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Shrinking atmosphere


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It would have been more helpful if you had used some more precise terminology. Are you talking about the thermosphere?


Since it expands and contracts with solar activity, you need to be more clear in what you are asking.

Edited by mikegarrison
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2 hours ago, InterestedDavid said:

Contracting. Having less depth.

You mean like a pond getting shallower ?

In a pond, the water can get shallower because :

1. There's less water on it.

2. The "level depth" has decreased due to increase in the base (basin ?) height.

In that case, there are a few different thing between air ("free" gasses) and liquid (incompresible fluid) :

* Gasses expands and contracts significantly.

* Gasses distribute evenly - density reduces with less compression (so where there's less gravity and overlying mass - it's usually away from Earth's center). This means

* There are no clear boundaries of gas layers, unlike water/liquid layers (except in some exotic phases, like supercritical fluid etc).

To my knowledge, there are no real way of knowing whether our atmospheric mass has decreased or increased or even stagnant.

One method usually employed to tell whether a gas is escaping the atmosphere at large is by comparing RMS speed of gasses with 1/6 of escape velocity at the site (the 1/6 coefficient comes from statistics). On the other hand, gas are continually produced from Earth itself - usually from volcanic source, alternatively from decays of minerals.

But here's the thing - the more you add energy to a gas, they can expand - they'll occupy a larger space. This means your escaping gas could instead be expanding the atmosphere at whole. Obviously, this is not the only case possible, but just a hint on the complication with free expansion. For instance, where does the atmosphere ends anyway ? There's still 1 atom in a cubic centimetre in intergalactic space, do they count as ours ?

Even more, we only talked about thermal behavior here. Many things that exist very, very high up are actually ions, which means they have a very intimate dance with electromagnetical phenomenon.

Edited by YNM
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9 hours ago, InterestedDavid said:

How much has the earth’s atmosphere shrunk since 1990?

It is not known if earth's atmosphere really shrinks. It looses something to space through atmospheric escape, something to the lithosphere through sequestration, it gains something through outgasing. It is in constant exchange with the other spheres through outgasing/weathering/sequestration, precipitation/vapourisation, metabolisms of organisms, decay of organic stuff etc. pp.

The atmoshperic loss to space is in the range of tens of tons/day (90 says our beloved Wikipedia but who knows where that is from :-)), but there is a lot of it in total. The total mass balance over longer terms is unknown, afaik.

So if you want to know how much was lost since a date, take the loss/day. For the balance one must use estimations. I know of no work that examines a dependency between climate change and toal balance, in contrary most models see the atmopshere as a closed thing.

Buying a breathing apparatus ("Perryair") is unnecessary :-)


Edit: in a few hundred million years, with a warmer sun and rising surface temperatures the scene will be different, of course :-)

Edited by Green Baron
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If it is changing volume at all it is not due to gas gain/loss, it will be to do with temperature.

Is it not a constant shrinking though, it is way more complex than that. For one, the global average temperatures are rising, which one would assume causes expansion, but weather patterns are being affected over oceans, which affects the amount of evaporation, affecting various atmospheric cycles. And the different layers of the atmosphere are not all affected in the same way, or even by the same cycles. The link between global average temperatures and atmospheric thickness is not a trivial one. To complicate matters further, apparently the sun, and its cycles, has a strong affect on atmospheric thickness as well.

I dont think the question "how much has it shrank since year X" is the right question to ask, perhaps "How much has the variability of the atmosphere changed since year X".

Its still not a simple question, but apparently the changes in 2008-9 were the largest since 1967, so theres a datapoint for you :)


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