Specific Heat of Seawater

The specific heat of seawater is the heat needed to raise one kilogram of seawater by one kelvin, near 3,990 J per kg per K at salinity 35 and 25 C, falling slightly as salinity rises and varying a few percent with temperature and pressure. It is about 4 percent below the 4,186 J per kg per K of pure water because dissolved salts hold less heat per mass. This high value is why the ocean stores roughly 1,000 times more heat than the atmosphere per unit area for the same temperature change. TEOS-10 fixes 3991.867 J per kg per K as the constant defining Conservative Temperature.