April 12, 2000
Hello and good diving !
Does the saturation of oxygen increase or decrease
with the increase in depth and pressure of fresh or salt water.
As in the saturation of oxygen at ten feet and that of 10,000 ft.
? I know the temp. of the water affects saturation, but does pressure
Thanks for the information, from a great site.
E.C. Perfusionist and Deep Diver
I sent your question back to my colleague, Dr. Susan Humphris at
Woods Hole Oceanographic so she could provide a detailed answer.
Here it is.
The only place in the ocean that the water can exchange oxygen
with the atmosphere is at the surface. Deep water originates by
sinking of surface waters. The temperature and salinity of the
surface water at any given place in the ocean will determine how
much oxygen can dissolve in it, and surface water is “saturated”.
Since most deep water originates from sinking of surface water
at higher (colder) latitudes, it has more oxygen in it than surface
waters at lower (warmer) latitudes. Once the water sinks out of
the zone of mixing, it is not in contact with the atmosphere any
more, so no oxygen can be added. However, oxygen is used (by organisms),
so as deep water circulates around the world, its oxygen concentration
“Saturation” is not a very helpful way to think of oxygen
concentrations of deep water for the following reason. If you take
seawater containing a given amount of oxygen from the surface and
send it into the deep ocean, its saturation decreases because pressure
is increasing, and so you could dissolve more oxygen into it. However,
it doesn’t really matter -- because there is no source or more
oxygen to dissolve into the water!
Thanks for your question and keep Diving and Discovering with us.
Dr. Susan Humphris