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Earth System Science Data The Data Publishing Journal
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 4.0 License.
Review article
17 Oct 2017
Review status
This discussion paper is a preprint. A revision of this manuscript was accepted for the journal Earth System Science Data (ESSD) and is expected to appear here in due course.
An Accurate and Homogeneous Altimeter Sea Level Record from the ESA Climate Change Initiative
Jean-Francois Legeais1, Michaël Ablain1, Lionel Zawadzki1, Hao Zuo2, Johnny A. Johannessen3, Martin G. Scharffenberg4, Luciana Fenoglio-Marc5, M. Joana Fernandes6,7, Ole Baltazar Andersen8, Sergei Rudenko9,10, Paolo Cipollini11, Graham D. Quartly12, Marcello Passaro9, Anny Cazenave13, and Jérôme Benveniste14 1Collecte Localisation Satellite (CLS), 31520 Ramonville-Saint-Agne, France
2European Centre for Medium-Range Weather Forecasts, Reading, UK
3Nansen Environmental and Remote Sensing Center (NERSC), Bergen, Norway
4University of Hamburg, Hamburg, Germany
5University of Bonn, Bonn, Germany
6Faculdade de Ciências, Universidade do Porto, 4169-007, Porto, Portugal
7Centro Interdisciplinar de Investigação Marinha e Ambiental (CIIMAR), 4450-208 Matosinhos, Portugal
8DTU Space, 2800 Kongens Lyngby, Denmark
9Deutsches Geodätisches Forschungsinstitut, Technische Universität München, 80333 Munich, Germany
10Helmholtz Centre Potsdam – GFZ German Research Centre for Geosciences, 14473 Potsdam, Germany
11National Oceanography Centre, Southampton, SO14 3ZH, UK
12Plymouth Marine Laboratory, Plymouth, PL1 3DH, UK
13LEGOS, 31400 Toulouse, France
14ESA/ESRIN, 00044 Frascati, Italy
Abstract. Sea Level is a very sensitive index of climate change since it integrates the impacts of ocean warming and ice mass loss from glaciers and the ice sheets. Sea Level has been listed as an Essential Climate Variable (ECV) by the Global Climate Observing System (GCOS). During the past 25 years, the sea level ECV has been measured from space by different altimetry missions that have provided global and regional observations of sea level variations. As part of the Climate Change Initiative (CCI) program of the European Space Agency (ESA) (established in 2010), the Sea Level project (SL_cci) aimed at providing an accurate and homogeneous long-term satellite-based sea level record. At the end of the first phase of the project (2010–2013), an initial version (v1.1) of the sea level ECV has been made available to users (Ablain et al., 2015). During the second phase (2014–2017), improved altimeter standards have been selected to produce new sea level products (called SL_cci v2.0) based on 9 altimeter missions for the period 1993–2015 ( Corresponding orbit solutions, geophysical corrections and altimeter standards used in this v2.0 dataset are described in details in Quartly et al. (2017). The present paper focuses on the description of the SL_cci v2.0 ECV and associated uncertainty and discusses how it has been validated. Various approaches have been used for the quality assessment such as internal validation, comparisons with sea level records from other groups and with in-situ measurements, sea level budget closure analyses and comparisons with model outputs. Compared to the previous version of the sea level ECV, we show that use of improved geophysical corrections, careful bias reduction between missions and inclusion of new altimeter missions lead to improved sea level products with reduced uncertainties at different spatial and temporal scales. However, there is still room for improvement since the uncertainties remain larger than the GCOS requirements. Perspectives for subsequent evolutions are also discussed.

Citation: Legeais, J.-F., Ablain, M., Zawadzki, L., Zuo, H., Johannessen, J. A., Scharffenberg, M. G., Fenoglio-Marc, L., Fernandes, M. J., Andersen, O. B., Rudenko, S., Cipollini, P., Quartly, G. D., Passaro, M., Cazenave, A., and Benveniste, J.: An Accurate and Homogeneous Altimeter Sea Level Record from the ESA Climate Change Initiative, Earth Syst. Sci. Data Discuss.,, in review, 2017.
Jean-Francois Legeais et al.

Data sets

The ESA Sea Level Essential Climate Variable v2.0
J.-F. Legeais, M. Ablain, L. Zawadzki, H. Zuo, J.A. Johannessen, M. G. Scharffenberg, L. Fenoglio-Marc, M. J. Fernandes, O. B. Andersen, S. Rudenko, P. Cipollini, G. D. Quartly, M. Passaro, A. Cazenave, and J. Benveniste
Jean-Francois Legeais et al.


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Short summary
Sea level is one of the best indicator of climate change and has been listed as one of the Essential Climate Variable. Sea level measurements have been provided by satellite altimetry for 25 years and the climate change initiative (CCI) program of the European Space Agency has been the opportunity to provide a long-term, homogeneous and accurate sea level record. It will help scientists to better understand the climate change and its variability.
Sea level is one of the best indicator of climate change and has been listed as one of the...