大地测量观测和相对海平面联合约束的冰川均衡调整模型
摘要
利用大地测量和历史相对海平面变化数据,结合地震剪切波层析模型,联合确定了新的末次冰期冰川均衡调整(GIA)模型,其中地慢黏滞度不仅沿径向而且沿横向变化.研究思路是,先尝试性地选择比例系数β,利用与地震剪切波速异常的线性关系,计算地幔黏滞度横向扰动,并与横向均匀的黏滞度参考模型叠加给出3D地慢黏滞度模型;再利用耦合拉普拉斯方程的有限元法算法进行GIA预测;然后,重复该过程,直到预测与观测之间的吻合满意为止.主要结论有:(1)给出了横向非均匀的地幔黏滞度模型(RF3L20(β=0.4)),发现了黏滞度显著的横向非均匀性和其对GIA预测的显著影响,指出横向非均匀不完全是由热效应引起的,可能还与化学组分等其他因素有关,该模型可用于地慢动力学研究.(2)给出了全球现今多种GIA预测速率,可为板块运动、陆地水储量、海水质量变化和冰川冰雪质量非平衡监测提供重要的改正.
The new model of the last glacial isostatic adjustment (GIA) is constrained simutaneously by the data sets from geodetic measurements, relative sea levels and seismic shear tomographic data. The viscosities in mantle for this model are allowed to vary both radially and laterally. Firstly, the scalling factor β is tentatively chosen for which the lateral perturbations in viscosity are computed based on the linear relation with seismic shear wave anomalies. These lateral perturbations in viscosity are then supperposed logarithmically on a laterally homogeneous reference viscosity model to give the total viscosities in the mantle layers. Based on this 3-D viscosity model, the GIA predictions are computed using the coupled-Laplace Finite-Element Method. Such processes will not end untill the predictions agree well with the observed data sets. The main results are as follows. Firstly, the laterally heterogeneous viscosity model (RF3L20(β=0. 4)) is determined from which the obvious lateral heterogeneities and the prominouced effects on GIA predictions are found. It is indicated the lateral heterogeneities are attributable not just to themal effects but also to lateral variations in chemistry and other factors. The RF3L20(β=0.4) model can be used to the modelling in mantle geodynamics. Secondly, the multiple present GIA rates are predicted that can be served as the important corrections for the monitoring of the tectonic motion, land water storage changes, ocean water mass variations and the non-equilibrium of the ice and snow.
The new model of the last glacial isostatic adjustment (GIA) is constrained simutaneously by the data sets from geodetic measurements, relative sea levels and seismic shear tomographic data. The viscosities in mantle for this model are allowed to vary both radially and laterally. Firstly, the scalling factor β is tentatively chosen for which the lateral perturbations in viscosity are computed based on the linear relation with seismic shear wave anomalies. These lateral perturbations in viscosity are then supperposed logarithmically on a laterally homogeneous reference viscosity model to give the total viscosities in the mantle layers. Based on this 3-D viscosity model, the GIA predictions are computed using the coupled-Laplace Finite-Element Method. Such processes will not end untill the predictions agree well with the observed data sets. The main results are as follows. Firstly, the laterally heterogeneous viscosity model (RF3L20(β=0. 4)) is determined from which the obvious lateral heterogeneities and the prominouced effects on GIA predictions are found. It is indicated the lateral heterogeneities are attributable not just to themal effects but also to lateral variations in chemistry and other factors. The RF3L20(β=0.4) model can be used to the modelling in mantle geodynamics. Secondly, the multiple present GIA rates are predicted that can be served as the important corrections for the monitoring of the tectonic motion, land water storage changes, ocean water mass variations and the non-equilibrium of the ice and snow.
引文
[1] 汪汉胜,Wu Patriok,许厚泽.冰川均衡调整(GIA)的研究.地球物理学进展,2009,录用 Wang H S, Wu P, Xu H Z. A survey of research in glacial isostatic adjustment. Progress in Geophysics (in Chinese), 2009, accepted
[2] Tushingham A M, Peltier W R. Ice-3G: a new global model of late Pleistocene deglaciation based upon geophysical predictions of post-glacial relative sea level change. J. Geophys. Res. ,1991,96:4497-4523
[3] Peltier W R. Ice age paleotopography. Science, 1994,265: 195-201
[4] Han D, Wahr J. The viscoelastic relaxation of a realistically stratified earth and a further analysis of post-glacial rebound. Geophys.J. Int. ,1995,120:287-311
[5] Johansson J M, Davis J L, Scherneck H G, et al. Continuous measurements of post-glacial adjustment in fennoscandia, 1: Geodetic Results. J. Geophys. Res.. 2002,107:ETG 3 :1-27
[6] Lidberg M, Johansson J M. Scherneck H, et al. An improved and extended GPS-derived 3D velocity field of the glacial isostatic adjustment ( GTA) in Fennoscandia. J.Geod. , 2007,81:213-230
[7] Sella G F, Stein S, Dixon T H, et al. Observation of glacial isostatic adjustment in 'stable' North America with GPS. Geophysical Research Letters , 2007 ,34:L02306
[8] Lee H, Shum C K, Kuo C Y, et al. Application of TOPEX altimetry for solid earth deformation studies. Terr. Atmos. Ocean. Sci. ,2008,19:37-46
[9] Lee H, Shum C K, Yi Y, et al. Laurentia crustal motion observed using TOPEX/POSEIDON radar altimetry over land. J. Geodynamics, 2008,46(3-5) :182-193
[10] Kuo C Y. Shum C K, Braun A,et al. Vertical crustal motion determined by satellite altimelry and tide gauge data in Fennoscandia. Geophys. Research Letters , 2004,31: L01608
[11] Kuo C Y , Shum C K, Braun A, el al. Vertical motion determined using satellite altimetry and tide gauges. Terr. Atmos. Ocean. Sci. , 2008,19(1-2) :21-35
[12] Tamisiea M E, Mitrovica J X, Davis J L. GRACE gravity data constrain ancient ice geometries and continental dynamics over Laurentia. Science,2007,316:881-883
[13] Spada G, Antonioli A, Cianetti S, et al. Glacial isostatic adjustment and relative sea-level changes: the role of lithospheric and upper mantle hetcrogeneitiesin a 3-D spherical Earth. Geophys. J. Int., 2006 ,165:692-702
[14] Zhong S, Paulson A, Wahr J. Three-dimensional finite-element modelling of Earth's viscoelastic deformation: effects of lateral variations in lithospheric thickness. Geophys. J. Int. , 2003,155(2) :679-695
[15] Wu P, Van der Wal W. Postglacial sea-levels on a spherical self gravitating viscoelastic earth:effects of lateral viscosity variations in the upper mantle on the inference of viscosity contrasts in the lower mantle. Earth and Planet. Sci. Lett, 2003,211:57-68
[16] Wu P, Wang H, Schotman H. Postglacial induced surface motions, sea-levels and geoid rates on a spherical, self-gravitating laterally heterogeneous earth. J. Geodynam. , 2005,39:127-142
[17] Latychev K, Mitrovica J X, Tromp J, et al. Glacial isostatic adjustment on 3-D earth models: a finite-volume formulation. Geophys. J. Int., 2005,161:421-444
[18] Paulson A, Zhong S, Wahr J. Modelling post-glacial rebound with lateral viscosity variations. Geophys. J. Int. ,2005,163 (1) :357-371
[19] Wu P. Using commercial finite element packages for the study of earth deformations, sea levels and the state of stress. Geophys. J. Int, 2004,158:401-408
[20] Wang H, Wu P. Effects of lateral variations in lithospheric thickness and mantle viscosity on glacially induced relative sea levels and long wavelength gravity field in a spherical, self-gravitating Maxwell Earth. Earth Planetary Science Letters ,2006,249:368-383
[21] Wang H, Wu P. Effects of lateral variations in lithospheric thickness and mantle viscosity on glacially induced surface motion on a spherical, self-gravitating Maxwell Earth. Earth Planetary Science Letters ,2006,244:576-589
[22] 汪汉胜,WuP,SchotmanH等.横向非均匀地球负荷问题的CLFE有限元算法的有效性.地球物理学报,2006,49(6) :1657-1664 Wang H S, Wu P, Schotman H, et al. Validation of the Coupled-Laplace-Finite-Element method for the loading problem of a laterally heterogeneous spherical Earth. Chinese J.Geophys. (in Chinese), 2006 ,49(6) :1657-1664
[23] 王志勇.横向非均匀地球模型的负荷响应[博士论文].北京:中国科学院研究生院,2007 Wang Z Y. Loading responses of laterally heterogeneous Earth models[Ph. D. thesis]. Beijing:Graduate University of Chinese Academy of Sciences, 2007
[24] Wang H, Wu P, van der Wal W. Using postglacial sea level, crustal velocities and gravity-rate-of-change to constrain the influence of thermal effects on mantle lateral heterogeneities. J.Geodynam. ,2008,46(35) :104-117
[25] Peltier W R. Postglacial variations in the level of the sea:implications for climate dynamics and solid-earth geophysics. Reviews of Geophys. , 1998, 36: 603-689
[26] Peltier W R. Global glacial isostasy and the surface of the ice age earth, the ICE-5G (VM2) Model and GRACE. Annual Review of Earth and Planetary Science ,2004,32: 111-149
[27] Farrell W E, Clark J A. On postglacial sea level. Geophys. J. Roy. Astro. Soc.,1976,46:647-667
[28] Mitrovica J X, Peltier W R. On postglacial geoid subsidence over the equatorial oceans. J. Geophys. Res. , 1991, 96:20053-20071
[29] Ivins E R, Sammis C G. On lateral viscosity contrast in the mantle and the rheology of low-frequency geodynamics. Geophys. J. Int., 1995,123:305-322
[30] Kaufmann G, Wu P, Ivins E R. Lateral viscosity variations beneath Antarctica and their implications on regional rebound motions and seismotectonics. J. Geodynam. , 2005,39(2) :165-181
[31] Ekstrom G, Dziewonski A. The unique anisotropy of the Pacific upper mantle. Nature, 1998,394:168-172
[32] Rodell M, Houser P R, Jambor U, et al. The global land data assimilation system. Bulletin of AmericanMeteorology Society, 2004,85(3) :381-394
[33] Swenson S, Wahr J. Post-processing removal of correlated errors in GRACE data. Geophysical Research Letters, 2006, 33,L08402
[34] Swenson S, Wahr J. Method for inferring regional surface-mass anomalies from Gravity Recovery and Climate Experiment (GRACE) measurements of time-variable gravity.Journal of Geophysical Research , 2002,107(B9) :2193
[35] van der Wal W, Wu P, Sideris M G,et al. Use of GRACE determined secular gravity rates for glacial isostatic adjustment studies in North-America. J. Geodynam. , 2008, 46(3-5) :144-154
[2] Tushingham A M, Peltier W R. Ice-3G: a new global model of late Pleistocene deglaciation based upon geophysical predictions of post-glacial relative sea level change. J. Geophys. Res. ,1991,96:4497-4523
[3] Peltier W R. Ice age paleotopography. Science, 1994,265: 195-201
[4] Han D, Wahr J. The viscoelastic relaxation of a realistically stratified earth and a further analysis of post-glacial rebound. Geophys.J. Int. ,1995,120:287-311
[5] Johansson J M, Davis J L, Scherneck H G, et al. Continuous measurements of post-glacial adjustment in fennoscandia, 1: Geodetic Results. J. Geophys. Res.. 2002,107:ETG 3 :1-27
[6] Lidberg M, Johansson J M. Scherneck H, et al. An improved and extended GPS-derived 3D velocity field of the glacial isostatic adjustment ( GTA) in Fennoscandia. J.Geod. , 2007,81:213-230
[7] Sella G F, Stein S, Dixon T H, et al. Observation of glacial isostatic adjustment in 'stable' North America with GPS. Geophysical Research Letters , 2007 ,34:L02306
[8] Lee H, Shum C K, Kuo C Y, et al. Application of TOPEX altimetry for solid earth deformation studies. Terr. Atmos. Ocean. Sci. ,2008,19:37-46
[9] Lee H, Shum C K, Yi Y, et al. Laurentia crustal motion observed using TOPEX/POSEIDON radar altimetry over land. J. Geodynamics, 2008,46(3-5) :182-193
[10] Kuo C Y. Shum C K, Braun A,et al. Vertical crustal motion determined by satellite altimelry and tide gauge data in Fennoscandia. Geophys. Research Letters , 2004,31: L01608
[11] Kuo C Y , Shum C K, Braun A, el al. Vertical motion determined using satellite altimetry and tide gauges. Terr. Atmos. Ocean. Sci. , 2008,19(1-2) :21-35
[12] Tamisiea M E, Mitrovica J X, Davis J L. GRACE gravity data constrain ancient ice geometries and continental dynamics over Laurentia. Science,2007,316:881-883
[13] Spada G, Antonioli A, Cianetti S, et al. Glacial isostatic adjustment and relative sea-level changes: the role of lithospheric and upper mantle hetcrogeneitiesin a 3-D spherical Earth. Geophys. J. Int., 2006 ,165:692-702
[14] Zhong S, Paulson A, Wahr J. Three-dimensional finite-element modelling of Earth's viscoelastic deformation: effects of lateral variations in lithospheric thickness. Geophys. J. Int. , 2003,155(2) :679-695
[15] Wu P, Van der Wal W. Postglacial sea-levels on a spherical self gravitating viscoelastic earth:effects of lateral viscosity variations in the upper mantle on the inference of viscosity contrasts in the lower mantle. Earth and Planet. Sci. Lett, 2003,211:57-68
[16] Wu P, Wang H, Schotman H. Postglacial induced surface motions, sea-levels and geoid rates on a spherical, self-gravitating laterally heterogeneous earth. J. Geodynam. , 2005,39:127-142
[17] Latychev K, Mitrovica J X, Tromp J, et al. Glacial isostatic adjustment on 3-D earth models: a finite-volume formulation. Geophys. J. Int., 2005,161:421-444
[18] Paulson A, Zhong S, Wahr J. Modelling post-glacial rebound with lateral viscosity variations. Geophys. J. Int. ,2005,163 (1) :357-371
[19] Wu P. Using commercial finite element packages for the study of earth deformations, sea levels and the state of stress. Geophys. J. Int, 2004,158:401-408
[20] Wang H, Wu P. Effects of lateral variations in lithospheric thickness and mantle viscosity on glacially induced relative sea levels and long wavelength gravity field in a spherical, self-gravitating Maxwell Earth. Earth Planetary Science Letters ,2006,249:368-383
[21] Wang H, Wu P. Effects of lateral variations in lithospheric thickness and mantle viscosity on glacially induced surface motion on a spherical, self-gravitating Maxwell Earth. Earth Planetary Science Letters ,2006,244:576-589
[22] 汪汉胜,WuP,SchotmanH等.横向非均匀地球负荷问题的CLFE有限元算法的有效性.地球物理学报,2006,49(6) :1657-1664 Wang H S, Wu P, Schotman H, et al. Validation of the Coupled-Laplace-Finite-Element method for the loading problem of a laterally heterogeneous spherical Earth. Chinese J.Geophys. (in Chinese), 2006 ,49(6) :1657-1664
[23] 王志勇.横向非均匀地球模型的负荷响应[博士论文].北京:中国科学院研究生院,2007 Wang Z Y. Loading responses of laterally heterogeneous Earth models[Ph. D. thesis]. Beijing:Graduate University of Chinese Academy of Sciences, 2007
[24] Wang H, Wu P, van der Wal W. Using postglacial sea level, crustal velocities and gravity-rate-of-change to constrain the influence of thermal effects on mantle lateral heterogeneities. J.Geodynam. ,2008,46(35) :104-117
[25] Peltier W R. Postglacial variations in the level of the sea:implications for climate dynamics and solid-earth geophysics. Reviews of Geophys. , 1998, 36: 603-689
[26] Peltier W R. Global glacial isostasy and the surface of the ice age earth, the ICE-5G (VM2) Model and GRACE. Annual Review of Earth and Planetary Science ,2004,32: 111-149
[27] Farrell W E, Clark J A. On postglacial sea level. Geophys. J. Roy. Astro. Soc.,1976,46:647-667
[28] Mitrovica J X, Peltier W R. On postglacial geoid subsidence over the equatorial oceans. J. Geophys. Res. , 1991, 96:20053-20071
[29] Ivins E R, Sammis C G. On lateral viscosity contrast in the mantle and the rheology of low-frequency geodynamics. Geophys. J. Int., 1995,123:305-322
[30] Kaufmann G, Wu P, Ivins E R. Lateral viscosity variations beneath Antarctica and their implications on regional rebound motions and seismotectonics. J. Geodynam. , 2005,39(2) :165-181
[31] Ekstrom G, Dziewonski A. The unique anisotropy of the Pacific upper mantle. Nature, 1998,394:168-172
[32] Rodell M, Houser P R, Jambor U, et al. The global land data assimilation system. Bulletin of AmericanMeteorology Society, 2004,85(3) :381-394
[33] Swenson S, Wahr J. Post-processing removal of correlated errors in GRACE data. Geophysical Research Letters, 2006, 33,L08402
[34] Swenson S, Wahr J. Method for inferring regional surface-mass anomalies from Gravity Recovery and Climate Experiment (GRACE) measurements of time-variable gravity.Journal of Geophysical Research , 2002,107(B9) :2193
[35] van der Wal W, Wu P, Sideris M G,et al. Use of GRACE determined secular gravity rates for glacial isostatic adjustment studies in North-America. J. Geodynam. , 2008, 46(3-5) :144-154
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