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61	Interdisciplinary Geosciences	ABS-132
The Preliminary Result of Dominant Frequency Profile and Seismic Hazard Estimation In Penajam Paser Utara Using HVSR Method Mawadah A. (1), Zulfakriza Z. (2), Widiyantoro S. (2,3), Supendi P. (4,5), Husni Y.M (6), Lesmana A. (6) 1) Earth Science Graduate Program, Faculty of Earth Science and Technology, Bandung Institute of Technology, Indonesia. 2) Global Geophysics Research Group, Faculty of Mining and Petroleum Engineering, Bandung Institute of Technology, Indonesia. 3) Faculty of Engineering, Maranatha Christian University, Bandung 40164, Indonesia. 4) Agency for Meteorology, Climatology, and Geophysics (BMKG), Jakarta 10720, Indonesia. 5) Department of Earth Sciences, Bullard Labs, University of Cambridge, Cambridge CB3 0EZ, UK. 6) Geophysical Engineering, Faculty of Mining and Petroleum Engineering, Bandung Institute of Technology, Indonesia. *e-mail: anismawadah12[at]gmail.com Abstract Sepaku Sub-district, which is located in Penajam Paser Utara Regency, East Kalimantan has been designated as the new capital city of Indonesia. One of the reasons for choosing this area was due to the lack of potential for natural disasters, especially earthquakes. However, based on the historical records of seismicity, several destructive earthquakes have occurred in East Kalimantan. Therefore, a study of the characteristics of local site is needed in order to assess the earthquake hazard potential in Penajam Paser Utara. In this study, the Horizontal to Vertical Spectral Ratio (HVSR) method was applied by utilizing microtremor data from 21 seismometers installed at the study area. The results of the HVSR analysis are the dominant frequency (f0) and amplification (A0) values obtained from the H/V curve. Based on the preliminary result, the highest f0 in the study area is 14.39 Hz and the lowest is 0.58 Hz. Meanwhile, the highest value for A0 is 6.41 and the lowest value is 1.25. Keywords: HVSR method- dominant frequency- amplification Share Link | Plain Format | Corresponding Author (Anis Mawadah)

62	Interdisciplinary Geosciences	ABS-135
Geospatial Aspects of Multi-Hazard Disaster Risk Management for Local Government Mitigation Strategy: Study Case Lebak District of Banten Province, Indonesia. Bambang Setyadji, Vera Sadarviana, Kosasih Prijatna Geodesy Research Group, Faculty of Earth Sciences and Technology , Bandung Institute of Technology, Jl. Ganesha 10, Bandung 40132, West Java, INDONESIA Abstract Several regencies/cities in Indonesia are regions that have multi-hazard potential. Disaster management is often unplanned and improvised. For areas identified as having multi-hazard potential, the preparedness, response, recovery, and mitigation should be carried out better. The local government must have strategic steps to deal with the possibility of disaster. The local government needs to formulate early warning, loss impact, and risk assessment in order to produce a disaster management strategy. Community needs, regional resources the quality of communication between stakeholders and their people characteristics become specific in the parameters used so that the strategy can be realized technically. Efforts that can be made are the preparation of strategic steps in the form of building systems on risk knowledge, monitoring and warning, response and dissemination capabilities, and communication. We elaborate the geospatial aspects on every stages of the disaster risk management (DRM) cycle in the Lebak district of Banten Province in Indonesia. Each stages of DRM need specific Geospatial data or information requirement in terms of resolution and quality. Furthermore, it leads to the precise estimation on reducing the risk caused by multi-hazards disaster. Keywords: Geospatial data science, multi-hazard, disaster, mitigation. Share Link | Plain Format | Corresponding Author (Bambang Setyadji)

63	Interdisciplinary Geosciences	ABS-137
Geomorphology of Cimaung Valley: Implications for Disaster Mitigation in Cimaung Sub-District and Surroundings Area, Bandung District Muhammad Agung Gumilar (a*), Riyan Hidyatulloh (a), Taufik Ismail (b,c), Billy Petrus Wehelmus (a), Rifo Rausyan Fikri (a), Elvis Okvianta (a), Dwigko Kurniawan Wandray (a), Mirzam Abdurrachman (b) a) Department of Geology, Indonesia College of Mineral and Technology, Bandung 40263, Indonesia *gumilara48[at]gmail.com b) Faculty of Earth Sciences and Technology, Bandung Institute of Technology, Bandung 40132, Indonesia c) Center of Geological Disaster Research, Indonesia Agency of Research and Innovation, Bandung 40135, Indonesia Abstract Cimaung Village is one of the villages part of the Cimaung District which is in the southern part of Bandung. Location is right at the confluence of three remaining volcanoes namely Mount Malabar, Mount Tilu and Mount Tanjaknangsi. Its existence in this valley is very vulnerable to geological disasters, such as floods, landslides, etc. Residual activity of the three volcanoes greatly influences the geomorphological conditions. Rocks produced from volcanic activity play an important role in the formation of a distinctive geomorphology. The rocks in the Cimaung area and its surroundings are the result of volcanic activity such as lava, lava and pyroclastic. Geomorphological analysis was carried out by analyzing river flow patterns, topographic maps, slopes and landsat imagery in the form of DEM (Digital Elevation Model) as well as direct observations in the field. Results of the geomorphological analysis are poured into geomorphological maps and maps of disaster-prone areas. Geomorphological unit in the study area consists of 11 (eleven) geomorphological units, in which morphological changes are still continuing today. Main control for significant morphological changes is controlled by human activities, weathering and land clearing will continue to this day. Keywords: Geomorphology- Disaster Mitigation- South Bandung Share Link | Plain Format | Corresponding Author (Muhammad Agung Gumilar)

64	Interdisciplinary Geosciences	ABS-140
Volcanostratigraphy of Cimaung Valley: Application and Combination of Landsat Imagery and Field Observations of Cimaung Sub-District, Bandung District, West Java Billy Petrus Wehelmus (a*), Rifo Rausyan Fikri (a), Elvis Okvianta (a), Taufik Ismail (b,c), Riyan Hidyatulloh (a), Muhammad Agung Gumilar (a), Dwigko Kurniawan Wandray (a), Mirzam Abdurrachman (b) a) Department of Geology, Indonesia College of Mineral and Technology, Bandung 40263, Indonesia billysaa0612[at]gmail.com b) Faculty of Earth Sciences and Technology, Bandung Institute of Technology, Bandung 40132, Indonesia c) Center of Geological Disaster Research, Indonesia Agency of Research and Innovation, Bandung 40135, Indonesia Abstract The research area is composed of rocks from the activities of three volcanoes, namely Mount Tanjaknangsi in the west, Mount Malabar in the east and Mount Tilu in the south which is located in Bandung Regency, West Java Province. This study aims to determine the surface geology mapped at a scale of 1:12,500 and to determine the volcanostratigraphy and geological history that make up the study area. Vulcanostratigraphy is made by integrating literature studies, direct field observations of rock outcrops, and petrographic analysis and analysis of satellite images in the form of topographic maps and satellite images, namely DEM (Digital Elevation Model) and ASTER (Advanced Spaceborne Thermal Emission and Reflection Radiometer). Results of the observations and analysis are poured into outcrop observation point maps, volcanostratigraphic profile maps, geological maps, cross-sectional geology and geological history blocks. Volcanostratigraphy of the study area is divided into 3 khuluk and 8 volcanic dunes and 24 rock units consisting of 18 lava units, 5 pyroclastic units and 1 lahar unit. There are at least 3 phases of volcanic formation in the geological history of the study area. The geological structure that develops in the study area is in the form of a primary structure, namely a joint with sheets showing an activity of lava flow and a secondary structure in the form of a volcanic crater structure which shows the remains of the eruption center of a volcano. Keywords: Vulcanostratigraphy- Landsat Imagery- Bandung Share Link | Plain Format | Corresponding Author (Billy Petrus Wehelmus)

65	Interdisciplinary Geosciences	ABS-141
Heavy Metal Distributions in the Carbonate Reef Environment of Tin-Rich Island: Surface Sediment Based Study Ayu Utami Nurhidayati (1), Dwi Amanda Utami (1), Sri Yudawati Cahyarini (1) (1) Paleoclimate and Paleoenvironment Research Group, Research Center for Climate and Atmosphere, Research Organization for Earth Science and Marime, National Research and Innovation Agency (BRIN), Komplek BRIN Gd. 70-80, Jl Sangkuriang, Bandung, Indonesia 40135 Abstract Belitung Island known as one of the tin producer in the world, as it lied in the South East Asian tin belt. The study was conducted in the North Belitung Island to investigate the heavy metal concentrations of sediment in the carbonate reef environment system. Thirteen sediment samples were collected from mixing zone riverbed, shoreline, and offshore of North Belitung. The concentrations of heavy metals were analyzed to assess the environmental pollution characteristics by using flame AAS (Atomic Absorption Spectrophotometry) method. The result indicated that the average concentrations of chromium (Cr), copper (Cu), and cadmium (Cd) were 0.016 - 0.080, 0.029 - 0.097, and 0.008-0.022 ppm, respectively. The calculation of geo-accumulation index (Igeo) was adopted in this study to evaluate the heavy metal pollution. The correlation between the heavy metal distribution and their potential influencing factor also discussed in this research. The Igeo values revealed that this research area has been unpolluted to moderately polluted by Cr and Cu, and unpolluted by Cd. Based on the contamination level to adverse biological effect, the heavy metals concentration in this research area has the lowest potential to adverse biological effect. However, this information is important to evaluate the heavy metals control in the carbonate reef environment affected by mining activity. Keywords: Heavy metals, surface sediment, reef carbonate, tin mining, AAS Share Link | Plain Format | Corresponding Author (Ayu Utami Nurhidayati)

66	Interdisciplinary Geosciences	ABS-142
Life Cycle Assessment (LCA) of Water Supply Systems for Slum Area in Indonesia Farhan I. W. Rohmat12, D. E. Irawan3, D. Rohmat4, Faizal I. W. Rohmat5* 1School of Life Science and Technology, Bandung Institute of Technology, Jalan Ganesha 10, Bandung 40132, Indonesia 2Agro-industrial Technology Education, Faculty of Technology And Vocational Education, Indonesia University of Education 3Faculty of Earth Sciences and Technology, Bandung Institute of Technology, Jalan Ganesha 10, Bandung 40132, Indonesia 4Faculty of Social Sciences Education, Indonesian University of Education, Jl. Dr. Setiabudi No.229, Bandung 40154, Indonesia 5Faculty of Civil and Environmental Engineering, Bandung Institute of Technology, Jalan Ganesha 10, Bandung 40132, Indonesia Abstract The amount of surface water and groundwater in slum areas in West Kalimantan, Indonesia, is very abundant. However, its quality does not meet the requirements as a source of clean water, and it causes the community to depend on the provision of clean water by the government (Municipal Water Supply, MWS) through a monopoly company. Drinking water supply areas or independently collecting rainwater (Rainwater Harvesting, RWH). In this case, water supply through MWS and RWH systems is considered a promising and sustainable alternative to be implemented in slum areas. The resulting environmental and health impacts are unknown at each stage of the clean water production process through these two systems. This study aims to compare the environmental and health impacts related to the production of clean water through the MWS and RWH systems to help make decisions on the development of water supply relevant to environmental and health issues. Eleven life cycle impact assessment (LCIA) indicators have been assessed using a functional unit of 1 m3 of clean water (non-potable). Our results show that RWH outperforms MWS on all environmental and health impact indicators. RWH is also considered easier to implement in slum areas and can be chosen as an alternative to the water supply that needs to be a priority for further development. The RWH model used in this study can be used in other slum areas locally in Indonesia and globally in various parts of the world with the same characteristics. Keywords: Life Cycle Assessment, Municipal Water Supply, Rainwater Harvesting, Slum Area Share Link | Plain Format | Corresponding Author (Farhan Ilham Wira Rohmat)

67	Interdisciplinary Geosciences	ABS-145
The Ocean Atmosphere Couple Modeling In Spatiotemporal Prediction Of Coastal Inundation Due To Storm Surge (Case Study Of Tropical Cyclone Seroja 2021) Bagus Primohadi Syahputra, Ahmad Fadlan Department of Meteorology, School of Meteorology Climatology & Geophysics, Perhubungan 1 Street No. 5, Bintaro-South Tangerang, Banten, 15221, Indonesia Abstract Tropical Cyclone Seroja causes high waves in the waters of East Nusa Tenggara which causes coastal flooding and causes casualties due to the absence of a storm surge inundation warning. The purpose of this research is to model storm surge conditions when the Seroja Tropical Cyclone occurs and determine the configuration for mitigating future storm surge events. The data used are GFS data, Himawari Satellite, Jason Satellite, Landsat/Sentinel Satellite, Tidal sea level elevation data, Surface rainfall observation data and other supporting data. The method used is a multi-ensemble combination with a satellite assimilation scheme in WRF modeling as input data for coastal modeling using DELFT3D. The output results are then verified using an artificial intelligence image processing method. The results obtained are multi-ensemble assimilation satellite modeling which produces estimates with fairly good accuracy which results in a seawater intrusion model with fairly good spatial verification. These results are expected to be the basis for mitigating storm surge events if tropical cyclones occur near mainland Indonesia in the future. Keywords: WRFDA 3DVAR, DELFT3D, Multi Ensemble, Image Processing, Storm Surge Share Link | Plain Format | Corresponding Author (Bagus Primohadi Syahputra)

68	Ocean Sciences	ABS-1
Comparative and Analytical Study of the Sea Currents Data from High-Frequency Radar and Acoustic Doppler Current Profiler in The Bali Strait (Case Study: April 24th - May 3rd, 2019) Yoshua Ade Nugroho(a*), Imma Redha Nugraheni(b), Muhammad Najib Habibie(c), Hastuadi Harsa(c), Roni Kurniawan(c), and Tahir Daniel Hutapea(c) (a)Frans Kaisiepo Meteorological Station Jl. M. Yamin, Biak Kota, Biak Numfor, Papua, 98111, Indonesia *yoshua.meteo[at]gmail.com (b)Department of Meteorology, School of Meteorology Climatology and Geophysics Jl. Perhubungan I No. 5, Pondok Aren, Tangerang Selatan, Banten, 15221, Indonesia (c)Research and Development Center, Meteorological Climatological and Geophysical Agency Jl. Angkasa I No. 2, Kemayoran, Jakarta Pusat, DKI Jakarta, 10610, Indonesia Abstract A High Frequency Radar (HF Radar) operating at 4.4 - 50 MHz was used as part of the The Bali Strait Wave and Current Survey Project by Indonesian Meteorological Climatological and Geophysical Agency (BMKG) Research and Development Center on April 24th - May 3rd 2019. The radar system observed the sea surface currents of the northern part of Bali Strait from two sites separated by about 6 km. Measurements were taken every half an hour for each location on a 0.5 x 0.5 km grid. In order to examine the performance of HF Radar, observed data from HF Radar were compared to sea surface currents measured by two Acoustic Doppler Current Profiler (ADCP) deployed 20 m below the sea surface. Additional information was also conducted from the ADCP to determine the characteristics of the radial velocity and direction of sea currents for each layer. The radar and ADCP currents radial velocity were in the same range of distribution with the radar tended to overestimate the ADCP, and only well-correlated in the first high tide and second low tide period. There was a distortion in the directional measurement of the radar because of the influence from the surface winds right above the sea level. In addition, the characteristics of the ocean currents radial velocity in the Bali Strait showed good persistence in the lower layer rather than the upper layer to the surface. Keywords: HF Radar- ADCP- sea currents Share Link | Plain Format | Corresponding Author (Yoshua Ade Nugroho)

69	Ocean Sciences	ABS-10
ASSESSMENT OF VERTICAL ACCURACY PERFORMANCE FROM A PORTABLE HYDROGRAPHIC SYSTEM DUE TO INSTRUMENT SPECIFICATIONS, BOAT INSTALLATION, AND LAUNCH OPERATION Abubakar Aliyu Alhassan(a*), Poerbandono(b) a)Department of Geodesy and Geomatics Engineering. Faculty of Earth Sciences and Technology, Institut Teknologi Bandung. b)Hydrography Research Group, Faculty of Earth Sciences and Technology, Institut Teknologi Bandung Abstract With the growing development of portable survey equipment and platforms, hydrographic data acquisition is being offered by multiple selections of devices and mode of installations. The mounting and installation of hydrographic survey devices are most of the time tailored to the boat or platform dimension. The use of portable equipment is hence indispensable with a wide selection of combined options from the market. Consequently, sensor offsets and device performance are hence unique in every survey launched. With that, persistent accuracy performance shall always be verified. This paper examines the capability of portable deployments of multibeam echosounder (MBES) on distinct types of survey boats. The examination is primarily based on error budget modeling and field tests. In this contribution, we develop an error budget model to approximate the propagating uncertainty from the contributing sources of measurement uncertainties. The model only considers the vertical sources of error in MBES survey as it constitutes the largest contributors to hydrographic data quality. Verification of the model by means of field tests is carried out on two separate locations using different boats and device^s configurations. The verification indicates our proposed model can independently identify the survey quality in accordance with the International Hydrographic Organization standards, regardless of the options of devices and their installations. This study could be beneficial in assessing the vertical accuracy of any portable survey systems and helps hydrographic surveyors to design the best strategy of device selection and installation prior to carrying out the measurement. Keywords: Error budget, total propagating uncertainty, bathymetry, Jacobian matrix Share Link | Plain Format | Corresponding Author (Aliyu Alhassan Abubakar)

70	Ocean Sciences	ABS-28
Characterizing Coastline and Sediment Interaction in The North Coast of Java using Satellite Images Efrat N. Nainggolan and Asep Saepuloh Geological Engineering, Faculty of Earth Sciences and Technology, ITB, Jl. Ganesha No. 10, Bandung, West Java 40132, Indonesia Abstract Sediments are the main material for forming morphology in coastal areas. Sediment originated from rock fragmentation due to weathering which can take place physically, chemically, or biologically. Changes in the morphology of coastal areas can be occurred through erosion, transportation, and deposition mechanisms. Sedimentation in the coastal environment originates from the presence of sediments originating from the mainland and is basically the main factor in forming the beach. The large amount of sedimentation process caused rapid changes in the coastline presented by capes form in the coastal area. Characterizing the coastline and sediment interaction is necessary to understand the physical condition of the coast including the ongoing processes for further purposes such as hazard mitigation and coping capacity of the land for infrastructure. The Cirebon Coast is selected as study area due to rapid city development and infrastucture. To characterize coastline and sediment interaction, we used temporal hydrological index derived by Landsat images such as nomalized different water index (NDWI), modified normalized difference water index (MNDWI), water ratio index (WRI) and normalized difference moisture index (NDMI). We also used vegetation index such as normalized different vegetation index (NDVI), soil adjusted vegetation index (SAVI) and modified soil adjusted vegetation index (MSAVI). Accordingly, we characterized succescfully the Cirebon coastline into six categories: abrasion, accretion, sedimentation to erosion, erosion to sedimentation, sedimentation to stable, and erosion to stable. The sediments of Cirebon coastline are characterized by muddy beaches, fine-sized sediment material, and sandy beaches with medium to coarse sediment material. Keywords: Cirebon, coastline, sediment, hydrological index, vegetation index, Landsat Share Link | Plain Format | Corresponding Author (Efrat N. Nainggolan)

71	Ocean Sciences	ABS-30
Coastline Change and Abrasion Prediction using Time Series Satellite Images in the North Coast of Java: Study Case Indramayu Regency, West Java, Indonesiae Just Try to Submit This Sample Abstract ErvaAuliaFauzunora, Asep Saepuloh, Very Susanto Geological Engineering, Faculty of Earth Sciences and Technology, ITB, Jl. Ganesha No. 10, Bandung, West Java 40132, Indonesia Abstract Coastal areas have continuous change due to the interaction between sea and land, which causing abrasion and accretion generally. Indramayu Regency is one of the regencies that has sea waters on the north coast of Java and has a coastline of around 114 km. The coastal of Indramayu regency has characteristics as a sandy beach which has a dominant process of abrasion which is triggered by the process of digging beach sand and converting mangrove land into ponds. Obtaining changes in the coastline and beach materials, we applied remote sensing observation to obtain shoreline data periodically. Currently, satellite images support the availability of Landsat data in a relatively short time and large coverage area. The use of remote sensing technology is supperior to support field surveys with limitation of time and observation coverage. We have used Landsat 7 and 8 images within the past 10 years to detect coastline changes and predict abrasion in study area based on Normalized Difference Water Index (NDWI) and Digital Shoreline Analysis System (DSAS) methods. Preliminary results from the analysis that has been carried out indicate shoreline changes that are dominated by abrasion. Abrasion occurs almost along the coastline, and accretion only occurs at a few points. This is triggered by the characteristics of the coast, as well as the land use being converted. Keywords: Coastline, Landsat, Indramayu, NDWI, DSAS. Share Link | Plain Format | Corresponding Author (Erva Aulia Fauzunora)

72	Ocean Sciences	ABS-37
A closer look to submarine landslide deposits beneath the Makassar Strait and its ability to generate tsunami Rizqi Valentra (a*), Rima Rachmayani (b), Benyamin Sapiie (c) a) Earth Science Study Program, Faculty of Earth Science, Bandung Institute of Technology, Bandung, Indonesia *rizqi.valentra[at]gmail.com b) Oceanographic Research Group, Faculty of Earth Science, Bandung Institute of Technology, Bandung, Indonesia c) Geodynamics and Sedimentology Research Group, Faculty of Earth Science, Bandung Institute of Technology, Bandung, Indonesia Abstract In 2020, several Mass Transport Deposits (MTD) were identified beneath the Makassar Strait. These deposits which formed since 2.6 Mya were considered as the product of submarine landslide that was not caused by a seismic activity but by rapid sedimentation from Mahakam Delta and slope erosion and deposition by Indonesian Throughflow. With volume range that could reach more than 600 km3, these deposits were spread along the west side of the Makassar Strait. Although these deposits had been mapped, the volume of each deposit and the formation process are still questionable. It is also unknown whether these gigantic MTDs were tsunamigenic or not. In this research, more data was used to examine the MTDs through different point of view and tsunami model was run using NHWAVE and FUNWAVE-TVD. Looking at both interior and exterior features of the largest MTD, it was found that this MTD was deposited in a slumping process which moved very slow rather than in a gravity fall so that it may not be able to generate tsunami even though the volume of the mass could reach hundreds of kilometers. It was also proven through the tsunami model that the impact of a tsunami that caused by a 280 km3 and a 180 km3 of landslides would be decreased significantly when the velocities were reduced up to ten times from the original. Keywords: Makassar Strait- Submarine Landslide- Mass Transport Deposit- Tsunami Model Share Link | Plain Format | Corresponding Author (Rizqi Valentra)

73	Ocean Sciences	ABS-39
A more realistic slope failure scenarios underneath the Makassar Strait and its potency to cause tsunami around the eastern part of Kalimantan Rizqi Valentra (a*), Rima Rachmayani (b), Benyamin Sapiie (c) a) Earth Science Study Program, Faculty of Earth Science, Bandung Institute of Technology, Bandung, Indonesia *rizqi.valentra[at]gmail.com b) Oceanographic Research Group, Faculty of Earth Science, Bandung Institute of Technology, Bandung, Indonesia c) Geodynamics and Sedimentology Research Group, Faculty of Earth Science, Bandung Institute of Technology, Bandung, Indonesia Abstract Gigantic Mass Transport Deposits were found underneath the Makassar Strait during a research in 2020. These deposits were formed 2.6 Mya and assumed as the products of submarine landslide events. Through a closer look at the interior and the exterior part of the largest deposit found, it was found that this deposit formed in a very slow movement of mass that transported little by little forming hundreds of kilometers cubic deposit. It is safe to say that these giant deposits are not tsunamigenic. However, these finding did not eliminate the possibility of the slope on the west side of the Makassar Strait being failed. While trying to examine the largest MTD, this research found much smaller size deposits that might move faster that those with huge volume. Through NHWAVE and FUNWAVE, these deposits could cause a VII - VIII class tsunami on some area in the East Kalimantan. This tsunami can cause few people washed away, small vessels damaged, and wooden buildings demolished. Though the scenarios were still rough and the resolution of bathymetry data used could be improved, the result of this research could be used as a preliminary to examine the tsunami hazard on the affected areas since these places located really close to the soon to be capital city of Indonesia. Keywords: Makassar Strait- Submarine Landslide- Tsunami Model Share Link | Plain Format | Corresponding Author (Rizqi Valentra)

74	Ocean Sciences	ABS-48
Rip Current Hazard Assessment for Tourism Safety in Bay of Pelabuhan Ratu, Sukabumi Ari Saputra, Rima Rachmayani, Ankiq Taofiqurohman Bandung Institute of Technology, Padjadjaran University Abstract Sukabumi Regency is one of the regencies in West Java with beautiful and attractive coastal areas for tourism sector that supports the regional economic development. However, rip current are occurred on several beaches at the Loji Beach, Batu Bintang Beach, Pelabuhan Ratu Beach, Citepus Beach, Karang Hawu Beach, and Kebon Kelapa Beach. Rip current is the currents move from coastline toward the seas at varying speeds and the currents are often endanger for the tourist. This study aims to obtain the rip current hazard index and identify the safety period for tourism and determine the best management to improve tourist safety at Pelabuhan Ratu Bay. The present study used wave data, Java Sea bathymetry data, sediment type data, and relative tide range data. Pelabuhan Ratu Bay has a characteristic depth that ranges from 0 - 1800 meters and a coastal slope of 1 - 3 degree. The wave height at Pelabuhan Ratu Bay ranges from 0.4 to 1.2 meters. Depth differences, coastal morphological conditions, and wave height are factors that cause rip currents at Pelabuhan Ratu Bay. Rip current hazard assessment is based on the Rip Current Hazard Assessment Guide (RNLI). Based on the evaluation results of the rip current hazard index at Pelabuhan Ratu Bay, it is 1 to 4 means included in the category safety to very dangerous. The period that is considered relatively safe for tourism based on hazard index of rip current is in June to November because the wave height in those months are lower than other months. Keywords: Hazard Index, Rip Current, Pelabuhan Ratu Bay Share Link | Plain Format | Corresponding Author (Ari Saputra)

75	Ocean Sciences	ABS-49
Study of driving force and surface current patterns in Labuan Bajo from High Frequency Radar Data in October-December 2018 Yustika Baharsyah (a*), Aradea R. Hakim (b), Andri Ramdhani (b), Rima Rachamayani (b) Oceanography, Bandung Institute of Technology Jalan Ganesha 10, Bandung 40132, Indonesia Abstract Surface current data was processed in Labuan Bajo from October to December 2018 to analyse them spatially and temporally and to determine the driving force of surface currents. The current data set is derived from measurements of High Frequency (HF) radar, which operates on the electromagnetic wave spectrum at high frequency or short wave. The average wind speed over three months is 4.39 m/s, with winds primarily from the north and northeast, with the west monsoon strengthening and the east monsoon weakening. With a semidiurnal tidal type, the average elevation value for three months is 1.52 meters. The study area demonstrates that shallow waters have currents that move southward or approach the island of Komodo at irregular speeds, influenced by small islands. Because of the deep bathymetry, the current moves to the west following the wind direction, at a constant speed. The direction of the current indicates that the tides influence current movement in shallow water, whereas the wind influences current movement offshore. The correlation and filtering results show that the influence of tides is greater than the influence of wind at each review point. However, the wind^s influence remains strong, particularly offshore. EOF mode 1 has a variance of 56.2% because of tides, mode 2 has a variance of 26.6% because of bi-weekly variability, and mode 3 has a variance of 17.2% because of the intra-seasonal period. Keywords: Surface current- HF radar- wind, tide- filtering- FFT- Correlation- EOF Share Link | Plain Format | Corresponding Author (Yustika Baharsyah)

76	Ocean Sciences	ABS-55
Seabed Sediments Classification using Multifrequency MBES Bathymetry Data. Khomsin (a,b), Mukhtashor (b), Danar Guruh Pratomo (a), Suntoyo (b) (a) Geomatics Engineering Department ITS Surabaya (b) Ocean Engineering Department ITS Surabaya Abstract Recently, most bathymetric surveys utilized multi-beam echo sounder (MBES) multi-frequency on a ping-by-ping basis, meaning that the depth is measured with different frequencies in several consecutive pings. However, the measured inter-frequency depth in a similar location may be different due to the varying capability of a frequency in penetrating the signal through water and to the seabed sediment. Nevertheless, the depth difference opens the possibility of conducting seabed sediment classification. The hypotheses are that the higher and smaller differences indicate a softer (mud) and more rigid (coral) sediment, respectively. This study attempted to perform seabed sediment classification using a neural network model for testing the hypotheses using MBES multi-frequency data in Bedford Bay of Canada in 2017 obtained from the R2Sonic Multispectral Challenge. Input to the model is the difference of measured depth from frequencies, resulting in a sediment class as output. With 19 stationery-labeled datasets, the test was conducted in a 10-fold cross-validation. The average accuracy was 98.5%, indicating a positive correlation between the thickness of the sediment and the type of sediment that was validated. Keywords: bathymetric difference, multifrequency, sediment classification, neural network Share Link | Plain Format | Corresponding Author (Khomsin Khomsin)

77	Ocean Sciences	ABS-57
Bathymetric Difference Analysis using Multifrequency Multibeam Echosounder Khomsin (a), Mukhtashor (b), Danar Guruh Pratomo (a), Suntoyo (b) (a) Geomatics Engineering Department ITS Surabaya (b) Ocean Engineering Department ITS Surabaya Abstract The primary purpose of a bathymetric survey is to make a nautical chart used for navigational safety purposes. For the safety of the ship^s berth at the port, multitemporal and multifrequency bathymetry data can describe how much sedimentation occurs in the channel or port pool. The bathymetric survey equipment uses acoustic methods such as singlebeam echosounder (SBES) and multibeam echosounder (MBES). The last decades of the development of MBES are multifrequency MBES- the advent of multibeam echo sounders has enormously increased the efficiency, accuracy, and spatial resolution of coastal and ocean mapping. Multifrequency MBES, on a ping-by-ping basis, provides multifrequency data with a single survey platform. The purpose of multifrequency MBES is to get a better detection resolution of the subsurface. By conducting surveys with five modes simultaneously (200kHz, 250kHz, 300 kHz, 350 kHz, and 400 kHz), the user can reduce the effect of this subsidence to get an accurate picture of the seabed. This study aims to bathymetric analysis using multifrequency MBES in shallow coastal water. This study shows that the density of each frequency is 1/5 of the original data. Each frequency of the digital bathymetric model (DBM) is almost similar. Based on the formed DBM, the depth value of the study site ranges from -2.5 m to -11 m LWS. The maximum bathymetric difference is 35 cm between a depth of 200 kHz and 400 kHz. The difference in bathymetry between 250 kHz and 350 kHz is only in the range of -5 cm to 5 cm. The range dredging volume inter frequencies is between 0.015 m3/m2 and 0.080 m3/m2. Keywords: digital bathymetric model, dredging volume, density, shallow coastal water, bathymetric difference Share Link | Plain Format | Corresponding Author (Khomsin Khomsin)

78	Ocean Sciences	ABS-63
Coastline Change Analysis using Landsat-8 on Rebana Metropolitan Area, West Java Tri Kies Welly (a*), Wiwin Windupranata (b) a) Magister Program of Geodesy and Geomatic Engineering, Faculty of Earth Science and Technology, Institut Teknologi Bandung Jl. Ganesha, 10, Bandung, 40132, Jawa Barat, Indonesia *25121022[at]mahasiswa.itb.ac.id b) Hydrography Research Group, Departement of Geodesy and Geomatic Engineering, Faculty of Earth Science and Technology, Institut Teknologi Bandung Jl. Ganesha, 10, Bandung, 40132, Jawa Barat, Indonesia Abstract The Rebana metropolitan area is an industrial area development covering Cirebon-Patimban-Kertajati to support accelerated economic growth, especially in the West Java region. In order to minimize failures in supporting the development targets of the Rebana metropolitan area, it is necessary to carry out spatial planning with consideration of the hazard aspects in the development area, one of the aspects that need to be studied further is the dynamics of the coastal area such as coastline changes that occur due to erosion or sedimentation. Analysis of erosion and sedimentation is essential for further studies to be carried out regarding the factors that cause erosion and sedimentation and how to protect and prevent them in the future. This research utilizes remote sensing techniques and integrated geographic information systems (GIS) to identify coastline changes from 2017-2022 in the coastal areas of Subang, Indramayu, and Cirebon districts which are included in the Rebana metropolitan area. In this study, Landsat-8 satellite imagery is used to identify and quantify Spatio-temporal changes that occur in the coastal area of the Rebana metropolitan area in 6 years. The Normalized Difference Wetness Index (NDWI) algorithm is used to separate wet and dry objects which are interpreted as bodies of water and land. Thresholding the results of the NDWI algorithm along with the on-screen digitization approach was carried out for coastline extraction. The calculation of coastline changes is carried out using the Digital Coastline Analysis System (DSAS) so that the rate of change of coastline in the study area is obtained. During the study period, the results showed that the average erosion rate in the Rebana metropolitan area was -3.66 m/year and the average sedimentation rate was +6.28 m/year, where the greatest erosion rate occurred in Kapetakan sub-district, Cirebon Regency with an average speed -7.63 m/year, and the greatest sedimentation rate occurs in Pusakanagara sub-district, Subang Regency with an average speed +24.64 m/year. Karangampel Subdistrict in Indramayu Regency has 79.89%, the widest erosion area of its total coastline length, and Balongan Subdistrict, Indramayu Regency has the widest sedimentation, 91.37% of the total coastline length. Keywords: Coastline Change, DSAS, NDWI, Rebana Metropolitan Area Share Link | Plain Format | Corresponding Author (Tri Kies Welly Welly)

79	Ocean Sciences	ABS-66
SEA SURFACE TEMPERATURE BEFORE AND AFTER THE CORAL BLEACHING EVENT AND CROWN-OF-THORNS-SEASTAR (COTS) OUTBREAKS IN PULAU LAYANG LAYANG, MALAYSIA MOHD AZAMUDDIN MOHD HASSAN(a*), EJRIA SALEH(a), DANIELLA HAN(a), IVONNE MILICHRISTI RADJAWANE(b) GANDHI NAPITUPULU(b) a) BORNEO MARINE RESEARCH INSTITUTE UNIVERSITI MALAYSIA SABAH, 88400 KOTA KINABALU, SABAH, MALAYSIA *azamuddinums[at]gmail.com b) Department of Earth Sciences, Faculty of Earth Sciences and Technology, Institut Teknologi Bandung, Bandung, Indonesia Abstract Sea Surface Temperature SST is a strong indicator of marine productivity and pollution. It influences the dynamics of climate patterns and impacts marine life and ecosystems. During the Covid-19 pandemic 2019 and 2020, massive coral bleaching events and crown-of-thorns-seastar COTS outbreaks have occurred at Pulau Layang Layang, Malaysia. However, no study was carried out due to the movement control order imposed by the Malaysian government and its remote location, about 272 km from Sabahs mainland. Nevertheless, the advancement of todays technology makes it easier to obtain SST data from satellites. The objectives of this paper are to identify SST at different seasonal monsoons and to determine the SST in Pulau Layang Layang during and after the coral bleaching event. The monthly SST data 2020 to 2022 was retrieved from MODIS Level 3 SST Thermal IR 8 Day 4km V2019.0 at the lagoon and offshore of Layang Layang Island. In-situ SST measurements were obtained from the tide gauge between 20th June 2022 and 26th June 2022. During the Northeast and Southwest monsoons, the average SST was 28.20 degree C and 30.45 degree C, respectively. However, the average SST was increased to 30.92 degree C between May to September 2020 during the SWM which may contribute to massive coral bleaching on the island. The warmer sea temperature is an important co-factor promoting COTS outbreaks. The SST back to normal in 2022 where the in-situ and satellite data were less than 30.05 degree C. However, the landscape of the coral reefs was changed, and may take years to recover to the original condition. Keywords: Sea surface temperature- Coral reef- Moonsoon- Pulau Layang Layang Share Link | Plain Format | Corresponding Author (MOHD AZAMUDDIN MOHD HASSAN)

80	Ocean Sciences	ABS-76
Integration Map (Multibeam Echo Sounder, Side Scan Sonar, and Magnetometer): Pramuka Island Case Study Barnabas Jamot Tambun(a*), Wiwin Windupranata (b) a)Magister Geodesy and Geomatics, Faculty of Earth Sciences and Technology, Institut Teknologi Bandung *tambunbarnabas[at]gmail.com b)Research Group of Hydrography, Faculty of Earth Sciences and Technology, Institut Teknologi Bandung Abstract Tabularasa shipwreck was a Sekolah Tinggi Pariwisata training ship that sank in Pramuka island in 1995 because of the damage in the ship^s engine room. Some parts of the shipwreck have been completely covered with coral reefs, make this uniqueness becomes the added value of this site for a tourist attraction in diving activities. The shipwreck sites potency which are suitable for marine ecotourism development not accompanied by the availability of bathymetry data that supports tourism, especially in diving activities. Due to the data requirements, research was carried out on July 2022 in Pramuka Island by Complex Multi-disciplinary Field project (CMFP) survey by Institute Technology Bandung CAT-A program. Highly resolved bathymetric data are available from Multibeam Echo Sounder (MBES) to detect shipwreck position, side scan sonar (SSS) to generate image data, and Magnetometer to test ferrous object, following the International Hydrographic Organization (IHO) standard considered as 1a order with depth independent (a) less than 0.5m. The field project results indicate that shipwrecks can be identified at depths up to 27-35m. Following through the advantages of these instruments, we develop an integration map to support tourism activities. Keywords: shipwreck- bathymetric survey- IHO- Integration map Share Link | Plain Format | Corresponding Author (Barnabas Jamot Tambun)

81	Ocean Sciences	ABS-84
Evaluation of GNSS Reflectometry Method for Sea Level Estimation in Indonesia Lisa A. Cahyaningtyas (a*), Dudy D. Wijaya (a), Bambang Setyadji (a), Ivonne M. Radjawane (b), Hansan Park (c), Rega Himawan (d) (a) Geodesy and Geomatics Engineering, Institut Teknologi Bandung, Bandung 40132, Indonesia (b) Oceanography, Institut Teknologi Bandung, Bandung 40132, Indonesia (c) Marine Technology Cooperation Research Center - Cirebon Center, Cirebon 45611, Indonesia (d) PT Wisesa Berkah Bumi, Jakarta 133220, Indonesia Abstract Over the last decade, GNSS reflectometry (GNSSR) has been developed as a technique for observing sea level height using data from GNSS satellite observations. GNSSR estimates sea level height from the phase center antenna using the reflection of the extracted GNSS signal at sea level. With a large number of tidal stations equipped with GNSS antennas, GNSSR has the potential to be implemented in Indonesia. GNSSR observations can also cover sea surface areas tens to hundreds of kilometers away from where the antenna is located in coastal areas. Furthermore, the installation of a GNSS antenna at a safe height on land allows for the observation of sea levels during extreme conditions such as storms and cyclones. To employ GNSSR effectively, several factors must be considered, including signal-to-noise ratio (SNR) data analysis, data processing, filtering control variables, and increased frequency extraction. This study will focus on increasing temporal resolution by identifying the best control variables for each study area. This study used three months of GPS and GLONASS satellite SNR data from two stations, Barus and Morotai. The separated multipath data is then analyzed using the Lomb-Scargle Periodogram (LSP) based on its spectral frequency. The results of GNSSR sea surface height observations were validated using tide gauge data from both stations. Based on the test results, the RMSE values were 8.7 cm at the Barus station and 8.4 cm at the Morotai station. When GNSS-R results are compared to tide gauge data, they show a high correlation, with 0.955 at the Barus station and 0.982 at the Morotai station. Furthermore, the residual vector values from the comparison of the main tidal constants (K1, O1, S2, and M2) from tidal and GNSSR sensor data show relatively small values, namely less than 10 cm at both stations. Based on these findings, the GNSSR method can be used to complement tidal sensor data by applying proper quality control. Keywords: GNSS reflectometry, sea level, multipath Share Link | Plain Format | Corresponding Author (Lisa Ayu Cahyaningtyas)

82	Ocean Sciences	ABS-91
Determination of Indonesia Marine Deflection of Vertical from Multi-Mission Altimetry Satellite Data Ahmad Fauzan(a*), Dudy Darmawan Wijaya(a), Ivonne Milichristi Radjawane(b), Hansan Park(c) a)Geodesy Research Group, Institut Teknologi Bandung Jalan Ganesha 10, Bandung 40132, Indonesia *Corresponding Author^s email: ahmdfauznn[at]gmail.com b)Oceanography Research Group, Institut Teknologi Bandung Jalan Ganesha 10, Bandung 40132, Indonesia c)Marine Technology Cooperation Research Center Abstract The geoid is a closed surface that can represent the geometry of the earth and an equipotential surface of gravity that coincides with the mean sea level. Based on data collection, the geoid is divided into land geoid and marine geoid. This research will focus on marine geoid. Marine geoid with high accuracy can be obtained from measurements of shipborne and airborne, but both have limitations in terms of global coverage that is not dense, requires a long time, low temporal resolution, and the data is difficult to access for political reasons thus that it is not possible to use it for modeling marine geoid with a large area. Currently, satellite altimetry is the most important technology for constructing marine geoids because of its uniform global distribution, closer measurement points, consistent level of precision, requires less time, high temporal resolution, and can be used in all weather. Based on the Regulation of the Head of the Geospatial Information Agency (BIG) Number 13 of 2021 concerning the Indonesian Geospatial Reference System (SRGI), it is stated that the vertical reference system used in Indonesia is INAGEOID. The marine geoid component in INAGEOID was obtained from DTU17 which uses data from many altimetry satellite missions, namely CryoSat-2, Jason-1, and SARAL/AltiKa with accuracy in the range of 10 to 20 cm. This accuracy value is still not sufficient as a reference in the large-scale mapping of 1:1,000, namely 5 cm. To improve the accuracy of the geoid, it is necessary to select the right altimetry satellite data and processing methods. The sea geoid is obtained from sea surface height (SSH) measured by altimetry satellites. In order to reduce long wavelength errors in SSH measurements such as satellite orbit errors, signal propagation errors, and topographical errors, SSH gradient calculation is carried out by subtracting between two adjacent SSH points and then dividing by the sphere distance between them. For short distances, the gradient SHH equals the deflection of vertical (DOV). Furthermore, used the inverse Vening Meinesz (IVM) method to convert it into a geoid. This research will carry out high-accuracy DOV determinations from multi-missions altimetry satellite data, namely SARAL/AltiKa, CryoSat-2, Jason-1/2/3, Topex/Poseidon, Sentinel-3A, Sentinel-3B, and Envisat. DOV filtering is done to remove noise that collides with the signal on the shortwave. The DOV that has been filtered is then converted into sea gravity and validated with sea gravity data as a result of shipborne measurements. With this research, it is expected that the accuracy of marine geoid in Indonesia will be less than 5 cm. Keywords: Marine deflection of vertical- satellite altimetry- Indonesia Share Link | Plain Format | Corresponding Author (Ahmad Fauzan)

83	Ocean Sciences	ABS-104
Mapping of Tsunami Evacuation Routes and Shelters in Batukaras Village, Pangandaran Regency, Indonesia Berto Noven, Farras Rizky Haffizh Institut Teknologi Bandung Abstract Abstract- Batukaras is a village located in the Southern Coast of Java Island. The village is part of Pangandaran Regency, one of the top tourist destinations in West Java. Every year, the village attracts national and international tourists to Batukaras beach, famous as a surfing destination. However, the village has seen records of tsunami as recently as 2006, where a tsunami from a 7.7 magnitude earthquake struck the village and caused the death of hundreds and economic losses valued at millions of rupiahs. A series of activities aimed to increase disaster preparedness in the village has been done ever since. Recently, a team from ITB Research and Community Service Institute (LPPM) has made an effort to identify IOC-UNESCO Tsunami Ready indicators in Batukaras Village. Part of the effort is to identify and map the evacuation shelters and signages around the village. Based on the data collected from the field survey, an analysis of the evacuation route was carried out using the network analysis method to obtain the most effective evacuation route to an evacuation location that was considered safe from a tsunami disaster. The results of the evacuation route modeling will later be verified with data on evacuation time using motorbikes and running so that more comprehensive analysis results are obtained. The results of the mapping of tsunami evacuation routes and shelters in Batukaras will later be presented in WebGIS so that later it can be utilized by the local village government as well as visitors in Batukaras Village. Our study resulted in a successful mapping of evacuation routes and shelters in Batukaras Village. Furthermore, the data can be used towards the fulfillment of the IOC-UNESCO Tsunami Ready indicators in Batukaras Village. Keywords: Tsunami, Batukaras, SIG Share Link | Plain Format | Corresponding Author (Berto Noven Marsekal)

84	Ocean Sciences	ABS-109
Zooplankton abundance during the transition and southeastern monsoon season in the Liang coastal waters, Ambon P. Pitriana (1*), H A Mulyadi (2), M S Abdul (3), W Purbiantoro (3), A Basit (4) 1. Research Center for Biosystematics and Evolution, National Research and Innovation Agency (BRIN) - Indonesia 2. Research Center for Oceanography, National Research and Innovation Agency (BRIN) - Indonesia 3. Research Center for Deep-sea, National Research and Innovation Agency (BRIN) - Indonesia 4. Research Center for Climate and Atmosphere, National Research and Innovation Agency (BRIN) - Indonesia Abstract Knowledge of the zooplankton communities, including their interactions with ocean physics, is essential to better understanding the marine environment. In this study, we observed an abundance of zooplankton during the transition period (April - May) and early southeastern monsoon (June) in the Liang coastal waters, Ambon Moluccas - Indonesia. The abundance of zooplankton has been determined using NORPAC net (0.33 mm mesh size) with a sampling depth from the sea surface to 15 meters. In addition, we also measured ocean physics parameters, such as temperature, salinity, dissolved oxygen, phosphate-P, and nitrate-N. Results suggest that the average zooplankton abundance in the transition period (April) was 1,680 individuals/m3, with the most dominant zooplankton was Larvacea (Appendicularia). While in May, the average zooplankton abundance was 3,964 individuals/m3, and copepod Acrocalanus sp. was the most abundant zooplankton. During the southeastern monsoon (June), the abundance of zooplankton slightly decreased to 3,771 individuals/m3, with the most plenteous zooplankton was Larvacea (Appendicularia). Moreover, copepod Rhincalanus was only identified in April and did not found in May and June. Furthermore, Pyrocypris sp., Acetes sp., Mysis sp., and Leptochela larvae were present during May and absent in two periods of the observations. In contrast, Cephalopoda larvae tended to occur only in June. Keywords: zooplankton, monsoon, transition, southeastern, Ambon Share Link | Plain Format | Corresponding Author (Pipit Pitriana)

85	Ocean Sciences	ABS-113
Investigation of Mesoscale Eddies Properties in the Southeastern tropical Indian Ocean: A Comparison between Observation and Reanalysis Data M. Rizqi Ramadhan (*a), Rahaden Bagas Hatmaja (b) a) Oceanography Departement, Bandung Institute of Technology, Ganesa 10, Bandung, 40132, Indonesia *rizqiramadhan[at]students.itb.ac.id b) Research Center for Climate and Atmoshphere, National Research and Innovation Agency Abstract The southeastern tropical Indian Ocean (SETIO) is characterized by high mesoscale eddies activity, as the result of baroclinic instabilities that are associated with the South Java Current (SJC), South Equatorial Current (SEC), and Indonesian Throughflow (ITF), which play a key role in ocean dynamics, environment, and bio-system of this region. Satellite altimetry data and the GLORYS12V1 CMEMS reanalysis ocean product were used to investigate the features of mesoscale eddies in the SETIO. An autonomous eddy tracking system was used to identify the eddies. Along 2019, a total of 263 and 217 eddies were spotted and tracked based on satellite and reanalysis data, respectively. The results elucidates that the analysis of mesoscale eddies variability in ocean reanalysis data shows consistent manner with altimetry observations. Cyclonic eddies appeared to be more abundant and smaller compared to anticyclonic eddies. Larger amplitudes and radii are related with high eddy kinetic energy zones near the SJC, SEC, and ITF outflow. Furthermore, this study strengthens the quantitative understanding of mesoscale eddies dynamics in this region, including eddy formation and propagation. Keywords: altimetry- mesoscale eddies- reanalysis ocean data- Southern Tropcial Indian Ocean Share Link | Plain Format | Corresponding Author (Muhammad Rizqi Ramadhan)

86	Ocean Sciences	ABS-116
Chlorophyll-a Variability in Upwelling Regions in Labuan and Kariamta Strait Gandhi Napitupulu1, Ivonne Milichristi Radjawane1, Ejria Saleh2, Rais Abdillah1, Mohd Azamuddin2 1Department of Earth Sciences, Faculty of Earth Sciences and Technology, Institut Teknologi Bandung, Bandung, Indonesia 2Borneo Marine Research Institute, Universiti Malaysia Sabah, Sabah, Malaysia Abstract Information about sea surface chlorophyll-a variability has an important role as predictive means of the potential fish catching area. The aim of this research is to study sea surface chlorophyll variability at temporal and spatial scale in upwelling areas during the ENSO (El Nino Southern Oscillation) and Indian Oscillation Dipole Mode (IOD). The study sites take place in Labuan (Malaysia) and Karimata Strait (Indonesia). Sea surface chlorophyll variability was analyzed using Global Ocean Biogeochemistry Hindcast data. Sea surface chlorophyll value varies in time and area from an inter-annual variation of global climate (El Nino, positive IOD, El Nino, negative IOD). The range of chlorophyll-a value is 0.2-1.3 mg/m3. Chlorophyll-a value started to increase in March to the peak in April and after that decreased to normal in Karimata strait. The value of chlorophyll-a value started to increase in December to the peak in February and after that decreased to normal in Labuan. Empirical Orthogonal Function is used to decompose chlorophyll-a data. ENSO index has a negative correlation with PC-1 which shows La Nina increases chlorophyll-a value, and El Nino decreases chlorophyll value at JJA, MAM, and DJF periods. ONI index positively correlates with PC-1 which shows positive IOD increases chlorophyll-a value and negative IOD decreases chlorophyll value at SON periods. Chlorophyll-a in Kariamta Strait and Labuan at MAM and DFF period slightly influence by ENSO compared to IOD, which negatively correlates with the ENSO index and chlorophyll-a. Keywords: Chlorophyll-a Karimata strait Labuan Variability Upwelling Share Link | Plain Format | Corresponding Author (Gandhi Napitupulu)

87	Ocean Sciences	ABS-121
Data Reconstruction Of Sea Surface Temperature In Fish Management Area 713 (FMA-713) in Indonesia Waters by Using Machine Learning Susanna Nurdjaman, Rheno A Wicaksono, Aditya R Kartadikaria, Muhammad Rais Abdullah Faculty of Earth Science and Technology, Bandung Institute of Technology Jalan Ganesha 10, Bandung 40132, Indonesia rheno.armand07[at]gmail.com Abstract The FMA-713 in Indonesia is water that has dynamic of temperature changes due to interactions with the Pacific Ocean and cause upwelling at several points. Sea surface temperature data can be obtained by measuring with satellite imagery. However, there are drawbacks to measurements using satellite imagery, namely missing data when measuring sea surface temperature due to cloud cover. In this study, a machine learning method was used to reconstruct sea surface temperature data using a backpropagation neural network algorithm. The data used in this research is data captured with MODIS Satellite with spatial resolution of 4,63 km from 2003 to 2021. the data are separated into test data (4 years) and training data with the variant length of 5 years, 10 years and 15 years. Reconstruction of empty data was carried out by means of single-step prediction and an RMSE value of 0.7 oC was obtained. After reconstructing the blank data, the reconstructed data is used as input for reconstructing the occurrence of sea surface temperature data. This program is made with 4 scenarios, these scenarios are scenario 1 (reconstructed data is empty data), scenario 2 (empty data is filled with zero values), and scenario 3 (empty data is filled with average values) and Scenario 4 (empty data is filled with a value of 28). Accurate results were obtained in reconstructing sea surface temperature where the 4 scenarios had a correlation value of r = 0.96. The results show that scenarios 3 and 4 are the most accurate scenarios compared to the other 2 scenarios with RMSE values ranging from 0.7 oC (scenarios 3 and 4), 12.76 oC (scenario 2), while scenario 1 resulting in the most poor performance compared to the other scenarios. Keywords: The FMA-713, Sea Surface Temperature, Machine learning, Backpropagation Neural Network, data reconstruction Share Link | Plain Format | Corresponding Author (Rheno Armand Wicaksono)

88	Ocean Sciences	ABS-123
Long-term trend and variability of ocean heat content in the Indonesian Maritime Continent Subekti Mujiasih(1)(2),Mochamad Furqon Azis Ismail(1),Abdul Basit(1),Herlina Ika Ratnawati(1), Rahaden Bagas Hatmaja(1), Johanis Dominggus Lekalette(1) (1) Research Center for Climate and Atmosphere, National Research and Innovation Agency (BRIN), Jl. Dr. Djunjunan No. 133 Bandung 40173, West Java, Indonesia (2) GeoHydrodynamics and Environment Research (GHER), Department of Astrophysics, Geophysics and Oceanography (AGO), University of Liege, Sart-Tilman B5a, 4000 Liege, Belgium Abstract The evolution of 64 years of the ocean heat content for the upper 300 meters (OHC300) in the Indonesian Maritime Continent, viz the Banda Sea, the Sulu Sea, the Java Sea, and the Karimata Strait, was investigated to understand its long-term trend variability and its association with El Nino-Southern Oscillation (ENSO) and Indian Ocean Dipole (IOD). The result showed a positive trend in all basins except the Banda Sea. The most significant rise was the Sulu Sea. The fluctuation of OHC300 in the Java Sea and the Karimata Strait followed the trend of IOD and ENSO, in which the OHC300 increased significantly during El Nino and positive IOD. In contrast, OHC300 in the Banda Sea and the Sulu Sea changed conversely compared to the IOD and ENSO. Keywords: Ocean heat content 300 meters, Banda Sea, Sulu Sea, Java Sea, Karimata Strait Share Link | Plain Format | Corresponding Author (Subekti Mujiasih)

89	Ocean Sciences	ABS-124
Ecosystem model simulation in the eastern Indonesian Sea using ECOHAM: model description and validation Suliskania Nurfitri (a), Johannes Paetsch (b), Thomas Pohlmann (b) a) Research Group of Oceanography, Bandung Institute of Technology, Jalan Ganesha 10, Bandung 40132 Indonesia b) Institute of Oceanography, University of Hamburg, Bundesstrasse 53, D-20146 Hamburg, Germany Abstract The eastern Indonesian Sea comprises the Banda and Arafura Seas are subjected to monsoonal winds. Previous studies suggest upwelling in this region during the southeast monsoon from June to August, indicated by lower sea surface temperatures and elevated chlorophyll-a concentrations. We employed a three-dimensional (3D) biogeochemical model ECOHAM (ECOsystem model HAMburg) to understand upwelling mechanisms that drive high chlorophyll-a concentration in this area. ECOHAM is forced by ocean currents derived from HAMSOM (HAMburg Shelf Ocean Model), river run-off, atmospheric deposition, wind stress, and solar radiation. Since it is the first application of ECOHAM in a tropical region, particularly the Indonesian Sea, here we describe model parameterization and settings. In addition, we also present the model validation to nutrient and chlorophyll-a data from observations. Keywords: ECOHAM- Upwelling- Ecosystem model Share Link | Plain Format | Corresponding Author (Suliskania Nurfitri)

90	Ocean Sciences	ABS-125
THE TIMING AND MAGNITUDE OF A HOLOCENE SEA-LEVEL HIGHSTAND IN THE SUNDA SHELF: A REVIEW Septriono Hari Nugroho (a,b*), Yan Rizal (a), Yahdi Zaim (a), Eko Yulianto (b), Abdurahman Prasetyadi (c) a) Department of Geological Engineering, Institut Teknologi Bandung, Jl. Ganesha No.10, Bandung, West Java, Indonesia 40132 b) Research Center for Geological Disaster, National Research and Innovation Agency (BRIN), Jl. Sangkuriang, Bandung, West Java, Indonesia 40135 c) Research Center for Data and Information Science, National Research and Innovation Agency (BRIN), Jl. Sangkuriang, Bandung, West Java, Indonesia 40135 Abstract Knowledge on the timing and magnitude of past sea-level changes in ^far-field^ sites is essential for studying sea-level change, as one of climate change mitigation measures, and for the hope of understanding future sea-level change. Reconstructions of past sea levels, especially on the Holocene Sunda shelf, have been performed by several researchers. The relative sea-level change signal on the Sunda shelf is characterized by the presence of the Mid-Holocene High Stand (MHHS). However, differences in sea level magnitude during the mid-Holocene highstand in this region are controversial. Collected a total of 27 Holocene sea-level reconstruction studies in the Sunda shelf region and reviewed them by first dividing the study area into his five geographic subregions. Each researcher used a different sea level index, such as mangroves or peat, shells, pollen, tidal deposits, diatoms, delta deposits, beach rocks and ridge deposits, shells and corals, sea notches, oysters, microatolls, bivalves. Based on critical assessments of validated relative sea-level indices, we found that there are serious problems related to the correct interpretation of sea-level indices and their relationship to mean sea level, and the quality of dating. A consistent methodology across the Sunda continental shelf for analyzing sea level data is lacking. Future sea level analyzes from far-field sites should include the use of consistent methodologies that allow meaningful comparisons between studies. This will help settle the ongoing debate about the magnitude and timing of MHHS. Keywords: mid-Holocene, sea level, highstand, Paparan Sunda Share Link | Plain Format | Corresponding Author (Septriono Hari Nugroho)

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