Holocene sea-level changes in Southeast Asia 1 2 3 4 5 1 M. Bender , T. Mann ,D. Kneer , P. Stocchi , J. Jompa , A. Rovere Sea Level & Coastal Changes SLCC Acknowedgments: This work is supported through the grant SEASchange from the Deutsche Förderungsgemeinschaft (DFG) as part of the Special Priority Program (SPP) 1889 Regional Sea Level Change and Society“ (SeaLevel). The Sea Level and Coastal Changes group research is supported by the Institutional Strategy of the University of Bremen, funded by the German Excellence Initiative [ABPZuK-03/2014] and by ZMT, the Leibniz Centre for Tropical Marine Research 1: MARUM – Center for Marine Environmental Sciences, University of Bremen, Bremen, Germany 2: ZMT – Leibniz Centre for Tropical Marine Research, Bremen, Germany 3: Alfred-Wegener-Institut, Bremerhaven, Germany 4: NIOZ Royal Netherlands Institute for Sea Research, Den Burg, Texel, Netherlands 5: Universitas Hasanuddin - Department of Marine Science Indonesia - Makassar RSL results from fossil microatolls in the Spermonde Archipelago, Indonesia, SE Asia Affiliations References modern microatoll fossil microatoll In this study we surveyed fossil microatolls on ﬁve new islands and living microatolls and compared the relative sea level (RSL) estimates with previous data provided by Mann et al., 2016. Figure 1) the locations and close- ups of the surveyed islands. Panel a-b) provide overview of study areas, sorted by letters as indicated in b). The islands Panambungan (g) and Barrang Lompo (i) were surveyed by Mann et al., 2016. The red S. indicates a third island from Mann et al., 2016 where only living microatolls are found. This island is not shown here (see ﬁgure 3 for LMA elevations). Figure 2) All related RSL curves derived from fossil microatolls and their modern counterparts. Panel a) the positions of the islands are indicated by letters and colors and correlate to RSL graphs. All islands show comparable RSL results except the data set from Barrang Lompo, which shows a noticeable low RSL curve. The two studies from De Klerk, 1982 and Tjia et al.1972 show RSL results up to 6 meter above the present sea level, whereas the new data and the data by Mann et al., 2016 show RSL results of less than one meter above today. One possible explanation is that the earlier RSL results reﬂect extreme storm or tsunami events. Additionally, the GIA predictions mismatch the data and therefore,we propose to explore diﬀerent ice models e.g. ICE-6G by Peltier et al., 2015 or ANICE ( De Boer et al., 2014). Figure 4) RSL indicator points for the Spermonde Archipelago and the ICE-5G GIA model (Peltier, 2004) and ﬁve diﬀerent mantle viscosities for the same area. The gray band indicates the lowest and highest GIA prediction for this region. Shown are two marine limiting points from Tjia et al.,1972, 16 marine and two terrestrial limiting and one index point by De Klerk,1982, 21 sea-level index points from Mann et al.,2016 and the 24 newly surveyed data points. Comparison with data from literature -0.4 -1 -0.8 -0.6 -0.2 0 Elevation [m] Sanane -1 Sanrobengi Barrang Lompo Panambungan Tambakulu n=24 n=23 n=20 n=17 n=51 Our results for the living microatoll surveys show a clear geographic trend in the HLC. The highest HLC was measured on Sanrobengi. This island is placed only one km from the coast of Southwest Sulawesi. The HLC from Sanane, Panambungan and Barrang Lompo diﬀer slighty from each other but they are within a comparable range. These islands are located in the middle of the Archipelaho. On Tambakulu the HLC signal is the lowest. It is placed at the outer part of Spermonde ~70 km from the coast of the mainland. This trend might be based on diﬀerences in the local mean sea level or partial tides from the coast to open ocean due to a deepening bathymetry. Figure 3) a boxplot of the average HLC (Height of Living Coral) of living microatolls on all surveyed locations. n= the amount of surveyed individuals. Living Microatoll survey and HLC averages