Perspectives of Transient Tracer Applications and Limiting Cases

The concentrations of a number of radioisotopes and gases—including chlorofluorocarbons (CFCs), sulfur hexafluoride, and carbon dioxide (CO2)—have increased significantly in the atmosphere during the past century. These compounds dissolve in the surface ocean and are subsequently carried into the ocean interior, acting as “tracers” of complex oceanic mixing and circulation processes. Some of these compounds, such as CFCs, are entirely anthropogenic in origin (i.e., they are produced solely as a result of human activity). Studies of the changing distributions of dissolved CFCs in the ocean provide a unique and extremely sensitive tool to help estimate the rates at which the ocean can take up anthropogenic CO₂ and heat. Observed tracer distributions can also be used to evaluate and improve numerical models of ocean circulation.

International programs involving NOAA and other agencies are in place to monitor, at approximately 10-year increments, the evolving global distributions of a number of these tracers in the subsurface ocean. This paper discusses mathematical techniques that use CFCs along with several other tracers (with different time histories) to obtain improved estimates of the rates of ocean mixing and circulation processes, highlighting regions of the Southern Ocean where these tracer-based techniques are especially useful.

For more information about this research article, visit EGU's Ocean Science journal article page here.