Sea level variations along the coasts of Sumatra and Java were investigated to determine the coastal upwelling signal that is linked to local sea surface temperature (SST) variability. We used Indonesian tidal station data together with satellite SST data and atmospheric reanalysis data. The sea level variations along the southern coast of Java have a significant coherence with remote wind, local wind, and local SST variations, with an intraseasonal time scale of 20–50 days. Assuming that a coastal upwelling signal would appear as a sea level drop (SLD), we focused on intraseasonal‐scale SLD events in the data. Significant upwelling signals are frequently observed during both the boreal summer and winter. To evaluate the impact of the coastal upwelling on local SST, we examined statistical relationships between sea level and SST variations. The results demonstrated that events that occurred during April–August were associated with local SST cooling. The horizontal distribution of the SST cooling was analogous with annual mean SST, suggesting the importance of intraseasonal‐scale coastal upwelling in forming the climatic conditions of the southeastern tropical Indian Ocean.

Karimata strait and the java sea is one of the most densely shipping lanes in the maritime country of Indonesia. Information of a significant wave is needed to safety navigation. The prediction of a significant wave mostly employs the modeling using wind as input data to produce an early warning warning prediction. Characteristic of a significant wave shows the maximum wave height in the strait and the java sea karimata occurs in west monsoon (January) and east season (August) every year. Especially at the peak of west monsoon (January) maximum wave height reach 1.5-3 meters in Karimata Strait, and reach 0.5-2.5 meters in Java Sea. The frequency of significant wave occurences mostly extend until February, where wave height in Java Sea will stay the same (0.5-2.5 meters), while in Karimata Strait is little bit decrease (1-2.5 meters). Recommended to all sea transportation users, in those regions during January and February, to avoid using ship with the hull is less than 3 meters height.Keywords: significant wave characteristic, Karimata Strait, Jawa Sea, Wind, Modeling

This study presents the assessment and seasonal variation of wave energy along the southern coast of Java, Bali, and Nusa Tenggara Waters. For this purpose, the WAVEWATCH-III numerical model was used to simulate the Significant Wave Height in the study region over 25 years covering the time interval of 1991–2015. Wind field data input for the model was a combined dataset of Cross-Calibrated Multi-Platform, Navy Global Environmental Model, and Navy Operational Global Atmospheric Prediction System. In general, the simulation results showed that there was a good potential of wave energy along the southern coast of Java and Bali with the value of higher than 20 kW/m. Furthermore, it was found that there were 12 points which were considered to be the most promising high wave energy potential spots along the near-shore coastal waters of the Java and Bali southern coast. There was a noticeable seasonal variation of wave energy along the study area associated with tropical monsoon climates, which led to the highest value in the period of June to August for about 40 kW/m and the lowest value in the period of December to February for about 20 kW/m. All the selected points for wave energy exhibited dominant wave propagation between northward and northeastward. Moreover, there was an evident increasing trend of wave energy with the peak value appearing in 2005 for all stations.

Indonesia mempunyai peran yang cukup besar dalam negosiasi internasional untuk mengelola dampak dari perubahan iklim. Peran tersebut antara lain dengan menyelenggarakan the 13th Conference of the Parties to the UNFCCC di Bali yang menghasilkan the Bali Action Plan. Peran pada isu perubahan iklim di atas merupakan konsekuensi logis dari besarnya bahaya dan kerentanan wilayah Indonesia terhadap fenomena global tersebut, antara lain di wilayah pesisir dan laut. Secara lebih spesifik, wilayah Indonesia bagian timur memiliki karakteristik bahaya dan kerentanan terhadap perubahan iklim. Kenaikan muka air laut dengan laju sekitar 0,6-0,8 cm/tahun, yang dapat menimbulkan dampak pada wilayah pemukiman, infrastruktur, dan ekosistem di wilayah pesisir serta pulau-pulau kecil. Sementara itu, peningkatan intensitas El Niño dan La Niña menyebabkan terjadinya perubahan pola arus dan sirkulasi laut seperti Arus Lintas Indonesia di Selat Makassar yang akan berdampak pada hasil tangkapan ikan. Selanjutnya, karakteristik gelombang laut juga mengalami perubahan sebagai akibat dari perubahan variabilitas iklim yang berdampak pada sektor transportasi laut. Selain itu, peningkatan intensitas La Niña, menyebabkan kenaikan intensitas pemutihan terumbu karang (coral bleaching) sebagai akibat dari kenaikan suhu permukaan laut yang drastis. Mengingat besarnya dampak dan kerentanan di wilayah Indonesia bagian timur tersebut, perlu disusun strategi adaptasi, yang meliputi strategi proteksi, akomodasi, dan retreat-adaptation.

We discovered that the local wind was not the only factor that contributed to the formation of eddies in the area. The difference in South Java Current (SJC) flow compared to the Indonesian Throughflow (ITF) and South Equatorial Current (SEC) flow as well as the difference in the relative velocity between the currents in the area led us to suspect that shear velocity may be responsible for the formation of eddies. The results from our model corroborated our prediction about shear velocity. Therefore, we attempted to explain the appearance of eddies in the SETIO based on the concept of shear velocity. By observing and documenting the occurrences of eddies in the area, we found that there are 8 cyclonic and 7 anticyclonic eddies in the SETIO. The distribution and frequency of the appearance of eddies varies, depending on the season.