Banda Sea and the Indonesian Throughflow variability during the past 700,000 years
Oceanography
Final Report Abstract
The Banda Sea is the most important sea along the only low-latitude conduit between the ocean basins today, called the Indonesian Throughflow (ITF). Here, mixing of water masses originating from the southern and northern Pacific Ocean takes place, which together with a strong tidal mixing, cause a change in the vertical profile of the ITF before entering the Indian Ocean. Despite its critical role in shaping the ITF today, past changes in the vertical profile of the Banda Sea and their effect on the ITF are unknown. In this project we made use of shell stable oxygen isotopes and trace element composition of two planktic foraminifera species in core MD01-2380 to reconstruct surface and thermocline temperature and salinity of the Banda Sea over the past ~820,000 years (820 kyr). Our results show that surface and thermocline temperatures varied between 23-29 °C and 17-23 °C, respectively, and changed nearly in sync with the atmospheric carbon dioxide with a 100-kyr (eccentricity) cycle. The difference between the two temperature records indicates changes in the vertical profile of the ITF and shows an additional cyclicity at precession band (19-23 kyr). Reconstructed seawater stable oxygen isotope values, a measure of past changes in salinity, reveal periodicities at eccentricity, precession and obliquity (41 kyr) bands, both for the surface and thermocline waters. We find no relationship between the upper water column conditions in the Banda Sea and sea-level changes during the past nine glacial terminations, suggesting that the exposure and inundation of large shelf areas in this region did not affect the vertical profile of the ITF. These findings support, in part, the hypothesis that precession-paced changes in the state of the ENSO controlled the ITF vertical profile, rather than sea-level changes.
Publications
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A high-resolution reconstruction of SST and paleoproductivity from the Banda Sea, Indonesia across the mid-Brunhes event (last 820 kyr). 14th International Conference on Paleoceanography (ICP), Bergen, Norway, 29.08. – 02.09.2022
Li, Z., Mohtadi, M., Tsai, H.-L., Chang, Y.-P., Kienast, M., Lee, S.-Y., Groeneveld, J. & Chen, M.-T.
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A high-resolution reconstruction of SST and paleoproductivity from the Banda Sea, Indonesia across the mid-Brunhes event (last 820 kyr). 6th Symposium on Marine Environmental Sciences, Xiamen, China, 09.01. - 12.01.2023
Li, Z., Mohtadi, M., Tsai, H.-L., Chang, Y.-P., Kienast, M., Lee, S.-Y., Groeneveld, J., Timmermann, A. & Chen, M.-T.
