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The Gulf of Madura is heavily utilized for shipping, fishing, and oil exploration. These activities impact the marine environment. This study aims to describe the spatial and temporal variability in oceanographic parameters, vertical current structures, trends, and ocean health conditions based on oceanographic parameters estimated from the OHI value. The data used in this research consists of INDESO and Marine Copernicus data. The results of the study show that monsoon phenomena greatly influence temperature and salinity in the Gulf of Madura, with temperature increasing and salinity decreasing during the northwest monsoon, and vice versa during the southeast monsoon. An analysis of oceanographic variables over the past 12 years showed an increase in salinity and nitrate variables, and a decrease in other variables. The trend fluctuation is still within the quality standard for seawater according to government regulation number 22 of 2021. The results of the calculation of the ocean health index show that the Gulf of Madura is in a fair condition with a value of 0.63. This finding can be used to manage and utilize marine space sustainably without deteriorating the ocean’s health.

Activities such as fishing ports and power plants on the coast of Pelabuhanratu Bay have recently developed and hence, their input of metal-containing waste may influence the seawater quality of the bay as the fishing grounds. This study aimed to determine the potential sources (i.e., anthropogenic and natural) and pollution status in sediments. Sediment samples were collected once at 10 stations in the bay using a Van Veen grab. The geochemical partitioning of non-residual and residual phases of metals was used to assess the anthropogenic and natural sources, respectively. The status of metal contamination was evaluated by determining the geo-accumulation index (Igeo), contamination factor (CF), and pollution load index (PLI). Generally, Cu was dominant in residual fractions ranging 62.79-81.24%, while Zn ranged 39.56-66.02%. This suggests that Cu and Zn in Pelabuhanratu Bay are naturally sourced. Furthermore, the average geo-accumulation index of Cu was categorized as unpolluted (-0.86), and Zn was lightly polluted (0.87). The CF of Cu indicates the uncontaminated category (0.85), whereas Zn indicates a moderate contamination category (CF = 1.54). The pollution level (PLI) in Pelabuhanratu Bay is generally lightly polluted (PLI 1,135).

secondary pathway of Indonesian Throughflow (ITF) that enters from its inflow portal of the northern Maluku Sea is assumed to recirculate in the Banggai - Maluku Sea, where its upper-layer circulation returns into the Pacific and deeper flows continue southward into Seram/Banda Sea via Lifamatola Strait. However, direct observation in this key region is still limited. Here, using direct CTD (Conductivity Temperature Depth) casts and shipboard ADCP (Acoustic Doppler Curent Profiler) measurement datasets from BUDEE (Banggai Upwelling Dynamics and Ecosystem Experiment) cruise in September 2023, we study stratification and structure of ITF water and its circulation in a meridional section along 125E. The results show the water mass stratification of the mixed layer having a depth of 0-75m with a temperature range of 26-29°C, while the thermocline layer has a depth of 28-407m with a temperature range of 23-26°C, and the deep layer has a depth of 407-1000m with a temperature value of 4-12°C. The current pattern of the Banggai Sea Maluku Sea at a depth of 52-400m is more dominantly influenced by non-tidal currents, the influence of tidal currents only covers a depth of 52m less than non-tidal currents.

Banggai Waters is in the western Maluku Sea, where the secondary pathway of Indonesian Throughflow passes and seasonal coastal upwelling takes place in this region, providing a high marine productivity and potential fishing ground. This study aims to describe water mass stratification and circulation using CTD casts and SADCP section datasets from the BUDEE cruise in September 2022 onboard RV Baruna Jaya VIII. The results show that mixed layer depth varies between 43-112 m with a mean temperature of 25.82(± 0.88) ºC. North Pacific water origin (NPSW and NPIW) is present in this southern section. The depth of chlorophyll maximum is much shallower in the upwelling center. Furthermore, for the first time, we identified a strong northward flow from the Bote Strait, disrupting Banggai upwelling water with cooler and fresher Banda water. Estimates of northward transport volume through this strait is about 0.531 Sv.

Indonesian seas have been known as the hotspot for internal waves (IWs) generation sites. The sinking tragedy of the Indonesian Naval Submarine, KRI Nanggala 402 on 21 April 2021 in the northern Bali Sea was highlights the need of detecting, mapping, and characterizing internal waves in Indonesian waters are compulsory mainly in the Indonesian Archipelago Sea Lanes (IASLs). IASLs is a gateway for sea crossings which can be used by civil navigations, intercontinental trade, and foreign military. This study focused on mapping the distribution and characteristics of internal waves qualitatively using EA 600 Single beam Echosounder (SBES) of the Indonesian Naval Vessel, KRI Rigel 933 during The Jala Citra Expedition 2-2022 Banda. The measurements were conducted around the IASLs route in the Bali Waters, Banda Waters and Buru Waters. The results show that the typical highfrequency non-linear internal waves (HFNWs) with an amplitude of less than 10 m were observed intermittently during the expedition, detected mostly in the narrow passages, rough topography and shallowing waters. Typical characteristics of internal solitary waves (ISWs) were also observed with typical amplitudes of ~20 - 65 m. An ISWs extreme events found in this study verified the "turbulent water" that was reported in in the IASLs around the Underwater Seamount (US) Nieuwerkerk waters, in 1925 during the Snellius Expedition. The detection of internal wave events using acoustic equipment, the single beam echosounder is considered effective which can later be used as the guidance for marine activities in the water column. [ABSTRACT FROM AUTHOR]

The eastward propagation of atmospheric waves along the equatorial band from the central equatorial Indian Ocean to the western Pacific Ocean passing through the Indonesian Maritime Continent (IMC), known as the intraseasonal Madden Julian Oscillation (MJO) event, plays an important role on modulating both atmospheric and upper ocean dynamics along its path. This study aims to investigate the MJO active phase dynamics and its impact on changes in near-surface seawater temperature and mixed layer depth (MLD) anomaly in the Banda Sea Indonesia, using multi-datasets of atmospheric reanalysis, satellites derived sea surface temperature (SST), and Argo float between 2017 - 2018. This study revealed that the MJO waves propagate eastward along the southern equator-line over the IMC and pass through the Banda Sea, associated with significant decreased on Outgoing Longwave Radiation (OLR) and increased in zonal wind speed at 850hPa. The study result shows anomalous increased on surface wind speed and SST cooling during of MJO active phase. The amplitude peaks of filtered ocean-atmosphere variables range between 30 - 60 days. Argo float datasets in the Banda Sea for the first time captured upper ocean responses to the arrival of the MJO active phase, as characterized by a negative temperature anomaly of ~0.3°C in the surface mixed layer, large temperature anomaly of ~0.8°C in the thermocline layer and the deepening of the MLD of ~25 m. Hence, the MJO active phase impacts significantly on surface and vertical temperature cooling and regulate upper ocean mixing intensity in the Banda Sea. [ABSTRACT FROM AUTHOR]

The Tomini is one of the largest gulf in Indonesia. The gulf also has a unique profile and adjacent to Maluku Sea which is the eastern route of the Indonesian Throughflow. The purpose of this research is to investigate and analyze the circulation patterns that occur inside the gulf of Tomini and Maluku Sea as well as the variability of physical parameters such as temperature, salinity and transport volume and to correlate the driving factors of ocean-atmosphere phenomena that affect these physical parameters using the INDESO model dataset from January 2008 to December 2014 (7 years). The results showed that the surface circulation in the gulf and Maluku Sea flows southeastward to the Lifamatola Strait during the northwest and 1st transition, during the southeastern season the circulation flows leaving Maluku Sea through the ITF entry to the Pacific and Sulawesi Seas, and then flows southeastward during 2nd transition. The seawater temperature in the study area ranges between 28.6 - 32.0°C and the salinity varies between 32.2-34.4 psu. Vertical structure of zonal current in the gulf reveals velocity range from 0.02-0.3 Sv and the surface layer current is dominated by the westward flow, while at 20-60 m depth the flow is eastward. The mean transport volume at transects 123°E is about -0.028 (±0.2578) Sv. Variability of transport volume revealed spatial anomalies and periodicity on the intra-seasonal, semi-annual, annual, and inter-annual time-scales. Those are significantly coherence with zonal and meridional winds forcing in the Indo-Pacific region. [ABSTRACT FROM AUTHOR]

This study investigates the coherency of volume transport between Halmahera throughflow and current major system in the western equatorial Pacific Ocean (Mindanao Current – MC, New Guinea Coastal/Under Current – NGCC/NGCUC, and North Equatorial Counter Current – NECC). The validated daily ocean general circulation model datasets of INDESO (2010-2014) were used in this study. The results showed that the estimated average transport volume was 25.6 Sv flowing southward through MC, 34.5 Sv flowing eastward through NECC, 18.3 Sv flowing northwestward through NGCC/NGCUC, and 2.5 Sv flowing southward through the Halmahera Sea. The variability of volume transport was dominated by intraseasonal, semiannual, and annual time-scales. The increased transport of NECC corresponded to the intensification of MC and NGCC/NGCUC transports. NGCC/ NGCUC significantly controlled the South Pacific water inflow into the Halmahera Sea because of the positively high correlation between NGCC/NGCUC transport and Halmahera throughflow transport. [ABSTRACT FROM AUTHOR]

Seasonal upwelling phenomenon in the Arafura Sea plays an important role on supplying upwelled nutrient-rich water to sustain biogeochemistry processes and thus contributes to high marine primary productivity and fisheries resources in this region. The objective of this research was to investigate physical process and dynamics of upwelling by analyzing stratification of seawater properties, evolution of surface ocean-atmosphere parameters, and current structure and transport volume in the northern Arafura Sea. The multi-datasets in 2017 were used in this study, acquired from field CTD measurement, satellite-derived sea surface parameters, and the ocean general circulation model outputs, which were processed and analyzed using the available standard procedure. It was found that upwelling event was associated with a sharp subsurface thin layer that upsloping isotherms (23.5 - 25.5 °C), isohalines (33.50 - 34.25 psu), and isopycnals (21.8 - 23.2 kg/m³) from the shelf-break region to the inner shelf region at a distance of approximately 167 km. This barrier layer separated the first surface mixed layer from the second mixed layer beneath the subsurface layer. The model suggests that the current in these two layers is in the opposite direction, to the west in the first layer as a response to the Ekman drift and to the east in the second layer as a current extension from deep Aru basin. Therefore, upwelling dynamics here is not only generated by the southeasterly monsoon winds from May (onset) to November (termination) that transport warm and fresh surface water away from the shelf, but also modulated by the presence of strong inflow currents beneath subsurface that supply colder saltier nutrient-rich water into the shelf. During the upwelling period, mean transport volume in the upper 25 m depth between Aru and Papua at 134.25°E was -0.28 (±0.34) Sv (westward), but the transport volume between 25m and 110m depth was +1.06 (±0.29) Sv (eastward), suggesting this inflow may regulate the upwelling and supply Arafura shelf water. [ABSTRACT FROM AUTHOR]