Coastal sea level (COSELE)
Final Report Abstract
Goal of the project COSELE was the provision and evaluation of improved coastal altimeter data and to study the sea level variability in coastal regions and regionally. Improved altimeter data in the coastal areas and inland have been produced using ad-hoc retracking of the altimeter waveforms. The data are usable up to 3-5 km from the coast. The three fundamental parameters of satellite altimetry: sea surface height above the reference ellipsoid (SSH), significant wave height (SWH) and wind speed at 10 meter above the sea surface (U10) have been successfully validated in the German Bight, which represents an ideal validation area thanks to the availability of in-situ and model data of high quality. The network of insitu data consisting of tide gauges, GNSS stations and off-shore platforms has been used for validation of inhouse retracked and external data. The network has been also selected for a first validation of the SAR CryoSat-2 data and has contributed to a first evaluation of the CryoSat-2 altimeter data in SAR mode. In our analysis we could show the higher precision and accuracy of the altimeter data processed in SAR mode compared to the pseudo pulse-limited data. We have also compared coastal sea level variability measured by tide gauge stations and co-located altimeter data. From the analysis in the Indonesian region we have concluded that, even if the regional sea level change is still primarily caused by natural climate variability, the imprint of anthropogenic effects on regional sea level is locally strong. In detail, we have shown that sea level change is closely linked to the ENSO mode of variability and is spatially homogeneous at both interannual and decadal scales. The rates of absolute eustatic sea level rise derived from satellite altimetry through a 20-year long precise altimeter observation are in average higher than the global mean rate. Several tide gauge records indicate an even higher sea level rise relative to land because of the land vertical movement. Subsidence has been found in Jakarta and in three other tide gauge stations. The use of tide gauges and co-located altimetric measurements represents an interesting alternative to the use of GPS measurements to estimate land vertical movement. We have shown that clearly sea level rise represents a major treat for low-lying highly populated coastal regions worldwide. It is expected that the regional sea level rise will strongly affect particular regions with direct impacts including submergence of coastal zones, rising water tables and salt intrusion into groundwater. It can possibly also exacerbate other factors as flooding associated to storms and hurricanes, as well as ground subsidence of anthropogenic nature. Needed are interdisciplinary studies in selected regions where the sea level rise is particularly critical. In summary the project results have shown that interdisciplinary studies are mandatory to interpret the observations and analyse the causes of the sea level observations in view of climate change. An integrated approach of merging remote sensing data with in situ measurements and ocean and hydrological models is therefore highly desirable, both for oceanography and for marine gravity and geodesy on the regional, basin and global scales. A very interesting result of our project has been the identification of the German Bight as a validation region. We had first proposed the region in 2011 to CNES for the validation of Pistach data. After the study on Pistach and the application to Cryosat-2 data the area has been finally selected for the ESA-Climate Change Initiative project phase II. The increased international collaboration resulting from this validation exercise has allowed us to gain additional experience in both pulse-limited and SAR altimetry processing. Both “coastal” an “in-land” water is a promising application of altimeter data. The scientific community is intensively working in this direction. We therefore intend to continue our analysis along this path.
Publications
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Sea level change in the Gulf of Thailand from GPS-corrected tide gauge data and multi-satellite altimetry, Global and Planetary Change 76, 137- 151, 2011
Trisirisatayawong I., Naeije M., Simons W. and Fenoglio-Marc L.
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(2012). A Study on the conformance of altimetry and in situ surface data near coast, in Proceedings of the 20 Years of Progress in Radar Altimetry Symposium, Venice, Italy, 24-29 September 2012, Benveniste, J. and Morrow, R., Eds., ESA Special Publication SP-710, 201
Fenoglio-Marc L., R. Weiss, S. Dinardo, M. Becker, A. Sudau
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Sea Level Change and Vertical Motion from Satellite Altimetry, Tide Gauges and GPS in the Indonesian Region, Marine Geodesy, 35:sup1, 137-150
Fenoglio-Marc L., T. Schöne, J. Illigner, M. Becker, P. Manurung and Khafid
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(2013), Decadal variability of the net water flux at the Mediterranean Gibraltar Strait, Global and Planetary Change 100,1–10
Fenoglio-Marc L., A. Mariotti, G. Sannino, B. Meyssignac, A. Carillo, M.V. Struglia
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(2013). Validation of CryoSat-2 Observations in SAR Mode in the German Bight, Proceedings Living Planet Symposium Edinburgh, SP-ESA, ESA Publications Division
Fenoglio-Marc L., Dinardo, S., Scharroo R., Roland A., Lucas B.,Weiss R., Detour Sikiric M., Becker M., Benveniste J.
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(2015) "Validation of Significant Wave Height From Improved Satellite Altimetry in the German Bight," Geoscience and Remote Sensing, IEEE Transactions on , vol.53, no.4, pp. 2146,2156, April 2015
Passaro, M.; Fenoglio-Marc, L.; Cipollini, P.
