All Climate Events

Thursday, January 26, 2017. 12:00 PM. Webinar: Transient Tracers for climate and ocean health assessments. Toste Tanhua, GEOMAR (Kiel, Germany). Sponsored by National Oceanic and Atmospheric Administration. More information here.

Transient tracers are a group of (chemical) compounds that can be used in the ocean to quantify ventilation, transit time distribution and transport time-scales. These compounds are ideally conservative in sea-water and a well-established source function over time at the ocean surface, or have well-defined decay-functions. Measurement of transient tracers in the interior ocean thus provides information on the time-scales since the ocean was ventilated, i.e. in contact with the atmosphere. Knowledge of the transit time distribution (TTD) of a water-mass allows for inference of the concentrations or fates of other transient compounds, such as anthropogenic carbon or nitrous oxide. Commonly measured transient tracers are the chlorofluorocarbons (CFCs) 11 and 12, although in the past also CFC-113 and CCl4 have been measured. More recently also the related compound sulphur hexafluoride (SF6) is regularly measured since it provides information on ventilation of the fast ventilated parts of the ocean. Exciting new techniques might allow for a global survey of Argon-39, a isotope with a 269 decay half-time.

Knowledge about ventilation is key to quantify the transport of (climate) perturbations from the surface to interior ocean. For instance, the ocean is storing about 95% of anthropogenic global warming (heat content) and about 30% of anthropogenic carbon. A system of global sustained observations of interior ocean transient tracer observations will help to answer several societal relevant questions articulated in, for instance, climate agreements and SDG-14.
Here I will present some basic concepts of transient tracers, and put that in a global context with focus on societal benefits.