Studying changes of sea level and water storage for coastal regions in West-Africa, using satellite and terrestrial data sets

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Several West-African countries are located besides the Atlantic Ocean, being exposed to coastal as well as Sahel-type precipitation regimes. To these countries, global warming poses multiple severe economic and societal threats: saltwater intrusion by sea level rise reduces freshwater availability, and changes in the terrestrial water cycle may be accompanied by increased frequency, duration or magnitude of droughts and floods. It is clear that these effects are linked and should be observed and monitored in an integrative approach. Knowledge concerning the hydrological cycle, freshwater availability and water storages is indispensible for water resource management. Hydrological modeling plays a central role for determining spatio-temporal patterns of fluxes and storages but the quality of the predictions depends on boundary conditions and on data availability and quality for model comparison. Data from the Gravity Recovery and Climate Experiment (GRACE) mission have found applications for studying the water cycle for West Africa, yet a particular challenge for studying coastal regions with GRACE is posed by the leakage effect, occurring where the signals from ocean and land are overlaid.In the proposed activity, we suggest to 1) study methods for the integrated analysis of sea level and water storage for coastal regions, using space-borne (GRACE, SMOS, ASCAT, ERS1/2 and radar-altimetric), oceanographic, and terrestrial (tide-gauge, hydrological) data and models, 2) investigate and quantify ongoing effects of climate change with particular emphasis on the coastal areas of several West-African countries, and 3) improve hydrological modeling at the regional scale by assimilating space-borne data into dynamic models of the terrestrial hydrological cycle.Seen that GRACE data analysis and interpretation will play a key role in assessing water mass change, it is clear that sharpening its spatial resolution beyond what can be reached with standard products is essential for what we propose. Therefore, we will reprocess level-1b instrument data using a regional analysis approach tailored to the specific challenges of the land-ocean interface.