Euboea) Island, suggest that a major topographic feature, the 17 km long and 15 km wide Nileas depression (NDpr), corresponds to a previously undetected graben structure, bounded by fault zones of ENE–WSW to NE–SW general strike. These fault zones have been active in the Quaternary, since they affect the Neogene deposits of the Limni–Histiaia basin. They strike transverse to the NW–SE active fault zones that bound northern Evia in the specific area and are characterised along most of their length by subtle geomorphic signatures in areas of extensive forest cover and poor exposure.The NDpr was formed during the Early–Middle Quaternary, after the deposition of the Neogene basin fill. During the Middle–Late Quaternary, the NW–SE fault zones that bound northern Evia have been the main active structures, truncating and uplifting the NDpr to a perched position in relation to the northern Gulf of Evia graben and the submarine basin on the Aegean side of the island. The present-day morphology of the NDpr, with an interior (floor) comprised of Middle Pleistocene erosional surfaces extensively dissected by drainages, was shaped by erosion during this uplift. Judging from their geomorphic signatures, the fault zones that bound the NDpr must have been characterised by low or very low rates of activity during the Late Quaternary. Yet, that they may still be accommodating strain today is suggested by moderate earthquakes that have been recorded within the NDpr.The fault zone at the SE flank of the NDpr (Prokopi–Pelion fault zone) may be very important in terms of earthquake segmentation of the active NW–SE Dirfys fault zone that controls the Aegean coast of northern Evia, given that the intersection between the two presents striking morpho-structural similarities with the intersection of two fault zones with the same directions on the mainland (the Atalanti and Hyampolis fault zones), which is known to have acted as a barrier to the propagation of the Atalanti earthquake ruptures in 1894. 相似文献
53.
José A. Font Harald Dimmelmeier Anshu Gupta Nikolaos Stergioulas 《Monthly notices of the Royal Astronomical Society》2001,325(4):1463-1470
Axisymmetric pulsations of rotating neutron stars can be excited in several scenarios, such as core collapse, crust- and core-quakes or binary mergers, and could become detectable in either gravitational waves or high-energy radiation. Here, we present a comprehensive study of all low-order axisymmetric modes of uniformly and rapidly rotating relativistic stars. Initial stationary configurations are appropriately perturbed and are numerically evolved using an axisymmetric, non-linear relativistic hydrodynamics code, assuming time-independence of the gravitational field (Cowling approximation). The simulations are performed using a high-resolution shock-capturing finite-difference scheme accurate enough to maintain the initial rotation law for a large number of rotational periods, even for stars at the mass-shedding limit. Through Fourier transforms of the time evolution of selected fluid variables, we compute the frequencies of quasi-radial and non-radial modes with spherical harmonic indices l =0 , 1, 2 and 3, for a sequence of rotating stars from the non-rotating limit to the mass-shedding limit. The frequencies of the axisymmetric modes are affected significantly by rotation only when the rotation rate exceeds about 50 per cent of the maximum allowed. As expected, at large rotation rates, apparent mode crossings between different modes appear. In addition to the above modes, several axisymmetric inertial modes are also excited in our numerical evolutions. 相似文献
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55.
Christos A. Kontovas Harilaos N. Psaraftis Nikolaos P. Ventikos 《Marine pollution bulletin》2010,60(9):1455-18097
This paper reports on recent analysis of oil spill cost data assembled by the International Oil Pollution Compensation Fund (IOPCF). Regression analyses of clean-up costs and total costs have been carried out, after taking care to convert to current prices and remove outliers. In the first place, the results of this analysis have been useful in the context of the ongoing discussion within the International Maritime Organization (IMO) on environmental risk evaluation criteria. Furthermore, these results can be useful in estimating the benefit of regulations that deal with the protection of marine environment and oil pollution prevention. 相似文献
56.
Margarita Tzali Sarantis Sofianos Anneta Mantziafou Nikolaos Skliris 《Ocean Dynamics》2010,60(3):585-596
The impact of the Black Sea Water (BSW) inflow on the circulation and the water mass characteristics of the North Aegean Sea
is investigated using a high-resolution 3D numerical model. Four climatological numerical experiments are performed exploring
the effects of the exchange amplitude at the Dardanelles Straits in terms of the mean annual volume exchanged and the amplitude
of its seasonal cycle. Larger inflow of low salinity BSW influences the water characteristics of the whole basin. The largest
salinity reduction is encountered in the upper layers of the water column, and the most affected region is the northeastern
part of the basin. The winter insulation character of the BSW layer (low-salinity layer) is reduced by the seasonal cycle
of the inflow (minimum during winter). The maximum atmospheric cooling coincides with the minimum BSW inflow rate, weakening
the vertical density gradients close to the surface and thus facilitating the vertical mixing. The inflow rate of BSW into
the North Aegean Sea constitutes an essential factor for the circulation in the basin. Increased inflow rate results into
considerably higher kinetic energy, stronger circulation and reinforcement of the mesoscale circulation features. Although
the position of the front between BSW and waters of Levantine origin does not vary significantly with the intensity of the
BSW inflow rate, the flow along the front becomes stronger and more unstable as the inflow rate increases, forming meanders
and rings. The changes in the intensity of BSW inflow rate overpower the wind and thermohaline forcing and largely determine
the general circulation of the North Aegean Sea. 相似文献
57.
George Vargemezis Panayiotis Tsourlos Alexandros Stampolidis Ilias Fikos Dimitrios Ballas Nikolaos Papadopoulos 《Studia Geophysica et Geodaetica》2012,56(4):1063-1078
In this paper the main results from the implementation and interpretation of a geophysical survey carried out in Chalkidiki (Northern Greece) are presented. The objective of the geophysical survey was to study the general geological conditions of the area (stratigraphy and tectonism) and to focus on the hydrogeological behaviour of the geological formations in the area. The ultimate target was to point out the most promising locations for the successful construction of hydro wells. Since direct hydrogeological information was not available, three different geophysical techniques were applied in order to follow a step by step approach to the exploration of the study area. Firstly, the Very Low Frequency (VLF) electromagnetic method was applied since the majority of the area was dominated by the formation of ophiolites and water flow was possibly expected only in fractured zones at a relatively small depth. Secondly, at the locations of the conductive zones detected by the VLF survey additional Electrical Resistivity Tomography (ERT) sections at different scales were measured to provide more detailed information about the geometrical characteristics of them. Finally, Self-Potential (SP) measurements along the same profiles were conducted in order to provide supplementary information concerning the nature of the conductive zones such as the possible relation with electrokinetic sources. The combined interpretation of the geophysical data proved very efficient for deciding the most promising locations for the construction of hydro wells. 相似文献
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60.
Nikolaos P. Nikolaidis Gary A. Robbins Michelle Scherer Brian McAninch Gordon Binkhorst Jay Asikainen Steven L. Suib 《Ground Water Monitoring & Remediation》1994,14(3):150-159
The vertical distribution and partitioning (between the solid and aqueous phase) of chromium in a glaciofluvial aquifer in northeastern Connecticut were assessed. Most of the chromium (99 percent of its mass) is bound to the soil. Retardation is primarily the result of binding to organic matter and adsorption to iron oxide coatings. However, other attenuation mechanisms also appear to be significant. If the degree of chromium binding observed here is representative of other chromium contaminated sites, pump-and-treat remediation will not remove the vast amount of chromium from the subsurface. However, most of the chromium may be immobile, and removal may not be required following the initial pumping to remove the mobile fraction. Further knowledge of the mechanisms that bind chromium to the soil, their reversibility, and their kinetics is essential to developing effective remediation strategies. 相似文献