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Ocean circulation and global climatic changes over the last three inter glacials. A contribution to the coordinated program : the study of the last two glacial cycles with particular emphasis on the initiation of the glaciations

Cel

To build, for modellers and other climate researchers, a high
quality data base describing the detailed changes in the North
Atlantic surface and deep water properties and circulation over
the last 250.000 years. A special emphasis is given on the
interglacials and the inception of the glaciations. To integrate
the results in a global climatic framework, specially with
respect to the thermohaline circulation, the extent of sea ice,
evolution of the major ice sheets and the global carbon cycle.


The study will involve the construction of records of very
high-resolution (about 100--300 years) from high quality sediment
cores representative of the main areas and water masses of the
North Atlantic Ocean, Norwegian Sea, and the Southern Ocean.

Analyzed proxies will cover the changes in foraminiferal, diatom,
and dyno-flagellate species distribution, oxygen and carbon
isotopic ratio in planktic and benthic foraminifera, organic and
inorganic traces geochemistry, organic and mineral carbon
content, colour reflectance and magnetic susceptibility of the
sediments. Deconvolution of the effect of the bioturbational
mixing, will permit an ultimate resolution of 100 to 400 years.
Sea surface temperature will be estimated using the fossil fauna
specific distribution and the bio-marker Uk37, and salinity will
be derived from the foraminifera delta 18O, after correction
for the
effect of temperature on isotopic fractionation. The data will
allow the estimation of density differences between surface and
deep waters, and thus constrain the changes in vertical
thermohaline structure between interglacial and glacial periods,
and during the rapid climatic transitions.

Additional cores will be studied at lower resolution (approximately 1-2 kyrs)
to map the spatial distribution of the same parameters, with
water depth and along North-South and East-West transects through
the North Atlantic Ocean, at specific time intervals during the
same period, to prepare simulations with Ocean General
Circulation Models.

Isotopic stage 3 (the period between 40 and 20 kyrs BP) will be
used as special target, as it is accessible to 14C dating.
Rapid interactions between the dynamics of ice sheets and ocean
thermohaline circulation have been evidenced during that period.
These interactions will be studies in detail using specific
tracers of the ice input (ice rafted detritus) in cores located
at proximity of the main ice sheets.

Zaproszenie do składania wniosków

Data not available

System finansowania

CSC - Cost-sharing contracts

Koordynator

Centre National de la Recherche Scientifique (CNRS)
Wkład UE
Brak danych
Adres
Avenue de la Terrasse
91198 Gif-sur-Yvette
Francja

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Koszt całkowity
Brak danych

Uczestnicy (5)