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INDOMIX: Physical and geochemical transformations within the Indonesian throughflow

by TIM last modified Nov 20, 2020 10:39 AM



The general scientific objectives of the INDOMIX project are to study the internal tides, the associated turbulent mixing and the chemical and physical transformations of the water masses when transiting through the Eastern Indonesian Seas. A collaborative project (PI: Ariane Koch-Larrouy) was conducted off the Indonesian archipelago and put together physicists and geochemists to study vertical mixing in this region.

Scientific Rationale

The Indonesian archipelago is a region of strong water mass transformation. This region is characterized by intense vertical mixing because strong internal tides remain trapped in semi-enclosed seas, with the result that a large amount of tidal energy remains available for vertical mixing. To study the internal tides, the associated turbulent mixing and the chemical and physical transformations of the water masses of the Eastern Indonesian Seas, a collaborative project was conducted in that area. To achieve our goals, we combined geochemical tools (Rare Earth concentrations, Nd isotopic composition, radium isotopes, 227Ac, and trace element concentrations on the particulate samples) and physical observations (hydrophysical (CTD)-current profile (LADCP) and Microstructure (VMP 600) measurements)



Rare Earth (REE) concentrations and Nd isotopes: These parameters are good tracers of processes occurring at the land-ocean interface. They are also tagging the different water masses with different signatures, which allows following water mass trajectories and mixing, far from any lithogenic input. Sample volumes of 10 L where collected, filtered on board. An aliquote of 500 ml was dedicated to the measurement of the Rare Earth concentrations. Filtered particles were stored for the analysis of the solid REE and the lithogenic tracers.

 Results and perspectives


Neodymium concentrations measured at stations S0 (located at the entrance of the through flow) and S4 (located in the Banda Sea) reported in Fig.2 (top) show:


Pieter van Beek, Catherine Jeandel, François Lacan, Marc Souhaut, Marie Labatut, Nolwenn Lemaitre, Moustafa Belhadj, Ariane Koch-Larrouy





Peer review articles related to this project: 

Koch-Larrouy A., Atmadipoera A., van Beek P., Madec G., Aucan J., Lyard F., Grelet J., Souhaut M., 2015. Estimate of tidal mixing in the Indonesian archipelago from multidisciplinary data, Deep-Sea Research I 106, 136–153.


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