Dr. Toste Tanhua
Transient tracers are substances that have a time-dependent concentration that can be explored to learn about circulation and ventilation time-scales. Our working group is mainly working with the chlorofluorocarbon (CFC) compounds 12 and 11, and the compound sulfur hexafluoride (SF6). These compounds are released to the atmosphere and enter the ocean through air-sea exchange. Accurate measurements of these compounds in the ocean interior is the focus of our practical work, and we use this information to calculate properties like the mean age of a water mass, or the concentration of anthropogenic CO2.
In addition to measuring transient tracers, we are conducting deliberately released tracer experiments. This means that we inject an artificial tracer (CF3SF5) on a well-defined density layer in the interior ocean. By measuring the dispersion of the tracer over time we can draw conclusions on the lateral and vertical mixing rates, as well as the large scale transport (advection) of the tracer.
We are also exploring the possibility to utilize other transient tracers to complement the tracer we already use. A suite of different tracers is useful to, for instance; better understand how the mixing in the ocean interior varies over the ocean and over time. We are currently developing a GC-MS based system to simultaneously measure a wide range of tracers in one water samples. This is based on the so called Medusa system that was developed about 10 years ago for atmospheric measurements of a wide range of climate relevant trace gases. This is a project in cooperation with Birgit Quack.