Australia: The Land Where Time Began

A biography of the Australian continent 

Subsurface Barrier Layer Thickness

When the top of the thermocline is higher in the water column than the top of the halocline the ocean's surface layer, above the thermocline, is separated into 2 layers, the surface mixed layer and the subsurface, the so-called barrier layer after (Godfrey & Lindstrom, 1989; also section 3.3 in Lucas & Lindstrom, 1991; Sprintall & Tomczak, 1992). Then the temperature in the barrier layer is equal to, or sometimes higher than, that of the surface mixed layer, the stability of the water column being controlled by the salinity stratification. There are strong consequences on the air-sea interactions of this barrier layer as it insulates thermodynamically the deep, cold ocean water from the atmosphere, their thickness being a proxy of the amplitude of their thermodynamic barrier effect.

The subsurface barrier layer temperatures (BLT) are estimated directly from instantaneous profiles with data at observed levels, as is done with the surface mixed layer depths. The authors¹ define the BLT as an individual station measuring both temperature and depth, following most previous authors, through 2 depths described above (e.g. Vialard & Delecluse, 1998; Cronin & McPhaden, 2002).

Sources & Further reading

1. Ifremer  French Research Institute for Exploration of the Sea