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Author Topic: Does Freshwater Runoff in the Arctic change Ocean Circulation to Unlock Methane  (Read 5331 times)

prokaryotes

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Quote
Arctic freshwater input into the North Pacific could serve as a catalyst for methane hydrate destabilization, an event suggested as a precursor to the onset of the PETM.
http://climatestate.com/magazine/2013/08/does-freshwater-runoff-in-the-arctic-change-ocean-circulation-unlock-methane-hydrate-in-the-deep-ocean/

Looking for commentary.
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TerryM

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From the linked article:



"When air temperatures increase above a mean annual air temperature of 28C, permafrost begins to thaw.[/size] "[/color][/b][/i]
[/size][/color]
[/size]28C =82.4F & if a portion of the Arctic reaches this an an annual mean there won't be many of us around to worry about CH4[/color]
[/size][/color]
[/size]There may be cause for concern, but the temperature mentioned seems far from what is expected.[/color]
[/size][/color]
[/size]Terry[/color]

Anne

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Just resized what Terry said:

"When air temperatures increase above a mean annual air temperature of 28C, permafrost begins to thaw. "

28C =82.4F & if a portion of the Arctic reaches this an an annual mean there won't be many of us around to worry about CH4.

There may be cause for concern, but the temperature mentioned seems far from what is expected.


Good point.

TerryM

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Thanks so much Anne


I'm going to have to start previewing my posts. This is the second time in as many weeks.


Thanks again
Terry

Phil

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28c is evidently a typo....

here is an exemple of litterature on the subject

"When air temperatures increase above a mean annual air temperature of -2 ºC, permafrost begins to thaw."
http://www.acia.uaf.edu/PDFs/ACIA_Science_Chapters_Final/ACIA_Ch08_Final.pdf

A recent swiss study put the thresold at 1,5 C
http://www.sciencenews.org/view/generic/id/348585/description/Moderate_climate_warming_could_melt_permafrost

prokaryotes

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Thanks for pointing this error out Terry, this happened when you copy parts from the PDF into a browser editor, some characters changed apparently.

Fixed that now and

Quote
Notably,however, the maximum projected air temperature increases in these areas are about 58C (greatest near the coasts), compared to the almost two-fold greater projected increases in temperature over the Arctic Ocean.

to - according to the study paper.

Quote
Notably,however, the maximum projected air temperature increases in these areas are about 5C (greatest near the coasts), compared to the almost two-fold greater projected increases in temperature over the Arctic Ocean.

The character "°" got changed to "8" from that particular study paper.
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prokaryotes

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A recent swiss study put the thresold at 1,5 C
http://www.sciencenews.org/view/generic/id/348585/description/Moderate_climate_warming_could_melt_permafrost

Actually that study just states

Quote
During the warmest period studied, some 400,000 years ago, global temperature was 1.5 degrees higher than in preindustrial times.

That could still mean that at mean above -2C permafrost thaw is initiated.
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ggelsrinc

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A recent swiss study put the thresold at 1,5 C
http://www.sciencenews.org/view/generic/id/348585/description/Moderate_climate_warming_could_melt_permafrost

Actually that study just states

Quote
During the warmest period studied, some 400,000 years ago, global temperature was 1.5 degrees higher than in preindustrial times.

That could still mean that at mean above -2C permafrost thaw is initiated.

It's possible methane hydrates were destabilized in the deep ocean during the PETM. I don't think it's possible for methane hydrates to be destabilized in permafrost during the PETM.


ggelsrinc

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http://www.pnas.org/content/early/2013/09/13/1309188110.abstract#corresp-1

http://thinkprogress.org/climate/2013/10/08/2750191/petm-co2-levels-doubled-55-million-years-ago-global-temperatures-jumped/


Certainly changes the game if true.

idunno posted the report:

http://thingsbreak.files.wordpress.com/2013/10/evidence-for-a-rapid-release-of-carbon-at-the-paleocene-eocene-thermal-maximum.pdf

Prove it!

I commented on methane hydrates under permafrost and there was no massive glaciation to have methane hydrates under permafrost during those times. The only permafrost was alpine and the times were before the Himalayas. There weren't even massive glaciers in Antarctica to lock away methane hydrate at that time and massive glaciation is required to lock methane hydrate. It was a very different world than today.

There is isotopic evidence of volcanic activity, but it isn't conclusive. The hypothesis of massive methane hydrate release is reasonable, but a bolide impact in the ocean may not leave traces we can discover to date. It's possible methane hydrate could destabilize by ocean circulation changes, but the evidence of even a pre arctic connection between that area and the Pacific Ocean during PETM isn't very convincing. Very little research has been done researching the ocean currents of the past.

I've heard both sides of a global warming debate use PETM to support their beliefs. What happened during PETM is a big scientific unknown. If I want to know it all, I need to distinguish what I know, what I don't know and don't confuse the two. There is nothing wrong with believing something, but it isn't knowledge until proven. It shouldn't be mixed in our minds as facts.