Unbound O2 Depletion?

Rixter;

Thank you for taking the time to reply. I see Wik is showing a balance between natural releases of O2 and consumption.

I have seen other literature that shows a seasonal variation combined with a slight annual reduction in atmospheric O2. --- http://132.239.121.69/publications/ralph/3_Seasonal.pdf

It would seem reasonable to conclude the gas concentrations between the oceans and the atmosphere would seek equilibrium. If this is correct then the oceans would not only serve as a producing source by supporting oxygenic photosynthesis but also serve as a reservoir of stored O2 from when the atmosphere had higher concentrations of O2. If this is the case then atmospheric O2 would not show a decrease until the stored O2 in the oceans was depleted to the point of equilibrium. The trending O2 concentrations in the oceans should be an indication of where atmospheric concentrations are headed?

This more than a bit out of my box but I find it interesting.

Oxygen is the most abundant element in the Earth's crust, but not the Earth as a whole. In the Earth as a whole the most abundant element is iron I believe.

Also at some point in Earth's history the oxygen in the atmosphere was higher than today's, about 35%. And before photosynthesis started about 3.5 billion years ago there was no oxygen in the atmosphere, if that adds anything to it.

When the terrestrial temperatures were very high, a very intense oxidative process occurred, forming oxides of iron, silicon, carbon, etc.probably exhausing the existent oxygen. A return of free oxigen probably occurred when forms of photosintetic life appeared. But in this process the free oxygen is not stable. When the live organisms die and decay they consume in the process the oxigen they produced . So , no permanent free oxigen is generated to sustain animal life. The only explanation I found for the generation of the free oxygen we have is that at some period of the evolution of the planet a large amount of forests became under ground, isolated from the atmosphere, not suffering putrefaction,retaining carbon isolated from atmosphere. That was, then, the origin of the free oxygen and the fossil fuels. In that case there is a very interesting aspect, the danger of CO² is acompanied by the danger of free oxygen extinction !!

That's an interesting point I hadn't thought of before (no doubt other people have).

As atmospheric pressure ~ 1 bar = 10tonne/m², and O₂ content in air = 23% w/w, that's 2.3tonne O₂/m² earth surface. If all that came from CO₂, carbon locked up underground = 2.3*12/32 = 0.86tonne/m², average over whole Earth, which doesn't seem unreasonable as an average.

I wouldn't think the O₂ in minerals varies significantly nowadays (different in Earth's early history, as you say).

http://www.bbc.co.uk/science/earth/earth_timeline/first_life

Stromatolites

Your question brings to mind something that I had read regarding the geologic history of the Earth.

Initially, after formation by agglomeration of cosmic rocks, the planet was a lifeless ball of volcanic material with no atmosphere as we know it today. At any rate, as the volcanoes calmed and cooled electrical storms broke down whatever atmosphere existed and resulted in the formation of water.

After years, maybe even centuries of rains, oceans were formed and one celled creatures began to propagate, combining into multi-celled lifeforms that used the carbon dioxide in solution and produced oxygen as a by product of respiration..

I know I don't have the whole story, but basically these simpler life-forms generated all of the oxygen on the planet.

What sticks in my mind is illustrations of life living in the oxygen depleted pools of water formed by the various geysers and steam vents in Yellowstone Park.

Wish I could remember the source-any help would be appreciated.

"What sticks in my mind is illustrations of life living in the oxygen depleted pools of water formed by the various geysers and steam vents in Yellowstone Park." -----------------------

I doubt we would want to take that evolutionary path. I would prefer naturally cycled unbound O2 at healthful levels.

I wonder what the numbers look like in terms of production and consumption of O2.

Maybe natural unbound O2 is such an abundant resource that it can be treated like inexhaustible world fisheries and forests.

I wish some Atmospheric Chemists would jump in this point. Explaining if and how the gas levels in the atmosphere and oceans would seek equilibrium.

A quick spin up on the physics of gases moving between the salt water oceans and the atmosphere. Partial Pressures and Concentrations for Dummies.

It would be very helpful to me.

"I doubt we would want to take that evolutionary path."

I wasn't advocating it either, but when I post at 3 AM, my brain isn't fully engaged.

I probably should have stopped after my opening comments regarding the initial conditions of the planet at its formation. I was just trying to relate the generation of oxygen to a lifeless (as we know it) chunk of rock.

If I recall correctly, oxygen becomes toxic at 26-27 percent, and 19.5 percent is usually the set point for oxygen concentrations too low for human activity without breathing apparatus.

The Scripps O2 program website indicates a slight worldwide decrease in atmospheric O2 concentrations over the past few decades.

Given Henry's Gas Law; O2 would have been "stored" as ocean solute when atmospheric O2 levels were somewhat higher than in this emerging Anthropocene; and that any appreciable reduction in atmospheric O2 concentration would require that "stored" oxygen in the ocean come out of solution.

In my review of this subject I noted that Billfish habitat compression due to ocean de-oxygenation amounted to over 15% of total volume since 1960.

It is probable that atmospheric de-oxygenation is playing a significant role in trending ocean de-oxygenation; beyond that caused from eutrophication and increasing water temperature?

Oxygen coming out of ocean solute is unsustainably supporting atmospheric oxygen levels; and atmospheric oxygen levels are still decreasing.

The oxygen concentration window for mammals is quite small; that window is much smaller for oxygen dependent aquatic life.

As the ocean solute is depleted what happens to the rate of atmospheric de-oxygenation?

"We find that the global oceanic oxygen content of 227.4 ± 1.1 petamoles (10¹⁵ mol) has decreased by more than two per cent (4.8 ± 2.1 petamoles) since 1960,"

http://www.nature.com/nature/journal/v542/n7641/abs/nature21399.html

We are in trouble.

“Phytoplankton Population Drops 40 Percent Since 1950”

The most concerning thing about this is that most people have no idea what this means. Well here it is plain and simple. Unless these trends are reversed it means the extinction of our species.

A 40 percent reduction in the population of an organism that produces 50 percent of the oxygen extrapolates to a 20 percent reduction in oxygen production. Currently rising ocean temperatures are forcing oxygen out of solution yet atmospheric oxygen is still declining.

Unless we find a way to regenerate the fundamental natural processes that support our planet’s biome there is no future for our progeny. It is that simple.

These fundamental natural processes should have been taught to us as children. Had that occurred the probability is high that we would now be taking steps to rebuild those natural processes.

No; we will not be able to maintain a technology that can sustain even a minimal population because of the critical mass of labor required to produce that technology. We get one chance to get it right; we either find a way to regenerate the natural processes that sustain our planet’s chemistry or we go the way of the Passenger Pigeon; and we take most other species with us.

https://www.scientificamerican.com/article/phytoplankton-population/