Perubahan Kedalaman & Ketebalan Termoklin pada Variasi Kejadian ENSO, IOD & Monsun di Perairan Selatan Jawa Hingga Pulau Timor ( Charge of Thermocline Thickness & Depth on the Variation of ENSO & IOD Events in the Waters of the Southern Java to Timor Isl)

Abstract

Lapisan termoklin berperan dalam identifikasi kedalaman lapisan renang dari ikan tuna. Identifikasi perubahan kedalaman termoklin pada variabilitas ENSO (El Nino Southern Oscilation), IOD (Indian Oscillation Dipole Mode) dan Monsun, dikaji berdasarkan data CTD(Conductivity-Temperature-Depth) dan argofloat yang terakumulasi dalam Word Ocean Data (WOD) dari tahun 1985–2011. Data angin dari National Centre for Environmental Prediction (NCEP), data-data intensitas hujan dari Badan Meteorologi dan Geofisika (BMG) dan data-data indek anomali iklim global (SOI SouthOscillation Index), NINO3.4 dan IOD) digunakan untuk melengkapi analisis permasalahan. ENSO, IOD dan Monsun ditemukan semuanya berpengaruh terhadap kedalaman batas atas, batas baw ah, dan ketebalan termoklin. Secara umum ditemukan kedalaman batas atas pada musim timur lebih dalam daripada saat musim barat. Berdasarkan variasi antar tahunan iklim global ditemukan bahwa batas atas pada kejadian El Niño umumnya lebih dangkal (rerata 50,9–51,7 m) daripada saat La Niña (rerata 58,4–60,2 m). Sebaliknya batas bawah termoklin pada saat El Niño ditemukan lebih dalam (rerata 262,9–281,8 m) daripada saat La Niña (rerata 204,5–259,6 m). Ketebalan termoklin pada saat El Niño ditemukan umumnya lebih tebal (rerata 211,2–230,9 m) daripada saat La Niña (rerata 144,4–201,2 m). Faktor tingginya curah hujan sebagai indikator besarnya tutupan awan berpengaruh terhadap batas bawah termoklin, semakin tinggi curah hujan maka semakin dangkal batas bawah termoklin. Disamping faktor tersebut faktor tingginya anomali SST (seawater surface temperature) di NINO3.4 dan besarnya nilai IOD berpengaruh terhadap variabilitas kedalaman batas atas dan batas bawah termoklin. Semakin tingginya nilai anomali SST di NINO3.4 dan semakin besar nilai IOD (+) maka batas atas termoklin akan semakin dangkal dan batas bawahnya makin dalam.

Kata kunci: Termoklin , ENSO, IOD, Monsun, perairan selatan Jawa, Timor

Thermocline layer is needed on depth identification of tuna-like fish swimming area. Identification of thermocline depth changes due to ENSO (El Nino Southern Oscilation), IOD (Indian Oscillation Dipole Mode) and monsoon variability were determined based on CTD(Conductivity-Temperature-Depth) and argofloat data accumulated in the Word Ocean Data (WOD) from 1985–2011. The wind data was collected from National Centre for Environmental Prediction (NCEP), rainfall intensity (from Indonesian Meteorology and Climatology Agency), and climate anomaly index of global climate change (SOI (SouthOscillation Index), NINO3.4 and IOD) were also used to support problem analysis. ENSO, IOD and monsoon determined as influencing upper and lower threshold and thermocline thickness. In general the depth of upper threshold in the eastern monsoon was deeper compare to in the western monsoon. It was also identified that, based on global climate annual variation, the upper threshold during El Niño fenomenon was shallower (average range of 50.9 m–51.7m) compare to the threshold during La Niña (58.4 m–60.2 m). On the other side the lower threshold during El Niño was deeper (262.9m–281.8 m) compare to the threshold during La Niña (204.5 m–259.6 m). The thermocline thickness itself during El Niño was found thicker (211.2 m–230.9 m) compare to La Niña (144.4 m–201.2 m). Heavy rainfall precipitation, as an indicator of cloud coverage, was determined as influencing the thermoc line lower threshold where the bigger rainfall precipitation the shallower lower threshold found. The high anomaly of Sea Surface Temperature (SST) in NINO3.4 and high value of IOD was also significantly influenced the thermocline upper and lower threshold variability. The higher anomaly value of SST in NINO3.4 and the bigger IOD(+) value resulting shallower upper threshold and deeper lower threshold.

Key words: Thermocline, ENSO, IOD, Monsoon, southern waters of Java, Timor