Occurrence of temperature inversions in the upper layer of the ocean

Summary

Bathythermograms just off the northern edge of the Gulf Stream often show temperature inversions, while those in the Gulf Stream and the Sargasso Sea do not show such features. A similar situation was found in the Kuroshio area. TheT-S curve obtained off Cape Hatteras with a bathysalinograph and a bathythermograph indicates that the temperature inversions correspond to high salinity and less stable density stratification. Sequential surface temperature charts suggest that the inversions may be caused by sinking of the warm and saline Gulf Stream water. When such water is driven into the slope water region, it is cooled by mixing or heat transfer to the atmosphere, but retains its high salinity and sinks. A simple mathematical model is developed based on an assumption that an isolated water mass is enclosed in a parcel with a flexible and permeable membrane. The initial density inside the parcel is different from the one outside and the water mixes with the surrounding water. When it is assumed that mixing of temperature occurs faster than that of salinity, the isolated Gulf Stream water sinks to an equilibrium depth, causing temperature peaks and inversions in the subsurface layer.