Skip to comments.Thawing permafrost 50 million years ago led to extreme global warming events
Posted on 04/09/2012 6:18:02 AM PDT by Red Badger
In a new study reported in Nature, climate scientist Rob DeConto of the University of Massachusetts Amherst and colleagues elsewhere propose a simple new mechanism to explain the source of carbon that fed a series of extreme warming events about 55 million years ago, the Paleocene-Eocene Thermal Maximum (PETM), and a sequence of similar, smaller warming events afterward.
"The standard hypothesis has been that the source of carbon was in the ocean, in the form of frozen methane gas in ocean-floor sediments," DeConto says. "We are instead ascribing the carbon source to the continents, in polar latitudes where permafrost can store massive amounts of carbon that can be released as CO2 when the permafrost thaws."
The new view is supported by calculations estimating interactions of variables such as greenhouse gas levels, changes in the Earth's tilt and orbit, ancient distributions of vegetation, and carbon stored in rocks and in frozen soil.
While the amounts of carbon involved in the ancient soil-thaw scenarios was likely much greater than today, implications of the study appear dire for the long-term future as polar permafrost carbon deposits have begun to thaw due to burning fossil-fuels, DeConto adds. "Similar dynamics are at play today. Global warming is degrading permafrost in the north polar regions, thawing frozen organic matter, which will decay to release CO2 and methane into the atmosphere. This will only exacerbate future warming in a positive feedback loop."
He and colleagues at Yale, the University of Colorado, Penn State, the University of Urbino, Italy, and the University of Sheffield, U.K., designed an accurate model―elusive up to now―to satisfactorily account for the source, magnitude and timing of carbon release at the PETM and subsequent very warm periods, which now appear to have been triggered by changes in the Earth's orbit.
Earth's atmospheric temperature is a result of energy input from the sun minus what escapes back to space. Carbon dioxide in the atmosphere absorbs and traps heat that would otherwise return to space. The PETM was accompanied by a massive carbon input to the atmosphere, with ocean acidification, and was characterized by a global temperature rise of about 5 degrees C in a few thousand years, the researchers point out. Until now, it has been difficult to account for the massive amounts of carbon required to cause such dramatic global warming events.
To build the new model, DeConto's team used a new, high-precision geologic record from rocks in central Italy to show that the PETM and other hyperthermals occurred during periods when Earth's orbit around the sun was both highly eccentric (non-circular) and oblique (tilted). Orbit affects the amount, location and seasonality of solar radiation received on Earth, which in turn affects the seasons, particularly in polar latitudes, where permafrost and stored carbon can accumulate.
They then simulated climate-ecosystem-soil interactions, accounting for gradually rising greenhouse gases and polar temperatures plus the combined effects of changes in Earth orbit. Their results show that the magnitude and timing of the PETM and subsequent hyperthermals can be explained by the orbitally triggered decomposition of soil organic carbon in the circum-Arctic and Antarctica.
This massive carbon reservoir at the poles "had the potential to repeatedly release thousands of petagrams of carbon to the atmosphere-ocean system once a long-term warming threshold was reached just prior to the PETM," DeConto and colleagues say. Until now, Antarctica, which today is covered by kilometers of ice, has not been appreciated as an important player in such global carbon dynamics.
In the past, "Antarctica and high elevations of the circum-Arctic were suitable locations for massive carbon storage," they add. "During long-term warming, these environments eventually reached a climatic threshold," with permafrost thaw and the sudden release of stored soil carbon triggered during the Earth's highly eccentric orbits coupled with high tilt.
The model described in the paper also provides a mechanism that helps to explain relatively rapid recovery from hyperthermals associated with orbital extremes occurring about every 1.2 million years, which had until now been difficult.
Overall, they conclude, "an orbital-permafrost soil carbon mechanism provides a unifying model accounting for the salient features of the hyperthermals that other previously proposed mechanisms fail to explain." Further, if the analysis is correct and past extreme warm events can be attributed to permafrost loss, it implies that thawing of permafrost in similar environments observed today "will provide a substantial positive feedback to future warming."
“polar permafrost carbon deposits have begun to thaw due to burning fossil-fuels,”
So what was the cause of the permafrost thaw 50 MY ago? Fer shur it was not burning fossil fuels.
This is an unfounded assertion based on political correctness and imposition of Official Reality.
“what caused the permafrost to thaw?”
Apparently you are unaware of man’s massive burning of carbon-based fuels 55 million years ago....
More seriously, this I believe is the explanation:
“PETM and other hyperthermals occurred during periods when Earth’s orbit around the sun was both highly eccentric (non-circular) and oblique (tilted)”
I gather that this is a “feedback” explanation: initial warming caused by variations in Earth’s orbit that placed it closer to the sun triggers a release of carbon which in turn creates a global warming effect that amplifies this initial warming, so then the patterns keeps repeating/amplifying. Of course, if it keeps amplifying, it’s not obvious to me (I’m no climate scientist) what makes the cycle stop and reverse. Nevertheless, as explained, the cycle sounds plausible, and note that there is ZERO contribution of humans to make it happen!
Maybe it used to be cloudy all the time.
True. Also true is that WINTER for us is SUMMER for those in the Southern Hemisphere.
The point is that whether closer or further away, the temp of the Earth doesn't change, or the change is so small it is negligible.
Today, on Anthony Watt’s blog, is an important discussion directly related to this topic:
Did Shakun et al. really prove that CO2 preceded late glacial warming? [Part 1]
I have an even simpler model of global warming that these idiots seem to have missed: Warming causes Thawing
I validate this model every time I take a chicken out of the freezer. Some how these geniuses want us to believe the opposite i.e. that the initial warming that caused the melting in the first place is NOT responsible for the subsequent warming. I simply don't buy it.
Tilted? in relation to what? And why would that matter?
However, let's go with that theory.
initial warming caused by variations in Earths orbit that placed it closer to the sun triggers a release of carbon which in turn creates a global warming effect that amplifies this initial warming, so then the patterns keeps repeating/amplifying.
If the Earth occupies a HIGHLY ECCENTRIC orbit, then not only is it CLOSER to the SUN for a short amount of time but it is also FURTHER from the SUN for a much longer amount of time.
This would make it an iceball that gets ICE burnt off it's equator once a 'year'. (Wonder how long a 'year' was back then?)
And since neither of these is true of the Earth's orbit currently, the basis for their model is false.
I a related story I caught the very end of James Cameron’s new documentary about the Titanic on the National Geographic Channel. He spends the last minute whining about the next “iceberg” to hit us all, global warming. Avoid this show at all costs.
Ah, yes; UMass/Amherst, my alma matter. Where snarly, IQ 80 “victims of a racist, homophobic, sexist, white society” can get a “Doctorate in Social Justice.” ANYTHING coming out of UMass that is not engineering, physical science, or forestry, has become a huge pile of crap.
Read the original article and they blame the perma frost melting because of burning of fossil fuel. It’s still ‘man made’.
The picture of the North Slope is missing one very important feature: the trillions of mosquitoes that inhabit that place! In the summer the swarms are so thick they blot out the sun, therefore preventing the permafrost from melting. Perhaps in the Eocene there were no mosquitoes?
“Now... what caused the permafrost to thaw?”
My follow up question: What caused the permafrost to refreeze? according to their theories, there should have been a runaway greenhouse effect that would have left the Earth “warm” forever. How do their models explain all the organic matter now frozen?
I thought Warming caused thawing....
How does somebody propose that “thawing” could possibly be a driving mechanism for warming?
Oh...I forgot, these are the same clowns who failed to recognize that Warming causes the increase in CO2 levels, so they’ve grown accustomed to inverting cause and effect.
Now now. Stop bringing logic in to the mix. The bottom line for all of this nonsense is that when Momma Earth decides she’s done with us there isn’t anything we can do about it. You can’t run and you can’t hide so we all might as well have a good time while we can.
Helping keep mankind warm for almost 65 years.
What IS a Doctorate in Social Justice.?.............
Way back in the Stone Age when I went to college, we were taught never to make your data fit the problem...........
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