近半个世纪以来随着全球变暖，海平面变化已成为全球气候变化过程中一个重要的响应参数。目前，研究海平面变化主要是采用海洋测高卫星和全球验潮站资料。自1993年以来，海洋测高卫星不仅可以覆盖全球，还可以提供全球或区域上的地心海平面变化，但是相比于验潮站而言存在数据时间短、仪器漂移误差等缺点。验潮站虽然具有多达百余年的数据资料，却存在陆地垂直位移、站点分布稀疏和不均匀等缺点。因此，本项目旨在综合测高卫星数据和验潮站资料的优点首次重构出过去七十年全球海平面的时空变化。对海平面进行重构之前，则需要：（1）利用改进的算法估计出陆地垂直位移量并给出验潮站数据得到的地心海平面变化；（2）遴选出质量较优的卫星测高数据产品并改正其仪器漂移误差；（3）考虑及包括极地海洋海平面对于全球海平面的贡献。

Under an increasingly warmer Earth and the corresponding ablation of the world’s ice reservoirs, accurately measuring relative sea-level rise, understanding its geophysical causes and thus improving the fidelity of sea-level projections, is a significant scientific and societal problem facing mankind. Satellite radar altimeter missions have been providing continuous and near-global geocentric sea level measurements since 1991–1992, but the span of data records (<30 years) is still too short to isolate the definitive sea-level rise signal from other signals or error sources. In addition, there are reported radar altimeter or microwave radiometer instrument drifts, or other drifts including temperature/oscillator corrections to altimeter data, which collectively are detrimental to allow accurate determination of global sea-level rise trend. In contrast, globally sparsely located tide gauges have long-term (~100 years) records, but are susceptive to vertical land motion (VM) at tide gauge benchmarks, and is thought to be not optimally geographically located to enable the estimation of the true global mean sea-level rise trends. The technique of sea-level reconstruction has been developed to combine tide gauge records and altimeter data to mitigate the deficiencies of the two techniques, and to estimate sea-level trends covering the global ocean Current limiting errors include knowledge of VM at tide gauges and possible altimeter instrument drift errors, contaminating the sea-level trend estimates. .Therefore, there is a critique need to improve tide gauge and radar altimeter sea-level reconstruction techniques to jointly estimate sea-level trends and VMs, and to mitigate potential altimeter drifts. Here we propose to develop the technique to jointly estimate the vertical motion at the tide gauges, altimeter instrument drifts, with geocentric sea-level rise trends covering the world’s global ocean over the last seven decades. We propose the following approaches: (1) to improve the iterative joint estimation algorithm via sea-level reconstruction and integrating short-term altimeter and long-term tide gauge data records; (2) to inter-compare and validate available altimeter data products, including integrating multi-radar altimeter (Level 2) data records using the Radar Altimeter Data System (RAD) software, CNES AVISO+ (Archiving, Validation and Interpretation of Satellite Oceanographic Data), and ESA Sea-Level Climate Change Initiative (CCI) gridded data products; (3) to mitigate nonlinear vertical motion at tide gauge sites due to seismic motion and glacier ablation dynamics; and (4) to validate the estimated VM and altimeter drift solutions using the TIGA (CGPS@Tide Gauges) velocities from Universite de La Rochelle. The anticipated result includes the estimate of global sea-level trends covering the polar ocean, separating VM signals, and resolving/validating potential altimeter drifts, over the last seven decades.