Has the puzzle of rapid climate change in the last ice age been solved?
Bremerhaven, Germany, August 19th, 2014. Over the past one hundred thousand years cold temperatures largely prevailed over the planet in what is known as the last ice age. However, the cold period was repeatedly interrupted by much warmer climate conditions. Scientists have long attempted to find out why these drastic temperature jumps of up to ten degrees took place in the far northern latitudes within just a few decades. Now, for the first time, a group of researchers at the Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research (AWI), have been able to reconstruct these climate changes during the last ice age using a series of model simulations.
The surprising finding is that minor variations in the ice sheet size can be sufficient to trigger abrupt climate changes. The new study was published online in the scientific journal Nature last week and will be appearing in the 21 August print issue.
During the last ice age a large part of North America was covered with a massive ice sheet up to 3km thick. The water stored in this ice sheet is part of the reason why the sea level was then about 120 meters lower than today. Young Chinese scientist Xu Zhang, lead author of the study who undertook his PhD at the Alfred Wegener Institute, explains. “The rapid climate changes known in the scientific world as Dansgaard-Oeschger events were limited to a period of time from 110,000 to 23,000 years before present. The abrupt climate changes did not take place at the extreme low sea levels, corresponding to the time of maximum glaciation 20,000 years ago, nor at high sea levels such as those prevailing today – they occurred during periods of intermediate ice volume and intermediate sea levels.” The results presented by the AWI researchers can explain the history of climate changes during glacial periods, comparing simulated model data with that retrieved from ice cores and marine sediments.
How rapid temperature changes might have occurred during times when the Northern Hemisphere ice sheets were at intermediate sizes
During the cold stadial periods of the last ice age, massive ice sheets covered northern parts of North America and Europe. Strong westerly winds drove the Arctic sea ice southward, even as far as the French coast. Since the extended ice cover over the North Atlantic prevented the exchange of heat between the atmosphere and the ocean, the strong driving forces for the ocean currents that prevail today were lacking. Ocean circulation, which is a powerful “conveyor belt” in the world’s oceans, was thus much weaker than at present, and consequently transported less heat to northern regions.
During the extended cold phases the ice sheets continued to thicken. When higher ice sheets prevailed over North America, typical in periods of intermediate sea levels, the prevailing westerly winds split into two branches. The major wind field ran to the north of the so-called Laurentide Ice Sheet and ensured that the sea ice boundary off the European coast shifted to the north. Ice-free seas permit heat exchange to take place between the atmosphere and the ocean. At the same time, the southern branch of the northwesterly winds drove warmer water into the ice-free areas of the northeast Atlantic and thus amplified the transportation of heat to the north. The modified conditions stimulated enhanced circulation in the ocean. Consequently, a thicker Laurentide Ice Sheet over North America resulted in increased ocean circulation and therefore greater transportation of heat to the north. The climate in the Northern Hemisphere became dramatically warmer within a few decades until, due to the retreat of the glaciers over North America and the renewed change in wind conditions, it began to cool off again.
“Using the simulations performed with our climate model, we were able to demonstrate that the climate system can respond to small changes with abrupt climate swings,” explains Professor Gerrit Lohmann, leader of the Paleoclimate Dynamics group at the Alfred Wegener Institute, Germany. In doing so he illustrates the new study’s significance with regards to contemporary climate change. “At medium sea levels, powerful forces, such as the dramatic acceleration of polar ice cap melting, are not necessary to result in abrupt climate shifts and associated drastic temperature changes.”
At present, the extent of Arctic sea ice is far less than during the last glacial period. The Laurentide Ice Sheet, the major driving force for ocean circulation during the glacials, has also disappeared. Climate changes following the pattern of the last ice age are therefore not to be anticipated under today’s conditions.
“There are apparently some situations in which the climate system is more resistant to change while in others the system tends toward strong fluctuations,” summarises Gerrit Lohmann. “In terms of the Earth’s history, we are currently in one of the climate system’s more stable phases. The preconditions which gave rise to rapid temperature changes during the last ice age do not exist today. But this does not mean that sudden climate changes can be excluded in the future.”
The paper:
Xu Zhang, Gerrit Lohmann, Gregor Knorr, Conor Purcell:
Abrupt glacial climate shifts controlled by ice sheet changes.
Nature, DOI: 10.1038/nature13592
During glacial periods of the Late Pleistocene, an abundance of proxy data demonstrates the existence of large and repeated millennial-scale warming episodes, known as Dansgaard–Oeschger (DO) events1. This ubiquitous feature of rapid glacial climate change can be extended back as far as 800,000 years before present (bp) in the ice core record2, and has drawn broad attention within the science and policy-making communities alike3. Many studies have been dedicated to investigating the underlying causes of these changes, but no coherent mechanism has yet been identified3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15. Here we show, by using a comprehensive fully coupled model16, that gradual changes in the height of the Northern Hemisphere ice sheets (NHISs) can alter the coupled atmosphere–ocean system and cause rapid glacial climate shifts closely resembling DO events. The simulated global climate responses—including abrupt warming in the North Atlantic, a northward shift of the tropical rainbelts, and Southern Hemisphere cooling related to the bipolar seesaw—are generally consistent with empirical evidence1, 3, 17. As a result of the coexistence of two glacial ocean circulation states at intermediate heights of the ice sheets, minor changes in the height of the NHISs and the amount of atmospheric CO2 can trigger the rapid climate transitions via a local positive atmosphere–ocean–sea-ice feedback in the North Atlantic. Our results, although based on a single model, thus provide a coherent concept for understanding the recorded millennial-scale variability and abrupt climate changes in the coupled atmosphere–ocean system, as well as their linkages to the volume of the intermediate ice sheets during glacials.
“The surprising finding is that minor variations in the ice sheet size can be sufficient to trigger abrupt climate changes.”
The Northern hemisphere ice sheet melts by two thirds every summer. (The temperature fluctuation is also around 30C from mid winter to mid summer.) I wonder what they mean by “minor variations” because we see major variations every year.
Models again?
Seems to me like they programmed the response from the climate model that they wanted. Now, if they have physical evidence for their claims, then it might be worth considering. But really, what difference will it make to the life of any human in the next thousand years if they are right?
Alfred Wegener?….what did he ever know?!!!
Knows nothing about ocean currents too.
Is this more of that ‘settled science’ again ?
Seriously it seems that every real piece of research that comes out underlines just how little claimate scientists really know about the subject. Clearly they cannot ‘know’ that alterations in the height of ice sheets triggered a warm period, At best its a hypothesis (guess) based on computer models and a lot of assumptions.
I propose the CGAW crowd switch from computer to female models. It’d be a lot less tedious and have the same predictive powers.
They’re looking in the right direction. The ocean circulation system. Their model gains credibility by acting like a nonlinear chaotic system that in certain regimes can switch between alternative attractors. Such (Hopf) bifurcations are the classic hallmark of nonlinear dynamics approaching the border of chaos.
Note also no real role for CO2 which only gets a perfunctory nod.
A way to visualise such system is as a landscape of stability in which a high peak represents an unstable hard to achieve state while a low elevation is a valley of stability toward which the system like a ball rolled over the landscape naturally settles. In a bi-stable system you have two neighboring valleys of stability. High mountains between the two valleys would prevent the system moving from one valley to the next. However of you have a mountain pass or a “saddle” of lower elevation linking the two valleys, the system only needs a smaller “push” to roll it from one valley to the next through the pass. This is the thermodynamic landscape of bistability.
I occasionally comment about the importance of the N. Atlantic-Arctic link to climate change
Denmark straits, the major feature of the area, is the main bottleneck on the superhighway in the oceans global circulation. On both sides to the north and the south of the straits the Great Ocean Conveyer belt
http://www.grida.no/climate/ipcc_tar/slides/large/04.18.jpg
releases massive amounts of heat (several hundred watts/ m2).
Secular magnetic field delta (usually an indication of the earth’s crust-mantle events ) for the area (from both paleo and instrumental records) also closely matches the Loehle’s (non tree rings) GT reconstruction.
Tectonic activity (according to data 1860 to present) in the N. Atlantic – Arctic environs follows the closely integrated sunspot number for the period.
Solar magnetic field cannot penetrate to the depths of the Earth’s core, and yet the solar magnetic field (22 year cycle) and a much larger magnetic ripple superimposed on the Earth’s field (orders of magnitude greater than the heliospheric field at the earth’s orbit) have same frequency and are in phase.
Energy in the equal measure across the centuries, comes from the above, but the ‘control knob’ most likely comes from the below.
I don’t buy it. Firstly, the D/O events are VERY rapid in the rising temperature phase – some ice profiles from Greenland showing a major shift from one year to the next. Whilst it is the case that only a consistent shift in wind direction can do this, it is also the case that wind directions around the Greenland ice-cap and the Iceland/Norwegian Seas are controlled by the track of cyclones – which are themselves directed by the jetstream (and not the other way around, as some would imagine). A shift from a tight westerly jet to a loopy meridional jet is what best would account for major shifts in wind patterns in this region. And the jets are controlled by….? Well, some time back NASA’s Drew Shindell thought these changes were controlled by the UV status of the Sun. But he went on to work on other more important things like ‘global warming’ under James Hansen’s direction. Low UV leads to loose and loopy jets with less containment of Arctic cold air masses. Low UV is associated with very low sunspot numbers and low solar magnetic field status.
Further, between 50,000 and 30,000 BP there are two sets of warming cycles, of roughly 10k years each, but with a pronounced Fibonacci series periodicity – where each peak decays slowly, as would an harmonic series, and the breadth of the peak has an 8:5:3:2:1 ratio. This pattern does not entirely disappear during the Holocene – but is certainly obscured – for example, the 5-part of the cycle is suppressed, but the 8 (Holocene Climate Optimum), 3 (Minoan warm period), 2 (Roman warm period) and 1 (Medieval warm period) are clear. The current warm period may be the tail of the series – the final 1, or the beginning of a new series – implying a long period of warmth. Thus far, these patterns are ignored because nobody has a clue where such a series could originate!
Some researchers have held that the exit from an ice-age is actually a more extreme version of the D/O event. I would not be surprised if there was a 100,000 year magnetic periodicity – and this would then compete with the orbital theories – which are regarded by many as insufficient in any case to explain the sudden rises.
These Greenland changes correspond to temperature, wind and ocean currents shifts throughout the North Atlantic, with knock-on effects in other ocean basins, some of which are in any case subject to shifts in jetstream and vortex tracking, and hence these reflect global shifts – such as the Little Ice Age has proven to represent.
“But this does not mean that sudden climate changes can be excluded in the future.”
So tampering with the atmosphere could cause us to freeze or burn up.
10 degrees in 87000 years Hmm
I think that, by using the words “dramatic temperature changes,” they snuck this paper by the Alarmist gatekeepers. In actual fact they are describing a cycle, in some senses like an ice-age version of the AMO. This is dangerous turf to tread, for once you start to admit the existence of such cycles then, rather than a “Death Cycle,” the decreases of sea-ice between 1979 and 2012 becomes half-a-cycle, and perfectly normal and natural.
I had my own ideas about how nature engineers such a cycle, and our host was kind enough to print it here: http://wattsupwiththat.com/2014/01/09/author-of-its-own-demise-musings-on-the-amo/
Now we need, as Ray Boorman above rightly states, more of the “physical evidence” from the historical record, to back up the above paper’s claims. However I don’t think this paper should be mocked without serious consideration. Not that it will help me pay my heating bill this winter, but better understanding the AMO and other ocean cycles could result in better responses to the cards nature deals out, (far better than the idiotic responses idiotic governments are coming up with now.)
RE: Peter Taylor says:
August 21, 2014 at 2:22 am
I like your ideas, but you need to be aware you can’t just state that the jet stream influences the surface storm track, and there is no interaction back between the surface and the jet stream. Or, well, you can say it, but if you observe the arctic you might note a few things that could make you modify your statement.
One thing I’ve noticed is that storms seem to prefer open water to ice-covered areas. Just as hurricanes weaken over land, arctic lows weaken over ice-covered areas, likely because they lose their supply of rising warmth and moisture.
Just for the fun of it, observe the behavior of lows in the arctic as winter comes on, but before the ice has grown back. When the icecap is cold to the north, and the tundra is cold to the south, they seem to like to ripple along the area of open water between. That may be a case where the surface is effecting the higher levels of the atmosphere. Just an idea.
A lot of the ice-melt comes from warm water under the ice. If a shift in currents under the ice could change the areas that were ice-covered, I think the storm track might be changed as well.
Spam filter ate my last comment. I probably shouldn’t have used the word “idiotic.” Sorry.
Lewis P Buckingham on August 21, 2014 at 2:22 am
phlogiston says:
August 21, 2014 at 2:10 am
‘Note also no real role for CO2 which only gets a perfunctory nod.’
It would be interesting to know what the role of CO2 is in their opinion since they do cite ,
‘minor changes in the height of the NHISs and the amount of atmospheric CO2 can trigger the rapid climate transitions via a local positive atmosphere–ocean–sea-ice feedback in the North Atlantic’
Is this CO2 ‘trigger’ part of the model, or just the change in the ocean currents triggered by heightened ice sheet formation.
I did not read yet the full paper. So indeed its hard to be clear exactly what role they ascribe to co2. They may be playing the invert-cause-and-effect trick by confusing an increase in co2 responsive to increasing sea temperatures as some kind of driving role for co2. Or maybe not.
I’m guessing that since co2 was mentioned only once in the abstract and as the second item in a pair of factors after ice thickness, that it is maybe just a genuflection and the paper looks beyond co2 myopia in an enlightened way.
Caleb, went back and read your Epic of last January. The reason why ice floats and doesn’t sink an allows the sea to freeze from the bottom up. is that at 4oC as the water gets ready to crystalize into ice it expands and its density decreases. That means that ice floats without any worries about salt contents etc etc.
Link between Arctic atmospheric pressure and North Atlantic SST (AMO) shown
HERE in de-trended versions, appears logical and looks benign enough, but one shouldn’t be deceived by appearance (and few years of delay in the AMO). It may be hard for the science (settled or un-settled) to come to terms with and accept only possible explanation, beyond just calling it coincidence.
“Nothing in nature is by coincidence…Something appears to be coincidence only because of our lack of knowledge.” Baruch Spinoza
Model fantasy.
The truly sudden changes of temperature in climate history show that what we are experiencing is not close to extreme by historical standards. The climate fear machine tends to skip past this pesky evidence.
Small changes in initial conditions producing huge changes in the overall system are characteristic of chaotic systems. This paper seems to be pointing at the climate system as chaotic. Not surprising.
RE: Ken Calvert says:
August 21, 2014 at 3:35 am
We are a little off topic, but the point I was making in that essay was not that ice floats, but that cold water sinks. Therefore, in theory at least, the surface water would sink before it got a chance to freeze, replaced by upwelling warm water from beneath. (Obviously this doesn’t happen to a degree that prevents the formation of the icecap, in reality.)
The above is only true for salt water. Fresh water is strange stuff, for once you get to roughly 36 degrees (F) cold water rises. If you took the temperature of a pond just before it froze the water at the surface would be 32.1 degrees, the water an inch down 33 degrees, the water two inches down would be 34 degrees, and so on. It is counter-intuitive, but true: Cold water rises.
A really cool thing happens in the spring, when that layer of cold water on top of a pond or lake is first exposed after ice melts. That layer of cold water is just sitting there minding its own business on top, colder than the water beneath, however cold water only floats on top of warmer water when it is above 36 degrees. On a bright, sunny day in the spring, especially when there is little wind, that surface layer can be warmed above 36 degrees, whereupon it becomes denser than the water beneath, and quite abruptly the entire surface of a still lake sinks. Called “overturning,” it can actually bring bits of dead pond-weed from the bottom up to the surface when it happens. It is strange to see, if you happen to be out fishing on that day, and can either make the fishing great or ruin it, depending on what fish you are after.
Like I said, water is strange stuff.
Correction to above comment: ” …cold water only floats on top of warmer water when it is BELOW 36 degrees.”
@Caleb – Thanks for the additional insight. YOur comments are food for thought.
To me, this is the type of situation in which climate models are most useful – speculation leading toward new possible insights. No government policy implications involved, in fact, if you read carefully, no real implications about today’s climate at all. It’s nice to see inquiries into our planet’s climate that do not appear to involve “me too” climate change motives. I found the post quite interesting and as a layman, understandable. Thanks, Anthony.
Findings? In a computer model? These guys really do believe the “puter” is the new laboratory, which it ain’t!
The climate in the Northern Hemisphere became dramatically warmer within a few decades until, due to the retreat of the glaciers over North America and the renewed change in wind conditions, it began to cool off again.
Uh, what caused the “change in wind conditions”?
Ice doesn’t melt just because it feels like melting; there must be an underlying cause for the ice to melt. Wouldn’t that cause be the reason for the climate to change?
As a result of the coexistence of two glacial ocean circulation states at intermediate heights of the ice sheets, minor changes in the height of the NHISs and the amount of atmospheric CO2 can trigger the rapid climate transitions via a local positive atmosphere–ocean–sea-ice feedback in the North Atlantic.
They just had to stick that in for the grant thingy.
At this point, my opinion is that humans understand about 1% of what drives climate changes over time periods longer than a year. Does anyone believe that our knowledge is more solid than that?
Caleb, your overturning (or simply ‘turning’) is why the city folks who get their water from lakes suffer with water that tastes and smells like dirt several times a year. As our area switched from wells to lakes as our water supply, the difference was spectacular. And not in a good way.
“Small variations in the climate system can result in dramatic changes in temperature”
1) Sound like the definition of a non-linear chaotic system. …. and so why would we expect a log-linear system with CO2 changes ?
2) Also sounds like the Lorenz’s Butterfly effect – theory developed in 1961 – 53 years ago. I am not sure why the above quote would be surprising to anyone in the field, unless they are completely unaware of the literature
I wish that researchers (and reporters) would stop using the term “ice age” when they are clearly referring to a “glacial epoch.” An “ice age” consists of several glacial epochs interspersed with interglacial periods. We are currently in an ice age. The previous ice age occurred 150 million years ago. These researchers should know better.
I am only listing one of the 4 which applies to this particular article which I have been addressing al along which is when the climate is close to a glacial/interglacial situation abrupt climatic changes are more likely to occur with GIVEN forcing.
This will be my only commentary limiting myself to one per day per topic.
MY FOUR FACTORS
1. The initial state of the global climate.
a. how close or far away is the global climate to glacial conditions if in inter- glacial, or how close is the earth to inter- glacial conditions if in a glacial condition.
b. climate was closer to the threshold level between glacial and inter- glacial 20,000 -10,000 years ago. This is why I think the climate was more unstable then. Example solar variability and all items would be able to pull the climate EASIER from one regime to another when the state of the climate was closer to the inter glacial/glacial dividing line, or threshold.
They had me interested right up until the last line of the first paragraph:
using a series of model simulations
Jeff L. says:
I am not sure why the above quote would be surprising to anyone in the field, unless they are completely unaware of the literature
Actually, unless they are completely uneducated on the subject in general!
One should not view the AMO as a closed system or primary driver of weather pattern changes. An ENSO signal arrives about 6 months later and shows up in the AMO data, rather consistently and noisily. Here is a paper explaining that ENSO signature in the Atlantic Multidecadal Oscillation Index (AMOI) data and suggests a 6 month lead time, meaning that the Multivariat ENSO Index (MEI) demonstrates a 6 month lead to that signal showing up in the Atlantic. The teleconnected forcing is likely an atmospheric bridge:
http://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=2&cad=rja&uact=8&ved=0CCgQFjAB&url=http%3A%2F%2Fwww.esrl.noaa.gov%2Fpsd%2Fpeople%2Fgilbert.p.compo%2FCompoSardeshmukh2008b.pdf&ei=JAj2U9OyOuS8igL5hoG4Cw&usg=AFQjCNFtMFvtLLNqno1X7llx3B9kr8WRqQ&sig2=EYxYPOFNdKZ-lyWpbGJlEQ&bvm=bv.73231344,d.cGE
I love the following 2010 paper about the impossible. As in removing the ENSO signal from the larger SST data on a global basis. The authors throw up their hands in the end and give in to the idea it can’t be done. It can’t be modeled and it can’t be removed. The AMO may be a darling child to study, but it is likely a child and not the adult. The adult in this mess is most likely the granddaddy of SST variation and trends: ENSO.
http://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=10&cad=rja&uact=8&ved=0CG8QFjAJ&url=http%3A%2F%2Fwww.esrl.noaa.gov%2Fpsd%2Fpeople%2Fgilbert.p.compo%2FCompoSardeshmukh2008b.pdf&ei=2AX2U4WjNeTUigKPkoHADw&usg=AFQjCNFtMFvtLLNqno1X7llx3B9kr8WRqQ&sig2=0DD3w8fGBFz1XzkSS5Goiw&bvm=bv.73231344,d.cGE
But you will love the unexpected ending. There are plenty of papers that propose that the AMO then triggers changes in the North Pacific.
http://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=2&cad=rja&uact=8&ved=0CCYQFjAB&url=http%3A%2F%2Fgfdl.noaa.gov%2Fbibliography%2Frelated_files%2Froz0704.pdf&ei=2Qr2U9jbMsmaigKigYFY&usg=AFQjCNFgh4S4QtV0X3ZYzwU8ylYpIby95A&sig2=5qGPQkmGZuCMwq0guCK0xg
And the two together, the PDO and the AMO, can wreak havoc with a decades worth of Sunday afternoon outings.
http://oceanworld.tamu.edu/resources/oceanography-book/oceananddrought.html
Scientists have long attempted to find out why drastic temperature jumps of up to ten degrees take place in the far northern latitudes within just a few hours.
Fixed it
A big problem with computer models is that the results depend not only on what assumptions you put into the model, but also what you don’t put in.
Some major problems with this particular model include:
1. “The rapid climate changes known in the scientific world as Dansgaard-Oeschger events were limited to a period of time from 110,000 to 23,000 years before present. The abrupt climate changes did not take place at the extreme low sea levels, corresponding to the time of maximum glaciation 20,000 years ago, nor at high sea levels such as those prevailing today – they occurred during periods of intermediate ice volume and intermediate sea levels.”
This statement is dead wrong–both the oxygen isotope ratios and temperature curves from the GISP2 ice core show that the most sudden warming that brought the last Ice Age to a close occurred abruptly 15,000 years ago when ice sheets were at their maximum extent and sea level was at its lowest. The ice sheets had been at their late glacial maximums for several thousand years when, out of the blue, temperatures suddenly soared 13 C (23 F) in something like 100 years, causing wholesale melting of the ice sheets. Then, just as abruptly, temperatures turned around and cooled 10 C (18 F) by 14,000 years ago. Temperatures then fluctuated up and down( but not so intensely) at intermediate levels for about 1,000 years. 12,700 years ago, temperatures took another nosedive into the Younger Dryas cold period and remained at full glacial conditions for 1,000 years. During the Younger Dryas, temperatures repeatedly changed abruptly from cool to warm (the Dansgard-Oeschger events). 11,500 years ago, another great warming spike caused temperatures to soar 12 C (21 F) in about 100 years (at one point, around 20 degrees in 40 years), then continued warming at slower rates for a total warming of 17 C (30 F) from 11,700 to 10,000 years ago. (Keep in mind that these temperatures are for Greenland, not global, but they correlate very well with temperature conditions in the rest of the world). These abrupt, multiple, intense changes (back and forth) at full glacial conditions (not ‘intermediate’) hardly sound like changes caused by gradual changes in ocean/atmospheric conditions.
2. All of the five most significant colder temperature changes that occurred during the past 500 years (the Little Ice Age) coincided with low sunspot intervals, lower total solar irradiance, lower solar magnetic flux, and increases in the production rates of beryllium-10 and carbon-14 (isotopes created in the upper atmosphere by increase in cosmic ray flux rates). These are not mere coincidences–such good correlation is not random chance, but must be due to cause-and-effect circumstances. None of this, of course, made it into the computer model simulations.
There are other serious problems with the methodology in this paper, but the bottom line is that (1) their initial premise of changes occurring only during ‘intermediate’ glacial conditions is dead wrong, and (2) sunspot intervals, lower total solar irradiance, lower solar magnetic flux, and increases in the production rates of beryllium-10 and carbon-14 argue strongly for other factors not included in their models. Thus, their conclusions cannot be considered valid.
Looking at their figures, ( http://www.nature.com/nature/journal/v512/n7514/full/nature13592.html ) they do not seem to get the sea level correct. They forgot that all water depths 120 metres down were land surfaces. So no Baltic sea, no water cooling the N. Pacific thru the Bering Straight, no Hudson Bay and all the islands of N Canada had no water currents. Also the seem to not realize how much Arctic Ice melt is due to warmer fresh water run off from the land. With glaciers all around, no run off.
Read a thought provoking article where the author (I forgot who) questioned whether if the deep ocean heating would go up because of the undersea volcanoes, do to the ice cap preventing evaporative heat loss, like a pot boiling with or without a cover.
With a chaotic, multivariate complex system model of the climate, even if it is perfect, you might be able to demonstrate rapid climate change but you can never predict it (incomplete knowledge of initial conditions and insufficient computing power). Therein lies the rub and so the IPCC’s scenarios instead of predictions. I think the best bet is to observe patterns and project ahead (e.g. the Holocene is cooling down and we’re heading into a glaciation). All the fancy model stuff does is give your guesses a patina of scientism with which to fool the funding agencies.
The temperature record is really a record of ice sheet extent: land ice plus sea ice, land ice being about a thousand times thicker than sea ice and requiring a thousand times longer to melt. Ice melts on clear summer days, and gets an extra 80W/m^2 when orbital conditions are right. Albedo feedback is on the order of 30W/m^2 at peak insolation. GHG feedback is 1 or 2 watts, 24/7, which means little on a winter night over ice. Ice sheets create their own climate, which might be expected to replicate that of the Antarctic to some extent; at any rate, hard to model.
Clearly Milankovitch cycles trigger ice ages, where land ice responds at periods in the same ballpark, lagging by thousands of years. Over the long term sea ice grows and melts in tandem with the big ice sheets, but sea ice can respond on short order to short term influences and create sudden changes in average global temperature as recorded in the ice cores. Secondary positive feedback loops of sea ice would be a thousandth as long as those of land ice. –AGF
Don Easterbrook says:
August 21, 2014 at 8:41 am
You are correct. Fluctuations occur on about the same period during glacial maximum, normal glacial and interglacial conditions. During glacials, they’re called D/O events and Bond cycles during interglacials. The size of the fluctuations is greater during glacials because the moves start from such low temperatures.
During glacials there are also Heinrich events at fairly regular intervals.
“Secondary positive feedback loops of sea ice would be a thousandth as long as those of land ice.” –I sure got that backwards! –AGF
Caleb,
I’m not a scientist, but a pond in which there is no mixing current is very different than an ocean in which there is. Ocean heat moves by both conduction and convection. Ponds without anything to move the water layers around, can only move heat by conduction. Cold water does not “rise” to the top of a pond. The contact with the air that has become colder than the water at the surface causes the water at the surface to lose heat to the air as the two attempt to reach equilibrium. The thermal insulating properties of the land at the bottom and sides of the pond allow the water beneath the surface to hold onto its warmer temperatures longer than the water at the surface, which is in contact with the air. Air both warms AND cools faster than both water and land. Thus the water in contact with it will cool faster than the warmer layers beneath the surface can adjust for the temperature differences between them and reach thermal equilibrium with each other.
“Many studies have been dedicated to investigating the underlying causes of these changes, but no coherent mechanism has yet been identified”
We really don’t know.
We have plenty of experts in various related fields that think they know. They present/sell their theory with a high level of confidence and with compelling facts. Proxy data is great but it can/will send you down the wrong path at times.
If the measurements line up consistently a certain way, it’s a clue but there is still much more missing pieces to the puzzle than their are discovered pieces.
Over the last 100 years, our ability to actually measure the atmosphere, oceans, sun and related elements gives us the ability to see everything as it is actually happening………..and we are still missing some key pieces needed to solve the puzzle.
Regarding pieces of the puzzle we find that we think are from 100,000 years ago or millions of years ago. They can tell us with high confidence about something that happened in the past. We can guesstimate the time frame but could be off.
I think that sometimes, we might be trying to fit those pieces into the wrong puzzle. An even more powerful force, with no evidence left behind could be entirely responsible for causing what we think our only evidence must have caused.
We can’t be sure about any changes that involved our relationship with the sun or other things, that even right now, we are trying to figure out.
Our biggest limiting factor is that the real key to the entire puzzle requires capturing/measuring changes as they occur and they occur on a geological time scale, with humans only doing this for a tiny fraction of time on that scale.
The sun may be obliging to some extent at this fraction in time, with it’s recent cycle changing enough for us to compare it to previous cycles.
Don Easterbrook,
I sent you an email last week to ask a question about whether or not it was possible to tie the “new” pingos to the explosion/impact of the Chelyabinsk meteor last year. Researchers discovered that the ultrasonic sound and percussion waves were powerful enough to be detected by seismographic instruments around the world. They were detected circling the planet TWICE before dissipating. If there was that much subterranean disturbance/energy in play, is it possible that it could have loosened ice cores in the pingos enough to cause them to burst ? As remote as these locations are, for them to not be noticed for a year isn’t unusual. Any way to check satellite images from just prior and after impact for comparison?
So is it minor variations in ice sheet size that trigger abrupt climate changes, or is it abrupt climate changes that trigger variations in ice sheet size? How do they tell the cause from the effect? Do ice sheets vary in size on their own without any changes occurring in the climate first?
Louis says:
August 21, 2014 at 11:31 am
Comparing June insolation at 65°N with δ18O here: http://en.wikipedia.org/wiki/Milankovitch_cycles#mediaviewer/File:Vostok_420ky_4curves_insolation.jpg
leaves no room for doubt as to the cause: the earth’s orbit; not CO2, not CH4. It is impossible for functions of correlating periodicity to have anything but a common cause. If you lived in the tropics you could be oblivious to ice ages, but where lasting ice appears or disappears there is no separating climate from ice extent, or local temperature, or global temperature. –AGF
PS, I guess I didn’t get that last line backwards.
Clearly the Gulf Stream turns south. This winter sea ice in the Arctic will quickly was incremental.
http://earth.nullschool.net/#current/ocean/surface/currents/overlay=sea_surface_temp/orthographic=-46.10,50.00,837
“There are apparently some situations in which the climate system is more resistant to change while in others the system tends toward strong fluctuations,” summarises Gerrit Lohmann. “In terms of the Earth’s history, we are currently in one of the climate system’s more stable phases. The preconditions which gave rise to rapid temperature changes during the last ice age do not exist today. But this does not mean that sudden climate changes can be excluded in the future.”
Uh-Huh….
Aphan says:
Don Easterbrook,
I sent you an email last week to ask a question about whether or not it was possible to tie the “new” pingos to the explosion/impact of the Chelyabinsk meteor last year. Researchers discovered that the ultrasonic sound and percussion waves were powerful enough to be detected by seismographic instruments around the world. They were detected circling the planet TWICE before dissipating. If there was that much subterranean disturbance/energy in play, is it possible that it could have loosened ice cores in the pingos enough to cause them to burst ? As remote as these locations are, for them to not be noticed for a year isn’t unusual. Any way to check satellite images from just prior and after impact for comparison?
I didn’t get your email–don’t know why. The biggest problem with the methane explosion idea is that there is no evidence of debris blown out of the depression. This looks for all the world like a classic pingo caused by bowing up of the surface by ice from below, breaching of the top to allow melting, and melting out a hole. There are many hundreds of these in this area. As they mature they don’t as fresh as this one but still retain the rim of bowed up material.
Where have all the money gone?……. When will they ever learn……
Let’s see how fast you could change the ice in the Arctic. Please compare the September 2012 and 2013.
http://ocean.dmi.dk/arctic/static_maps/min_seaice_extent1979_2013nsidc.png
Contrary to the education given by propagandists to newer meteorological students, the sun is NOT a solid state device with precise quality control. It is a variable of unknown set and MUST be the variable that all climate science is solved for. It is the ONLY source of energy input into the system and ignoring it is equivalent to ignoring the state of a Bunsen burner when studying specific heat.
Arguing about anything without first solving all variables to the sun is hearsay and not even an anecdote.
Yes, I posted again.
The entire thread is full of people playing into the hands of the warmists; arguing the minutia before determining the merit OR the possibility.
ren,
What matters in the global warming debate is global ice cover, no?
Dbstealey
Growth of ice in the Arctic means the the temperature drop across the northern hemisphere, particularly in Canada and Scandinavia.
http://igloo.atmos.uiuc.edu/cgi-bin/test/print.sh?fm=08&fd=20&fy=2013&sm=08&sd=20&sy=2014
What happens in the winter when a warm front does not reach to Scandinavia?
http://www.opc.ncep.noaa.gov/Loops/GRTOFS/currents/GRtofs_Curr_Atl_03_Day_flash.shtml
This would all be very well if all Dansgaard-Oeschger events followed the ”quick warming – slow cooling” pattern.However they don’t. Especially the shorter events are characterized by a final cooling phase (typically half to two thirds of the total cooling) that is almost as fast as the initial warming.
Image here: http://en.wikipedia.org/wiki/File:Grip-ngrip-do18-closeup.png
This more or less precludes glacial build-up as an explanation, for while an icecap could theoretically collapse in a relatively brief time-frame there is no way it can build-up equally fast, since the accumulation of ice is limited by precipitation.
It is worth noting that during the Younger Dryas stadial, for which we have very good evidence, both the initial cooling and the warming at the end of the stadial were very abrupt – on the order of a few decades or less.
I find this report interesting and plausible. When I was in high school the concept of fluidics and fluidic computers caught my attention and ever since I have wanted to get more involved in it. Many kinds of circuits can be made, in this context bistable switches, monostable and astable (oscillators). In all of these instances a type of positive feedback exists and the system is inherently unstable (chaotic). A sllight push (puff of air) pushes the main stream into one chamber or the other, producing a venturi effect vacuum that if steered correctly maintains the stream of air in the chamber just reached (bistable), or sucks it into the chamber just abandoned (oscillator).
The important thing is that the switching air flow is of much less magnitude that the main stream and this is important for the circuit since you need to be able to draw a bit of air from the resulting chamber to do useful things without disrupting the stabilty.
http://www.google.gg/patents/US3676238
http://www.dantecdynamics.com/flow-discharge-vectoring-using-a-miniature-fluidic-actuator