Agus S. Atmadipoera, Agus S.
Oceanography Division, Department of Marine Science and Technology, Bogor Agricultural University (IPB Bogor), Bogor-Indonesia

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TURBULENT MIXING IN OMBAI STRAIT Suteja, Yulianto; Purba, Mulia; Atmadipoera, Agus S.
Jurnal Ilmu dan Teknologi Kelautan Tropis Vol 7, No 1 (2015): Elektronik Jurnal Ilmu dan Teknologi Kelautan Tropis
Publisher : Jurnal Ilmu dan Teknologi Kelautan Tropis

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Abstract

Ombai Strait is one of the exit passages of Indonesian Throughflow (ITF) which conveys hotspot of strong internal tidal energy. Internal tide is the one of main energy which causes mixing processes in the oceans and could lead to changes in water mass characteristics. The purpose of this research was to estimate the turbulent mixing by using Thorpe analysis. Nine CTD cast were obtained for one tidal cycle (24 hours) in Ombai Strait. The results showed the average value of the turbulent mixing is 833.5 x 10-4 m2s-1, the highest found in deep homogeneous layer (2383.4x 10-4 m2s-1), followed by mixed surface layer (103.0 x 10-4 m2s-1) and thermocline (14.2 x 10-4 m2s-1). This Turbulent mixing value is much higher than the previous measurement in Indonesian Sea. This is presumably due to the strong internal tidal energy and its interaction with existing deep sill in Ombai Strait. Keywords: Indonesian throughflow (ITF), Ombai Strait, turbulent mixing
OBSERVATION OF COASTAL FRONT AND CIRCULATION IN THE NORTHEASTERN JAVA SEA, INDONESIA Atmadipoera, Agus S.; Kusmanto, Edi; Purwandana, Adi; Nurjaya, I Wayan
Jurnal Ilmu dan Teknologi Kelautan Tropis Vol 7, No 1 (2015): Elektronik Jurnal Ilmu dan Teknologi Kelautan Tropis
Publisher : Jurnal Ilmu dan Teknologi Kelautan Tropis

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Abstract

The structure and spatial extent of a coastal front and circulation in the shallow (<55 m depth) northeastern Java Sea in Indonesia was investigated with a new dataset of high-resolution conductivity-temperature-depth (CTD) and along-track shipboard acoustic Doppler current profiler (SADCP) during a DIKTI-LIPI 2010 joint research cruise on R.V. Baruna Jaya 8.  The coastal front separates fresh warm coastal water derived mainly from Barito River discharge and the saline, cool Java Sea water.  The surface fresh water plume extends approximately 760 km from the Barito River estuary to the south, and its thickness varies from the surface to 10 m and 20 m depth, depending on its proximity to the fresh water source.  The front is aligned a northeast and east direction, probably related to a meandering of strong northeastward monsoon current in the eastern part of the Java Sea during the observation time. Keywords: hydrographic measurement, coastal front, Matasiri Islands, Barito River, the northwest monsoon current
CHARACTERISTICS AND VARIABILITY OF THE FLORES ITF AND ITS COHERENCE WITH THE SOUTH JAVA COASTAL CURRENT Atmadipoera, Agus S.; Hasanah, Paradita
Jurnal Ilmu dan Teknologi Kelautan Tropis Vol 9, No 2 (2017): Elektronik Jurnal Ilmu dan Teknologi Kelautan Tropis
Publisher : Bogor Agricultural University

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Characteristics and transport variability of the Indonesian Throughflow (ITF) in the western Flores Sea (FS) and its coherency with the South Java Coastal Current (SJCC) fluctuation are investigated using validated ocean general circulation model output (2008-2014) from the INDESO configuration.  The results show that near-surface circulation in the study area is characterized by two distinct regimes:  strong southwestward ITF flow and quasi-transient anti-cyclonic eddies. Vertical dimension of ITF crossing 7.5°S is about 112 km width, 250 m depth, and high velocity core at thermocline >0.3 m/s.  Transport volume estimates along this latitude is -4.95 Sv (southward).  Bifurcation of ITF flow appears north offshore Lombok Island where -2.92 Sv flowing into Lombok Strait and the rest flowing eastward into FS. Meanwhile, vertical dimension of SJCC crossing 114°E is about 89 km width, 120 m depth, and high velocity core at sub-surface >0.35 m/s. Mean transport of SJCC is +2.65 Sv. Coherency between Flores ITF and SJCC transport variability on intra-seasonal scales is significantly high, e.g., on 30 day period (coher=0.92) and phase-lags of 0.6-day with SJCC leading to Flores ITF. This result confirmed previous studies, related to intrusion of coastally trapped Kelvin waves into Flores Sea via Lombok Strait. Keywords: Indonesian Throughflow, western Flores Sea, South Java Coastal Current
GENETIC DIVERSITY OF OLIVE RIDLEY Lepidochelys olivacea ASSOCIATED WITH CURRENT PATTERN IN CENDRAWASIH BAY, PAPUA Bahri, Samsul; Atmadipoera, Agus S.; Madduppa, Hawis H.
Jurnal Ilmu dan Teknologi Kelautan Tropis Vol 9, No 2 (2017): Elektronik Jurnal Ilmu dan Teknologi Kelautan Tropis
Publisher : Bogor Agricultural University

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Abstract

Cendrawasih Bay is habitat for olive ridley (Lepidochelys olivacea) which is directly adjacent to the Pacific Ocean. The presence and the diversity of L. olivacea in Cendrawasih Bay has been threatened. Genetics can be the key to conservation because they play an important role in maintaining population and recovering from damage. This study aims to determine the genetic diversity of L. olivacea and its association to the current pattern in the waters of Cendrawasih Bay. Samples of L. olivacea (n=20) were collected in Kwatisore (n=8) and Yapen Island (n=12) in Cendrawasih Bay waters from August 2015 to December 2016. The molecular analysis was based on 791-bp fragment of D-Loop on the non-coding region gen. The current pattern analysis was performed through INDESO data and visualized by using Ferret software. Phylogenetic analysis showed that 2 groups of L. olivacea from a total of 2 haplotypes, whose population from Kwatisore was dispersed in two haplotypes, while the population from Yapen Island was only dispersed in one haplotype. Populations from Kwatisore showed higher variations than populations from Yapen Island. The current pattern analysis suggests that the two study sites, Kwatisore and Yapen islands are different. Both populations are only connected by the Northwest monsoon currents period that indicates a little geneflow between this populations. Thus causing differences variation between Kwatisore and Yapen Island populations genetically. Keywords: genetic diversity, current pattern, coral triangle, olive ridley
SPATIAL AND TEMPORAL VARIATION OF INDONESIAN THROUGHFLOW IN THE MAKASSAR STRAIT Atmadipoera, Agus S.; Horhoruw, Selfrida M.; Purba, Mulia; Nugroho, Dwi Y.
Jurnal Ilmu dan Teknologi Kelautan Tropis Vol 8, No 1 (2016): Elektronik Jurnal Ilmu dan Teknologi Kelautan Tropis
Publisher : Bogor Agricultural University

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Abstract

Using outputs of INDESO model, this study investigated vertical structure, spatial and temporal variation of the Indonesian Throughflow in Makassar Strait (M-ITF). It was shown that the main axis of persistent southward jet of M-ITF formed a unique path following the western shelf slope along the strait, which was associated with a high kinetic energy (KE) region from near-surface down to the thermocline layer. Furthermore, a drastic jump of KE appeared in the narrow and deep Libani Chan-nel (near 3°S) where the strait's width shrinks significantly, thus an elevated flow velocity was needed to maintain transport volume balance. Here, maximum southward velocity at thermocline exceeded 1.2 m/s. Spatial pattern of M-ITF can be described by the first EOF mode which accounts for 79 % of the total variances. It exhibited that contours of the flow amplitudes were similar to M-ITF path, and the largest amplitude was located near the Libani Channel. Out-of-phase relationship of the flow was found between M-ITF and eddies circulation that developed in the edges of the strait. Corresponding temporal fluctuation of the first EOF mode indicated that M-ITF variabilities varied from intra-seasonal to inter-annual scales. Annual fluctuation of M-ITF was seen from EOF mode-2 (at thermocline layer) and mode-3 at lower-thermocline. Cross-spectra analysis revealed that variability of M- ITF (e.g. on annual scale) at northern entrance was highly coherent to the fluctuations of North Equatorial Current (NEC) and Mindanao Current (MC), suggesting that variability of M-ITF was remotely influenced by the Pacific low-latitude western boundary currents. Keywords: INDESO model, Indonesian Throughflow, Makassar Strait, EOF, Cross-Spectra Analysis