Collaborative Research: Calculation of Antarctic Gravity Field from GRACE Satellite Data and Comparison with Independent Measurements

这是一项处理GRACE卫星距离、距离变化率和距离加速度数据的建议，目的是获得空间分辨率在35至100公里之间的南极大地水准面图。从这个大地水准面得出的自由空间重力应该从根本上改变我们对南极大陆地质结构和历史的看法，就像GEOSAT使命影响我们对世界海洋板块构造的理解一样。然而，由于资源有限，GRACE项目小组将不使用该范围及其导数来生成沿沿着卫星地面轨迹的重力场的高空间分辨率估计。新的大地水准面和导出的自由空间重力场将需要开发一种算法，以处理距离、距离变化率和距离加速度数据，并将其转换为自洽的大地水准面。将把全球重力环境卫星导航卫星系统得出的重力场与海洋、航空重力和陆地测量以及南极大陆的主要地质特征进行比较，以评估波长分辨率。这一比较将需要综合航空和海洋数据集，并为某些航空勘测确定冰下地形。一旦新的大地水准面和推导出的费-空气重力已经产生，整个大陆的冰下地形可以估计通过最佳的协同克里格插值可用的基岩测量和大地水准面，联合描述地形的空间变化的统计关系，和大地水准面和地形的空间相关性。冰下地形也将使用另一种方法-帕克反演法来确定。这些产品将提供给冰盖建模社区。新的整个大陆的冰下地形将与测高的冰面高度结合使用，以计算南极冰盖体积的新估计数，该估计数可用于根据氧同位素数据校准全球海平面曲线目前和最大可能变化的海平面曲线。新的冰下地形估计还将用于解释南极的地质结构及其形成过程。这项研究将在几个领域产生更广泛的影响和学术价值：（a）冰下地形图以及对南极冰量的更好估计将对南极气候演变倡议的科学目标作出重要贡献。东南极冰盖的成核模型依赖于高质量的冰下地形模型，以及整个冰盖的排水模型。(b)如果GRACE导出的重力方法被证明是成功的，可以应用于北极地区，甚至整个世界。虽然北极重力场在北纬82度以南（ERS-1轨道覆盖范围）质量很高，但仍然存在很大的极差。通过卫星测量绘制世界上这些难以到达地区的主要地质特征图，将是在了解北极和南极板块构造特征方面向前迈出的重要一步，并将大大扩展最近对该区域的海洋地质和构造研究。

This is a proposal to process the GRACE satellite range, range-rate, and range-acceleration data with a goal to obtain a map of the geoid over the Antarctic with spatial resolution between 35 and 100 km. The free-air gravity derived from this geoid should fundamentally change our view on geological structure and history of the Antarctic continent in much the same way that the GEOSAT mission impacted our understanding of plate tectonics in the world's oceans. Due to resource limitations, however, the GRACE project team will not use the range and its derivatives to generate high spatial resolution estimates of the gravity field along the satellite ground track. The new geoid and derived free-air gravity field will require development of an algorithm to process the range, range-rate and range acceleration data and convert them to a self-consistent geoid. The GRACE-derived gravity field will be compared with marine, airborne gravity and land-based surveys as well as with major geological features of the Antarctic continent to assess wavelength resolution. This comparison will require the integration of the airborne and marine data sets and determination of the subglacial topography for some of the airborne surveys. Once the new geoid and derived fee-air gravity have been generated, the continent-wide subglacial topography could be estimated via an optimal co-kriging interpolation of the available bedrock measurements and the geoid, joint with the statistical relationships describing the spatial variation of topography, and the spatial correlation of the geoid and topography. The subglacial topography will be also determined using an alternative approach, the Parker inversion method. These products will be made available to the ice sheet modeling community. The new continent-wide subglacial topography will be used in combination with altimetric ice surface elevations to calculate a new estimate of Antarctic ice sheet volume, which can be used to calibrate the eustatic sea-level curve from oxygen isotope data for the present and maximum possible variations of the global sea level curve. The new subglacial topography estimates will also be used to interpret geologic structures of the Antarctic and the processes responsible for their formation. This research will have several areas of broader impact and intellectual merit: (a) the map of subglacial topography, together with an improved estimate of the Antarctic ice volume, will be an important contribution to the science goals of the Antarctic Climate Evolution initiative (ACE). Modeling the nucleation of the East Antarctic ice sheet relies on high-quality subglacial topography models, as well as modeling the drainage of the entire ice sheet. (b) The proposed GRACE-derived gravity approach, if proven to be successful, can be applied to the Arctic region and indeed to the entire world. While the Arctic gravity field is of high quality south of 82 N (ERS-1 orbit coverage), a large polar gap remains. Mapping the main geological features in these hard-to-reach parts of the world from satellite measurements would be a significant step forward in understanding the plate tectonic features of the Artic and Antarctic and should extend significantly recent marine geological and tectonic studies of the region.