Johan Sandström

Who was Johan Sandström?

Johan Wilhelm Sandström, usually cited as J. W. Sandström, was a Swedish oceanographer.

He is most famously known for conducting a series of classical experiments at Bornö oceanographic station in Sweden that were reported in Sandstrom. His experiments concerned themselves with the causes of ocean currents, particularly those found in fjords. Sandstrom was principally concerned with the role of heating and cooling in driving such currents, and in the larger-scale ocean circulation in general.

Sandstrom asserted that thermal circulation can cause vigorous, steady circulation only if heating occurs at greater depths than cooling. This is known today as Sandström's theorem. Sandstrom's theorem represents an attempt at extending the well known result of classical thermodynamic theory that in order for a heat engine to perform positive work over a cycle, the work of expansion needs to occur at greater pressure than the work of contraction. Sandstrom's theorem is therefore technically true, as long as expansion in the fluid is caused by heating and contraction by cooling, and that greater depths occur at greater pressures.