Hunting a New Ocean Tracer



A useful method to obtain integrated estimates of vertical mixing in the ocean over a long period of time and a large area is the release of a tracer. Recent large-scale tracer release experiments conducted in the Southern Ocean, such as the Diapycnal and Isopycnal Mixing Experiment (DIMES [see Gille et al., 2007]), and in the equatorial Atlantic will rely on a new tracer chemical called trifluoromethyl sulfur pentafluoride (SF5CF3), which is likely to become a standard for future experiments. Here we report results from the first injection of pure SF5CF3 into the ocean, which was carried out in a deep basin of the Baltic Sea.

Using the Baltic Sea as a natural laboratory for the investigation of physical mixing processes, this pilot study aims at improving our understanding of one of the most puzzling mixing properties in stratified ocean basins: Almost independent of the basin's size, the basin-scale vertical mixing rates exceed the rates inferred from local turbulence measurements in the basin center by approximately 1 order of magnitude [see, e.g., Ledwell and Bratkovich, 1995].