The effective elastic lithosphere under the Cook-Austral and Society islands     

Stephane Calmant  Anny Cazenave 《Earth and Planetary Science Letters》1986,77(2)

We have determined the elastic thicknessT_e of the oceanic lithosphere along two volcanic chains of the South Central Pacific: Cook-Austral and Society islands. We used a three-dimensional spatial method to model the lithospheric flexure assuming a continuous elastic plate. The model was constrained by geoid height data from the SEASAT satellite.Along the Cook-Austral chain the elastic thickness increases westward, from 2–4 km at McDonald hot spot to 14 km at Rarotonga. At McDonald seamount, however, the data are better explained by a local compensation model. The observed trend shows an increase ofT_e with age of plate at loading time. However, the elastic layer under the Cook-Austral appears systematically thinner by several kilometers than expected for “normal” seafloor, suggesting that substantial thermal thinning has taken place in this region. Considering the apparent thermal age of the plate instead of crustal age improves noticeably the results. Along the Society chainT_e varies from 20 km under Tahiti to 13 km under Maupiti which is located 500 km westward. When plotting together the Society and Cook-AustralT_e results versus age of load, we notice that within the first five million years after loading,T_e decreases significantly while tending rapidly to an equilibrium value. This may be interpreted as the effect of initial stress relaxation which occurs just after loading inside the lower lithosphere and suggests that the presently measured elastic thickness under the very young Tahiti load ( 0.8 Ma) is not yet the equilibrium thickness.  相似文献   

Possible dynamical evolution of the rotation of Venus since formation   总被引：1，自引：0，他引：1  

Bernard Lago  Anny Cazenave 《Earth, Moon, and Planets》1979,21(2):127-154

The past evolution of the rotation of Venus has been studied by a numerical integration method using the hypothesis that only solar tidal torques and core-mantle coupling have been active since formation. It is found quite conceivable that Venus had originally a rotation similar to the other planets and has evolved in 4.5×10⁹ years from a rapid and direct rotation (12-hour spin period and nearly zero obliquity) to the present slow retrograde one.While the solid tidal torque may be quite efficient in despinning the planet, a thermally driven atmospheric tidal torque has the capability to drive the obliquity from 0° towards 180° and to stabilize the spin axis in the latter position. The effect of a liquid core is discussed and it is shown that core-mantle friction hastens the latter part of the evolution and makes even stronger the state of equilibrium at 180°. The model assumes a nearly stable balance between solid and atmospheric tides at the current rotation rate interpreting the present 243 day spin period as being very close to the limiting value.A large family of solutions allowing for the evolution, in a few billions years, of a rapid prograde rotation to the present state have been found. Noticeably different histories of evolution are observed when the initial conditions and the values of the physical parameters are slightly modified, but generally the principal trend is maintained.The proposed evolutionary explanation of the current rotation of Venus has led us to place constraints on the solid bodyQ and on the magnitude of the atmospheric tidal torque. While the constraints seem rather severe in the absence of core-mantle friction (aQ15 at the annual frequency is required, and a dominant diurnal thermal response in the atmosphere is needed), for a large range of values of the core's viscosity, the liquid core effect allows us to relax somewhat these constraints: a solid bodyQ of the order 40 can then be allowed. ThisQ value implies that a semi-diurnal ground pressure oscillation of 2 mb is needed in the atmosphere in order for a stable balance to occur between the solid and atmospheric tides at the current rotation rate. No model of atmospheric tides on Venus has been attempted in this study, however the value of 2 mb agrees well with that predicted by the model given in Dobrovolskis (1978).  相似文献   

The Earth's Rotation and Atmospheric Circulation–I Seasonal Variations     

Kurt Lambeck  Anny Cazenave 《Geophysical Journal International》1973,32(1):79-93

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Terrestrial water dynamics in the lower Ganges—estimates from ENVISAT and GRACE   总被引：1，自引：0，他引：1  

Haris Hasan Khan  Arina Khan  Shakeel Ahmed  Marie-Claude Gennero  Kien Do Minh  Anny Cazenave 《Arabian Journal of Geosciences》2013,6(10):3693-3702

In this study, the hydrodynamics of lower Ganges basin in India has been monitored using radar altimetry data from environmental satellite (ENVISAT) mission and microgravity data from the Gravity Recovery and Climate Experiment (GRACE) mission. River stage time series have been constructed for different virtual stations on the lower Ganges. Time series for the integrated water volume changes from microgravity measurements have also been constructed to characterize the seasonal and interannual fluctuation patterns in water storage and flux. The ENVISAT dataset indicates an average seasonal river stage fluctuation of 8 m in the lower Ganges River. The GRACE dataset reveals a seasonal fluctuation ranging from 0.18 to 0.40 m in the vertically integrated total water storage in the lower Ganges basin. The two independent datasets show broad similarity in the lower Ganges basin and outline the importance of space-based techniques for monitoring continental water resources.  相似文献   

Spatial trend patterns in the Pacific Ocean sea level during the altimetry era: the contribution of thermocline depth change and internal climate variability   总被引：1，自引：0，他引：1  

H. Palanisamy  A. Cazenave  T. Delcroix  B. Meyssignac 《Ocean Dynamics》2015,65(3):341-356

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The Earth's Rotation and Atmospheric Circulation —II. The Continuum     

Kurt Lambeck  Anny Cazenave 《Geophysical Journal International》1974,38(1):49-61

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Geoid anomalies across Pacific fracture zones     

Jean-Charles Marty  Anny Cazenave  Bernard Lago 《Geophysical Journal International》1988,93(1):1-23

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Numerical experiment applicable to the latest stage of planet growth     

Anny Cazenave  Bernard Lago  Kien Dominh 《Icarus》1982,51(1):133-148

A three-dimensional numerical model was developed with the goal of studying limited dynamical problems relevant to the latest stage of planet growth in the accretion theory. A small number of large protoplanets (～ Moon size) of different masses, moving around the Sun, are considered. The dynamical evolution and growth of the population is studied under mutual gravitational perturbations, accretion, and collisional fragmentation processes. Gravitational encounters are treated exactly by numerical integration of the N-body problem. Outcomes of collisional fragmentation are modeled according to the results of R. Greenberg et al. (1978, Icarus, 35, 1–26). In the present work, we consider 25 protoplanets with uniform mass distribution in the range 2 × 10²⁵?4 × 10²⁶ g on heliocentric orbits in the Earth zone. These bodies are initially confined to a small volume of space to permit gravitational perturbations by close approaches and collisions within a finite length of integration time. The dynamical evolution of the swarm is followed for four different sets of initial ranges in semimajor axis, eccentricity, and inclination: Δa=0.01, 0.02, 0.04, 0.08 AU; Δe= 0.005, 0.01, 0.02, 0.04; Δi=0°3, 0°6, 1°2, 2°4. Among other results, it is found that average eccentricities and inclinations evolve toward a steady state such that $\text{i}\text{?}\text{1}\text{2}\text{,}\text{e}$; it is also found that, whatever the initial conditions, the population evolves toward a quasi-equilibrium relative velocity distribution corresponding to a Safronov parameter value $\text{θ?10}$. Moreover, the growth process of the growing planet presents very similar behavior in the four cases considered, except for the time scale of evolution, which increases with the initial range of orbital elements. Earlier works of this kind have been presented by L.P. Cox and J.S. Lewis (1980, Icarus, 44, 706–721) and by G.N. Wetherill (1980b, In Geol. Soc. Canad. Spec. Publ., p. 20), although a number of differences exist between the three approaches.  相似文献   

Global land water storage change from GRACE over 2002–2009; Inference on sea level     

William Llovel  Mélanie Becker  Anny Cazenave  Jean-François Crétaux  Guillaume Ramillien 《Comptes Rendus Geoscience》2010,342(3):179-188

Global change in land water storage and its effect on sea level is estimated over a 7-year time span (August 2002 to July 2009) using space gravimetry data from GRACE. The 33 World largest river basins are considered. We focus on the year-to-year variability and construct a total land water storage time series that we further express in equivalent sea level time series. The short-term trend in total water storage adjusted over this 7-year time span is positive and amounts to 80.6 ± 15.7 km³/yr (net water storage excess). Most of the positive contribution arises from the Amazon and Siberian basins (Lena and Yenisei), followed by the Zambezi, Orinoco and Ob basins. The largest negative contributions (water deficit) come from the Mississippi, Ganges, Brahmaputra, Aral, Euphrates, Indus and Parana. Expressed in terms of equivalent sea level, total water volume change over 2002–2009 leads to a small negative contribution to sea level of –0.22 ± 0.05 mm/yr. The time series for each basin clearly show that year-to-year variability dominates so that the value estimated in this study cannot be considered as representative of a long-term trend. We also compare the interannual variability of total land water storage (removing the mean trend over the studied time span) with interannual variability in sea level (corrected for thermal expansion). A correlation of ∼0.6 is found. Phasing, in particular, is correct. Thus, at least part of the interannual variability of the global mean sea level can be attributed to land water storage fluctuations.  相似文献   

A validated fast algorithm for simulation of flooding events in plains     

D. Dalponte  P. Rinaldi  G. Cazenave  E. Usunoff  L. Vives  M. Varni  M. Vénere  A. Clausse 《水文研究》2007,21(8):1115-1124

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