Intensity of Indonesian Throughflow during the Heinrich Stadial 1 Period in the Makassar Strait Using Planktonic Foraminifera Approach
Niken Sitalaksmi Siagian (a*), Marfasran Hendrizan (b), Rima Rachmayani (c), Dian Handiani (d)

a) Study Program of Oceanography, Faculty of Earth Sciences and Technology, Bandung Institute of Technology, Jl. Ganesha, No. 10, Bandung 40132, West Java, Indonesia
*niken.sitalaksmi[at]gmail.com
b) Paleoclimate and Paleoenvironment Research Group, Research Center for Climate and Atmosphere, Research Organization for Earth Sciences and Maritime, National Research and Innovation Agency Republic of Indonesia (BRIN), Jl. Sangkuriang, Bandung 40135, West Java, Indonesia
c) Research Group of Environmental and Applied Oceanography, Faculty of Earth Sciences and Technology, Bandung Institute of Technology, Jl. Ganesha, No. 10, Bandung 40132, West Java, Indonesia
d) Geodetic Engineering Program Study, Faculty of Civil and Planning Engineering, Institut Teknologi Nasional - Itenas Bandung, PHH Mustofa street, No. 23, West Java, Indonesia

Abstract

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 marine sediment core TR1926B (0.227^{\circ}N, 117.790^{\circ}E, 616 m water depth). The Depth of Thermocline (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 suggested due to an El Ni\tilde{n}o-like phenomenon. The intensity of ITF is also known to have weakened based on the S-N temperature gradient (south (S)-north (N)).

Keywords: Indonesian Throughflow (ITF), Heinrich Stadial 1 (HS 1), Makassar Strait, Planktonic Foraminifera

Topic: Ocean Sciences