Global mean sea level(GMSL) change is one of the important indicators of global climate change and is a crucial scientific issue of continuing interest. As satellite altimeter data, the Gravity Recovery and Climate Ex...Global mean sea level(GMSL) change is one of the important indicators of global climate change and is a crucial scientific issue of continuing interest. As satellite altimeter data, the Gravity Recovery and Climate Experiment(GRACE) and Argo continue to be updated, especially with the release of GRACE Follow-On(GRACE-FO) data, making it necessary to combine these latest data to estimate sea level change. Determinations on whether the GRACE and GRACE-FO observation systems provide unbiased global observation data have not been effectively evaluated. Therefore, this research mainly investigated the consistency of GRACE and GRACE-FO observation data in studying GMSL change. By comparing the sum of the GMSL calculated by the two gravity satellites and Argo data with the GMSL calculated by satellite altimeters, the discrepancy between GRACE-FO + Argo and satellite altimeter data is about 7.9 ± 2.3 mm, which is likely derived from the inconsistency between GRACE and GRACE-FO data.展开更多
Earthquakes perturb both the ocean bottom topography due to displacements of sea floor and the geoid due to mass redistribution, which induces the relative sea level(RSL) change. However, the relative global mean sea ...Earthquakes perturb both the ocean bottom topography due to displacements of sea floor and the geoid due to mass redistribution, which induces the relative sea level(RSL) change. However, the relative global mean sea level(GMSL) change is zero in that sea water mass is conserved. But the absolute GMSL change is not zero because earthquakes displace total ocean mass with respect to the Earth’s center of mass(CM) which remains unchanged after an earthquake. This displacement, i.e. the absolute GMSL change, may be detectable by altimetry since the satellites are orbiting around CM. In this paper, we proposed a method to estimate co-seismic absolute GMSL change caused by earthquakes based on the point dislocation theory for a spherically symmetric, non-rotating, elastic and isotropic(SNREI) Earth.This change can be directly connected to the perturbation of ocean bottom topography. We first computed co-seismic displacements as well as the change in geo-potential and solved the sea level equation to validate the insignificance of the oceans’ feedback, i.e. the loading effect due to RSL change, to co-seismic displacements. The results imply that the loading effect due to RSL change is negligible on displacements while is considerable on geoid. We then computed the absolute GMSL change caused by co-seismic vertical and horizontal displacements by making use of the integrated Green’s function method. The numerical results show that a large earthquake may raise the absolute GMSL by magnitude of sub-millimeter and the recent three large events cause GMSL to rise about one millimeter, in which the contribution from horizontal displacement is non-negligible.展开更多
基金This research was supported financially by the NNSFC(41774088,41331066,42104084,and 41474059)the Key Research Program of Frontier Sciences CAS(Chinese Academy of Sciences)(QYZDY-SSW-SYS003)。
文摘Global mean sea level(GMSL) change is one of the important indicators of global climate change and is a crucial scientific issue of continuing interest. As satellite altimeter data, the Gravity Recovery and Climate Experiment(GRACE) and Argo continue to be updated, especially with the release of GRACE Follow-On(GRACE-FO) data, making it necessary to combine these latest data to estimate sea level change. Determinations on whether the GRACE and GRACE-FO observation systems provide unbiased global observation data have not been effectively evaluated. Therefore, this research mainly investigated the consistency of GRACE and GRACE-FO observation data in studying GMSL change. By comparing the sum of the GMSL calculated by the two gravity satellites and Argo data with the GMSL calculated by satellite altimeters, the discrepancy between GRACE-FO + Argo and satellite altimeter data is about 7.9 ± 2.3 mm, which is likely derived from the inconsistency between GRACE and GRACE-FO data.
基金financially supported by the "973" project of China (Grant No. 2014CB845902)the NSFC projects(Grant Nos. 41874026, 41374025 and 41621091)
文摘Earthquakes perturb both the ocean bottom topography due to displacements of sea floor and the geoid due to mass redistribution, which induces the relative sea level(RSL) change. However, the relative global mean sea level(GMSL) change is zero in that sea water mass is conserved. But the absolute GMSL change is not zero because earthquakes displace total ocean mass with respect to the Earth’s center of mass(CM) which remains unchanged after an earthquake. This displacement, i.e. the absolute GMSL change, may be detectable by altimetry since the satellites are orbiting around CM. In this paper, we proposed a method to estimate co-seismic absolute GMSL change caused by earthquakes based on the point dislocation theory for a spherically symmetric, non-rotating, elastic and isotropic(SNREI) Earth.This change can be directly connected to the perturbation of ocean bottom topography. We first computed co-seismic displacements as well as the change in geo-potential and solved the sea level equation to validate the insignificance of the oceans’ feedback, i.e. the loading effect due to RSL change, to co-seismic displacements. The results imply that the loading effect due to RSL change is negligible on displacements while is considerable on geoid. We then computed the absolute GMSL change caused by co-seismic vertical and horizontal displacements by making use of the integrated Green’s function method. The numerical results show that a large earthquake may raise the absolute GMSL by magnitude of sub-millimeter and the recent three large events cause GMSL to rise about one millimeter, in which the contribution from horizontal displacement is non-negligible.
