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Global Sea Level Budget Assessment: Preliminary Results From ESA's CCI Sea Level Budget Closure Project

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Abstract

Studies of the sea level budget are a means of assessing and understanding how sea level is changing and what are the causes. Closure of the total sea level budget implies that the observed changes of global mean sea level as determined from satellite altimetry equal the sum of observed (or otherwise assessed) contributions, namely changes in ocean mass and ocean thermal expansion and haline contraction. Here, ocean mass changes can be either derived from GRACE satellite gravimetry (since 2002) or from assessments of the individual contributions from glaciers, ice sheets, land water storage, snow pack and atmospheric water content. Estimates of thermosteric sea level are obtained from ocean in situ measurements with additional plans for the inclusion of satellite derived Sea Surface Temperature information. Misclosure of the sea level budget indicates errors in some of the components or contributions from missing or unassessed elements in the budget. ESA's Climate Change Initiative (CCI) has conducted a number of projects related to sea level. Among those projects, the Sea Level CCI project, the Greenland and Antarctic Ice Sheet CCI projects and the Glaciers CCI project directly benefit from satellite altimetry data. The Glaciers CCI project and the Sea Surface Temperature CCI project provide additional insights into phenomena related to sea level change. The aim of the ongoing CCI Sea Level Budget Closure project is to use the CCI data products, together with further data products provided by the project partners to re-assess the sea level budget. Specifically, the project further develops and analyzes products based on the CCI projects mentioned above in conjunction with in situ data for ocean thermal expansion (e.g., Argo), GRACEbased ocean mass change assessments, and modelbased data for glaciers and land hydrology. The work benefits from directly involving the expertise on the product generation for all the involved sea level contributions.