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Wednesday, March 8, 2017

Interglacials and Phosphine

As usual in my blogs, this theory is a bit of speculation; a hypothesis or if you like brainstorming so read it as such.  

First let's get the terminology right.  We are in the middle of an ice age which started some 2.5million years ago. It is called the pleistocene although some define the Plistocene as having started 1.8m years ago.   Within this ice age have been approximately 30 glacials and an equal number of interglacials.  At present we are in the Holocene interglacial and the previous one, centered about 125,000 years ago, was the Eemian (given different names by various scientists).  The Holocene started about 20,000 years ago by definition, at the peak of the recent glacial but melting really got underway about 11,500 years ago.

Not to get too precious about this but we have to decide what words we are going to use for which periods. It is confusing to the layman and doesn't aid in informing the general public.  Above is the way I learned it but any terminology would be fine with me as long as we all agree on what we mean when we say 'ice age".

What is problematic is to explain is why Carbon dioxide rises steeply as the ice melts and oddly enough seems to follow the ice melting rather than leading it.  The most accepted theory today has to do with the ocean circulation powered by the production of heavy, cold salty water at both ends of the earth and the relationship between the temperature of the surface of the sea and the amount and speed it can take up Carbon dioxide (or release it) from/to the atmosphere.  The basic physics is pretty simple and undeniable.  Cold water can hold more Carbon dioxide than warmer water.  The chain of cause and effect after this is a tad more tenuous.

The following hypothesis in no way negates the ocean current/water-temperature theory.  It is just  suggesting another source of Carbon dioxide as the ice melts.

Regardless of the source, what seems to happen is that as the ice begins to melt, Carbon dioxide rises a little later and  the released Carbon dioxide then accelerates the melt.

Previously, I  hypothesized that over the approximately 100,000 years that ice covered large parts of the continents, a huge amount of methane clathrate would have accumulated under the ice.  Methane clathrate forms when methane is in contact with water under a pressure equivalent to about 300m of water or more.  The cooler the temperature the less pressure is needed but under sufficient pressure a clathrate can exist even up to 30 degrees C.  This higher temperature clathrate is not really relevant to our discussion since the bottom of deep ice sheets tends to be around zero degrees C so clathrates will begin to form when the ice reaches, say 400m or so.  The extra depth is necessary since the top 70m or so of the ice tends to be firn (porous snow which is turning into ice due to the weight of snow above it) which is lighter that ice.  All above figures are approximate.

Incidentally, there is also a carbon dioxide clathrate so any Carbon dioxide coming out of the ground to meet the bottom of a deep glacier would likely form a clathrate as well.  The formula for Carbon dioxide clathrate is thought to be CO2.6H2O*

* In a Carbon dioxide saturated clathrate, there is a sixth of a mole (gram mollecular weight) of Carbon dioxide for every mole of water.  So a mole of water (18g) could contain 7.3g of carbon dioxide(a sixth of 44g)  In a liter of saturated CO2 clathrate you would have 407g of CO2.  This is 9.26 moles of Carbon dioxide.  Since one mole of any gas occupies 22.4liters at STP, then one liter of methane clathrate at STP would release 207 liters of the gas if it disintegrated.  Pretty amazing, no? The formula for saturated methane hydrate is CH 4 · 5.7H 2O.  Work out what volume of methane could be released from one kg of water ice saturated methane  to form methane hydrate.

 
The source of the methane includes organic material buried by the ice, which when deprived of oxygen decays by methanogenesis.  Other sources are deposits of coal, oil, tar sands, natural gas and shales.  Since an accumulation of ice tends to push down the land  approximately a third of the height of the ice (ie a km of ice will depress the land a third of a km) a sort of natural fracking may occur.  In other words,  cracks could well be opened up which would release gas that had been capped by layers of impermeable rock. In addition there are methane seeps all around the world which would create clathrates under ice without any need to invoke the cracking of the earth under the weight of ice.

I'm not sure what the composition of "swamp gas" is but when you operate a biogas generator, the composition of the gas is approximately 70% methane and 30% Carbon dioxide.  If this is similar for organic material breaking down under an ice sheet then both CH4 and CO2 clathrate would accumulate.

I also hypothesized that since the ice at the height of a glacial would be pushing  into areas too warm for ice to form, it would only need a nudge from the Milankovitch cycle to start the melt.  If sufficient melting occurred then enough  methane would be released to produce a negative feed back and accelerate the process.  Hence the transition into an interglacial.

Note that the greater the ice sheet, the more unstable which may explain why every Milankovitch nudge didn't cause an interglacial in the latter half of the present ice age. Apparently it was necessary for the ice sheet to be really big and hence really unstable.

When I suggested the methane theory to a number of scientists, they assured me that such an outpouring of the very powerful greenhouse gas, methane, would appear in the ice cores from Greenland and Antarctica.  Further they said that there is no evidence that methane converts to Carbon dioxide within ice bubbles.  When the analysis was done and no methane signature was found.  I argued that methane has a half life of about 7 years and so would disappear rather rapidly and the Firn layer is some 70m deep and so gas exchange would occur through this layer, softening the edges of the signature.  I was assured that there still would be a methane signature and none was found.

So,,, what if the methane ignited as it was released from under the ice.  One could suggest lightening as an igniter but this seems rather unlikely and once the methane is sufficiently diluted in the air, it is no longer ignitable.  Methane will ignite when it is between 5 and 15 percent of the air.  Of course pure methane will ignite at the edges where it is mixing with the air, just like happens in your gas hob.   If it came out in sufficient quantities and with sufficient velocity, it would produce its own mini lightening and ignite but this too seems to be somewhat far fetched to explain the ignition of all this methane from all sources.

No, the methane, if it is ignited and thus is responsible for the increase in atmospheric carbon dioxide, it has to be ignited as it enters the air before it has been diluted too much to burn and it needs a source of ignition that it carries with it.

Then I remembered phosphine (PH3)  It is also produced by the rotting of organic material in swamps along with diphosphane (P2H4) which is the main component of swamp gas. This is observed around the world in swampy areas. A common name for this in English is Will o' the Wisps.

From Wikipedia (Sorry, links don't work.  They work in the original article)
In modern science, it is generally accepted that most ignis fatuus are caused by the oxidation of phosphine (PH3), diphosphane (P2H4), and methane (CH4). These compounds, produced by organic decay, can cause photon emissions. Since phosphine and diphosphane mixtures spontaneously ignite on contact with the oxygen in air, only small quantities of it would be needed to ignite the much more abundant methane to create ephemeral fires.[32] Furthermore, phosphine produces phosphorus pentoxide as a by-product, which forms phosphoric acid upon contact with water vapor. This might explain the "viscous moisture" described by Blesson.

All this is great but leaves a huge number of questions unanswered.  Since two ice sheets are in the process of disintegrating at present (West Antarctic and Greenland) we may see evidence for or against this hypothesis as the ice melts.

Questions:
1/ Are there indeed large amounts of methane (and Carbon dioxide) stored under the ice sheets as  clathrates.

2/ Do these deposits contain phosphine and diphosphane.

3/  Has anyone observed a  Methane coming from under an ice sheet, say, when a river appears from under the ice and which therefore exposes part of the bottom of the ice sheet to atmospheric pressure. (low pressure allows clathrates to break down)

4/  Has anyone ever observed the spontaneous ignition  of methane (other than above swamps where it regularly occurs).  Note that in daylight, a methane flame is almost invisible.

5/  If there is phosphine and diphosphane in such methane deposits, what happens to it as methane plumes rise through ocean water.  Is it scrubbed out or does it rise with the methane.  The composition of the gas could be quite different from an outpouring of gas on land and a gas plume rising from the ocean bottom. For instance, if a mixture of methane and Carbon dioxide bubbles were rising through a column of water, likely the Carbon dioxide would be scrubbed out.  It would, though, show up as a decreased alkalinity of the surrounding sea water.  I don't know what the relationship is between water and phosphine and diphospane.

To increase the credibility of the above hypothesis for the source of at least some of the carbon dioxide that is seen in the atmosphere as the ice sheets melt, we would have to see a similar phenomenon with the presently disintegrating ice sheets.

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