Sirkulasi Laut dan Biogeokimia di Kawasan Teluk Cendrawasih

Teluk Cendrawasih (TC) merupakan salah satu teluk terbesar di Indonesia dan merupakan teluk semi tertutup yang memiliki biodiversitas hayati laut tinggi. Lokasi TC yang berada dekat ekuator dan berhadapan dengan Ekuator Samudera Pasifik bagian barat diduga memiliki dinamika dan variabilitas laut yang unik. Penelitian ini bertujuan untuk mengkaji pola sirkulasi laut, variabilitas arus, biogeokimia serta pengaruh fenomena El Nino Southern Oscillation (ENSO) di kawasan TC. Dataset deret-waktu yang digunakan adalah keluaran model sirkulasi laut dari Infrastructure Development of Space Oceanography (INDESO) dari tahun 2008-2015. Hasil penelitian terungkap bahwa pola sirkulasi arus permukaan di luar teluk dicirikan dengan pembalikan arah arus dua kali dalam setahun yang sejalan dengan pembalikan angin muson, sedangkan di dalam TC arus permukaan cenderung selalu mengalir keluar teluk. Sirkulasi di kedalaman 110 m dicirikan dengan dominasi Arus Pantai Papua (APP) yang bergerak secara permanen sepanjang tahun menuju barat laut dan terlihat terbentuk pusaran arus (eddy) pada musim timur. Arus muson terlihat sampai kedalaman 50 m, sedangkan APP berada pada kolom dari 50 m sampai 200 m (di Selat Biak) dan sampai 1000 m (di sisi Pasifik) dengan kecepatan maksimum 0,75 m/s. Rerata dan simpangan baku dari volume transpor APP adalah -25,25 (±11,1) Sv, sedangkan di Selat Biak -0,8756 (±0,5) Sv. Variabilitas dari transpor APP didominasi periodisitas tahunan.  Rerata volume transpor di pintu masuk barat TC adalah 0,03 (±0,1096) Sv dimana variabilitasnya pada periode intra musiman.  Variabilitas beberapa parameter biogeokimia di TC dan Pasifik didominasi periodisitas antar tahunan, tahunan dan intra musiman. Variasi antar tahunan dari parameter tersebut berkoherensi kuat dengan suhu permukaan laut di kawasan ekuator Pasifik, sebagai wilayah ENSO

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

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. Keywords: current, equatorial Pacific Ocean,  zonal winds, sea surface height, Halmahera Se

Detecting change in the Indonesian Seas

© The Author(s), 2019. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Sprintall, J., Gordon, A. L., Wijffels, S. E., Feng, M., Hu, S., Koch-Larrouy, A., Phillips, H., Nugroho, D., Napitu, A., Pujiana, K., Susanto, R. D., Sloyan, B., Yuan, D., Riama, N. F., Siswanto, S., Kuswardani, A., Arifin, Z., Wahyudi, A. J., Zhou, H., Nagai, T., Ansong, J. K., Bourdalle-Badie, R., Chanuts, J., Lyard, F., Arbic, B. K., Ramdhani, A., & Setiawan, A. Detecting change in the Indonesian Seas. Frontiers in Marine Science, 6, (2019):257, doi:10.3389/fmars.2019.00257.The Indonesian seas play a fundamental role in the coupled ocean and climate system with the Indonesian Throughflow (ITF) providing the only tropical pathway connecting the global oceans. Pacific warm pool waters passing through the Indonesian seas are cooled and freshened by strong air-sea fluxes and mixing from internal tides to form a unique water mass that can be tracked across the Indian Ocean basin and beyond. The Indonesian seas lie at the climatological center of the atmospheric deep convection associated with the ascending branch of the Walker Circulation. Regional SST variations cause changes in the surface winds that can shift the center of atmospheric deep convection, subsequently altering the precipitation and ocean circulation patterns within the entire Indo-Pacific region. Recent multi-decadal changes in the wind and buoyancy forcing over the tropical Indo-Pacific have directly affected the vertical profile, strength, and the heat and freshwater transports of the ITF. These changes influence the large-scale sea level, SST, precipitation and wind patterns. Observing long-term changes in mass, heat and freshwater within the Indonesian seas is central to understanding the variability and predictability of the global coupled climate system. Although substantial progress has been made over the past decade in measuring and modeling the physical and biogeochemical variability within the Indonesian seas, large uncertainties remain. A comprehensive strategy is needed for measuring the temporal and spatial scales of variability that govern the various water mass transport streams of the ITF, its connection with the circulation and heat and freshwater inventories and associated air-sea fluxes of the regional and global oceans. This white paper puts forward the design of an observational array using multi-platforms combined with high-resolution models aimed at increasing our quantitative understanding of water mass transformation rates and advection within the Indonesian seas and their impacts on the air-sea climate system. IntroductionJS acknowledges funding to support her effort by the National Science Foundation under Grant Number OCE-1736285 and NOAA’s Climate Program Office, Climate Variability and Predictability Program under Award Number NA17OAR4310257. SH was supported by the National Natural Science Foundation of China (Grant 41776018) and the Key Research Program of Frontier Sciences, CAS (QYZDB-SSW-SYS023). HP acknowledges support from the Australian Government’s National Environmental Science Programme. HZ acknowledges support from National Science Foundation under Grant No. 41876009. RS was supported by National Science Foundation Grant No. OCE-07-25935; Office of Naval Research Grant No. N00014-08-01-0618 and National Aeronautics and Space Administration Grant No. 80NSSC18K0777. SW, MF, and BS were supported by Center for Southern Hemisphere Oceans Research (CSHOR), which is a joint initiative between the Qingdao National Laboratory for Marine Science and Technology (QNLM), CSIRO, University of New South Wales and University of Tasmania

Campagne INDOMIX : Container de prélèvement d'échantillon d'eau pour analyse

Prélèvement de très grande quantité d'eau pour la mesure de l'Actinium et du Radium radioactif

Campagne INDOMIX : bateau Marion Dufresne

Campagne INDOMIX. Juillet 2011 à Bord du Marion Dufresne dans les mer Indonésiennes

Campagne INDOMIX : Rosette (mesure température, salinité, oxygène et courants)

Mesure de la Température, de la Salinité de l'Oxygène et des courants à l'aide de capteurs montés sur la rosette

Déploiement d'un courantmètre ADCP lors de la campagne INDOMIX

Campagne INDOMIX. Juillet 2011 à Bord du Marion Dufresne dans les mer Indonésiennes. Déploiement d'un ADCP pour mesurer les courants de 0 à 600m de fond