Is water at the bottom of the ocean oxygen deficient?

[MulderFBI]

Is water at the bottom of the ocean oxygen deficient? Compared to water at the higher levels.

 

[HAYAO]

Is water at the bottom of the ocean oxygen deficient? Compared to water at the higher levels.

I am not entirely sure, but I think I've read somewhere that it is. Intuitively speaking, it does sound plausible. The only factor that may increase the oxygen concentration at lower level of ocean is water pressure. I think every other factors (such as lack of atmospheric contact, water temperature although it won't go below 4 deg, relative lack of plants, etc.) decreases the oxygen concentration at lower ocean level.

 

[MulderFBI]

Thank you, I wanted to verify that claim. One of the explanations I've found is that it's because water at the bottom is very dense (especially at the 4 deg layer). That density stops it from absorbing oxygen (and other gases) through for example diffusion or convection but I'm not sure it's true.

 

[HAYAO]

Thank you, I wanted to verify that claim. One of the explanations I've found is that it's because water at the bottom is very dense (especially at the 4 deg layer). That density stops it from absorbing oxygen (and other gases) through for example diffusion or convection but I'm not sure it's true.

I am not an expert, but I wouldn't be surprised if that was true.

EDIT: The density of water don't change that much, even comparing between sea level and bottom of the ocean. And at 4 deg layer, it remains pretty much the same. Nonetheless, diffusion indeed may be one of the biggest reason for the low oxygen concentration at low ocean depth.

 

[MulderFBI]

Why is that? I'm pretty sure water at 4deg is at the most dense point so I would say it is denser than on higher levels when temperature rises.

 

[HAYAO]

Why is that? I'm pretty sure water at 4deg is at the most dense point so I would say it is denser than on higher levels when temperature rises.

Well, I said "don't change that much", which means it still does change a little. It probably changes around 0.01 g/cm³ comparing sea level and the bottom of the ocean, if not, less. Density of sea water is around 1.025 - 1.027 at sea level. So a 1% difference (or less) is a minor difference to me.

 

[MulderFBI]

You are right the difference is not that big:

"This is a simple density-depth ocean water profile. You can see density increases with increasing depth. The pycnocline are layers of water where the water density changes rapidly with depth. This density-depth profile is typical of what you might expect to find at a latitude of 30-40 degrees south.
Windows to the Universe original image"

 

[jim mcnamara]

Meromictic water, water that never intermixes with surface water is anoxic, promoting the growth of anaerobic bacteria - the kind of bacteria that were common on Earth prior to an oxygen atmosphere. This can happen in deep lakes, and is often found at the bottom of fjords. Hadalpelagic is the term more often used for ocean basin closed canyons
Discussion on lakes: https://en.wikipedia.org/wiki/Meromictic_lake

There is a whole lot more to this topic- dead zones and so on. This talks about O₂ in the entire water column of the ocean.
http://www.fondriest.com/environmental-measurements/parameters/water-quality/dissolved-oxygen/

Is a great resource it has interesting discussions and graphics.

 

[Bystander]

http://www.soest.hawaii.edu/oceanog...2013/Chem_composition_of_SW-2013_handouts.pdf

 

[MulderFBI]

Thank you for great resources!