ORCID Profile
0000-0002-5250-8039
Current Organisations
University of Alabama
,
Badan Riset dan Inovasi Nasional Republik Indonesia
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Publisher: Copernicus GmbH
Date: 06-02-2019
Publisher: Elsevier BV
Date: 10-2019
Publisher: IOP Publishing
Date: 10-2020
DOI: 10.1088/1755-1315/584/1/012017
Abstract: The Banda Sea is a semi-enclosed marginal basin in the eastern tropical Indonesian waters. The circulation in the region displays strong seasonality in response to the seasonally reversing monsoon wind system. Yet, the basin is one of the least studied regions when it comes to the circulation dynamics – until now. Here, we present an analysis of an Array of real-time geostrophic oceanography (Argo) floats data during the period August 2017 to August 2019. The aim of the study is to investigate the spatial and temporal variability of circulation in the Banda Sea. Our study demonstrates the presence of cyclonic circulations, upwelling and downwelling with strong seasonal variability in the eastern part of Banda Sea off Maluku Island. It appears from the Argo temperature-salinity data that the subsurface cold and salty water shoals up during the southeast monsoon due to Ekman transport. Our study highlights the importance of Argo floats in elucidating the circulation in the Banda Sea.
Publisher: Springer Science and Business Media LLC
Date: 20-05-2022
DOI: 10.1038/S41467-022-30076-2
Abstract: The primary Antarctic contribution to modern sea-level rise is glacial discharge from the Amundsen Sea sector of the West Antarctic Ice Sheet. The main processes responsible for ice mass loss include: (1) ocean-driven melting of ice shelves by upwelling of warm water onto the continental shelf and (2) atmospheric-driven surface melting of glaciers along the Antarctic coast. Understanding the relative influence of these processes on glacial stability is imperative to predicting sea-level rise. Employing a beryllium isotope-based reconstruction of ice-shelf history, we demonstrate that glaciers flowing into the Amundsen Sea Embayment underwent melting and retreat between 9 and 6 thousand years ago. Despite warm ocean water influence, this melting event was mainly forced by atmospheric circulation changes over continental West Antarctica, linked via a Rossby wave train to tropical Pacific Ocean warming. This millennial-scale glacial history may be used to validate contemporary ice-sheet models and improve sea-level projections.
Publisher: Copernicus GmbH
Date: 09-01-2019
DOI: 10.5194/OS-2018-142
Abstract: Abstract. Cross-shelf processes drive the exchange of water between the continental shelf and western boundary currents, leading to the import and export of heat, freshwater, sediments, nutrients, plankton, fish larvae, and other properties. Upwelling is an important process which modulates those exchanges. It regulates primary productivity, which in turn promotes higher trophic levels and fisheries. In this paper, we investigate upwelling events in the East Australian Current (EAC) intensification zone off Southeast Queensland through the analysis of remotely-sensed Chlorophyll-a (Chl-a) and Sea Surface Temperature (SST) as well as wind and ocean reanalysis products. A particular focus is on identifying the likely mechanisms that drive upwelling events during the austral autumn to winter which are evident from cold SST and enhanced Chl-a concentrations. Four complementary Upwelling Indices (UIs) are derived. Chl-a (UIChla) and SST (UISST) based indices characterize the oceanic response to upwelling, while indices based on wind (UIw) and current (UIc) data capture the forcing of upwelling. The spatial and temporal variability of all UIs is examined over the continental shelf. It reveals distinct seasonal patterns. For the northern region, UIs identify the well-known Southeast Fraser Island Upwelling System. It prevails during the austral spring to early summer and is driven by current- and upwelling favourable wind. In contrast, upwelling is enhanced over the southern shelf during austral autumn to winter. About 70 % of all UISST and UIChla identified upwelling events occur during this period. A case study is presented that provides observational evidence for the existence of a shelf-break upwelling. Simultaneous downwelling favourable wind stress and upwelling favourable current-driven bottom stress establish a flow convergence in the bottom boundary layer (BBL). These convergent BBL flows force upwelling of cold and nutrient-rich slope waters as evident from negative SST anomaly and enhanced Chl-a in austral autumn to winter. It is evident from these results that the shelf region is characterised by two distinct seasonally reoccurring upwelling regimes.
Publisher: Elsevier BV
Date: 12-2020
Publisher: American Geophysical Union (AGU)
Date: 06-2021
DOI: 10.1029/2021JC017204
Abstract: The Indo‐Australian Basin (IAB) constitutes a crucial water route for the global ocean's circulation between the Pacific and Indian Oceans. Locally generated eddies contribute to the continued westward transport of water away from the IAB. In this paper, results from the first comprehensive regional ocean eddy census are discussed. A hybrid eddy census and tracking algorithm is used to analyze satellite altimetry data from 1993 to 2018. A total of 2,792 eddies were identified and tracked. Cyclonic eddies and anticyclonic eddies exhibit geographical segregation in terms of their dynamic characteristics. Larger litudes, radii, and absolute vorticities are associated with high eddy kinetic energy regions located in the vicinity of the South Java Current, South Equatorial Current, and Indonesian Throughflow. The eddies are grouped into three duration‐based classifications providing the first systematic insight into understanding their physical characteristics, formation, and distribution in the IAB.
Publisher: Wiley
Date: 31-07-2020
Publisher: IOP Publishing
Date: 02-2020
DOI: 10.1088/1755-1315/441/1/012097
Abstract: We observed the spatial pattern of physical oceanographic parameters, namely seawater turbidity and light transmission around the coastal waters of Cisadane. The observations were taken in July and November 2014 at 18 stations distributed in surrounding coastal waters of Cisadane. Water turbidity and light transmission were measured using CTD SBE 19 censor that could record simultaneously vertical profile of water turbidity and light transmission. The station’s position was determined using a GPS instrument. The results showed that seawater turbidity and light transmission exhibit two distinct spatial and temporal variation which is closely associated with the monsoonal wind system in the region.
Publisher: Elsevier BV
Date: 2023
DOI: 10.2139/SSRN.4526988
Publisher: Chiang Mai University
Date: 11-07-2022
Abstract: Abstract Upwelling plays a crucial role in driving cross-shelf circulation between the continental shelf and boundary currents. It is well known that upwelling results in the exchange of heat, nutrients, fish larvae, and other properties. It controls primary productivity, which promotes higher trophic levels and fisheries. Upwelling can be identified by at least three physical variables: wind, sea surface temperature (SST), and chlorophyll-a (Chl-a). The intensity of upwelling can then be calculated using the Upwelling Index (UI), which is based on these three variables. Wind-based UI (UIET), SST-based UI (UISST), and Chl-a-based UI (UICHL) were calculated using satellite-derived and reanalysis data from 2002 to 2017. Those three UIs were analyzed spatially and temporarily to determine the differences in upwelling strength and duration. The most appropriate UI for explaining the South Java upwelling system in our domain was determined through the correlation analysis. The monthly mean climatology of all UI (UIET, UISST, and UICHL) reveals the seasonal variation, which is high during the southeast (SE) monsoon. The strongest correlation between UISST and Chl-a with the smallest lag times suggested that South Java upwelling in our domain can be identified better using SST-based UI (UISST) than through the Ekman mass transport-based UIET, particularly in the east, relevant to the earlier study. Keywords: Chlorophyll-a, Upwelling Indexes, South Java Upwelling
Publisher: IOP Publishing
Date: 03-2021
DOI: 10.1088/1755-1315/718/1/012006
Abstract: Over recent decades, warming events in the tropical Indian Ocean (IO) have been documented in both the western and eastern IO. However, the manifestation of marine warming events in the Indonesian waters is still lacking in information. This paper presents the first case study of long-term warming events and short-term extreme warming events off the coast of West Sumatra using Sea Surface Temperature (SST) data covering 37 years (1982-2018). A statistical climate toolbox is applied to quantify the marine warming rates, including Marine Heatwaves (MHWs) identification. Decadal trends in marine warming are positive across the study region indicate significant warming rates with the average value of about 0.15°C decade −1 . In line with the long-term marine warming, MHW events off West Sumatra has been revealed to be increasing in its occurrences, duration, and intensity. Much of this significant increase in MHW properties has occurred during the period 2015-2018. The MHW events off West Sumatra appear to be influenced by El Niño Southern Oscillation (ENSO), particularly during strong El Niño and La Niña periods. These marine warmings trend and MHW events have never been documented and quantified before in the waters around West Sumatra.
Publisher: IOP Publishing
Date: 06-2021
DOI: 10.1088/1755-1315/789/1/012001
Abstract: The north and south Pacific waters influenced the water mass profile in the eastern inflow region of Indonesian throughflow (ITF), including Halmahera Sea, Maluku Sea, and Sangihe–Talaud Waters. Pacific waters are characterized by the strong salinity stratification in the upper-ocean (0–300m depth). Repeated annual oceanographic observations in the eastern inflow region of ITF found anomalous upper-ocean salinity profiles during the 2014–2017 periods. At the end of 2015 (El Niño condition), saltier salinity and nearly homogeneous salinity profile ( .6 PSU) in the upper-ocean were found, and it is expected due to the decreasing precipitation rate. Conversely, freshening of upper-ocean salinity (33.5 – 34.6 PSU) was found during the weak La Niña condition in 2017. An increased precipitation rate might cause this condition for five months in a sequence (varies within +22% to 112% higher than its monthly mean). In between, the weak El Niño and weak La Niña condition in 2014 and 2016 are more likely to show a similar salinity profile to the strong El Niño 2015 and weak La Niña 2017, respectively. There is a slight reduction (increase) of precipitation rate during 2014 (2016), but it does not lead to a drastic increase (freshening) of salinity as indicated in 2015 and 2017. This study also suggests the less effect of MJO on the precipitation rate and salinity anomalies in the eastern inflow region of ITF, especially during its active phase in 2017.
Publisher: IOP Publishing
Date: 06-2021
DOI: 10.1088/1755-1315/789/1/012002
Abstract: 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 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.
Publisher: Springer Science and Business Media LLC
Date: 19-04-2022
DOI: 10.1038/S41467-022-29617-6
Abstract: The Indonesian Throughflow plays an important role in the global ocean circulation and climate. Existing studies of the Indonesian Throughflow have focused on the Makassar Strait and the exit straits, where the upper thermocline currents carry North Pacific waters to the Indian Ocean. Here we show, using mooring observations, that a previous unknown intermediate western boundary current (with the core at ~1000 m depth) exists in the Maluku Sea, which transports intermediate waters (primarily the Antarctic Intermediate Water) from the Pacific into the Seram-Banda Seas through the Lifamatola Passage above the bottom overflow. Our results suggest the importance of the western boundary current in global ocean intermediate circulation and overturn. We anticipate that our study is the beginning of more extensive investigations of the intermediate circulation of the Indo-Pacific ocean in global overturn, which shall improve our understanding of ocean heat and CO 2 storages significantly.
Publisher: Elsevier BV
Date: 06-2017
Publisher: Springer Science and Business Media LLC
Date: 23-02-2023
DOI: 10.1186/S40562-023-00266-X
Abstract: For the first time, the processes controlling the variations of mixed layer temperature (MLT) and salinity (MLS) in the Banda Sea are quantified using data from a single Argo float in combination with satellite and reanalysis outputs from August 2017 to August 2019. This augments previous studies that utilized ocean model data only. We document the presence of a barrier layer and quantify the roles of air-sea heat and mass exchanges, horizontal advection, and vertical entrainment in the seasonal variability of MLT and MLS. We find that heat gains and losses at the air-sea interface are the main contributor to the warming and cooling of the MLT. Seasonal changes in MLS are driven by advection of low salinity water rather than freshwater fluxes from precipitation and evaporation. This is particularly the case during the late northwest and monsoon transition period from February to April when low salinity is advected eastward from the Java Sea into the Banda Sea.
Publisher: American Geophysical Union (AGU)
Date: 03-2023
DOI: 10.1029/2022JC018731
Abstract: An autonomous underwater glider was deployed in the Maluku Channel during 1 December 2018 through 21 February 2019 to measure temperature and salinity profiles of the upper ∼1,000 m continuously. The measurements suggest intraseasonal variations of the Pacific water mass intrusions into the Maluku Channel, which has not been reported before. The North Pacific Tropical and Intermediate Waters are found to intrude episodically into the eastern Maluku Channel at the depths of 130–180 m and 250–300 m, respectively, during January through February of 2019, each lasting for a few days to a week. The Antarctic Intermediate Water was present in the middle and western Maluku Channel between 600 and 800 m with intraseasonal variability. The South Pacific Subsurface Water was only found to intrude into the eastern Maluku Channel between 250 and 300 m during the first two transections in early December of 2018. Concurrent meter data from three moorings in the Maluku and Talaud‐Halmahera Channels are used to verify the water mass movement. The subsurface and intermediate water mass variations here are found to be closely related to the swing of the Mindanao Current near the Maluku Channel. These intraseasonal water mass intrusions are important aspects of water exchange between the western Pacific Ocean and the Indonesian seas.
Publisher: Springer Science and Business Media LLC
Date: 08-11-2022
DOI: 10.1007/S10661-022-10649-W
Abstract: Freshwater on small islands is generally limited and relies on rainwater and groundwater. This study aimed to assess changes in shallow groundwater quality on Pari Island, Indonesia. Pari Island is a small island with an area of 41.32 ha and belongs to a monsoon climate. Also, being a residential island, it attracts many tourists. The approach was to assess the shallow groundwater quality of ten wells during the dry and wet seasons. Changes in water quality were evaluated using traditional hydrochemical analysis methods (Schoeller, Piper, and Gibbs diagrams) and ion ratios. Shallow groundwater quality in the study area showed different responses depending on the season. Therefore, each well responded differently to changes represented by changes in water quality. The change is controlled by various factors: evaporation (or water balance), geology, aquifer characteristics, tides, wind direction, and wave height. These factors trigger the fluctuation of groundwater and seawater interface, affecting the amount of rainwater and seawater transported to the freshwater aquifer layer. This water volume transported affects the process of rock weathering, dissolution, and dilution of contaminants in shallow groundwater.
Publisher: Polish Academy of Sciences Chancellery
Date: 26-07-2023
Publisher: Springer Nature Singapore
Date: 2023
Publisher: Elsevier BV
Date: 12-2021
Publisher: Elsevier BV
Date: 03-2031
Publisher: American Meteorological Society
Date: 12-2021
Abstract: 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 ≡ 10 6 m 3 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.
Publisher: American Meteorological Society
Date: 2023
Abstract: 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 ≡ 10 6 m 3 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. 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 CO 2 storages.
Publisher: Springer Science and Business Media LLC
Date: 27-04-2023
Publisher: American Meteorological Society
Date: 08-2018
Abstract: The Maluku Channel is a major opening of the eastern Indonesian Seas to the western Pacific Ocean, the upper-ocean currents of which have rarely been observed historically. During December 2012–November 2016, long time series of the upper Maluku Channel transport are measured successfully for the first time using subsurface oceanic moorings. The measurements show significant intraseasonal-to-interannual variability of over 14 Sv (1 Sv ≡ 10 6 m 3 s −1 ) in the upper 300 m or so, with a mean transport of 1.04–1.31 Sv northward and a significant southward interannual change of over 3.5 Sv in the spring of 2014. Coincident with the interannual transport change is the Mindanao Current, choked at the entrance of the Indonesian Seas, which is significantly different from its climatological retroflection in fall–winter. A high-resolution numerical simulation suggests that the variations of the Maluku Channel currents are associated with the shifting of the Mindanao Current retroflection. It is suggested that the shifting of the Mindanao Current outside the Sulawesi Sea in the spring of 2014 elevates the sea level at the entrance of the Indonesian Seas, which drives the anomalous transport through the Maluku Channel. The results suggest the importance of the western boundary current nonlinearity in driving the transport variability of the Indonesian Throughflow.
Publisher: Elsevier BV
Date: 08-2018
Location: United States of America
Location: Indonesia
Start Date: 2021
End Date: 2023
Funder: Alexander von Humboldt-Stiftung
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