The stratigraphic evolution of the Indus Fan and the history of sedimentation in the Arabian Sea   总被引：6，自引：1，他引：6  

Clift  Peter  Gaedicke  Christoph  Edwards  Rosemary  Il Lee  Jae  Hildebrand  Peter  Amjad  Shahid  White  Robert S.  Schlüter  Hans-Ulrich 《Marine Geophysical Researches》2002,23(3):223-245

The Indus Fan records the erosion of the western Himalayas and Karakoram since India began to collide with Asia during the Eocene, 50 Ma. Multi-channel seismic reflection data from the northern Arabian Sea correlated to industrial well Indus Marine A-1 on the Pakistan Shelf show that sedimentation patterns are variable through time, reflecting preferential sedimentation in deep water during periods of lower sea-level (e.g., middle Miocene, Pleistocene), the diversion of sediment toward the east following uplift of the Murray Ridge, and the autocyclic switching of fan lobes. Individual channel-levee systems are estimated to have been constructed over periods of 10⁵–10⁶ yr during the Late Miocene. Sediment velocities derived from sonobuoys and multi-channel stacking velocities allow sections to be time-depth converted and then backstripped to calculate sediment budgets through time. The middle Miocene is the period of most rapid accumulation, probably reflecting surface uplift in the source regions and strengthening of the monsoon at that time. Increasing sedimentation during the Pleistocene, after a late Miocene-Pliocene minimum, is apparently caused by faster erosion during intense glaciation. The sediment-unloaded geometry of the basement under the Pakistan Shelf shows a steep gradient, similar to the continent-ocean transition seen at other rifted volcanic margins, with basement depths on the oceanward side indistinguishable from oceanic crust. Consequently we suggest that the continent-ocean transition is located close to the present shelf break, rather than >350 km to the south, as previously proposed.  相似文献   

Diffusion in coronas around clinopyroxene: modelling with local equilibrium and steady state,and a non-steady-state modification to account for zoned actinolite-hornblende     

J. R. Ashworth  J. J. Birdi  T. F. Emmett 《Contributions to Mineralogy and Petrology》1992,109(3):307-325

Retrograde coronas of Caledonian age, between clinopyroxene and plagioclase in the Jotun Nappe Complex, Norway, illustrate the effects of diffusion kinetics on mineral distributions among layers and on the compositions of hornblende-actinolite. One corona type comprises a symplectite of epidote + quartz adjacent to plagioclase, and a less well-organized intergrowth of amphibole + quartz replacing clinopyroxene. The observed mineral proportions imply an open-system reaction, but the similarity of Al/Si ratios in reactant plagioclase and product symplectite indicates approximate conservation of Al₂O₃ and SiO₂. The largest inferred open-system flux is a loss of CaO, mostly derived from consumption of clinopyroxene. The approximate layer structure, Pl|Ep + Qtz|Hbl + Qtz|Act±Hbl + Qtz|Cpx, is modelled using the theory of steady-state diffusion-controlled growth with local equilibrium. To obtain a solution, it is necessary to use a reactant plagioclase composition which takes into account aluminous (epidote) inclusions. The results indicate that, in terms of Onsager diffusion coefficients L _ii , Ca is more mobile than AL (L _CaCa/L _AlAl3.) (where means greater than or approximately equal to). This behaviour of Ca is comparable with that of Mg in previously studied coronas around olivine. Si is non-diffusing in the present modelling, because of silica saturation. Oxidation of some Fe²⁺ to Fe³⁺ occurs within the corona. Mg diffuses towards its source (clinopyroxene) to maintain local equilibrium. Other coronas consist of two layers, hornblende adjacent to plagioclase and zoned amphibole + quartz adjacent to clinopyroxene. In the zoned layer, actinolitic hornblende forms relict patches, separated from quartz blebs by more aluminous hornblende. A preliminary steady-state, local-equilibrium model of grain-boundary diffusion explains the formation of low-Al and high-Al layers as due to Al immobility. Zoning and replacement are qualitatively explained in terms of evolution of actinolite to more stable aluminous compositions. This is modelled by a non-steady-state modification of the theory, retaining local equilibrium in grain boundaries while relatively steep zoning profiles develop in grain interiors through slow intracrystalline diffusion. Replacement of actinolite by hornblende does not require a change in P–T conditions if actinolite is a kinetically determined, non-equilibrium product. The common preservation of a sharp contact between hornblende and actionolite layers may be explained by ineffectiveness of intracrystalline diffusion: according to the theory, given sufficient grain-boundary Al flux, a metastable actinolite + quartz layer in contact with hornblende may be diffusionally stable and may continue to grow in a steady state.  相似文献   

Application of a coupled ice‐ocean model to the Labrador Sea     

Lawrence A. Mysak  Shiling Peng  Rosemary G. Wood 《大气与海洋》2013,51(2):232-255

Abstract

The steady, coupled ice‐ocean circulation model of Willmott and Mysak (1989) for a meridional channel is applied to the Labrador Sea for the winter season. The model consists of a thermodynamic reduced‐gravity ocean combined with a variable thickness ice cover that is in thermal equilibrium. Upon specifying the forcing fields of surface air temperature, wind stress and water temperature along the open southern boundary, the winter climatological ice‐edge position, ice thickness, ocean circulation and temperature fields are determined in the channel domain. The sensitivity of the results to the various model parameters is examined. In particular, the optimum heat exchange coefficients for the interfaces of air‐water, ice‐water and air‐ice are found.

The model ice‐edge position compares favourably with the 50% winter climatological ice concentration isoline obtained from an analysis of 32 years (1953–84) of sea‐ice concentration data. The simulations of the ocean temperature and ice thickness are also quite realistic according to the observed records available. The model is also applied to two specific winters (1981 and 1983) during which anomalous sea‐ice and weather conditions prevailed in the Labrador Sea.  相似文献   

Vigorous star formation in a bulge-dominated extremely red object at z= 1.34     

Garret Cotter  Chris Simpson  Rosemary C. Bolton 《Monthly notices of the Royal Astronomical Society》2005,360(2):685-692

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Observations of metallic species in Mercury’s exosphere     

Rosemary M. Killen  Andrew E. Potter  E. Todd Bradley  Carrie M. Anderson 《Icarus》2010,209(1):75-87

From observations of the metallic species sodium (Na), potassium (K), and magnesium (Mg) in Mercury’s exosphere, we derive implications for source and loss processes. All metallic species observed exhibit a distribution and/or line width characteristic of high to extreme temperature - tens of thousands of degrees K. The temperatures of refractory species, including magnesium and calcium, indicate that the source process for the atoms observed in the tail and near-planet exosphere are consistent with ion sputtering and/or impact vaporization of a molecule with subsequent dissociation into the atomic form. The extended Mg tail is consistent with a surface abundance of 5-8% Mg by number, if 30% of impact-vaporized Mg remains as MgO and half of the impact vapor condenses. Globally, ion sputtering is not a major source of Mg, but locally the sputtered source can be larger than the impact vapor source. We conclude that the Na and K in Mercury’s exosphere can be derived from a regolith composition similar to that of Luna 16 soil (or Apollo 17 orange glass), in which the abundance by number is 0.0027 (0.0028) for Na and 0.0006 (0.0045) for K.  相似文献   

Monte Carlo modeling of sodium in Mercury’s exosphere during the first two MESSENGER flybys     

Matthew H. Burger  Rosemary M. Killen  E. Todd Bradley  Menelaos Sarantos  Nelly Mouawad 《Icarus》2010,209(1):63-74

We present a Monte Carlo model of the distribution of neutral sodium in Mercury’s exosphere and tail using data from the Mercury Atmospheric and Surface Composition Spectrometer (MASCS) on the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft during the first two flybys of the planet in January and September 2008. We show that the dominant source mechanism for ejecting sodium from the surface is photon-stimulated desorption (PSD) and that the desorption rate is limited by the diffusion rate of sodium from the interior of grains in the regolith to the topmost few monolayers where PSD is effective. In the absence of ion precipitation, we find that the sodium source rate is limited to ∼10⁶-10⁷ cm⁻² s⁻¹, depending on the sticking efficiency of exospheric sodium that returns to the surface. The diffusion rate must be at least a factor of 5 higher in regions of ion precipitation to explain the MASCS observations during the second MESSENGER flyby. We estimate that impact vaporization of micrometeoroids may provide up to 15% of the total sodium source rate in the regions observed. Although sputtering by precipitating ions was found not to be a significant source of sodium during the MESSENGER flybys, ion precipitation is responsible for increasing the source rate at high latitudes through ion-enhanced diffusion.  相似文献   

The RAVE survey: constraining the local Galactic escape speed     

Martin C. Smith  Gregory R. Ruchti  Amina Helmi  Rosemary F. G. Wyse  J. P. Fulbright  K. C. Freeman  J. F. Navarro  G. M. Seabroke  M. Steinmetz  M. Williams  O. Bienaymé  J. Binney  J. Bland-Hawthorn  W. Dehnen  B. K. Gibson  G. Gilmore  E. K. Grebel  U. Munari  Q. A. Parker  R.-D. Scholz  A. Siebert  F. G. Watson  T. Zwitter 《Monthly notices of the Royal Astronomical Society》2007,379(2):755-772

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Dounreay oil spill: Major implications of a minor incident     

Rosemary S. Bowman 《Marine pollution bulletin》1978,9(10):269-273

Few reports of oil spills on an exposed rocky shore have taken into account the background of natural events and the period over which the possible consequences of pollution and its treatment may come to light. This small incident has served as a cautionary tale, illustrating the pitfalls of instant assessment, and the type of baseline experience required for biological interpretation. It has also underlined the continuing inadequacy of the ecological advice available when treatment decisions have to be made.  相似文献   

Formation of subantarctic mode water in the southeastern Indian Ocean   总被引：1，自引：1，他引：1  

Jean-Baptiste Sallée  Nicolas Wienders  Kevin Speer  Rosemary Morrow 《Ocean Dynamics》2006,56(5-6):525-542

Subantarctic Mode Water (SAMW) is the name given to the relatively deep surface mixed layers found directly north of the Subantarctic Front in the Southern Ocean, and their extension into the thermocline as weakly stratified or low potential vorticity water masses. The objective of this study is to begin an investigation into the mechanisms controlling SAMW formation, through a heat budget calculation. ARGO profiling floats provide estimates of temperature and salinity typically in the upper 2,000 m and the horizontal velocity at various parking depths. These data are used to estimate terms in the mode water heat budget; in addition, mode water circulation is determined with ARGO data and earlier ALACE float data, and climatological hydrography. We find a rapid transition to thicker layers in the central South Indian Ocean, at about 70°S, associated with a reversal of the horizontal eddy heat diffusion in the surface layer and the meridional expansion of the ACC as it rounds the Kerguelen Plateau. These effects are ultimately related to the bathymetry of the region, leading to the seat of formation in the region southwest of Australia. Upstream of this region, the dominant terms in the heat budget are the air–sea flux, eddy diffusion, and Ekman heat transport, all having approximately equal importance. Within the formation area, the Ekman contribution dominates and leads to a downstream evolution of mode water properties.  相似文献   

Using a dynamical advection to reconstruct a part of the SSH evolution in the context of SWOT,application to the Mediterranean Sea   总被引：1，自引：1，他引：0  

Marine Rogé  Rosemary Morrow  Clément Ubelmann  Gérald Dibarboure 《Ocean Dynamics》2017,67(8):1047-1066

The main oceanographic objective of the future SWOT mission is to better characterize the ocean mesoscale and sub-mesoscale circulation, by observing a finer range of ocean topography dynamics down to 20 km wavelength. Despite the very high spatial resolution of the future satellite, it will not capture the time evolution of the shorter mesoscale signals, such as the formation and evolution of small eddies. SWOT will have an exact repeat cycle of 21 days, with near repeats around 5–10 days, depending on the latitude. Here, we investigate a technique to reconstruct the missing 2D SSH signal in the time between two satellite revisits. We use the dynamical interpolation (DI) technique developed by Ubelmann et al. (2015). Based on potential vorticity (hereafter PV) conservation using a one and a half layer quasi-geostrophic model, it features an active advection of the SSH field. This model has been tested in energetic open ocean regions such as the Gulf Stream and the Californian Current, and has given promising results. Here, we test this model in the Western Mediterranean Sea, a lower energy region with complex small scale physics, and compare the SSH reconstruction with the high-resolution Symphonie model. We investigate an extension of the simple dynamical model including a separated mean circulation. We find that the DI gives a 16–18% improvement in the reconstruction of the surface height and eddy kinetic energy fields, compared with a simple linear interpolation, and a 37% improvement in the Northern Current subregion. Reconstruction errors are higher during winter and autumn but statistically, the improvement from the DI is also better for these seasons.  相似文献