A note on turbulent perturbations of salinity in a partially mixed estuary     

J.R. West  K. Shiono 《Estuarine, Coastal and Shelf Science》1985,20(1):55-78

Measurements of salinity perturbations in a partially mixed estuary have been used to evaluate the usefulness of an inductive salinometer and to determine some of the characteristics of the salinity perturbations. The salinometer performed satisfactorily under most conditions. Although internal wave like effects were present, the turbulence fluctuations were dominant. The salinity fluctuations and the turbulent fluxes $\text{sw}$ and $\text{su}$ were found to behave in a manner similar to the density fluctuations in a thermally stratified atmospheric boundary layer and a laboratory open channel flow. A quadrant analysis suggested that the contribution of each quadrant to the turbulent flux changed with Ri. The turbulence parameters ν and c_γ were found to decrease and increase respectively as Ri increases.  相似文献   

Mass heterogeneities and convection in the earth's mantle inferred from gravity and core-mantle boundary irregularities   总被引：1，自引：0，他引：1  

Ondřej Čadek  Ctirad Matyska 《Pure and Applied Geophysics》1991,135(1):107-123

Mass heterogeneities in the earth's mantle are retrieved from the gravity data and the topography of the core-mantle boundary as well as the topography of the earth's surface. A mantle circulation induced by the heterogeneities is modelled by solving the Stokes problem for incompressible Newtonian fluid. The derived models of mantle motions correlate well with the plate tectonics and point at a close relation between the surface tectonic activity and the processes in the vicinity of the core-mantle boundary.  相似文献   

Opening of the Fram Strait gateway: A review of plate tectonic constraints   总被引：1，自引：0，他引：1  

  yvind Engen  Jan Inge Faleide  Toril Karlberg Dyreng 《Tectonophysics》2008,450(1-4):51-69

We have revised the regional crustal structure, oceanic age distribution, and conjugate margin segmentation in and around the Lena Trough, the oceanic part of the Fram Strait between the Norwegian–Greenland Sea and the Eurasia Basin (Arctic Ocean). The Lena Trough started to open after Eurasia–Greenland relative plate motions changed from right-lateral shear to oblique divergence at Chron 13 times (33.3 Ma; earliest Oligocene). A new Bouguer gravity map, supported by existing seismic data and aeromagnetic profiles, has been applied to interpret the continent–ocean transition and the influence of Eocene shear structures on the timing of breakup and initial seafloor spreading. Assuming that the onset of deep-water exchange depended on the formation of a narrow, oceanic corridor, the gateway formed during early Miocene times (20–15 Ma). However, if the initial Lena Trough was blocked by terrigenous sediments or was insufficiently subsided to allow for deep-water circulation, the gateway probably formed with the first well developed magnetic seafloor spreading anomaly around Chron 5 times (9.8 Ma; Late Miocene). Paleoceanographic changes at ODP Site 909 (northern Hovgård Ridge) are consistent with both hypotheses of gateway formation. We cannot rule out that a minor gateway formed across stretched continental crust prior to the onset of seafloor spreading in the Lena Trough. The gravity, seismic and magnetic observations question the prevailing hypotheses on the Yermak Plateau and the Morris Jesup Rise as Eocene oceanic plateaus and the Hovgård Ridge as a microcontinent.  相似文献   

法国“阿塔郎特”号海洋调查船上的重力取样     

程振波  刘振夏  王揆洋  崔金瑞 《海洋科学进展》1997,(3)

在海洋地质调查中，如何取得好的沉积物样品是每一位海洋地质学家所向往的，而获得好的沉积物样品的关键又很大程度上取决于先进的海洋调查仪器的使用。法国“阿塔郎特”号海洋调查船上的重力取样管不管在性能上，还是安全性上都瞰称世界上比较先进的取样设备。  相似文献   

Trends in biomass, density and diversity of North Sea macrofauna   总被引：6，自引：2，他引：6  

Heip  C.; Basford  D.; Craeymeersch  J. A.; Dewarumez  J. M.; Dorjes  J.; de Wilde  P.; Duineveld  G.; Eleftheriou  A.; Herman  P. M. J.; Niermann  U.; Kingston  P.; Kunitzer  A.; Rachor  E.; Rumohr  H.; Soetaert  K.; Soltwedel  T. 《ICES Journal of Marine Science》1992,49(1):13-22

  相似文献   

Cod migration patterns in relation to temperature: analysis of storage tag data   总被引：1，自引：0，他引：1  

Stensholt  Boonchai K. 《ICES Journal of Marine Science》2001,58(4):770-793

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冲绳海槽至马里亚纳海沟重力异常和地壳结构的初步研究     

王述功  高仰 《海洋科学》1989,13(2):24-27

根据我们实测的水深、重力连续剖面资料,计算了自东海至北斐济盆地的地壳厚度。本文旨在对冲绳海槽至马里亚纳海沟的重力异常和地壳结构进行初步的研究。该地段位于太平洋板块俯冲带以西,构造活动十分复杂、剧烈,并含有多种类型的地壳结构。  相似文献   

Tectonic core of a sedimentary drift: a potential ridge propagation feature beneath the Blake Outer Ridge     

Dayton Dove  Steven C. Jaume  Erin Beutel 《Marine Geophysical Researches》2007,28(1):1-11

The Blake Outer Ridge is a 480–kilometer long linear sedimentary drift ridge striking perpendicular to the North American coastline. By modeling free-air gravity anomalies we tested for the presence of a crustal feature that may control the location and orientation of the Blake Outer Ridge. Most of our crustal density models that match observed gravity anomalies require an increase in oceanic crustal thickness of 1–3 km on the southwest side of the Blake Outer Ridge relative to the northeast side. Most of these models also require 1–4 km of crustal thinning in zone 20–30 km southwest of the crest of the Blake Outer Ridge. Although these features are consistent with the structure of oceanic fracture zones, the Blake Outer Ridge is not parallel to adjacent known fracture zones. Magnetic anomalies suggest that the ocean crust beneath this feature formed during a period of mid-ocean ridge reorganization, and that the Blake Outer Ridge may be built upon the bathymetric expression of an oblique extensional feature associated with ridge propagation. It is likely that the orientation of this trough acted as a catalyst for sediment deposition with the start of the Western Boundary Undercurrent in the mid-Oligocene.  相似文献   

Changes in soils and vegetation in a Mediterranean coastal salt marsh impacted by human activities   总被引：10，自引：0，他引：10  

J. lvarez-Rogel  F.J. Jimnez-Crceles  M.J. Roca  R. Ortiz 《Estuarine, Coastal and Shelf Science》2007,73(3-4):510-526

This paper reports changes in vegetation distribution and species cover in relation to soil factors and hydrology in a semiarid Mediterranean salt marsh adjacent to the Mar Menor saline lagoon. Species cover, soil salinity, and the groundwater level were monitored between 1991 and 1993 and between 2002 and 2004, and total organic carbon, total nitrogen, total phosphorus, nitrates, ammonium and exchangeable phosphorus were measured in the soils in both study periods. In addition, three soil profiles were described in August 1992 and August 2004. The results indicate an elevation of the water table throughout the 13-year period, which was attributable to water flowing from areas with intensive agriculture. Flooding increased and soil salinity dropped in the most saline sites and increased in the least saline ones. The morphology of the soil profiles reflected the increase in flooding periods, due to the appearance of a greyer matrix in the deeper horizons and a more diffuse pattern of Fe mottles. Following these environmental changes, Sarcocornia fruticosa, Phragmites australis and Juncus maritimus strongly expanded at the wettest sites, which led to the disappearance of the original zonation pattern. The cover of Limonium delicatulum, in turn, decreased with the increase in moisture but increased following the increase in salinity. Changes in soil nutrients were only very evident in the sandy soils of the beach, probably due to the influence of organic debris deposited on the shoreline by the storms and due to the strong increase in the colonisation of this habitat by perennial species. According to the results obtained, control measures are needed in order to preserve habitat diversity in this and other salt marshes of this area. Monitoring of the vegetation distribution could be a useful tool to identify environmental impacts, in order to implement remedial actions.  相似文献   

Methodology and use of tensor invariants for satellite gravity gradiometry   总被引：2，自引：1，他引：1  

Oliver Baur  Nico Sneeuw  Erik W. Grafarend 《Journal of Geodesy》2008,82(4-5):279-293

Although its use is widespread in several other scientific disciplines, the theory of tensor invariants is only marginally adopted in gravity field modeling. We aim to close this gap by developing and applying the invariants approach for geopotential recovery. Gravitational tensor invariants are deduced from products of second-order derivatives of the gravitational potential. The benefit of the method presented arises from its independence of the gradiometer instrument’s orientation in space. Thus, we refrain from the classical methods for satellite gravity gradiometry analysis, i.e., in terms of individual gravity gradients, in favor of the alternative invariants approach. The invariants approach requires a tailored processing strategy. Firstly, the non-linear functionals with regard to the potential series expansion in spherical harmonics necessitates the linearization and iterative solution of the resulting least-squares problem. From the computational point of view, efficient linearization by means of perturbation theory has been adopted. It only requires the computation of reference gravity gradients. Secondly, the deduced pseudo-observations are composed of all the gravitational tensor elements, all of which require a comparable level of accuracy. Additionally, implementation of the invariants method for large data sets is a challenging task. We show the fundamentals of tensor invariants theory adapted to satellite gradiometry. With regard to the GOCE (Gravity field and steady-state Ocean Circulation Explorer) satellite gradiometry mission, we demonstrate that the iterative parameter estimation process converges within only two iterations. Additionally, for the GOCE configuration, we show the invariants approach to be insensitive to the synthesis of unobserved gravity gradients.  相似文献