Analisis Perubahan Garis Pantai dan Penutupan Lahan antara Way Penet dan Way Sekampung, Kabupaten Lampung Timur

Analisis terhadap Perubahan garis pantai dan penutupan lahan di pesisir Lampung Timur, antara Way Penet dan Way Sekampung dilakukan berdasarkan citra satelit LANDSAT-TM antara tahun 1991, 1999,2001 dan 2003. Observasi dan pengukuran kondisi pantai dan gelombang di lapangan dilakukan untuk mempelajari dinamika pantai. Dari rangkaian data citra satelit tersebut ditemukan bahwa garis pantai mengalami proses erosi dan sedimentasi yang cukup nyata pada bagian-bagian pantai tertentu. Erosi yang terjadi di bagian selatan di Desa Purworedjo, misalnya, bervariasi antara 90 - 600 m dalam kurun waktu 12 tahun (1991 - 2003). Sementara itu, ke arah utara dari desa ini proses sedimentasi bervariasi antara 90 - 550 m. Ke arah utaranya lagi, garis pantai mengalami erosi, kemudian sedimentasi. Bentuk morfologi garis pantai, variasi arah angin dan karakteristik gelombang ditelaah sebagai faktor yang berperan dalam Perubahan garis pantai tersebut. Intensitas Perubahan dan uraian dinamika pantai yang terjadi dapat digunakan sebagai acuan dalam menentukan tindakan mitigasi ekologi yang efektif untuk melindungi daerah tersebut

Karakter dan Pergerakan Massa Air di Selat Lombok Bulan Januari 2004 dan Juni 2005

Data CTD pada Januari 2004 dan Juni 2005 dan data ADCP pada Juni 2005 hasil ekspedisi oseanografi program INSTANT (International Nusantara Stratification and Transport) di Selat Lombok dianalisis untuk mempelajari karakter dan pergerakan massa air. Karakter massa air pada lapisan permukaan dan massa air Northern Subtropical Lower Water (NSLW) pada lapisan termoklin memperlihatkan perbedaan yang jelas antara kedua pengukuran yang diperkirakan berkaitan dengan Perubahan karakter dan pergerakan massa air di Laut Jawa dan Laut Flores. Akan tetapi karakter massa air North Pacific Intermediate Water (NPIW) dan massa air lapisan dalam tidak jauh berbeda. Arus geostropik yang ditentukan dari perbedaan kedalaman dinamik dari dua stasiun yang berdekatan menghasilkan variasi kecepatan yang terlalu besar dan kecepatan yang terlalu tinggi bila dibandingkan dengan kecepatan arus yang diukur secara langsung dengan ADCP. Kelihatannya jarak antar stasiun yang terlalu dekat (kurang dari 9 km) menyebabkan kecepatan arus yang tidak akurat

Spatial and Temporal Variation of Indonesian Throughflow in the Makassar Strait

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

Cohesive Sediment Transport Modeling on Inner Ambon Bay

The presence of cohesive sediment in the water column can reduce light penetration and affect photosynthesis process, and it can be disrupted the primary productivity of aquatic, and sedimentation of coastal waters. The objective of this research was to determine the cohesive sediment distribution pattern and the relationship with sedimentation. MIKE 3 FM modeling was used to understand the process of sediment transport and sedimentation on Inner Ambon Bay. Sediment transport modeling method was divided into two stages: the hydrodynamic modeling (baroclinic) and sediment transport (mud transport) modeling. The model results indicate current patterns in the Inner Ambon Bay is influenced by the tidal factor. Suspended sediment dispersed vertically from the surface to a depth of 30 m with concentration of about 3.5-15 Kg/m3. The maximum consentration of the suspended sediment occurs at head of the bay (around Waiheru, Passo, and Lateri). Model simulations for 30 days showed the rate of erosion is about 1.04-6.15 Kg/m2/s, while in Inner Ambon Bay the erosion about 9.07x10-8Kg/m2/s only occurred in T1 station. Sedimentation associated with the cohesive sediment accumulation and it was shown by bed level. In addition, the simulation showed bed level in sill ranged at 0.01-0.19 cm and 0.47 mm/day on average, while in the Inner Ambon Bay it ranged from 1.75-10.01 cm, and the sedimentation rate was approximately 39.9 mm/day

Intra-seasonal Variability of Near-bottom Current in the Halmahera Sea

The secondary entry portal of the Indonesian Throughflow (ITF) from the Pacific to Indian Oceans is considered to be via the Halmahera Sea (HS). However, few ITF studies have been done within the passage. This motivated the Internal Tides and Mixing in the Indonesian Througflow (INDOMIX) program to conduct direct measurements of currents and its variability across the eastern path of the ITF. This study focused on the intra-seasonal variability of near-bottom current in HS (129°E, 0°S), its origin and correlation with surface zonal winds and sea surface height over the equatorial Pacific Ocean. The result showed a strong northwestward mean flow with velocity exceeding 40 cm/s, which represented the current-following topography with the northwest orientation. Meridional current component was much stronger than the zonal component. The energy of power spectral density (PSD) of the current peaked on 14-days and 27-days periods. The first period was presumably related to the tidal oscillation, but the latter may be associated with surface winds perturbation. Furthermore, cross-PSD revealed a significant coherency between the observed currents and the surface zonal winds in the central equatorial Pacific zonal winds (180°E-160°W), which corroborates westward propagation of intra-seasonal sea surface height signals along the 5°S with its mean phase speeds of 50 cm/s, depicting the low-latitude westward Rossby waves on intra-seasonal band

Study of Shoreline Changes at Jeneberang River Delta, Makassar

The study of shoreline changes during 1990 - 2008 in the delta of the River Jeneberang, Makassar was conducted by evaluating sediment transport into and out of a cell. Longshore sediment transport was computed by considering the influence of heights and angles of the breaking waves. Results of calculation of sediment transport showed that the dominant of sediment transport was to the north during the arrival of the southwest and west waves, and to the south when the wave coming from the northwest. Comparison between shore profiles resulting from model and coastline satellite imagery showed similarity. The difference between the two tend to be occurred at the head land part of the shoreline. This was due to complexity of coastal dynamic at the area. The results of the 19 years shoreline simulation showed that there was a tendency of abrasion at the upsteam head land part as the wave energy tend to converge and accretion at the bay part as the wave energy tend to diverge. Abrasion mainly occurred at Tanjung Bunga (head land) where the coast retreat 181.1 m. Accretion occur in the bay area (Tanjung Merdeka) where the coast advance to the sea for about 59.8 m. The shoreline tend to be stable when the profile was straight such as Barombong Coast

Karakteristik Upwelling di Perairan Selatan Jawa pada Tahun Strong La Nina 2010 dan Super El Nino 2015

Upwelling pantai musiman di perairan Selatan Jawa diduga dapat dimodulasi oleh variabilitas antar-tahunan laut-atmosfer El Nino Southern Oscillation (ENSO). Penelitian ini bertujuan untuk menganalisis perbedaan karakteristik upwelling musiman selama kejadian La Nina 2010 dan El Nino 2015, berdasarkan multi-dataset dari keluaran model INDESO dan dari data satelit. Karakteristik yang berbeda dari upwelling musiman terlihat jelas. Di La Nina, variabel laut-atmosfer permukaan jauh lebih rendah daripada yang diamati di El Nino, kecuali untuk tingkat curah hujan, suhu permukaan laut, dan tinggi permukaan laut. Di La Nina, air laut yang lebih hangat (27-28°C) dan lebih tawar (<33,80psu) mendominasi di atas lapisan kedalaman 45m, yang menahan air dingin upwelling tetap di bawah permukaan. Sebaliknya, di El Nino, air bawah permukaan naik secara drastis dari isoterm 25-26°C dan isohalin dari 34,24-34,44psu tersingkapkan di permukaan laut. Indeks upwelling berbasis suhu adalah -2°C dan +4°C, menunjukkan ENSO telah sangat memodulasi intensitas upwelling. Arus Pantai Selatan Jawa (SJCC) yang kuat mengalir kearah timur hanya ditemukan pada kejadian La Nina. Aliran Arlindo yang persisten di selatan 9,5°S terlihat pada ENSO berbeda. Perkiraan angkutan Ekman yang diturunkan dari model arus meridional telah diintervensi secara kuat oleh kehadiran SJCC dan Arlindo