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SUMMARY:Impact of the Boundary Exchange on the Element Cycle - Catherine J
 eandel (LEGOS\, Toulouse\, France)
DTSTART:20081125T163000Z
DTEND:20081125T173000Z
UID:TALK14284@talks.cam.ac.uk
CONTACT:Francis Rowland
DESCRIPTION:Since the end of the eighties\, it is recognized that the Nd i
 sotopic composition (expressed as εNd ) varies from ca -13 in the North A
 tlantic to ca -5 in the Pacific. It has been clearly established that far 
 from any source of lithogenic material\, εNd is a conservative tracer of 
 water mass mixing. Since the range of εNd values of the deep waters are i
 mprinted in the metalliferous sediments\, they are used by paleoceanograph
 ers to trace the past variations of the thermohaline circulation. However\
 , many studies conducted in the present day ocean highlight that the Nd bu
 dgets based only on dust/riverine inputs were not able to reconcile the Nd
  content and εNd variations between the 3 oceanic basins (the "Nd paradox
 ").\n\nThe "missing source" was often suspected to be input from sediments
  deposited on oceanic margins although this has never been quantified. The
  results presented here partly solve this question by establishing that th
 e boundary exchanges at the oceanic margins appear as a key process for th
 e Nd cycle. Such process could affect the distributions of other reactive 
 elements\, until remote areas as the middle of the oceanic basins. Enlargi
 ng such studies to other trace elements and isotopic tracers is among the 
 goals of the forthcoming GEOTRACES program. 
LOCATION:Tilley Lecture Theatre\, Department of Earth Sciences
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