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The mean circulation and volume budgets in the upper 1200 m of the Maluku Sea are studied using multiyear current meter measurements of four moorings in the Maluku Channel and of one synchronous mooring in the Lifamatola Passage. The measurements show that the mean current in the depth range of 60–450 m is northward toward the Pacific Ocean with a mean transport of 2.07–2.60 Sv (1 Sv ≡ 106 m3 s−1). In the depth range of 450–1200 m, a mean western boundary current (WBC) flows southward through the western Maluku Sea and connects with the southward flow in the Lifamatola Passage. The mean currents in the central-eastern Maluku Channel are found to flow northward at this depth range, suggesting an anticlockwise western intensified gyre circulation in the middle layer of the Maluku Sea. Budget analyses suggest that the mean transport of the intermediate WBC is 1.83–2.25 Sv, which is balanced by three transports: 1) 0.62–0.93 Sv southward transport into the Seram–Banda Seas through the Lifamatola Passage, 2) 0.97–1.01 Sv returning to the western Pacific Ocean through the central-eastern Maluku Channel, and 3) a residual transport surplus, suggested to upwell to the upper layer joining the northward transport into the Pacific Ocean. The dynamics of the intermediate gyre circulation are explained by the potential vorticity (PV) integral constraint of a semienclosed basin. Significance Statement The Indonesian Throughflow plays an important role in the global ocean circulation and climate variations. Existing studies of the Indonesian Throughflow have focused on the upper thermocline currents. Here we identify, using mooring observations, an intermediate western boundary current with the core at 800–1000-m depth in the Maluku Sea, transporting intermediate waters from the Pacific into the Seram–Banda Seas through the Lifamatola Passage. Potential vorticity balance suggests an anticlockwise gyre circulation in the intermediate Maluku Sea, which is evidenced by the mooring and model data. Transport estimates suggest northward countercurrent in the upper Maluku Sea toward the Pacific, supplied by the Lifamatola Passage transport and upwelling from the intermediate layer in the Maluku Sea. Our results suggest the importance of the intermediate Indonesian Throughflow in global ocean circulation and overturn. More extensive investigations of the Indo-Pacific intermediate ocean circulation should be conducted to improve our understanding of global ocean overturn and heat and CO2 storages.

The currents and water mass properties at the Pacific entrance of the Indonesian seas are studied using measurements of three subsurface moorings deployed between the Talaud and Halmahera Islands. The moored current meter data show northeastward mean currents toward the Pacific Ocean in the upper 400 m during the nearly 2-yr mooring period, with the maximum velocity in the northern part of the channel. The mean transport between 60- and 300-m depths is estimated to be 10.1–13.2 Sv (1 Sv ≡ 106 m3 s−1) during 2016–17, when all three moorings have measurements. The variability of the along-channel velocity is dominated by low-frequency signals (periods > 150 days), with northeastward variations in boreal winter and southwestward variations in summer in the superposition of the annual and semiannual harmonics. The current variations evidence the seasonal movement of the Mindanao Current retroflection, which is supported by satellite sea level and ocean color data, showing a cyclonic intrusion into the northern Maluku Sea in boreal winter whereas a leaping path occurs north of the Talaud Islands in summer. During Apri–July, the moored CTDs near 200 m show southwestward currents carrying the salty South Pacific Tropical Water into the Maluku Sea.

The ocean currents in the Halmahera Sea are studied using a subsurface mooring deployed in the Jailolo Strait from November 2015 to October 2017. The subtidal currents of the mooring measurements are characterized by a two-layer system, with the current variability below about 200 m in opposite phases to that in the upper layer. The mean along-strait velocity (ASV) is toward the Indonesian seas in the whole water column, producing an estimated mean transport of 2.44 ± 0.42 Sv (1 Sv ≡ 106 m3 s−1). The errors of the transport calculation based on the single mooring measurements are estimated to be less than 15% using simulations of high-resolution ocean models. A weak current is observed to flow northward during 2017 at the bottom of the strait. The ASV variability is found to be dominated by an annual cycle both in the upper and lower layers. The total transport, however, is dominated by semiannual variability because of the cancelation of the annual transports in the upper and lower layers. The variability of the transport is suggested to be driven by the pressure difference between the Pacific Ocean and the Indonesian seas, as evidenced by the agreement between the satellite pressure gradient and the two-layer transports. The transport of the Jailolo Strait during the 2015/16 super El Niño is found to be nearly the same as that during the 2016 La Niña, suggesting that the interannual variability of the transport is much smaller than the seasonal cycle.

Vertical mixing in the northern Maluku Sea and Talaud Waters in February 2021. The spatial variability of water mass mixing in the northern Maluku Sea and Talaud waters are presented based on the results of Eastern Indonesia Expedition (EIT) 2021 using RV Baruna Jaya VIII-LIPI. The turbulent kinetic energy dissipation rate was obtained using the Kunze-Williams-Briscoe (KWB) Method calculated from CTD (Conductivity, Temperature, Depth) and LADCP (Lowered Acoustic Doppler Current Profiler) datasets. We found the dissipation rate in the core layer of North Pacific Subtropical Water (NPSW) and North Pacific Intermediate Water (NPIW) are in the order of 10-6 W/kg and 10-8 W/kg, respectively. The KWB Method used in this study is also proven comparable with the Thorpe Method.

The baseline observations of water current in the southeastern Mentawai waters using Shipboard Acoustic Doppler Current Profiler (SADCP) of the RV Baruna Jaya VIII in April 2013 were presented study. This study aims to reveal the current subsurface system in the internal western Sumatra waters, the southeastern Mentawai Islands waters. We found unique hydrodynamics in this region where the southeastward flows were observed in the upper 50 m yet persistent northwestward flow below. We suggest that the southeastward flows in the upper layer were the remaining Southeast Monsoon-driven circulations. The northwestward flows below were likely acting as counter-current due to continuity processes in this semi-enclosed sea. This counter-current exceeds 1 m s−1 at a depth of>125 m, a localized jet-like current. We propose to name this high magnitude current as Mentawaian Jet as it feeds the western Sumatra internal waters.

As one of the Indonesian Throughflow (ITF) outflow passages, the Sumba Strait is a meeting point for the Pacific and the Indian Ocean water mass. In order to study the long-term variability of ITF flowing via Sumba Strait, this research uses observational data from the Ekspedisi WIdya Nusantara (EWIN) research cruise conducted in August 2016 to validate the altimetric geostrophic surface current by referencing the shear velocity. Stating the referenced level to 700 m, geostrophic transport is calculated using the Monthly Isopycnal/Mixed-Layer Ocean Climatology (MIMOC) data. Over the period of 1993-2016, the results demonstrate a dominant seasonal pattern for the geostrophic variability. While the total geostrophic transport shows a main westward direction towards the Indian Ocean, the Sumba Strait provides only a small portion (less than 0.1 Sv) for westward ITF geostrophic current. Intraseasonally, the maximum transport occurs during the southeast monsoon. The reversal of South Java Current (SJC), which flows with the eastward direction heading to the Savu Sea, is observed as the intrusion for westward ITF in almost every monsoon season. Despite having an unclear year to year cycle, climate mode of the Indian Ocean may have more influence on the surface geostrophic variability at the Sumba Strait. On the other hand, ocean-atmosphere coupling in the Pacific Ocean has a role in regulating geostrophic transport variation within the Sumba Strait. Using a statistical approach, the findings emphasize that the throughflow may well be impacted as well as feedback on both ENSO and IOD since there is robustness in those variables.

Parameter kualitas air laut meliputi suhu, salinitas, pH, dissolved oxygen (DO), dan kekeruhan (turbiditas) merupakan faktor penting yang harus diukur secara kontinu untuk memonitor kondisi laut dan dampaknya bagi biota laut. Karang merupakan salah satu biota laut sangat sensitif terhadap perubahan kualitas air laut, khusunya suhu permukaan laut. Kondisi air laut yang melebihi ambang batas yang dapat ditolerir oleh karang, diduga dapat menghambat laju pertumbuhan maupun proses resiliensinya. Oleh karena itu penelitian ini bertujuan untuk memahami kondisi oseanografi dan kesesuaiannya dalam mendukung ekosistem terumbu karang. Pulau Pari dipilih menjadi area kajian karena wilayah ini memiliki keanekaragaman ekosistem terumbu karang yang cukup tinggi. Dalam penelitian ini dilakukan pengukuran kualitas air laut pada bulan Maret dan Juni 2015 di tiga stasiun pengamatan utama yaitu PR01 (Daerah Perlindungan Biota Laut), PR02 (Goba Pulau Tikus), dan PR03 (Bintang Rama) yang merupakan lokasi ekosistem terumbu karang. Selain itu dilakukan pula pengukuran di 14 stasiun pengamatan untuk mengetahui pola kualitas air secara spasial. Studi ini menghasilkan informasi suhu permukaan laut berada pada rentang 28.5 hingga 29.5 oC; salinitas air laut berada pada rentang 29.0 hingga 30.5 psu; pH berada pada rentang 8.3 hingga 8.43 satuan; turbiditas berada pada rentang 0 hingga 1.4 NTU; dan DO berada pada rentang 4 hingga 5.3 mg/L. Kualitas air laut pada dua bulan tersebut masih sesuai dengan baku mutu air laut khususnya bagi karang, yang ditetapkan oleh Menteri Lingkungan Hidup Republik Indonesia, kecuali untuk parameter DO pada bulan Juni 2015 yang berada di bawah ambang batas minimum.

The spatial current patterns in the Indonesian seas were mapped based on a wide range of snapshot observations during the Expedition of Widya Nusantara (EWIN 2014) Leg 1 in November 2014. The current profiles were measured using the Shipboard Acoustic Doppler Current Profiler (SADCP) of the RV Baruna Jaya VIII. This study is aimed to reveal the current system in the Indonesian seas from observation. Remarkable current patterns of the Indonesian throughflow (ITF) were observed penetrating via the Mindanao Strait, southern Makassar Strait, and Lifamatola Passage, including its recirculation in the northern Maluku Sea and in the Sulawesi Sea. These results suggested that during the late Southeast Monsoon (SEM), the upper layer ITF is still significantly penetrating the Indonesian seas. The indication of anticyclonic and cyclonic circulations in the upper 50 m and lower 75 m, respectively, was also observed in the western Banda Sea

Sea Surface Temperature (SST) data can be used to understand oceanography dynamics in Ambon Bay. However, a lack of continual and long time series in-situ SST data limited this study. To overcome this problem, the Sr/Ca composition in Porites coral taken from Outer Ambon Bay was used to reconstruct SST. The coral sample was sub-sampled monthly and analyzed using ICP-OES. Subsequently, the anchor point method was used to develop the chronology of the coral Sr/Ca based on ERSST v3b data. The regression equation results were Sr/Ca = -0.059 x SST + 10.32 (r = -0.699, n = 95, p < 0.05). The reconstructed SST based on these results was verified by in-situ data from May to November 2008. The difference was found to be 1.2-2.5 °C (σ = 0.05%). This results lead us to conclude that coral Sr/Ca reflects SST variation in Ambon Bay well. Based on the reconstructed SST, we found that the SST in Ambon Bay experiences an extreme seasonal variation, which is highly correlated to air temperature, wind speed, and length of sun radiation. Ambon Bay also experiences SST anomalies in some periods, which are dominantly affected by local atmospheric conditions rather than ENSO phenomena.

Trend of Sea Surface Temperature Increase and Coral Resilience After Bleaching Events of 2010 and 2016 in The Marine Tourism Park (TWP) of Pieh Island, Padang, West Sumatra. The coral bleaching event has hit almost all of Indonesia's waters at least 4 times (in the last 34 years), which the last two events (2010 and 2016) have been discussed rather deeply. However, detailed studies in a specific location, such as in Marine Tourism Park (TWP) of Pieh Island, Padang waters, West Sumatra Province that influenced by the water mass of Indian Ocean have not yet been studied. The aim of this paper is to examine the trend of sea surface temperatures (SST)’s increase in the TWP of Pieh Island in 2010 and 2016 coral bleaching, and the coral resilience after the events. In this study, the long-term SST data acquired from the Aqua MODIS satellite images were used intensively. Results show that the highest mean monthly SST called MMM that corals can be tolerated in the TWP of Pieh is 29.6 oC, higher than in all Indonesian waters (29.1 oC).The differences between the anomaly SST and the normal SST (MMM) or called Hot Spot (HS) has exceeded the average MMM in the 2010 bleaching event around 0.4-0.5 oC with its peak in April, and with alert-1 severity (Degree Heating Weeks (DHW) < 8 oC-weeks; which means that the coral has partial bleaching with patchy pattern).In 2016, the HS increased by an average of 0.5 ~ 1.0 oC with peaks in January-February and May-June and with the severity of Alert-2 (DHW ≥ 8 oC-weeks, which means corals experienced severe bleaching, over wider areas, and some of corals are died). One year earlier (2015), higher HS with an average value of 0.3-0.8 oC and DHW ~ 4 oC-weeks were also observed. This indicates that coral bleaching events in the TWP of Pieh Island is repeated and occurs for long periods.The trend of increasing SST in this TWP is 0.23oC/decade, lower than in the all Indonesian waters (0.36 oC/decade). This trend shows that coral reefs in Indonesian waters including this TWP have a high resilience to recover themselves from bleaching, since the trend of increasing SST < 1.0 oC/decade of the 11 coral resilience key factors, positive factors that support high coral resilience are low pollution/nutrients, low sedimentation (high water transparency), and low unfriendly of human activities, while the most negative one is the explosion of crown-of-thorns starfish, Acanthaster planci population as well as coral disease.

The regional INDESO model configured in the Indonesian seas from 2008 to 2016 is used to study the mechanisms responsible for the variability of the currents in the Sulawesi Sea of the Indonesian seas. The model simulation compares reasonably with the seasonal to interannual variability of the moored current meter observations in the upper 350m or so of the Maluku Channel during 2015 and 2016. The interannual variability of the currents in the eastern Sulawesi Sea in the model is found to be associated with both the Pacific and Indian Ocean remote forcing. Lag correlation analysis and a theoretical linear wave model simulation suggest that both the equatorial Kelvin waves from the Indian Ocean and the coastally trapped Kelvin waves from the western Pacific along the Philippine coast can propagate through the Indonesian seas and arrive at the Maluku Channel. In particular, from mid-2015 to 2016 the Indian Ocean Kelvin waves are found to significantly impact the sea level anomaly variability in the Maluku Channel. The results indicate the importance of Indo-Pacific planetary waves to the interannual variability of the currents in the Sulawesi Sea at the entrance of the Indonesian seas. Plain Language Summary The Indonesian seas provide a tropical connection for the climate systems over the tropical Pacific and Indian Oceans, the dynamics of which are not clear so far. This study uses a high-resolution computer model to simulate the currents measured by an acoustic current meter attached to a deep ocean mooring in the Maluku Channel of the northeastern Indonesian seas. Based on the successful simulation, the dynamics of the interannual variations of the circulation in the Maluku Channel are studied using the model and a simplified theoretical linear model. The interannual currents and sea level variability in the Maluku Channel are found to be affected by both the Indian Ocean Kelvin waves and the Philippine coastal Kelvin waves. It is found that the Indian Ocean Kelvin waves dominate the sea level variability in the Maluku Channel from mid-2015 to 2016. In early 2015, the sea level variability in the Maluku Channel is dominated by the coastal Kelvin waves from the east Philippine coasts. The results are important for the understanding of the circulation at the entrance of the Indonesian seas and of the Indo-Pacific interactions through the propagation of the planetary waves.

Water Mass Dynamics Around the Indonesia’s Outer Small Islands at North Papua Waters. Coastal area of Indonesia’s Outer Islands (PPKT) at North Papua Waters have a huge potential of marine resources which needs to be managed in sustainable ways. In order to make the processes of protection, conservation, rehabilitation, utilization, and enrichment of coastal resources work well, the study about environmental carrying capacity which includes ocean dynamics analysis around PPKT area is needed. Hereby, the study area were including coastal and off shore area of Jiew, Budd, Fani, Bras and Fanildo Island. The measurement of water mass and ocean current was conducted to analyze the impact of regional ocean dynamics to coastal waters of PPKT. This study found the domination of New Guinea Coastal Current (NGCC) at surface layer, the effect of Indonesian throughflow at subsurface layer (100 – 150m depth), and counter current towards northeast which is believed as a part of New Guinea Coastal Under Current (NGCUC) and Equatorial Under Current (EUC). This ocean current system carried South Pacific Subtropical Water (SPSW) noticed by maximum salinity of 35.4 PSU at 150m depth. There are spatial variability of mixed layer depth and slope of T-S curve at the western and eastern part of study area which might be caused by isopycnal mixing. However, the spatial and temporal variability of Sea Surface Temperature at this area is relatively small due to the presence of Western Paicific Warm Water Pool. With the small annual SST variability, strong ocean current and water mass mixing, this area has a potential for the development of marine ecosystem.

Sea Surface Temperatures (SSTs) is one of the most important oceanographic parameter that could affect the marine life, especially coastal ecosystem. SSTs data varies in hourly, daily, seasonal, annual, inter-annual, and even in longer time scales. This condition makes any studies using instantaneous measurement could turn into misleading report due to the lack of time series SSTs data. Thus, the aim of this study is to understand the seasonal and intra-seasonal SSTs dynamics in Pari Island using continuous measurement from temperature logger. This study found that the double peaks of SSTs in May and November are correspond to the period of transitional monsoon. Conversely, the two minimum SSTs in February and August were correspond to the peak of northwest monsoon and southeast monsoon respectively. In addition to seasonal pattern, the slightly dominant intra-seasonal variability of SSTs was found in the period of 57 and 86 days. Those predominant signals suggested represent the Madden-Julian Oscillation phenomena.

The coral bleaching event (CBE) which trigerred by increase in sea temperatures of 1-2˚C during El-Nino can make corals stressful or potentially dead. Many CBE research are conducted using sea temperature data measured through infrared thermal (TIR) satellite sensor. However, very few study use optical remote sensing data. This study aim to analyze the potential of optical Sentinel-2 (S-2) satellite data for monitoring during (Jun. 2016) and after (Jun. 2018) CBE in small islands of marine protected areas (TWP) of Pieh. A series image analysis procedure was conducted, i.e. simple DOS atmospheric correction; normalizating digital numbers (DN) of Blue, Green and Red bands of subject images during and after CBE to the reference image (before CBE. Dec. 2015) using “pseudo invariant feature (PIF)” approach; subtracting the DN of each bands of images during and after CBE to the reference image, and generating color composite of natural color with a contrast stretch. Result showed that this procedure can detected clearly the CBE. There was an average decreasing bleaching trend of 1.63 ha (15.8%), which indicated that some corals have recovered from thermal stress inside the TWP of Pieh. However, islands outside the TWP of Pieh, showed an increasing trend by an average of 0.50 ha (21.2%). The predation corals by the crown of thorn seastar, Acanthaster planci, whose population exploded after CBE was the main reason why CBE still detected both inside and outside the TWP of Pieh. This study shows the ability and potency of optical remote sensing data of S-2 satellite to monitor CBE, but need a lot of validation from many other sites. This result is very useful for supporting project such as COREMAP CTI.

Coral is one of the most important organisms in the coral reef ecosystem. There are several factors affecting coral growth, one of them is changes in sea surface temperature (SST). The purpose of this research is to understand the influence of SST variability on the annual linear growth of Porites coral taken from Ambon Bay. The annual coral linear growth was calculated and compared to the annual SST from the Extended Reconstructed Sea Surface Temperature version 3b (ERSST v3b) model. Coral growth was calculated by using Coral X-radiograph Density System (CoralXDS) software. Coral sample X-radiographs were used as input data. Chronology was developed by calculating the coral’s annual growth bands. A pair of high and low density banding patterns observed in the coral’s X-radiograph represent one year of coral growth. The results of this study shows that Porites coral extents from 2001-2009 and had an average growth rate of 1.46 cm/year. Statistical analysis shows that the annual coral linear growth decline...