IDENTIFIKASI EQUATORIAL UNDER CURRENT (EUC) DAN PENGARUHNYA TERHADAP UPWELLING DI PERAIRAN BARAT SUMATRA

• Main Author: Rama Adyaksa, Muh.
• Format: Final Project
• Language: Indonesia
• Subjects: Geologi, hidrologi & meteorologi
• Online Access: https://digilib.itb.ac.id/gdl/view/62568
• Institution: Institut Teknologi Bandung

Equatorial undercurrent (EUC) is an equatorial circulation that moves eastward and lies below the surface. EUC in the Pacific and Atlantic Oceans is a permanent EUC that is constant throughout the year, but in the Indian Ocean, EUC works on a seasonal scale. EUC works on a seasonal scale. EUC plays a role in water mass transport which directly affects the characteristics of water masses in the eastern Indian Ocean. The aims of the study were to identify the characteristics of EUC and upwelling, the effect of the presence of EUC on the upwelling in the western seas of Sumatra, and its activities during the active phase of the IOD. The data used is RAMA mooring data located at the equator 90° East, which consists of zonal current velocity (u), meridional current velocity (v), temperature, and salinity during the period 2005 – 2017. Data processing is performed by calculating the average monthly value of each parameter in the range of 2005-2017 to view the behavior of EUC and upwelling in the monthly period. EUC and upwelling are also analyzed in annual periods to see the effect of EUC and upwelling during IOD events in the Indian Ocean. EUC in the eastern Indian Ocean is a seasonal EUC identified at a depth of 80 – 180 m in February – May with current velocity of around 0.1 – 0.5 m/s, then re-identified in August – September around 0.1 – 0.3 m/s at a depth of 90 – 190 m. EUC transports a mass of water with a salinity of about 34.8 – 35.23 PSU, a temperature of about 16.77? – 21.45?, and a density of about 23 – 25.39 ????????????3? to the eastern Indian Ocean. Upwelling in the eastern Indian Ocean was identified in June – early August as seen from the positive vertical current velocity to a depth of 30 – 70 m, a decrease in temperature of around 18.28 – 21, an increase in salinity of around 34.97 – 35.42 PSU and a density of around 23 – 24.55 ????????????3?. In addition, during the upwelling, there was a shallowing of the thermocline layer from a depth of 74.54 m in May to 64.86 m in September. The existence of the EUC prevented an earlier upwelling in mid-March. EUC which coincides with a positive IOD results in an increase in the speed and duration of the occurrence of EUC, for example the EUC that occurred in the period July – September 2012 which coincided with a positive IOD phase increased the speed of the EUC by around 0.2 – 0.59 m/s. The EUC along with a negative IOD indicates that the EUC to the east is not identified and is experiencing a current reversal to the west. Upwelling is strengthened when there is a positive IOD as seen from the positive vertical currents identified up to a depth of 30 m, an increase in salinity and density, and a decrease in temperature. In addition, there was a significant silting of the thermocline layer of more than 13 m. Meanwhile, upwelling was not identified when a negative IOD occurred.