Sea level along the world’s coastlines can be measured by a network of virtual altimetry stations

For nearly 30 years, space-based radar altimetry has been routinely measuring changes in sea level at global and regional scales. But this technique designed for the open ocean does not provide reliable sea level data within 20 km to the coast, mostly due to land contamination within the radar echo in the vicinity of the coast. This problem can now be overcome through dedicated reprocessing, allowing the retrieval of valid sea level data in the 0-20 km band from the coast, and then the access to novel information on sea level change in the world coastal zones. Here we present sea level anomalies and associated coastal sea level trends at 756 altimetry-based virtual coastal stations located along the coasts of North and South America, Northeast Atlantic, Mediterranean Sea, Africa, North Indian Ocean, Asia and Australia. This new dataset, derived from the reprocessing of high-resolution (300 m) along-track altimetry data from the Jason-1, 2 and 3 missions from January 2002 to December 2019, allows the analysis of the decadal evolution of coastal sea level and fills the coastal gap where sparse sea level information is currently available

Exploring synergies between remote sensing products developed under the framework of ESA Baltic+ initiative: Sea Surface Salinity and Sea Level

Living Planet Symposium, 23-27 May 2022, Bonn, GermanyIn the frame of the ESA Regional Initiative, the Baltic+ contracts aim at developing research activities to advance the use of ESA and non-ESA Earth observations missions towards the achievement of major scientific challenges identified by Baltic Earth community for the next decade[1]. This includes, in particular: • Dedicated products for the Baltic: ocean colour, sea level, coastal altimetry, salinity, and new dedicated Sentinel-2 products. • Characterisation of biochemical exchanges (land-sea and air-sea) including salinity dynamics. • Characterising and closing the water cycle of the Baltic. • 4D reconstruction of ocean dynamics by integration of EO and modeling of the Baltic Sea. • Characterising and predicting major Baltic inflows. Baltic+ Salinity Dynamics and Baltic+ SEAL (Sea Level) projects have contributed to these challenges by developing dedicated products of sea surface salinity (SSS) and sea surface height (SSH), respectively. Here, we will explore the potential synergy between both products with a twofold purpose: to perform an inter-validation of both products, and to explore the potentiality of both datasets to address some of the scientific challenges identified by ESA and the Baltic Earth community. We will first explore the detection and monitoring of the Atlantic salinity inflow and its recirculation inside the basin by presenting a preliminary assessment of the consistency between structures detected in Baltic+ Salinity SSS maps and circulation patterns derived from Baltic+ SEAL altimetry observations [2,3]. As an example of application, we will analyse how SSS and SSH reflect the mean flow condition across the Danish straits and how they react by local wind conditions and larger atmospheric circulation patterns[4]. While ideally the characteristics of the full water column would be needed, the combination of SSS and altimetry data can help monitoring the inflow and the distribution of surface waters characterised by different densities. [1] https://eo4society.esa.int/regional-initiatives/baltic-regional-initiative/baltic-regional-initiative-science/ (last access 24th November 2021) [2] https://eo4society.esa.int/2021/03/22/expanded-capability-to-monitor-sea-level-at-higher-latitudes-with-new-ssh-products/ (last access 24th November 2021) [3] Passaro M, Müller FL, Oelsmann J, Rautiainen L, Dettmering D, Hart-Davis MG, Abulaitijiang A, Andersen OB, Höyer JL, Madsen KS, Ringgaard IM, Särkkä J, Scarrott R, Schwatke C, Seitz F, Tuomi L, Restano M and Benveniste J (2021) Absolute Baltic Sea Level Trends in the Satellite Altimetry Era: A Revisit. Front. Mar. Sci. 8:647607. doi: 10.3389/fmars.2021.647607 [4] Lehmann, A., W. Krauß, and H.-H. Hinrichsen (2002), Effects of remote and local atmospheric forcing on circulation and upwelling in the Baltic Sea, Tellus, Ser. A, 54(3), 299–316Peer reviewe