The Characteristics Of The Mixed Layer Depth During La Niña, El Niño, And Normal Years In The North Natuna Sea

Abstract

The Natuna Sea is one of the seas located in the northern part of Indonesia, which is influenced by several oceanographic climate phenomena, including the El Nino-Southern Oscillation (ENSO) system, such as La Nina and El Nino, which cause vertical temperature dynamics. This study aims to examine the relationship between La Nina, El Nino, and normal years on the variability of the mixed layer depth in the Natuna Sea. The study utilizes temperature data from the World Ocean Database (WOD) and Marine Copernicus for a period of 3 years, including years with La Nina, El Nino, and normal conditions, as well as mixed layer depth (defined by sigma theta) data from Marine Copernicus. The occurrence of La Nina, El Nino, and normal years is obtained from the Southern Oscillation Index (SOI). The research findings indicate a correlation between the SOI values and the Maximum Mixed Layer Depth (MLD) during weak and very weak El Nino and La Nina conditions, while the correlation is weak during normal years. During the La Nina, normal, and El Nino periods, the deepest MLD occurs during the west monsoon season at depths ranging from 7 to 60 meters. The shallowest MLD occurs during the first transition season at depths ranging from 7 to 25 meters. The MLD values during the east monsoon season range from 7 to 43 meters, and during the second transition season, the MLD ranges from 7 to 44 meters.