This is interesting, somehow the Earth managed to reduce a good portion of the Arctic Ice Cap during the Holocene Climate Optimum from approximately 10,000-6,000 years ago without the help of the industrial revolution, fossil fuels, or automobile emissions.
This new paper published in Quaternary Science Reviews finds Arctic sea ice extent and thickness was much less than present-day conditions and according to the authors,
“Arctic Ocean sea ice proxies generally suggest a reduction in sea ice during parts of the early and middle Holocene (∼6000–10,000 years Before the Present) compared to present day conditions.”
The authors show how 8 different proxy studies reveal extended periods lasting hundreds of years without perennial sea ice in the Arctic [ice-free conditions], and find solar insolation explains these changes. See figure 4 from the paper below.
The top graph shows simulated annual mean sea ice thickness [orange curve] was much less during the Holocene Climate Optimum ~13,000-6,000 years ago compared to the end of the 20th century at right side of graph. The bottom graph shows multiple proxies of sea ice with darker green indicating periods of less sea ice. Modern sea ice is at high levels in comparison to the rest of the Holocene.
Annual mean sea ice thickness for the three different simulations (Panel a) compared with results from published paleo-sea ice studies (Panel b). Black curve: constant surface albedo; red curve: dynamic surface albedo parameterization. The simulation implemented with a dynamic surface albedo parameterization was run from present time and backwards to address the importance of the initial state of the sea ice cover. The annual mean sea ice thickness from this simulation (orange curve) reveals a hysteresis of ∼1000 years. The annual mean insolation at 80°N shown with a stippled curve is based on the algorithm presented by Berger (1978). To compare the results from different paleo-sea ice studies a scale of sea ice concentration was inferred using the approach by Jakobsson et al. (2010). This scale must be considered as highly qualitative because none of the paleo-sea ice proxies provide absolute measures of past sea ice concentrations.
The paper:
Arctic Ocean perennial sea ice breakdown during the Early Holocene Insolation Maximum
Christian Stranne, Martin Jakobsson, Göran Björk
Arctic Ocean sea ice proxies generally suggest a reduction in sea ice during parts of the early and middle Holocene (∼6000–10,000 years Before the Present) compared to present day conditions. This sea ice minimum has been attributed to the northern hemisphere Early Holocene Insolation Maximum (EHIM) associated with Earth’s orbital cycles. Here we investigate the transient effect of insolation variations during the final part of the last glaciation and the Holocene by means of continuous climate simulations with the coupled atmosphere–sea ice–ocean column model CCAM. We show that the increased insolation during EHIM has the potential to push the Arctic Ocean sea ice cover into a regime dominated by seasonal ice, i.e. ice free summers. The strong sea ice thickness response is caused by the positive sea ice albedo feedback. Studies of the GRIP ice cores and high latitude North Atlantic sediment cores show that the Bølling–Allerød period (c. 12,700–14,700 years BP) was a climatically unstable period in the northern high latitudes and we speculate that this instability may be linked to dual stability modes of the Arctic sea ice cover characterized by e.g. transitions between periods with and without perennial sea ice cover.
http://www.sciencedirect.com/science/article/pii/S0277379113004162?np=y
h/t to The Hockey Schtick
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Someone please translate the following for the science challenged and what, if any, import it has in reference to CAGW?…
“This is interesting, somehow the Earth managed to reduce a good portion of the Arctic Ice Cap during the Holocene Climate Optimum from approximately 10,000-6,000 years ago without the help of the industrial revolution, fossil fuels, or automobile emissions.”
Between 4800 and 4400 years ago was one of the warmest periods in the Temperate Zone during the Holocene, this was when there was a rapid expansion in city building worldwide, much like the past few centuries. While in the Arctic this was one the coldest periods: http://snag.gy/BztF1.jpg
a bear is a bear . other bears don’t need ice to live. seals still have to go somewhere so the bears will follow them. biggest threat to polar bear is man who shoots them if they get too close.
@jim,
1) Trenberth’s “arctic death spiral” was in effect then, and is today, but for a completely different, manmade reason. Total nonsense, of course.
It seems in their rush to applaud this mainstream refereed climate science paper, people have skipped over the part about mean annual insolation in the Arctic being 5 W/m^2 higher in the Early Holocene than today (for entirely understood reasons), or that the authors are comparing modeled and proxy-derived Early Holocence Arctic ice cover to modern pre-industrial ice cover.
That the paper shows Arctic climate is extremely sensitive to external forcings.also seems to have escaped the celebrators’ notice, as does the fact that Earth is nowhere near a Northern Hemisphere insolation maximum but the ice is melting anyway.
That’s OK. Own goals still count.
ulric -nice contextualising pic.
i think if people still looking for eloquent images [a previous thread] showing global temps and where we are then yours sums it up.
Arctic sea ice extent less 6000 years ago than today?
Who would have thunk it?
See…
http://climatesanity.wordpress.com/2008/10/15/dont-panic-the-arctic-has-survived-warmer-temperatures-in-the-past/
Yet The warmist bless the marcott 10,000 study as gospel.
Jim Bo says:
March 24, 2014 at 6:44 am
Someone please translate . . .
They are saying ‘We don’t have a clue and hope you won’t notice if we throw in some big words’.
In addition, someone needs a course in writing. The phrase “ for the feedback to kick in” violates the rule to omit needless words, or in today’s lingo KISS. Why do they, given increased insolation, need a feedback or, if there was a feedback, why do they need increased insolation? Some reviewers call this “lazy writing.”
Magma says:
March 24, 2014 at 7:11 am
___________________
Your tirade might have been better without employing logical fallacies. It would have been more interesting if you would have given us what you think are the external forcings influencing Arctic sea ice melt. Even better, why is Antarctic ice at such great extent at Perihelion in Southern Hemisphere Summer?
“other real scientists in my home country of Somerset discovered that the lake-village dwellers ate Pelicans for breakfast (European birds now found only in Greece and the Danube delta)!”
Just for the record, Louisiana and the rest of the Gulf Coast are lousy with those things.
The only important thing here is the detection of a period of seasonal ice cover in the Arctic during the Holocene Climate Optimum, which was much warmer than today. There is no need for the postulated “dual stability modes”. When it is cold enough the ice stays around all year; when is is warm enough it doesn’t. Also, I notice the obligitory nod to AGW in the summary of the paper. During the HCO it was increased insolation, now it’s global warming causing the move to seasonal ice. There is no science here, just unsubstantiated speculation as to the cause. I am underwhelmed.
Study = Observation + Spin. Observation = Proxies indicate much less ice in the past. Spin = Much more ice today means CO2 catastrophe possibly imminent, assuming no summer ice is a catastrophe contrary to hundreds of years of that condition without catastrophe.
I’m going to go with polar bears became extinct 6,000 years ago, but re-evolved. But won’t be able to again because man-made CO2 or something. (/s)
who believes models
REPLY: Not all models are worthless, just like not all Mosher drive-by comments are worthless – Anthony
Well, Magma, the point remains; we have been told arctic ice is a tipping point feedback.
As for the notion that the ice was thinner in the past because of higher insolation, we have been told repeatedly the insolation is a presumed constant, the sun does not vary enough to effect our climate and that current warming is unprecedented, as evidenced by arctic (and hysterically, antarctic) sea ice decline.
To now make the claim that the lower sea ice in the distant past was caused by the sun and scientists knew this all along is disingenuous at best, completely fraudulent at worst.
You simply cannot have a scientific theory which is confirmed by every single line of evidence, regardless of the direction that evidence takes, and still call it science.
Even if catastrophic anthropogenic global warming were true, the evidence would still be mixed. For a perfect example of why that is, look no further than the “simple” law of gravity. Go release a helium filled balloon into the air and reconcile it to 9.8 m/s^2. Now go to the top of a building and release it on a windy day. Now consider Mars. Simple right?
Simple laws do not play well with massive chaotic systems. Our models are horribly flawed on their best day, and the “scientists” who are clearly living in the world of advocacy rather than science, keep having to explain why their predictions are completely unskillful.
Still think CO2 science is “simple” or “settled”? Okay then; you fail the basic scientific skepticism test. Go away and let the adults handle this.
What they may be overlooking is the refill of the Mediterranean Sea, Red Sea and Persian Gulf for example which took place about the time they Are looking at. That would have changed all the dynamics of the Atlantic. Conveyor Belt with warmer waters. See Johnson, Secrets of the Med Sea.
Lot of Dynamics here that Are being over looked. ICE Age studies a must.
Paul
One of the positive feedbacks that will drastically increase the warming is the release of methane currently frozen in the tundra of the north. That is supposed to be a really bad thing that will create a massive spiral of warming.
My question for the high priests of AGW is
1) Why did the methane not get released during the Holcene period to cause unprecedented warming
2) Since it apparently did not get released, does the methane have some form of internal mechanism that is able to differentiate between co2 warming on other forms of warming that it knows not to release unless it is co2 caused warming and
3) if the methane did get released during the holcene warming – then who put it back in the ground to get re-released.
Magma says:
March 24, 2014 at 7:11 am
Alan Robertson says:
March 24, 2014 at 7:18 am
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Magma is correct. This paper is disappointing in that, although it shows that the AGW assertions that Arctic sea ice cover is at unprecedented lows are wrong, it uses current GCMs to verify what the paleoproxies are already showing. The necessity of verifying the validity of proxies which were established as valid nearly forty years ago is pointless, especially using models which we know have have been shown to be consistently wrong. This paper seems more to be an exercise in showing that the models are valid because they correspond with what the proxies are showing.
Bob Kutz says:
March 24, 2014 at 8:09 am
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Bob, your response to Magma is unwarranted. The paleo evidence has been examined for nearly 40 years – since 1978 at least as referenced in the paper. That Climate Science has refused to recognize the validity of the proxies, or been ignorant of the previous studies, is what is being shown by this paper. They continue to use current GCMs as if they were not broken, and compare them to valid proxies, in order to make the point that their hypothesis is still correct and the models are valid. At the same time they refuse to recognize the evidence that, in the past, CO2 levels followed warming, not the other way around, so, IMO, their hypothesis about CO2 forcing is wrong and this is the basis of what is wrong with the models.
Mike Tremblay says:
March 24, 2014 at 8:42 am
Magma says:
March 24, 2014 at 7:11 am
Alan Robertson says:
March 24, 2014 at 7:18 am
——————————————–
Magma is correct… This paper seems more to be an exercise in showing that the models are valid because they correspond with what the proxies are showing.
_______________________
Howdy Mike,
I agree with your assessment of this paper. Perhaps I misinterpreted what Magma was saying. Maybe he’ll come back and clarify his remarks.
“speculate that this instability may be linked to dual stability modes of the Arctic sea ice cover characterized by e.g. transitions between periods with and without perennial sea ice cover.”
Oh Lord, bring them back to earth. I wonder if they have looked at a paper that has direct OBSERVATIONS of the lack of sea ice during the Holocene Climate Optimum!! Yes observations. How is this possible:
http://wattsupwiththat.com/2010/09/08/inconvenient-ice-study-less-ice-in-the-arctic-ocean-6000-7000-years-ago/
This study shows what you can do on a modest budget. They studied the beaches on the north coast of Greenland which these days is perennially bound in ice – even with our “alarming” summer extents and thicknesses that are to doom the planet. It is a classic. They looked at the raised beaches – higher sea levels (not much crustal rebound on Greenland), the plow marks made by ancient broken ice pack pushed onshore by wind, the beach itself which requires a good stretch of ocean with wind to build them and….wait for it… driftwood and other organic material that can be dated. Elegant and refreshing.
Reporting this research here is just another dog whistle to those for whom the political implications of AGW mean it can’t be true. Either that or they’re too stupid to understand that just because the Polar ice cap melted 6000 years ago when it was closer to the sun means it can’t also melt now because of the effect of greenhouse gases.
jamesibbotson says:
March 24, 2014 at 5:37 am
…
If increased insolation caused reduced ice in the past, whi do they assume its GHG levels in the present.
The graph is the explanation. According to that, the present annual mean insolation north of 80 degrees is lower than it was 16,000 years ago.
Adrian Metcalfe says:
March 24, 2014 at 9:24 am
Reporting this research here is just another dog whistle to those for whom the political implications of AGW mean it can’t be true. Either that or they’re too stupid to understand that just because the Polar ice cap melted 6000 years ago when it was closer to the sun means it can’t also melt now because of the effect of greenhouse gases.
____________________
Why don’t you smarten us up? When do you predict the Polar Ice caps will melt? How about those predictions about Arctic ice melt? Were you one of the smarter- than- everyone- else guys telling us that the Arctic would be ice free by 2013? Does Antarctic sea ice increase count?
jamesibbotson says:
March 24, 2014 at 5:37 am
If increased insolation caused reduced ice in the past, whi do they assume its GHG levels in the present.
ARGHHHHHHHH
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
Funding concerns, I am sure.