Reconciling ocean mass change and GIA from satellite gravity and altimetry (OMCG-2)

海洋质量变化（OMC）是海平面收支的重要组成部分。在从测高数据推断空间海平面变化时，需要OMC的知识，这对海洋热含量估计和理解地球能量收支有影响。GRACE卫星重力使命已被用于最近的OMC估计，和GRACE派生OMC越来越多地用于区域研究。然而，发表的估计OMC，从基本上相同的GRACE数据，往往不同意，即使在全球范围内。最近的研究从1.2到2.0毫米/年不等，往往声称不切实际的错误和预算关闭在0.1-0.2毫米/年的水平。这是从测高数据推断区域性当代海洋热含量变化的一个主要障碍，例如，为了确定海洋中的热汇和热输运。因此，该问题对于了解和预测东南亚海域的区域海平面变化具有特别重要的意义。该项目的中心假设与SPP第一阶段相同，即这些差异主要与（1）GRACE数据分析中的方法问题和（2）从GRACE数据中消除冰川均衡调整（GIA）影响的未解决问题有关。第一阶段（OMCG-1）解决了直接和反向OMC估计的关键方法差异。此外，OMCG-1还增进了对从综合大地测量卫星观测中区分GIA效应的区域关键要素的理解。OMCG-1正在进一步开发全球逆方法，并开始将区域GIA分离研究的结果纳入全球框架。第二阶段（OMCG-2）将a）研究从模型集合导出指纹的改进方法，B）研究浅层和深层空间分量的独立估计，c）研究整合原位Argo数据的潜在增益，d）采用一种基于时间序列的参数估计方法，对全球影响评估和冰量变化进行区域区分，最后，将冰盖上的测高作为全球反演中的附加观测量，以帮助分离GIA。我们将直接量化在全球和区域范围内导致海平面变化的物理过程。此外，我们还将为SPP内外的建模项目提供数据集。特别是我们对北方欧洲和东南亚的区域化数据将有助于改善这些地区的预测。

Ocean mass change (OMC) is a major component of the sea level budget. Knowledge of OMC is required when inferring steric sea level variability from altimetry, with consequences for ocean heat content estimates and for understanding the Earth energy budget. The GRACE satellite gravity mission has been instrumental for recent OMC estimates, and GRACE-derived OMC is increasingly used in regional studies. Yet, published estimates of OMC, from essentially the same GRACE data, tend to disagree even at the global scale. Recent studies vary from 1.2 to 2.0 mm/a, often claiming unrealistic errors and budget closure at the 0.1-0.2 mm/a level. This is a major obstacle for inferring regional contemporary ocean heat content change from altimetry, e.g. in order to localize the sinks and transports of heat in the ocean. The problem is thus of particular significance for understanding and predicting regional sea level change in South-East Asian seas. The central hypothesis of this project, unchanged to the first phase of the SPP, is that these discrepancies are mostly related to (1) method issues in the analysis of the GRACE data and (2) the unsolved problem of removing the effect of Glacial Isostatic Adjustment (GIA) from the GRACE data. The first phase (OMCG-1) has resolved crucial methodological discrepancies in direct and inverse OMC estimates. In addition, OMCG-1 has improved the understanding of key elements for regional separating the GIA effect from combined geodetic satellite observations. OMCG-1 is further developing the global inverse approach and starting to incorporate results from the regional GIA separation studies into the global framework. The second phase (OMCG-2) will a) investigate improved methods of deriving fingerprints from model ensembles, b) investigate independent estimation of shallow and deep steric components, c) investigate the potential gain of integrating in-situ Argo data, d) implement a time-series-based parameter estimation approach for regional separation of GIA and ice mass change f) assign apparent biases in regional GIA estimates by the use of GNSS, and g) finally, incorporate altimetry over ice sheets as an additional observable in the global inversion to aid the separation of GIA. We will directly quantify physical processes that contribute to sea-level change at global and regional scale. Moreover, we will provide data-sets for modeling projects inside and outside the SPP. Especially our regionalized data for Northern Europe and Southeast Asia will help to improve projections in these areas.