Joint Seminar: Dissecting the deep ocean ventilation: partial ages as a new diagnostic tool; impact of surface exchange rates

Assessing the pathways and renewal rate of deep ocean water masses is essential for the understanding of past and future Earth climate states. Water mass composition and timescales could be obtained from the observed distribution of tracers. However, stirring and turbulence result in a multitude of pathways. Therefore, deep water masses are composed of a mixture of source-water types whose exact contributions are difficult to extract. Further, tracer ages do not accurately estimate the actual ventilation time.

The concept of partial age, a generalization of the notion of age is presented. Partial ages, by recording the time spent in sub-domains of the global ocean, provide a more detailed description of the ventilation processes. The properties and possibilities of this new tool are discussed. Partial ages are directly related to the connectivity matrix characterizing the flow under study. There is also a clear link between these ages and water-mass composition and age. Their use in 3-D OGCMs helps evidencing differences in ventilation pathways which result in contrasting tracer distributions.

An important process affecting tracer-based ventilation estimates is the rate of exchange between the uppermost ocean layer and the atmosphere. Simulations with 3-D OGCMs show that benthic-planktonic radio-ages may overestimate the true age difference by several hundred years. I briefly discuss how new theoretical developments help assessing the main processes driving these age biases.




15:15 h


Bundesstr. 53, room 022/023
Seminar Room 022/023, Ground Floor, Bundesstrasse 53, 20146 Hamburg, Hamburg


Anne Mouchet, University of Liege


Tatiana Ilyina

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