Variasi Musiman Ketebalan Lapisan Termoklin di Perairan Barat Sumatra: Thermocline Layer Thickness in the Waters off the Western Coast of Sumatra

Abstract

Dinamika oseanografi di perairan barat Sumatra dapat dianalisis melalui karakteristik lapisan termoklin. Informasi mengenai ketebalan termoklin memiliki peran penting dalam mengidentifikasi variasi musiman dalam dekade terakhir. Penelitian ini bertujuan untuk mengkaji variasi musiman ketebalan lapisan termoklin di wilayah pantai dan lepas pantai barat Sumatra dengan menganalisis enam titik pengamatan yang mewakili kedua zona tersebut. Pendekatan yang digunakan adalah metode kuantitatif dan deskriptif, dengan memanfaatkan data temperatur vertikal rata-rata bulanan dari tahun 2010 hingga 2019 yang diperoleh dari situs Marine Copernicus. Pengolahan data dilakukan menggunakan perangkat lunak Panoply dan Microsoft Excel 2010, menghasilkan nilai rata-rata ketebalan termoklin musiman dan grafik deret waktu (time series). Hasil analisis menunjukkan bahwa ketebalan termoklin tertinggi tercatat sebesar 130,3 m di wilayah pantai Bengkulu pada musim peralihan I, dan mencapai 138,7 m di lepas pantai Lampung pada musim timur. Sebaliknya, ketebalan termoklin terendah terjadi pada musim barat, yakni sebesar 74,9 m, baik di wilayah pantai maupun lepas pantai Bengkulu dan Lampung, serta di perairan Aceh pada bulan Agustus. Ketebalan yang tinggi pada musim peralihan I di wilayah Bengkulu hingga Lampung disebabkan oleh adanya distribusi angin permukaan yang membawa massa air hangat sepanjang perairan barat Sumatra. Sementara itu, ketebalan termoklin yang lebih tipis pada musim timur mengindikasikan terjadinya proses upwelling di kawasan tersebut.The oceanographic dynamics of the western waters of Sumatra can be observed through the characteristics of the thermocline layer. Information on thermocline thickness is essential for understanding seasonal variations over the past decade. This study aims to identify the seasonal variability in thermocline thickness along the coastal and offshore regions of western Sumatra by analyzing six observation points representing both zones. A quantitative and descriptive approach was employed, utilizing monthly average vertical temperature data from 2010 to 2019, obtained from the Marine Copernicus database. Data processing was conducted using Panoply software and Microsoft Excel 2010, producing seasonal average thermocline thickness values and time series graphs. The results show that the highest thermocline thickness was recorded at 130.3 meters in the coastal area of Bengkulu during the first transitional season, and 138.7 meters in the offshore area of Lampung during the southeast monsoon. In contrast, the lowest thermocline thickness was observed during the northwest monsoon, reaching 74.9 meters from the coast to offshore regions of Bengkulu and Lampung, as well as in the coastal to offshore areas of Aceh in August. The increased thermocline thickness during the first transitional season in Bengkulu to Lampung waters is attributed to the distribution of surface winds transporting warm water masses along the western coast of Sumatra. Meanwhile, the thinner thermocline layer observed during the southeast monsoon suggests the occurrence of upwelling in the region