Java Sea Research Articles

Water paradox in Jakarta (Indonesia)

Indonesia is known as the largest archipelago in the world that is located in the equator line; particularly in a region characterized by a heavy rainfall with a generally high annual precipitation [1]. Jakarta, the capital city of Indonesia, is situated in the northern coast of Java Sea. Due to its geographical position, Jakarta benefits from a high precipitation, on average 2500 mm/year [2], but unevenly distributed timely and spatially. Moreover, Jakarta has 13 principal rivers across the city, but poor water quality. Besides, Jakarta’s artesian basin is productive, but intruded by brackish water from Java Sea. Thus, physically, Jakarta has an abundance of water. However, Jakarta deals with a severe crisis of clean water indicating a paradox: plentiful water resources yet limited clean water. The Jakarta’s inhabitants certainly need the water in their daily activities. This paradox eventually affects their water fulfillment, which attracts the attention of the actors, such as central government, provincial government, water service providers, environmental NGOs, etc.). Each actor probably responds differently, depending on his/her interests. This actors’ behavior constructs current water provision in Jakarta.Based on the issues above, this paper intends to illustrate the state of the art of water paradox in Jakarta. Besides, this paper tries to analyze how the actors respond to this paradox. To reach these objectives, we mobilizes the approach “multilevel and multi governance” because after the fall of General Suharto’s authoritarian government in 1998, Indonesia has entered to “democratic” and “good governance” era. It means that not only central government who involves in water but also other institutions including non-governmental ones. To collect the data, we mobilize primary sources from field works and secondary ones from government and non-government.There are several results of this research. Firstly, although human activities change the physical landscape of water provision in Jakarta, the nature still determines human. For example, due to the meander form of Jakarta’s rivers, water debit is naturally low creating difficulty during clean water production. Secondly, through the analysis of multilevel multi governance, in general we found that there are contradictive actions between the actors: tensions and conflicts, and cooperation. For example, although there is a schema of “Public Private Partnership” between the Government of Indonesia and its partners: Palyja and Aetra, the multinational companies that received water concession production, the conflict happens between them.

Hydrographic datum and GNSS heighting in the SW Java Sea, Indonesia: Comparison between observed and models of Sea Surface

There have been developments of GNSS heighting in hydrography. These are motivated by the need for improving the efficacy of hydrographic operations, through omission of shore-based tidal surveys and post-processed datum reduction of depth soundings. However, this will demand presence of hydrographic separation model (HSM) that defines the vertical relationship of any tidal datum used in hydrography to ellipsoid. In addition to that, a reliable technique for real-time positioning is also required. At the same time, the overall accuracy the use of the entire system (i.e. height datum, vertical positioning) must be identified. This paper discusses the prospect of using models of sea surface for the construction and operation of HSM for the SW Java Sea, Indonesia. The discussion is based on two models of sea surface: the analytically constructed sea surfaces (i.e. HAT, MSL, LAT) according to data from TPXO.7 missions and models of sea surface database published by the Indonesian Agency for Geospatial Information. In order to verify the operability of such models, observation of geodetic heights of instantaneous sea levels across an approximately 13.5 Nm sailing tracks between Pramuka (Seribu Islands) and Ancol (Jakarta) is made. It is evident that the work presented here results in deviation level in the order of several tens of centimetres. This provides reasonably quantified contribution to the error budget against the standard of depth accuracy for data presented on nautical charts as of Zone of Confidence A and hence confirm the prospect of using existing surface models and vertical positioning respectively for the construction and operation of HSM in the domain in question.

The improvement of ultrasonic sensor-based device for direct ocean wave measurement program at Western Java Sea – Indonesia

Sea wave measurement program in the Western Java Sea has been carried out comprehensively over a full one-year period. This activity requires tools that can work robustly and accurately in the long run in the open ocean environment; one of which is the result of modified tidal gauges based on ultrasonic sensors. Testing of modified device has been carried out simultaneously with the RBRduo wave recorder which is installed close to one another. The test was conducted at Ancol beach, Jakarta Bay, with a sampling frequency of 6 Hz, and the measurement time was carried out for 15 days. Measurement data were analyzed by applying the harmonic sea level elevation method, single wave evaluation, and statistical correlation methods. The results of the harmonic analysis show similar types of daily sea level elevations, as well as 9 (nine) daily elevation constituents that are mutually compatible with each other. Results of the wave analysis from the modified device show Hav = 11.9 cm, Hs = 15.4 cm, and Hmax = 41.1 cm, while the RBRduo instrument shows Hav = 11.8 cm, Hs = 18.1 cm, and Hmax = 39.9 cm. Statistical analysis of the wave data shows that the values produced indicate the results of measurements with the two devices have a high correlation. Therefore, it can be concluded that the modified instrument will be ready and reliable to be used for long-term wave measurements. A sample of measurements from the wave station at the Western Java Sea is shown by the end of this paper.

INCIDENCE OF DENGUE HEMORRHAGIC FEVER (DHF) IN SEMARANG COASTAL AREA: EPIDEMIOLOGY DESCRIPTIVE CASE AND BIONOMIC VECTOR

North Semarang sub-district is located on the coast of the Java Sea. The coastal area is characterized by high salt content on both the ground and the water compare to other areas. The high salt content environment should have limited the breeding of Dengue Hemorrhagic Fever (DHF) vectors; yet, quite high incidents of DHF cases are reported taken place in North Semarang coastal area. The aim of this study was to describe the epidemiology of DHF incidence, characteristic of cases, and bionomics vector in the coastal area of North Semarang sub-district. This study was applied descriptive observational design to analyze samples consisting of 62 dengue cases and 184 houses. The research variables consisted of coordinate of DHF cases, water salinity, House Index (HI), Container Index (CI), and Aedes species. Data were processed using SPSS in a bivariate manner; while, mapping was analyzed spatially using ArcGIS 10.3. A total of 184 houses were surveyed and 55 cases of DHF were identified. Most cases occurred in 6 -16 year age group (47.3%), water salinity ranged from 2-3%, indicating that the water in the coastal area tended to be brackish water. The results of the Pearson Correlation test showed that there was no relationship between HI and Incidence Rate (IR) of DHF in North Semarang District. Aedes aegypti was identified in a positive container, otherwise Aedes albopictus was not found. DHF cases mostly occurred in school age groups, and were distributed in all villages near or far from the beach. DHF vector could breed in areas with little brackish water, so that dengue transmission might occur in this area.

Evaluation on Habaring Hurung Pier Pontoon to Improve Service in East Kotawaringin Transport System, Central Kalimantan Province


 
 East Kotawaringin has a relatively large area, namely 16.796 km2 or 10.94 percent of the area of ​​Central Kalimantan province. With an area of ​​regional the East Kotawaringin divided into 17 districts, mostly lowlands. Kotawaringin East region which thousands of cities in Sampit City astronomically lies between 112⁰ 7 '29 "East until 113⁰ 14' 22" East and 1⁰ 11'50 "south latitude to 3⁰ 18 '51" South Latitude. Geographically, in the western part bordering Seruyan District, the north to east by Katingan, and directly adjacent to the southern part of the Java Sea. This district has a topography that varies between 3-85 meters above sea level.The pier is one of the parts that are used to perform an activity arrival and departure of ships, up and down the passenger and cargo handling. The role of the pier is very important to support these activities. To support these activities, the pier used must be in good condition so that the activities coming and departing ships, up and down the passenger and unloading can proceed smoothly. But Pier of Habaring Hurung infrastructure conditions in East Kotawaringin need attention, especially from the manager in this case is the Department of Transportation Kotawaringin East Central Kalimantan province as conditions dock floor height fixed type that does not correspond to the freeboard boat at low tide and condition-type floating dock made of wood and many parts have been weathered, the absence of mooring facilities, bridges poorly and docks are flooded due to the tilt of the wooden pier so that the activity of ships berthing and unloading at the docks less safe, smooth and comfortable for service users, Based on the analysis carried out that the need for evaluation and the addition of facilities and planning of facilities to improve existing services at Pier Habaring Hurung.
 

Some Cheilostomata (Bryozoa) from the Java Sea, central Indonesian Archipelago, with a description of Pleurocodonellina jeparaensis n. sp. (Smittinidae).

The Java Sea region has a high diversity of marine organisms of interest to scientists and tourists alike. Neglected among this diversity are intertidal bryozoans, relatively few of which have been reported from this area. Here we describe six species, one of which is new to science. These were collected from three shallow-water localities-Karimunjawa Marine National Park, Awur Bay and Panjang Island-in the south-central part of the sea. The five known species belong to the families Candidae, Poricellariidae, Onychocellidae, Lepraliellidae, and Phidoloporidae. The new species, Pleurocodonellina jeparaensis n. sp. (Smittinidae), is found at Awur Bay, attached to a bivalve shell fragment. Biogeographically, the suite of species is predominantly tropical Indo-West Pacific in distribution, representing a small fraction of the additional hundreds of species that are anticipated for the Java Sea region.

Kajian Risiko Penangulangan Tumpahan Minyak: Studi Kasus di Laut Jawa Bagian Barat

Risk of oil spill occured from oil exploration and production in marine should be effectively managed. This research is aim to obtain formula of oil spill risk analysis, risk mapping of oil spill in coastal area, and evaluated risk category in regard to be effectively risk management. The study area cover three coastal regions in western Java sea such as Kepulauan Seribu, Northern Java ( Banten, to Karawang coastline) and Eastern Lampung. Oil spill spreading modelling using Mike Zero from three spill sources (Cinta, Krisna and Widuri) resulted potentially impacted coastal by oil spill in certain - 8 months - period (January, February, March, April, May, June, July, and September). Study resulted the ALARP (As Low As Reasonable Practicable) matrix and risk category consist of high, moderate, low and very low category which have range value more than 9.47, 9.46 – 4.23,4.22 – 3.75, less than 3.74, respectively. Mostly, 77% of the impacted coastal ecosystem and resource have moderate to high risk. Distribution of risks dominantly occurred in west moonson rather than east moonson. The matrix of division priority of oil spill mitigation based on cumulative risk exposure have high priority during west moonson occured in division 6, 7, 13 and 15 which were impacted to ecosystem of shoreline, mangrove, coral reef, capture fishery, tourism, and sea port area. Meanwhile, during the east moonson, division 2 and 4 have priority to impacted to shoreline, mangrove ecosystem, marine culture, capture fishery and also tourism

Bacterial isolates from bryozoan Pleurocodonellina sp.: Diversity and antimicrobial potential against pathogenic bacteria

Abstract. Asagabaldan MA, Bedoux G, Bourgougnon N, Kristiana R, Ayuningrum D, Sabdono A, Trianto A, Radjasa OK. 2019. Bacterial isolates from bryozoan Pleurocodonellina sp.: Diversity and antimicrobial potential against pathogenic bacteria. Biodiversitas 20: 2528-2535. There is an urgent need to discover new compounds with antibacterial activity, which can be developed into lead structures for the treatment of human disease caused by multidrug-resistant (MDR) bacteria. In this study, we focussed on bryozoan-associated bacteria to screen them toward antibacterial activities, since the microbiome of these organisms can still be regarded as under-investigated. Most of the few publications about bryozoan-associated bacteria focused on taxonomy and the potential as producers of antibacterial natural products were neglected. Four specimens of bryozoan Pleurocodonellina sp. were collected from Teluk Awur, Jepara in Java Sea, Indonesia. Therefrom, 56 bacterial strains were isolated, and 17 displayed antibacterial activities against MDR bacteria Pseudomonas aruginosa, Klebsiella pneumoniae, Acinetobacter baumannii, Enterobacter cloacae, and methicillin-resistant Staphylococcus aureus (MRSA). Taxonomic identification of the bacteria by 16S rRNA gene sequencing revealed them belonging to the genera Virgibacillus, Pseudoalteromonas, Halomonas, and Bacillus. Most interestingly, the genus Virgibacillus was dominantly obtained from the Pleurocodonellina sp. specimens, i.e., 12 active isolates. Nevertheless, the best activities against MDR bacteria (both Gram-positive and Gram-negative) were contributed to isolates showing >99% identity to Pseudoalteromonas. The results further suggest adding the genus Virgibacillus as bacteria associated with bryozoan, since to the best of our knowledge there were no reports of this genus isolated from bryozoan.

Analisis Temporal Suhu Permukaan Laut di Perairan Indonesia Selama 32 Tahun (Era AVHRR)

One of the important factor that influences global climate dynamics is sea surface temperature (SST). Indonesian waters are semi-closed and located between the Pacific and Indian Oceans so that they have different characteristics of SPL in each region. The purpose of this research is to know the trend and local characteristics of Indonesian SST and adjacent areas in response to 6-monthly and seasonal variability with moving average method and correlation. The data used are SST data from AVHRR satellite with domain 15°N-15°S, 90°-145° E. The results showed of increase trend 0.34°C in Indonesian sea for 32 years (1981-2012). The characteristics of SST in Indonesian territory are closely related to the Mosoon cycle where in the East period in the northern region the Natuna Sea is warmer in contrast to the West monsoon period, in the southern part of the Arafura Sea to the warmer Sawu Sea and around the equator experiencing the warmest in the transitional period. The moving-average analysis shows that 6-monthly variability appears to be dominated in equatorial waters including the Java Sea and Banda Sea whereas seasonal variability occurs in the northern and southern regions of Indonesia's waters including the Pacific Ocean Oceans, the northwest Pacific Ocean and the southeast Indian Ocean. Based on correlation analysis, ENSO has a strong (negative) relationship in eastern Indonesia waters including the Sea in the northern part of Papua and the northwest Pacific Ocean while IOD has a strong (negative) relationship in the western Sumatra Sea, Banda Sea and Arafura Sea.

Surface Wave Tomography Using Seismic Ambient Noise Data for Subsurface Imaging beneath Bandung Basin, West Java and Its Surrounding

Seismic interferometry was applied to estimate the shear wave velocity structure beneath the Bandung Basin, West Java. The empirical Green’s function (EGFs) were obtained by cross-correlate each pairs of seismic stations from the temporary seismic network installed in the research area. In this research, we use Rayleigh wave dispersion data as the input for surface wave tomography. The obtained dispersion curves of Rayleigh waves are in the period range 1 - 12 s. The dispersion characteristics of EGFs was also analyzed to estimate the distribution of the ambient noise sources. Based on the symmetricity characteristics of the dispersive signals of EGFs from all two station pairs oriented relatively in N-S and W-E the seismic noise sources was originated from oceanic activity at the Coastline of Java Sea. Furthermore, the dispersion curves also show that the group velocities vary within range of 1.6–2 km/s. The inverted dispersion data into depth models provide the variation of shear velocity structures at depth 1–5 km in the range of 1–2.1 km/s. At depth 1–4 km, there appear high and low velocity contrast in the south of Mt. Tangkuban Perahu, which is may be related to the existence of Lembang Fault. Meanwhile, velocity models at depth 1–3 km show the lateral variation of shear wave’s velocity in the Bandung Basin. The high velocity structures within range 1.8–2.1 km/s lies in the Southwest toward Northeast in the middle of Bandung Basin. This structures divide Bandung Basin into two parts, Western part and Eastern part.

'X-ray gun' identifies sources of Song Dynasty porcelains from a shipwreck in the Java Sea

'X-ray gun' identifies sources of Song Dynasty porcelains from a shipwreck in the Java Sea

'X-ray gun' identifies sources of Song Dynasty porcelains from a shipwreck in the Java Sea

'X-ray gun' identifies sources of Song Dynasty porcelains from a shipwreck in the Java Sea

First record of the Mozambique tilapia, Oreochromis mossambicus Peters, 1852 (Perciformes, Cichlidae), on Kangean Island, Indonesia

In 2019 we captured specimens of Oreochromismossambicus Peters, 1852 from Batu Batu River, an estuary river on Kangean Island (Indonesia), a conservation area in the Java Sea. These records are among the first of this species from an island in the Java Sea. A description of morphological characters of sampled specimens is provided.

Holocene sea levels in Southeast Asia, Maldives, India and Sri Lanka: The SEAMIS database

We assembled a database of Holocene relative sea-level index points (n = 213) and marine (n = 211) and terrestrial (n = 122) limiting points for the broader South and Southeast Asian region including the Maldives, India and Sri Lanka. The standardized review of published age-elevation information from corals, deltaic, estuarine and mangrove deposits, beachrocks and tidal notches, yielded a new suite of relative sea-level index and limiting points produced according to a standardized protocol. Expected spatial variability in Holocene relative sea-level change due to glacial isostatic adjustment was accounted for, by first subdividing the study area into ten geographic sub-regions from the Central Indian Ocean to the Western Tropical Pacific, and second by comparing sub-regional relative sea-level data to model predictions of glacial isostatic adjustment. Results show that some of the regionally constrained relative sea-level data are characterized by significant inconsistencies that cannot be explained by glacial isostatic adjustment. Such inconsistencies of standardized relative sea-level data become particularly obvious in areas around the Red River Delta in Vietnam, the Gulf of Thailand, the northwest coast of Malaysia and the Spermonde Archipelago in Indonesia. Based on a critical evaluation of the reviewed relative sea-level indicators, we discuss possible sources of local divergence and identify regions where data are currently insufficient to constrain glacial isostatic adjustment predictions. The remaining quality-controlled and consistent relative sea-level data show that glacial isostatic adjustment and syn-/post-formational influences such as tectonic uplift, subsidence and compaction were the dominant local drivers of Holocene relative sea-level change. Collectively, the results of this review suggest that Holocene sea levels in South and Southeast Asia and surrounding regions have been controlled by a variety of global and local drivers and imply that additional index points from the Java Sea in Indonesia would be valuable to better assess the spatial variability, and to calibrate geophysical models of glacial isostatic adjustment.

PEMANFAATAN SISTEM INFORMASI GEOGRAFIS UNTUK MENENTUKAN LOKASI POTENSIAL PENGEMBANGAN KAWASAN INDUSTRI DI KABUPATEN PATI

Pati is one of the regency in Central Java Province which has a strategic position because it is crossed by the Java pantura line and also directly borders the Java Sea which is a trade route in Indonesia. In the case of the construction of an industrial area the use of spatial data and analysis of Geographic Information Systems (GIS) can be used to determine potential locations suitable for the construction of industrial estates without overriding the environment and society. The results of the analysis of eight parameters are slope slope (29.54%), land distance to the main road (29.36%), land distance to infrastructure and trade center (8.25%), land use (8.21%), soil type (7.22%), land distance to rivers (5.23%), land distance to energy networks (6.75%), and land distance to communication networks (5.44%). The weighted overlay analysis of the scoring values of each parameter produces a location that is very suitable for industrial estates (S1) covering an area of 1221, 431 ha, suitable for industrial estates (S2) covering an area of 83749,160 ha, quite suitable (S3) covering 55024,181 ha, not suitable (N1) covering an area of 9169,273 ha, and not suitable (N2) covering an area of 388,637 ha whereas based on the intersect map analysis of the results of overlays and maps of the Pati Regency RTRW, the most suitable location for the industrial area is 24,220 ha. From the calculation, the potential location that can be used for industrial estates in Pati Regency is 1197,211 ha. This location is in Margorejo district, Pati district, Juwana district, Batangan district, Sukolilo district, and Tambakromo district.

Exploring the Importance of the Mindoro‐Sibutu Pathway to the Upper‐Layer Circulation of the South China Sea and the Indonesian Throughflow

AbstractUsing a high‐resolution (0.1° × 0.1°) regional ocean model, this study investigates the impact of strait transport variability on the South China Sea (SCS) circulation and Indonesian throughflow, with a focus on the Mindoro‐Sibutu pathway via the Sulu Sea, upon closing various straits within the Maritime Continent. Closing the Sibutu Strait reduces the Luzon Strait throughflow into the SCS by 75%, and the Mindoro–Sibutu deep exchange is reversed, thus flowing into the SCS. No significant change occurs over the shallow Sunda Shelf of the southern SCS, which is primarily driven by local monsoon winds. The impact of closing the Karimata Strait is limited to the Sunda Shelf and the Java Sea. The Sibutu Strait throughflow is fundamental in governing the SCS's low salinity, buoyancy, and upper layer injection into the Makassar Strait, which is the primary component of the Indonesian throughflow, thus inhibiting the transport within the upper 200 m of the throughflow. Closing both the Sibutu and Karimata Straits increases the southward Makassar Strait throughflow transport by ~3 Sv, which is derived entirely from the Mindanao Current.

Infografis Sebagai Pendukung Berita In-depth Dalam Situs Berita Online

Tirto.id merupakan situs berita online yang dikenal dengan infografisnya. Informasi yang dimuat dalam Tirto.id umumnya merupakan laporan in-depth yang memiliki karakteristik tulisan dengan durasi panjang. Salah satu berita yang menarik adalah mengenai penjarahan bangkai kapal perang di perairan Indonesia berjudul “Misteri Raibnya Bangkai Kapal Perang Belanda di Laut Jawa” edisi 18 Januari 2018. Berita tersebut mnejadi laporan eksklusif Tirto.id. dengan durasi tulisan yang cukup panjang. Namun, kehadiran infografis merupakan satu cara memahami berita yang panjang lebih mudah dan cepat. Menggunakan metode studi kasus, penelitian ini bertujuan melihat fungsi infografis dalam berita in-depth. Hasil yang ditemukan adalah: (1) Infografis yang disajikan Tirto.id pada tulisan in-depth-nya memiliki beberapa karakteristik seperti penggunaan layout yang lebih formal dibandingkan layout infografis berita lainnya, data yang diinput memuat nilai berita, dan penggunaan warna-warna cerah serta ilustrasi yang menarik; (2) Kedalaman informasi yang disuguhkan infografis in-depth dirasa masih kurang jika dibandingkan dengan kedalaman berita itu sendiri, namun antara infografis dan isinya merupakan kesatuan yang saling melengkapi; (3) Penggunaan infografis dalam sebuah berita in-depth tidak lain sebagai penarik perhatian pembaca.

Preliminary study of the effect of nutrient enrichment, released by marine floating cages, on the coral disease outbreak in Karimunjawa, Indonesia

Coral disease is a significant factor causing the degradation of Karimunjawa coral reefs. The objective of this study was to determine the possible effects of nutrient enrichment, released by floating cages used for fish culture, on the coral disease outbreak in Karimunjawa National Park, Java Sea. The islands of Genting, Sambangan, and Seruni were selected as study sites as they represent islands with human habitation and a high intensity of mariculture activity, no human habitation and a high intensity of mariculture activity, and no human habitation or mariculture activity, respectively. The results show that the prevalence of coral diseases in Genting, Sambangan, and Seruni were significantly different (p < 0.01). However, there was no significant correlation between the nutrient concentrations (N and P) and coral disease prevalence (R 2=0.39; p = 0.07 for nitrate and R 2=0.42; p = 0.058 for phosphate). The nutrients on the islands affected by marine fish cages tended to increase. We suggest that the continuation of orderly ecosystem monitoring, with increasing sample sizes, in Karimunjawa is urgently needed.

Impact of Land Subsidence and Sea Level Rise Influence Shoreline Change in The Coastal Area of Demak

Climate change has a negative impact on the environment, one of which is the phenomenon of sea level rise. Sea level rise has a devastating effect on marine coastal areas such as shoreline abrasion. Sea level rise has caused a reduction in land, one area on the north coast of Java affected is located in Demak. Demak is a coastal area that has the potential for a shoreline abrasion because of sea level rise and a decrease in the land surface. Monitoring of shoreline changes needs to be monitored in order to find out the magnitude of the shoreline changes and the impact caused by reduced a mainland. One method that can be used to monitor shoreline changes is to use remote sensing technology. Satellite imagery can produce changes in shoreline abrasion without coming to the objects directly. This study aims to assess sea level rise and land subsidence resulting in changes in the shoreline in Demak. The data used are Jason-1 and Jason altimetry satellite data 2, Landsat 7 ETM + satellite imagery in 2011 and Landsat 8 in 2016. Altimetry satellite data is processed to obtain sea level rise on the coast of the Java Sea. Sea Level Anomaly (SLA) data processing uses Inverse Distance Weight (IDW) interpolation. The rise in sea level is determined by the analysis of linear trends from the processing of altimetry satellite data. The separation between water and land boundaries from Landsat satellite imagery uses the band ratio method on Green bands and NIR bands. shoreline changes are calculated using DSAS (Digital Shoreline Analysis System). The results of data processing obtained an average sea level rise in the Java Sea in 2011 to 2016 of + 6.80 mm/year. The highest increase was in Jakarta waters of +11.043 mm / year and the lowest was in Surabaya waters with an increase of +3.85 mm/year. The increase in Semarang waters was + 5.52 mm/year which was used as validation with the tidal data of Semarang. The average change in coastline in the Demak region is -119.08 m. Demak experienced a land subsidence of +2,078 to -8,376 cm/years. The biggest abrasion occurred in Sayung Subdistrict of -691 m. The largest accretion occurred in the District of Wedung + 512.48 m. Based on the results of the increase in water level in the coastal areas of the island of Java and land subsidence that occurred in Demak caused a fairly wide shoreline abrasion.

Maritime Continent water cycle regulates low-latitude chokepoint of global ocean circulation

The Maritime Continent (MC) is a low-latitude chokepoint of the world oceans with the Indonesian throughflow (ITF) linking the Indo-Pacific oceans, influencing global ocean circulation, climate, and biogeochemistry. While previous studies suggested that South-China-Sea freshwaters north of the MC intruding the Indonesian Seas weaken the ITF during boreal winter, the impact of the MC water cycle on the ITF has not been investigated. Here we use ocean-atmosphere-land satellite observations to reveal the dominant contribution of the MC monsoonal water cycle to boreal winter−spring freshening in the Java Sea through local precipitation and runoff from Kalimantan, Indonesia. We further demonstrate that the freshening corresponds to a reduced southward pressure gradient that would weaken the ITF. Therefore, the MC water cycle plays a critical role regulating ITF seasonality. The findings have strong implications to longer-term variations of the ITF associated with the variability and change of Indo-Pacific climate and MC water cycle.