Category Archives: oceanographic missions

« Exploring paleo-hydrology and its impact on sedimentary dynamic processes in the South China Sea » / MD 215

Funding

IFREMER

Project leader

C.Colin

Mission leaders

C. COLIN (GEOPS, France), Z. LIU (Tongji University, China) and A. Tien-Shun LIN (National Central University, Taiwan),

On-board scientific team

Thirty-five researchers and students from France (GEOPS, LSCE, IFREMER, and LOG laboratories), China (Key State Laboratory of Marine Geology, Tongji University) and Taiwan (Department of Earth Sciences du National Central University, National Sun Yat-sen University, Institute of Oceanography of the National Taiwan University).

Mission Hydrosed

The MD215 HYDROSED oceanographic campaign, conducted on board the Marion Dufresne, has allowed us to collect long marine sediment cores at sea water samples in the northern part of the South China Sea. The main scientific objective of the mission is to reconstruct the past hydrology of intermediate and deep water masses and also the climate of South East Asia and thus to estimate the impact on the dynamics of sediment transport to the ocean floor and earth-sea transfers.

The samples collected during the HYDROSED oceanographic campaign will allow us to:

1- Better constrain the origins and past variations of the intermediate and deep water masses in the northern part of the South China Sea and existing relationships with glacio-eustatic changes, the evolution of global thermohaline circulation (the Great Conveyor Belt) and regional climatic modifications;

2- Reconstruct past variability in the south-east Asian climate (the East Asian monsoon and the ENSO system) at a very high temporal resolution and to identify the potential impacts on deep sedimentation in the northern part of the South China Sea;

3- Reconstruct the past dynamics of sediment transfer from the continent (Taiwanese rivers) to the northern part of the South China Sea using a “source to sink” approach and to identify the climatic controls (paleo-typhoons, paleo-monsoons and changes in sea level);

4- Develop and/or improve geochemical tracers used for paleooceanographic reconstructions and increase our understanding of the distribution of neodymium isotopes *Nd) and concentrations of rare earth elements (REE) in a marginal sea that is greatly influenced by enormous discharges of freshwater and sediments from several Asiatic rivers.

 

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The objective of the Mingulay-Rockall mission (June 2016), conducted on board the Atalante, was to retrieve water samples and sediment cores in areas rich in deposits of deep coral with a view to using these records for paleooceanographic reconstructions.

The mission focused on two sample sites in particular:

1) The Mingulay site (in the Sea of Hebrides) characterized by the presence of cold water coral reefs (L. pertusa) which currently proliferate between depths of 100 and 150 m.

2) The Logachev site (SW of the Rockall Trough) also characterized by abundant coral colonies (L. pertusa and M. oculata) but at depths of about 750 m.

Mission Mingulay-Rockall

The project thus aims to conduct a multidisciplinary study based on these two sites (sedimentology, biology and geochemistry of corals) in order to reconstruct the growth history of these reefs as well as environmental changes (temperature, circulation of intermediate and sub-surface waters) over the course of the Holocene. We will this thus obtain reconstructions of the hydrology of the sub-surface and intermediate waters with unprecedented temporal resolutions at two sites located at different depths.

The project brings together research teams from Britain, Ireland and France and forms part of a national research effort which aims to study deep water coral ecosystems and to use fossil corals as natural archives that can provide high resolution reconstructions of past paleoclimatic changes (ANR HAMOC PI C. Colin).

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Monopol (Indian MONsOon PaleO-variabiLity) (2012-2016) & DIPOMOUSS (2019-2020)

Funding

ANR (2012-2016) / IFREMER (2019-2020)

Project leader

F. Bassinot (LSCE)

Partner Laboratories

GEOPS (Univ. Paris Saclay, campus Paris Sud Orsay)
CEREGE (CNRS-Univ. Aix-Marseille)
EPOC (CNRS – Univ. Bordeaux I)
IPGP (Univ. Paris-Diderot)
MNHN (Paris)
Tongji University (Shanghai)
China University of Geosciences (Pékin)
Peking University (Pékin)

The Indo-Asiatic monsoon is a major climatic phenomenon due to its economic and social impacts on one of the most densely populated regions of the world, and because of the scale of the heat and humidity transfers involved; in short, it is an essential element of the planet’s climate. The natural variability of the Indo-Asiatic monsoon, is however, not fully understood and its future evolution is difficult to model because of the complexity of the processes and the interactions involved (i.e. ocean dynamics, vegetation response, teleconnections with middle and high latitudes, monsoon/ENSO/IOD/ITF coupling).

The MONOPOL and DIPOMOUSS projects aim to study the water and sediments of the Tropical Indian Ocean (East and Central) in order to reconstruct the past variability of the Indo-Asiatic monsoon and its sensitivity to various types of forcing over the course of the Quaternary. They are based on the study of water samples and sedimentary cores taken in 2012 during the MONOPOL oceanographic expedition (on board the N/O Marion Dufresne II) and on further samples that will be taken in 2020 during the DIPOMOUSS campaign; the latter will employ rosettes, CASQ and CALYPSO corers and an interface (multi-tube) corer. The projects involve six laboratories – CEREGE, EPOC, GEOPS, IPGP, LSCE and MNHN- and are part of an international collaboration undertaken within the IGBP/PAGES – IMAGES programme (International Marine Global Changes Study).

Mission Monopol

Photograph of the Marion Dufresne taken during the MONOPOL oceanographic mission (Gulf of Bengal). Photo credit: Stéphanie Duchamp-Alphonse

In concrete terms, the paleooceanographic and paleoclimatic reconstructions are based on a multi-tracer approach which includes biological tracers (e.g. studies of calcareous nanofossil and pollen assemblages), sedimentary tracers and geochemical tracers (e.g. Ti/Al, δ18O, Mg/Ca). Past changes in alteration in the Himalayas linked to variations in the monsoon are identified on the basis of analysis of sedimentary tracers (clays, laser granulometry) and geochemical tracers (major and trace elements combined with Nd, Sr and Pb isotopes).
Our team focuses in particular on the Indian monsoon and its impact on the following dynamics: (i) Himalayan erosion and the transfer of sediments to the ocean as well as the distribution of Nd isotopes in the Bay of Bengal and their past evolution (the impact of erosion); (ii) Surface waters and thermocline/nutricline depth, which have a considerable impact on primary producers (particularly coccolithophores); and iii) the hydrology of subsurface and intermediate waters at the scale of glacial-interglacial cycles.

Mission Monopol

Photograph of the multi-corer used on board the Marion Dufresne, during the MONOPOL oceanographic mission: it allows samples to be taken from the water-sediment interface in the Gulf of Bengal. Photo credit: Stéphanie Duchamp-Alphonse