Coastal and Regional Sea Level Change and Subsidence - The Hazardous Potential in Indonesia and South East Asia (CoRSEA)

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Climate change and fluctuations are a natural phenomenon, which occurred over different temporal scales during the Earths history. Besides this natural variability, the question of human-induced changes of climate has gained increasing public awareness. Sea-level rise (SLR), which is widely recognized as one of the consequences of anthropogenic climate change, has a substantial social and economic impact. Another aspect receiving awareness is the hazardous potential of the combination of regional SLR and subsidence in highly populated coastal cities. Approximately 1/3 of the worlds population is living near the coast. Most of the largest cities of South East Asia are near-coastal, and thus vulnerable to SLR. This situation worsens for the regions suffering subsidence. Understanding sea level change and its near-time projection for coastal regions is essential to coastal planning, land use and economical development. For the last two decades, radar altimetry has played an important role in monitoring the sea level. Since the middle of the 80ties, several radar altimeters have acquired a substantial amount of sea level data but even today do not lead to consistent sea level estimates. Depending on the choice of corrections, distinctly different regional sea level trends are found. This project will address these deficiencies. The derivation of long-term trends is complicated by the fact, that climate-induced decadal and secular sea level changes can be concealed by seasonal, annual and interannual variations, which may act as noise masking trends. Long-term time series of sea level measurements are available only from tide gauges, which are sensitive to vertical land movements and are, thus, records of relative rather than absolute sea level. In recent years, GNSS technology became increasingly important to correct tide gauges for vertical changes. The accurate determination of sea level in combination with subsidence estimates of Megacities and the challenge of combining different geodetic methods to predict near-future sea level changes in urban areas is of paramount importance for the societies. We plan to (1) improve and combine state-of-art geodetic sensor data, including Altimetry, tide gauges, GNSS, and temporal gravity fields to quantify regional sea level changes with a global perspective and land subsidence respectively; (2) analyze sea level patterns especially for the coastal region in the area of Java and extensions to other SE Asia regions; (3) study local sea level changes, extreme sea level from tide gauge records and coastal flooding under the view of local subsidence, with a focus to Jakarta and Semarang; (4) combine sea level information with area information from other methods to assess vulnerability and to provide background information for socio-economic evaluation of past and recent sea level rise impacts and to better understand the feedback system between hazard and society and the interaction with communities.