[1] Results from sediment trap experiments conducted in the seasonal upwelling area off south Java from November 2000 until July 2003 revealed significant monsoon-, El Niño-Southern Oscillation-, and Indian Ocean Dipole-induced seasonal and interannual variations in flux and shell geochemistry of planktonic foraminifera. Surface net primary production rates together with total and species-specific planktonic foraminiferal flux rates were highest during the SE monsoon-induced coastal upwelling period from July to October, with three species Globigerina bulloides, Neogloboquadrina pachyderma dex., and Globigerinita glutinata contributing to 40% of the total foraminiferal flux. Shell stable oxygen isotopes (d 18 O) and Mg/Ca data of Globigerinoides ruber sensu stricto (s.s.), G. ruber sensu lato (s.l.), Neogloboquadrina dutertrei, Pulleniatina obliquiloculata, and Globorotalia menardii in the sediment trap time series recorded surface and subsurface conditions. We infer habitats of 0-30 m for G. ruber at the mixed layer depth, 60-80 m (60-90 m) for P. obliquiloculata (N. dutertrei) at the upper thermocline depth, and 90-110 m (100-150 m) for G. menardii in the 355-500 mm (>500 mm) size fraction corresponding to the (lower) thermocline depth in the study area. Shell Mg/Ca ratio of G. ruber (s.l. and s.s.) reveals an exponential relationship with temperature that agrees with published relationships particularly with the Anand et al. (2003) equations. Flux-weighted foraminiferal data in sediment trap are consistent with average values in surface sediment samples off SW Indonesia. This consistency confirms the excellent potential of these proxies for reconstructing past environmental conditions in this part of the ocean realm.
Abstract. Current variability at the Pacific entrance of the Indonesian Throughflow is investigated using direct current and hydrographic measurements. Two moorings with three current meters (depths of 350, 550, and 1050 m) and one conductivity-temperaturedepth profiler (260 m) were deployed at 4øl'N, 127ø31'E and 3ø11'N, 128ø27'E between Talaud Islands and Morotai Island (Indonesia) from February 1994 to June 1995. Data from four hydrographic surveys conducted mainly between Mindanao and New Guinea from 1994 to 1996 are also used. The onset of a strong northwestward flow was observed at the southern mooring during boreal winter. In contrast, a southwestward flow containing salty South Pacific water was observed there during boreal summer. This current pattern change matched monsoon change around the mooring sites, suggesting that this variability is a seasonal signal in this region. This current change may occur because of the meridional shift of the Halmahera Eddy associated with an enlargement/ diminishment of the Mindanao Dome. Our observation result during summer (the southwestward flow with the South Pacific water at the southern mooring) suggests that the Maluku Sea is one of the eastern routes of the Indonesian Throughflow. The current data also revealed that intraseasonal variability occurs in 50-day oscillations. Because the coherence between wind variability in the tropics with a period of 40-50 days (MaddenJulian Oscillation) and current variability with this period are >0.4, it is possible that the 50-day oscillation in the ocean current is induced by wind variability associated with the Madden-Julian Oscillation. The ocean eddy activity with an intrinsic period in this region may also be related to this 50-day oscillation.
IntroductionThe western equatorial Pacific Ocean is an important region in oceanography. For example, a warm water pool at the surface influences the E1 Nifio/Southern Oscillation (ENSO) phenomena. This region also includes an entrance to the Indian Ocean, that is, the Indonesian Throughflow, which is a part of "The Great Ocean Conveyer" [Broecker, 1991;Schmitz, 1996], and plays an important role in the global thermohaline circulation. Furthermore, there are complicated, strong, lowlatitude western boundary currents, which are probably influenced by the complex geometry and topography. The Asian monsoon, with its strong seasonal variability, is also an important aspect of this region. These features appear to be linked and may influence the global climate on a number of time-
[1] The sediment trap experiments have been carried out during the 2001/2002 El Niño/La Niña transition in the monsoon-driven and freshwater influenced upwelling system off South Java. The results indicate that enhanced precipitation rates and associated river discharges increase the CO 2 -uptake of the biological pump by increasing the organic carbon export and reducing the carbonate precipitation. The freshwater, furthermore, forms a buoyant low salinity surface layer that caps off the nutrient and CO 2 -rich subsurface waters which shortens the upwelling season during wet La Niña conditions. A reduced capping-effect during dryer El Niño conditions strengthens the upwelling and as shown by our model results increase CO 2 emission into the atmosphere along the freshwater influenced continental margins in SE Asia. By contrast El Niño weakens upwelling and reduces the CO 2 emission in the equatorial Pacific Ocean. Citation: Rixen, T., V. Ittekkot, B. Herunadi, P. Wetzel, E. Maier-Reimer, and B. Gaye-Haake (2006), ENSO-driven carbon see saw in the IndoPacific, Geophys. Res. Lett., 33, L07606,
Pengamatan pasut dilakukan untuk menentukan nilai komponen pasut yang nantinya dapat digunakan untuk keperluan kerekayasaan dan pemetaaan. Metode least squares dapat digunakan untuk menentukan komponen-komponen pasut selain metode Admiralty.
Metode penentuan komponen pasut dan prediksinya yang umum menggunakan beberapa metode, yaitu metode Admiralty, metode semi grafik, metode least squares dan lainnya. Metode yang umum digunakan adalah metode Admiralty, sedangkan metode lain jarang digunakan. Dengan berkembangnya teknologi komputer, maka berkembang pula metode alternatif lain. Salah satunya adalah metode least squares yang menggunakan bahasa program Matlab untuk eksekusinya.
Perhitungan menggunakan metode least squaresmenghasilkan nilai komponen amplitude yang mendekati nilai komponen hasil perhitungan metode Admiralty tetapi berbeda pada nilai fase. Metode least squares memberikan akurasi yang cukup baik pada hasil prediksi dan dengan komponen yang lebih banyak.
Indonesia merupakan daerah rawan gempa bumi karena dilalui oleh jalur pertemuan 3 lempeng tektonik. Jalur pertemuan lempeng berada di laut sehingga apabila terjadi gempa bumi besar dengan kedalaman dangkal maka akan berpotensi menimbulkan tsunami sehingga Indonesia juga rawan terkena bencana tsunami. Dalam pengolahan data tsunami, metode filtering yang digunakan adalah filtering metode Godin. Berdasarkan hasil pengolahan data dengan filtering metode Godin, dapat disimpulkan bahwa pada tsunami barat Sumatera 2012, sinyal gempa diterima oleh buoy tsunami stasiun 23401 pada pukul 08:50 UTC. Tsunami terjadi di buoy tsunami stasiun 23401 pada pukul 09:25 UTC, jadi rentang waktu antara kejadian gempa bumi dengan timbulnya tsunami pada buoy tsunami stasiun 23401 adalah 35 menit dengan tinggi tsunami 3,5 cm.
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