Propagation of tropical squall line-induced storm coastal inundation episodes in Java-Bali, Indonesia.

The short-lived tropical squall lines could trigger weather-related hazards to the northern part of the Indonesia Maritime Continent (IMC), such as Sumatra and Kalimantan. Herein, we investigated the rare propagation event of the long-lived Sumatra squall line associated with a severe storm surge that induced coastal inundation in Java-Bali with devastating impacts from 22 May-2 June 2020. With a comprehensive approach combining observational, numerical, and analytical studies, for the first time, we proposed the possible mechanism related to the long-lived squall line over the IMC, which represents the largest equatorial tropical region with the most complicated air-sea interaction area in the world. Our findings suggest that the long-lived squall line related to the supercell-like thunderstorm initiated from multicell over central Sumatra on May 20, 2020, continuously propagated southeastward until several days later reached Bali. The near-quasi steady convective line has 6 hours of time travel from central Sumatra to west Java. The supercell-like rapidly develops from multicell with a deep convective updraft under the strong and fast cold pool (∼13.8 m s-1). The further southeastward propagation of squall line with broken line type seems reinforced by low-level moist transport from the Java Sea. This study also suggested that this unusual event of a long-lived squall line might occur more frequently in the warming upper ocean in the IMC.

Simulated seasonal oceanographic changes and their implication for the small pelagic fisheries in the Java Sea, Indonesia.

Small pelagic fisheries in the Java Sea (JS) contributes to about 26.6% of the total marine fisheries resources, where their spatial-temporal variation is controlled by seasonal oceanographic changes. This study aims to investigate a relationship between seasonal reversal circulation and number of light-fishing vessels (VBD) dispersion that capture small pelagic fishes, using multi-datasets from a regional ocean circulation model, satellite-derived datasets, and pelagic fish landing datasets between 2010 and 2020. The model demonstrates that main axis of eastward (westward) monsoon current that brings warmer and fresher (cooler and saltier) water, confines much closer along the northern Java (southern Kalimantan) during the northwest (southeast) monsoon period. These changes are followed unprecedentedly by southward (northward) shift of VBD and high abundance of euryhaline (stenohaline) fish species. This new evidence implies that reversal monsoon current and surface component of Makassar Throughflow play a significant role on delineating potential small pelagic fishing ground and fish productions.

Stranded marine debris on the touristic beaches in the south of Bali Island, Indonesia: The spatiotemporal abundance and characteristic.

Stranded marine debris (MD) has become a hot topic on Bali Island because it threatens coastal tourism sustainability. This study aims to investigate the spatiotemporal abundance and characteristics of MD on 14 touristic beaches in Bali Island. Sampling is carried out twice every season by adapting methods from NOAA's MD program. We found that the average MD abundance and weight were 0.356 ± 0.366 items/m2 and 4.057 ± 3.892 g/m2, respectively. Plastic dominated the MD based on abundance (86.9%) and weight (40.1%). Plastic bags, straws, and plastic cups are the most common items among plastics. The MD is originated from Indonesia and is dominated by land-based sources. The beaches are categorized as dirty in the rainy seasons and clean in the dry seasons. Statistically, the MD based on abundance, weight, category, source, and level of cleanliness varied significantly between seasons.

Spatial and temporal distribution of microplastic in surface water of tropical estuary: Case study in Benoa Bay, Bali, Indonesia.

In 2010, Indonesia estimated as the second-largest country in the world that donates plastic to the sea. This study aims to investigate the spatial and temporal distribution of microplastics in tropical estuaries. The sampling was carried out in Benoa Bay with four repetitions representing the wet and dry seasons. Spatially it was found that the highest microplastic abundance around the Suwung landfill, while the lowest at Badung River Estuary, middle, and an inlet of the Benoa Bay. The highest percentage to the lowest microplastic based on the size was 500-1000 µm (37.9%), >1000 µm (35.7%), 300-500 µm (22.1%), and <300 µm (4.3%), while based on the shape were fragments (73.19%), foam (17.02%), fiber (6.38%), and granule (3.40%). No significant differences were found between the wet and dry seasons based on the abundance, but significantly varied based on size and shape. Polymers of microplastics were dominated by polystyrene, polypropylene, and polyethylene.

Modelling explicit tides in the Indonesian seas: An important process for surface sea water properties.

Very intense internal tides take place in Indonesian seas. They dissipate and affect the vertical distribution of temperature and currents, which in turn influence the survival rates and transports of most planktonic organisms at the base of the whole marine ecosystem. This study uses the INDESO physical model to characterize the internal tides spatio-temporal patterns in the Indonesian Seas. The model reproduced internal tide dissipation in agreement with previous fine structure and microstructure observed in-situ in the sites of generation. The model also produced similar water mass transformation as the previous parameterization of Koch-Larrouy et al. (2007), and show good agreement with observations. The resulting cooling at the surface is 0.3°C, with maxima of 0.8°C at the location of internal tides energy, with stronger cooling in austral winter. The cycle of spring tides and neap tides modulates this impact by 0.1°C to 0.3°C. These results suggest that mixing due to internal tides might also upwell nutrients at the surface at a frequency similar to the tidal frequencies. Implications for biogeochemical modelling are important.