THE INTENSITY OF INDONESIAN THROUGHFLOW (ITF) DURING THE HEINRICH STADIAL 1 PERIOD IN THE MAKASSAR STRAIT USING PLANKTONIC FORAMINIFERA APPROACH

• Main Author: Sitalaksmi Siagian, Niken
• Format: Final Project
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/85183
• Institution: Institut Teknologi Bandung

The Heinrich Stadial 1 (HS 1) was a deglacial event in the North Atlantic that occurred approximately 18,000 to 15,000 years ago. During this period, there was a reduction in the volume of warm tropical surface water flow to the North Atlantic such that heat accumulated in the Southern Hemisphere and tropical regions, including Indonesia. This inhibition of the distribution of sea surface water flow affects ocean and atmospheric circulation both regionally and globally. The objective of this study is to determine the paleoceanographic conditions in the Makassar Strait and to investigate the relationship between planktonic foraminifera abundance and changes in the intensity of the Indonesian Throughflow, using the TR1926B sediment core (0°13,664' N, 117°47,436' E, water depth 616 m). A proxy analysis of planktonic foraminifera was conducted to ascertain the sea surface temperature (SST) and depth of the thermocline (DOT) in the main channel of the Indonesian Throughflow (ITF) during extreme conditions in HS 1. The SST at HS 1 exhibits a warming trend with an average SST of 26.22°C, while modern conditions have an average of 29.17°C. The DOT was determined through a foraminifera analysis, which indicated that thermocline dwellers constituted 50- 78% of the population, while mixed layer dwellers accounted for 21-49%. The foraminifera analysis yielded evidence that the DOT was undergoing a process of shallower. These findings were corroborated by the results of the vertical temperature profile, which indicated a shallower of 7.5 meters in comparison to the modern profile. The cause of DOT shallower in the Makassar Strait is an El Niñolike phenomenon. The intensity of ITF is also known to have weakened based on the S-N temperature gradient (south (S)-north (N)). This result is supported by a weakening trend based on the reconstruction of the log(Zr/Rb) ocean current proxy.