<P> Deep ocean water (DOW) is the name for cold, salty water found deep below the surface of Earth's oceans . Ocean water differs in temperature and salinity . Warm surface water is generally saltier than the cooler deep or polar waters; in polar regions, the upper layers of ocean water are cold and fresh . Deep ocean water makes up about 90% of the volume of the oceans . Deep ocean water has a very uniform temperature, around 0 - 3 ° C, and a salinity of about 3.5% or as oceanographers state as 35 ppt (parts per thousand). </P> <P> In specialized locations such as the Natural Energy Laboratory of Hawaii NELHA ocean water is pumped to the surface from approximately 900 metres (3000 feet) deep for applications in research, commercial and pre-commercial activities . DOW is typically used to describe ocean water at sub-thermal depths sufficient to provide a measurable difference in water temperature . </P>

What is the temperature at bottom of ocean