CHANGES OF THERMOCLINE DEPTH AT THE SUMBA ISLAND OFFSHORE BASED ON PLANKTONIC FORAMINIFERAL ASSEMBLAGES AND ITS IMPLICATION TO EUTROPHICATION SINCE THE LAST DEGLACIATION (~18 ka BP): A PRELIMINARY STUDY

Changes of the thermocline depth (DOT) at the Sumba Island offshore are not well-known compared to the DOT changes in the Timor Sea, the main exit passage of the Indonesian Through-flow (ITF). Planktonic foraminiferal assemblages in cores collected from the southwest Sumba offshore (ST08) and Sumba...

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Bibliographic Details
Published in:Rudarsko-geološko-naftni zbornik 2021-01, Vol.36 (3), p.31-45
Main Authors: Ardi, Ryan Dwi Wahyu, Aswan, Aswan, Maryunani, Khoiril Anwar, Yulianto, Eko, Putra, Purna Sulastya, Nugroho, Septriono Hari
Format: Article
Language:English
Subjects:
applied micropaleontology
australian–indonesian monsoon
Deglaciation
Dipoles
El Nino
Eutrophic environments
Eutrophication
Holocene
indonesian throughflow
lesser sunda islands
Monsoons
Nutrient availability
Offshore
paleoceanography
Relative abundance
River flow
Runoff
Southern Oscillation
Surface water
Thermocline
Upwelling
Water masses
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Summary:Changes of the thermocline depth (DOT) at the Sumba Island offshore are not well-known compared to the DOT changes in the Timor Sea, the main exit passage of the Indonesian Through-flow (ITF). Planktonic foraminiferal assemblages in cores collected from the southwest Sumba offshore (ST08) and Sumba Strait (ST12, ST13, and ST14) were used as a tool to infer the DOT and paleoproductivity changes at the Sumba Island offshore. The DOT changes were indicated from the thermocline and mixed layer dwellers’ relative abundance while the paleoproductivity changes were indicated from the relative abundance of Neogloboquadrina dutertrei. This study suggests a contrast between the DOT pattern at the Sumba Island offshore and the DOT pattern in the Timor Sea during the Last Deglaciation–Holocene. The contrast DOT pattern indicated that the multi-millennial changes of the Australian-Indonesian monsoon (AIM) during the Last Deglaciation– Holocene were the main factors behind the DOT changes in this region while the effects of El Niño Southern Oscillation (ENSO) –like, Indian Ocean Dipole (IOD) –like, and ITF to DOT changes were minimal. Paleoproductivity enhancement at the Sumba Island offshore was not solely related to the monsoon-driven coastal upwelling intensification, which resulted in the DOT shoaling and eutrophic condition. The increase of nutrient availability in surface water due to river runoff increase and changes in the lifted water mass nature were also able to enhance productivity in this region.
ISSN:1849-0409
0353-4529
1849-0409
DOI:10.17794/rgn.2021.3.3