Tritium circulation tracer

The latter two approaches are related because natural and artificial tracers are used to calibrate or evaluate ocean models. A key aspect of these tracers is that they provide independent information on timescale, either because they decay or are produced at some known rate, for example, due to radioactivity, or because they are released into the ocean with a known time history. The different chemical tracers can be roughly divided into two classes. Circulation tracers such as radiocarbon, tritium- He, and the chlorofluorocarbons are not strongly impacted by biogeochemical cycling and are used primarily to quantify physical advection and mixing... 

Some anthropogenically introduced radionuclides and synthetic compounds are useful as ocean circulation tracers. These include tritium, bomb radiocarbon and CFCs. 

Roether W, Mutmich KO, Ostlund HG (1970) Tritium profile at the North Pacific (1969) Geosecs Intercallibration Station. J Geophys Res 75 7672-7675 Roether W, Schlosser P, Kuntz R, Weiss W (1992) Transient-tracer studies of the thermohaline circulation of the Mediterranean. In Winds and Currents of the Mediterranean Basin Reports in Metereology and Oceanography 41, Vol. 2. H Chamock (ed) p 291-317... 

Tracers serve as a dye with which to follow the circulation of ocean waters. There are conventional ocean tracers such as temperature, salinity, oxygen, and nutrients. There are stable isotope tracers such as oxygen-18, carbon-13, and there are radioactive tracers both naturally occurring (such as the uranium/thorium series, and radium), and those produced both naturally and by the bomb tests (such as tritium and carbon-14). The bomb contributions from the latter two are called transient tracers, as are the CFCs, because they have been in the atmosphere for a short time. This implies an anthropogenic source and a nonsteady input function. 

It is unusual to think of any type of atmospheric contamination - especially by a radioactive species -as beneficial however, bomb-produced radiocarbon (and tritium) has proven to be extremely valuable to oceanographers. The majority of the atmospheric testing, in terms of number of tests and production, occurred over a short time interval, between 1958 and 1963, relative to many ocean circulation processes. This time history, coupled with the level of contamination and the fact that becomes intimately involved in the oceanic carbon cycle, allows bomb-produced radiocarbon to be valuable as a tracer for several ocean processes including biological activity, air-sea gas exchange, thermocline ventilation, upper ocean circulation, and upwelling. 

Figure 4 Tracer results from a two-dimensional gyre model. The model represents the circulation on a constant density surface (isopycnal) in the main thermocline that outcrops along the northern boundary (shaded region). Thermocline ventilation is indicated by the gradual increase of tritium- He ages around the clockwise flowing gyre circulation. TU, tritium unit (1 TU = 1 atom/10 H...

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