Variabilitas Lapisan Termoklin dan Suhu Permukaan Laut saat Fenomena Indian Ocean Dipole di Perairan Barat Sumatera

Abstract

In sea-atmosphere interactions, the Indian Ocean Dipole phenomenon originating from the Indian Ocean is known to have an important influence on weather factors in the Western Waters of Sumatra. This study aims to identify the variability of the thermocline layer in the Western Waters of Sumatra during the IOD phenomenon. The data used is from vertical sea temperature model data on 50 layers with a depth of 0 - 400 meters in the NetCDF format (.nc) for 35 years (1980 – 2015). The data were processed using GrADS software to identify spatially the climatological mean, the variability during positive and negative IOD, and the propagation direction of Thermocline Layer and Sea Surface Temperature (SST. Surface current data, chlorophyll-a concentration, and rainfall data were also analyzed as supporting data. The results showed that the thermocline layer in the West Sumatra waters was at a depth of 104 to 114 m respectively. During positive IOD, the thermocline layer was getting shallower with the cooler SST, meanwhile during negative IOD, the thermocline layer is getting deeper (sinking) with the warmer SST. In general, the propagation of the thermocline layer and SST starts from the east part of the western waters of Sumatra. Based on the results of correlation analysis, there is a strong relationship between fluctuations in the Dipole Mode Index with the depth of the thermocline layer and SST conditions. Fluctuations in the thermocline layer and SST also affect the production of aquatic resources.

Dalam interaksi laut – atmosfer, fenomena Indian Ocean Dipole yang berasal dari Samudera Hindia diketahui memiliki pengaruh penting dalam faktor cuaca di perairan barat Sumatera. Penelitian ini bertujuan mengkaji variabilitas lapisan termoklin di Perairan Barat Sumatera saat terjadinya fenomena IOD. Data yang digunakan adalah dari data model suhu laut secara vertikal pada 50 lapisan dengan kedalaman 0 – 400 meter dalam format NetCDF (.nc) selama 35 tahun (1980 2015). Data diolah dengan software GrADS untuk mengidentifikasi secara spasial rata – rata klimatologis, variabilitas saat IOD positif dan negatif, serta arah penjalaran dari Lapisan Termoklin dan Suhu Permukaan Laut (SPL). Data arus permukaan, konsentrasi klorofil-a, dan data curah hujan juga dianalisis sebagai data pendukung. Hasil penelitian menunjukkan bahwa lapisan termoklin di perairan Barat Sumatera berada pada kedalaman 104 m hingga 114 m. Saat IOD positif, lapisan termoklin semakin dangkal dengan SPL secara umum semakin dingin, sedangkan saat IOD negatif lapisan termoklin semakin dalam (tenggelam) dengan anomali SPL semakin hangat. Propagasi lapisan termoklin dan SPL umumnya dimulai dari bagian timur wilayah perairan Barat Sumatera. Berdasarkan hasil analisis korelasi, terdapat kaitan yang kuat antara fluktuasi Dipole Mode Index dengan kedalaman lapisan termoklin dan kondisi SPL. Fluktuasi lapisan termoklin dan SPL juga berpengaruh terhadap produksi sumber daya perairan.