Electronic Theses and Dissertation

Laut Andaman merupakan perairan semi-tertutup di Samudra Hindia yang dinamika oseanografinya sangat dipengaruhi oleh sistem angin monsun dan fenomena iklim antar-tahunan seperti Indian Ocean Dipole (IOD). Penelitian ini bertujuan untuk menganalisis hubungan antara indeks IOD, yang direpresentasikan oleh Dipole Mode Index (DMI), terhadap dinamika Ekman pumping, serta memetakan pola distribusi spasial dan variabilitas temporal (musiman) Ekman pumping di perairan Laut Andaman selama periode September-Oktober-November (SON) tahun 2014-2024. Data yang digunakan meliputi data arah dan kecepatan angin ketinggian 10 meter dari ERA5 Reanalysis ECMWF serta data indeks IOD dari PSL-NOAA. Metode analisis dilakukan menggunakan estimasi teoretis wind stress curl untuk menghitung kecepatan vertikal Ekman pumping (W_E) serta uji korelasi linear Pearson. Hasil analisis spasial menunjukkan bahwa distribusi Ekman pumping tidak merata, di mana wilayah bagian selatan dan barat daya didominasi oleh nilai positif (W_E > 0) yang mengindikasikan fenomena upwelling (Ekman suction), sedangkan wilayah tengah hingga utara didominasi oleh nilai negatif (W_E < 0) yang mengindikasikan downwelling. Secara temporal, nilai DMI berkisar antara -1,2 hingga 1,8 dengan fluktuasi interannual yang dinamis. Hasil uji statistik menunjukkan adanya hubungan positif yang sangat lemah antara DMI dan Ekman pumping dengan nilai koefisien korelasi (r) sebesar 0,240 dan koefisien determinasi (R²) sebesar 0,058. Nilai tersebut mengindikasikan bahwa variabilitas IOD hanya berkontribusi sebesar 5,8% terhadap dinamika gerakan vertikal massa air di Laut Andaman, sementara 94,2% sisanya dikendalikan oleh faktor lain di luar IOD. Ketidakselarasan tren temporal juga membuktikan bahwa Ekman pumping lebih merespons variabilitas Wind stress curl (gradien spasial sirkulasi monsun regional) dan pengaruh geomorfologi lokal dibandingkan magnitudo indeks iklim global secara absolut. Kesimpulan dari penelitian ini menegaskan bahwa IOD bukan merupakan faktor utama pengendali variabilitas Ekman pumping di Laut Andaman.

Kata kunci: Laut andaman, indian ocean dipole, ekman pumping, wind stress curl, upwelling.

The Andaman Sea is a semi-enclosed body of water in the Indian Ocean whose oceanographic dynamics are strongly influenced by monsoon wind systems and interannual climate phenomena such as the Indian ocean dipole (IOD). This study aims to analyze the relationship between the IOD index represented by the Dipole Mode Index (DMI) and Ekman pumping dynamics, as well as to map the spatial distribution patterns and temporal (seasonal) variability of Ekman pumping in the Andaman Sea during the September-October-November (SON) period from 2014-2024. The data utilized include 10-meter wind direction and speed from ECMWF ERA5 Reanalysis and IOD index data from PSL-NOAA. Analysis methods involved theoretical wind stress curl estimation to calculate the Ekman pumping vertical velocity (W_E) and the Pearson linear correlation test. Spatial analysis results reveal an uneven distribution of Ekman pumping: the southern and southwestern regions are dominated by positive values (W_E > 0), indicating upwelling (Ekman suction), whereas the central to northern regions are dominated by negative values (W_E < 0), indicating downwelling. Temporally, DMI values ranged from -1.2 to 1.8, exhibiting dynamic interannual fluctuations. Statistical test results indicate a very weak positive relationship between the DMI and Ekman pumping, with a correlation coefficient (r) of 0.240 and a coefficient of determination (R²) of 0.058. These values indicate that IOD variability contributes only 5.8% to the dynamics of vertical water mass movement in the Andaman Sea, while the remaining 94.2% is governed by factors other than the IOD. The lack of alignment in temporal trends further demonstrates that Ekman pumping responds more to wind stress curl variability (spatial gradients of regional monsoon circulation) and local geomorphological influences than to the absolute magnitude of the global climate index. The conclusion of this study confirms that the IOD is not the primary factor controlling Ekman pumping variability in the Andaman Sea. Keywords: Andaman sea, indian ocean dipole, ekman pumping, wind stress curl, upwelling.