From ETH in Zurich, this interesting essay on the last glacial period has some interesting points to ponder. h/t to Sid Stafford – Anthony
The last glacial period was characterised by strong climatic fluctuations. Scientists have now been able to prove very frequent and rapid climate change, particularly at the end of the Younger Dryas period, around 12,000 years ago. These fluctuations were accompanied by rapid changes in circulation in the oceans and the atmosphere.
Sediment deposits in lakes are the climate archives of the past. An international team of researchers from Norway, Switzerland and Germany have now examined sediments originating from the Younger Dryas period from the Kråkenes Lake in northwest Norway. In the sediments, they found clues that point to a “climate flicker” at the end of the last glacial period, oscillating between colder and warmer phases until the transition to the stable climate of the Holocene, our current interglacial period. The short-term, strong fluctuations of the Younger Dryas would have dwarfed the “extreme weather phenomena” seen today, according to Gerald Haug, professor at the Department for Earth Sciences at ETH Zürich and co-author of the study, which was published online yesterday in “Nature Geoscience”.
Seasonal sediment deposits
Seasonal sediment accumulation, for example, gave scientists clues to these strong climate fluctuations. They can be read in lakes in a similar way to reading rings on trees. In warmer phases and melting glaciers, the accumulation of sediments increases. More clues on the changes in glacier growth were given by the element titanium, which is present in the sediments. Glaciers erode their bedrock, and in doing so concentrate the titanium contained in the sediments they are carrying. The sediments containing titanium are washed into the glacier’s draining lakes in the meltwater. The amount of sediment and the titanium content can therefore allow us to deduce when the glaciers were stable and when they melted. The researchers interpreted the maxims, recurring every 10 years, as phases of strong glacier activity caused by temperature fluctuations and thus as warmer times.
A seemingly self-preserving cycle
The scientists also examined a sediment core from seabed deposits of the same age in the North Atlantic. They reconstructed the original temperature and salt concentration of the water based on microfossils and the oxygen isotope ratio in the sediment. It was shown that the results from the lake sediments corresponded to those from the sea sediments. “The melting of glaciers was caused by the warm Gulf stream advancing into this region,” Gerald Haug explains. This increase in temperature caused the west winds to shift to the north and brought warm air to northern Europe. However, the meltwater draining into the Atlantic lowered the salt concentration and the density of the surface water, changing the convection in the ocean, which in turn allowed new sea ice to form. Subsequently, the Gulf Stream and the west winds were again forced out of the North Atlantic area and the region cooled down once again. These processes were repeated for around 400 years, until the current interglacial period was able to stabilise itself.
The Würm glaciation began around 100,000 years ago and lasted until around 10,000 years ago. In this period, there were strong fluctuations between warm and cold phases, particularly in the North Atlantic area. The Younger Dryas, which ushered in the current interglacial period, is one of the best-known and best-researched abrupt climate changes of that glaciation. It began around 12,900 years ago and at first caused an abrupt temperature drop in the northern hemisphere, as well as a temperature rise of up to 10°C in less than 20 years towards the end, around 11,700 years ago.
Unclear mechanisms
Up until now, there have been several studies which document the glacial conditions during the Younger Dryas period of 1,200 years. However, the mechanisms which caused it, sustained it and finally led to an interglacial period have yet to be fully understood. The researchers believe that further high-resolution studies of this type could give insights into how glacial periods are triggered and how they are brought to an end.
Discover more from Watts Up With That?
Subscribe to get the latest posts sent to your email.
How interesting.
What implications does this have for the theory of man-made global warming?
If I read the article correctly, it would seem that the current climate changes which are being recorded are not, in fact, unprecedented at all.
“They can be read in lakes in a similar way to reading rings on trees.”
Right. Let discourse begin.
The research supports what is quite well accepted by the scientific community about the transition at the end of the last glacial period and specifically the Younger Dryas event.
See also
http://www.ncdc.noaa.gov/paleo/abrupt/data4.html
It certainly puts the last century’s <1C climate fluctuation into perspective, ie. it’s miniscule by comparison.
And even IPCC reports accept that we don’t know what caused this and previous glacial-interglacial transitions – but you won’t find that admission unless you actually read the relevant chapters.
A possible reason for the climate fluctuations considered herein may be the occasional rapid release of ice-margin-lakes. In North America these lakes stretched in an arc across the front of the melting continental glacier. Timing, outlets, and names varied.
http://en.wikipedia.org/wiki/Lake_Agassiz
And also here, under geologic history
http://en.wikipedia.org/wiki/Mohawk_River
This one uses the common term “pro-glacial lake.”
The Straight of Juan de Fuca was also blocked with ice and a lake formed in Puget Sound. Then there are the Missoula Floods to consider. http://en.wikipedia.org/wiki/Missoula_Floods
When flood waters went down the Mississippi into the Gulf there would have been temperature, density, and mixing going on.
These episodes of the release of massive, fresh, ice-cold waters into the oceans are candidates for some of these “flickers.”
It should be noted that the same “flickering” conditions are not seen in antarctic record. My guess is that ocean circulation patterns drive the ice age cycle, since they only started a few million years ago when the americas joined. The southern hemisphere being the engine and the north hemisphere is the overdrive!
I also find it interesting that all glacial cycles have ended after a significant accumulation of dust in the antarctic ice, albedo reversal anyone?
cheers
Off Topic
Someone had been reading too much Jules Verne
http://www.telegraph.co.uk/earth/environment/globalwarming/4839985/Scientists-to-stop-global-warming-with-100000-square-mile-sun-shade.html
It’s all in the oceans, the climate’s energy store.
Chris (21:42:09) :
Other than the fact that the end of the Younger Dryas period has some pretty wild fluctuations which dwarfed the 20th century’s 0.6C/century climate warming, there’s not a whole lot in this to draw research that is applicable to our current climate conditions.
What this research is leading towards is a better understanding of what happened between 12,900 and 11,700 years ago. With that understanding some clever geologist will hopefully be able to dream up an hypothesis of the physical causes which caused what happened.
And to think that all this brouhaha is over a 1°C change over a period of a century. It pales in comparison to a 10°C change in 20 years time. People are so gullible.
deadwood (23:43:41):
I believe you miss an important point. Natural climate variability can be huge. It has happened in the past, it will happen in the future and, in fact, we should be getting close to a period where climate again becomes volatile as we are reaching the end of this interglacial if the duration of past interglacial periods is any indication.
All of this recent fuss comes from some unfounded expectation that climate is stable. It isn’t. We are all in a panic over a 1 degree change over a period of 100 years. That is such a small amount of change that it gets lost in the noise of natural variability. The expectation that climate should be stable and that somehow humans can impact the global climate to a measurable degree is basically made up out of whole cloth. There are no actual observations that back it up.
Yes, humans can impact the LOCAL climate to a great degree though modification of local environments through such things as deforestation, urban development, farming, and other land use changes but even with that, we impact only the part that is land. Part of what skews our vision of climate is that the observations we take are only on land and tend to be near developed areas. If one were to place a grid of buoys across the ocean, you would get a much clearer vision of what “global climate” actually is.
Having a temperature recording device downwind of a major metroplex doesn’t measure “climate” any more than having one mounted on an iceberg would.
“The researchers interpreted the maxims, recurring every 10 years, as phases of strong glacier activity caused by temperature fluctuations and thus as warmer times.”
Now human beings have a natural tendency to round things to the number of digits on their hands.
I would be fascinated to know whether they actually meant every 10 years, or every 11 years.
Is the raw data available to allow a correlation with sun-spot cycles?
studies of New Zealand Glaciers and histroical proxies for advances and retreats show frequent substantial advances and retreats as recorded by Prof Colin Burrows based on biological materials found, and published in a study of Von Haast’s work in the southern alps.
rapid climate change was a common occurance on the last few thousand years.
So, we have to give the traditional argument which is used for any previous climatic fluctuations. It goes like this.
We start out asserting that climate has never fluctuated and so modern warming is unprecedented. We maintain this as long as we can, using Hockey Stick papers, pointing out that everyone who thinks different is funded by Exxon, even when they are not.
However at some point we have to admit that younger Dryas or MWP or RWP really did happen. At that point we quickly reverse, and make the following argument.
This, we say, actually strengthens our case, because it shows that climate sensitivity is greater than you the denialists realized. You should be more worried about CO2, not less, because the YD, MWP and RWP all show that tiny amounts of rise in temp will lead to catastrophic perturbations. Therefore we have to stop CO2 emissions now. As WorldWatch suggests, take them by 2050 to below the levels of 1850.
So you see, we conclude triumphantly, you are screwed either way (that is a technical term of logic which you may not know, google it). If there was the natural variation you think, it shows todays warming is not unprecedented and you should be afraid and take action. If it was, well then obviously you should also be afraid and take action. Either way you must do what we suggest or die.
All your climate are belong to us. Resistance is futile. Thank you for your attention.
Surely the more they find that there are fluctuatations in temperature and ice extent greater than ours and within smaller time scales or similar ones. The less anybody will be able to conclude that carbon dioxide is the culprit. The more that this is the case the more emphasis will have to be given to other factors being responsible for climate variation that they are given not enough credence whilst carbon dioxide is seems the current flaw.
singularly it is expected that the earth recovers from an ice age, recent MWP data only reinforces the analogy of cyclical climate. ie that climate would on recent data have fluctuated back anyway. ( It is the scale of these periods and others that were unrepresented or not talked about). tThe research above furthers the idea that change is predominantly natural. (and open to variation).
I’ve always told people that if we can get to understand this temperature change of 10°C in 20 years, then I believe we will understand the true cause and effect of the current temperature fluctuations, aka climate change.
It’s amazing how many people are not aware of this historical event and are genuinely shocked at the change. Education is the key!
Over the Christmas holidays I re-read some of Jean Grove’s tome Little Ice
Ages Ancient and Modern (second edition 2004). It is an outstanding
instance of first rate scholarship. It is very detailed and very
carefully reasoned with fascinating historical minutiae. A very
satisfying read.
One thing is striking.
It is that during times of global warming there are periods of intense
cold, sometimes for several years; and during the periods of global
cooling there were warm stretches, also for several years. At the
time, therefore, without the benefit of long time series and
sophisticated analytic methodologies, you can’t tell what is
happening. The time frames of the global events are in the hundreds
of years. From the point of view of TC Mits (the celebrated man in
the street), there is the experience of the last few years which might
have been bitterly cold [or unseasonably warm], but now it is awfully
hot [or freezing cold]. TC can’t see the pattern. TC is an
existentialist!
The point is, of course, that we can’t see a trend that might only be
visible over time frames of hundreds of years.
Based on the time series we have, we can see the warming that’s
gradually been happening since the end of the little ice age around
the 1850s. But even so, there’s been global cooling events and global
warming events in that interval. Based on theories about the Sun and
climate and the rotation of the earth and climate one can make
something of a case for global cooling to come. These theories are, I
would argue, vastly better than the IPCC/AWG ideas, but they are still
rather speculative because there is so much we don’t understand and
insufficient data.
One of the fascinating vignettes of which Jean Groves gives excellent accounts is the attitude of the ecclesiastical authorities.
The advance of glaciers begins to cause massive destruction of fields,
live stock , villages, towns and great loss of life. There are
devastating floods, all sorts of catastrophes.
The clergy tells the people that this is God’s punishment for their
sinful ways. Bishops and priests come -sometimes for substantial fees
– to perform exorcisms to stop the glaciers and hopefully cause their
retreat. If the exorcism didn’t work, this was because the people
weren’t devoted enough: they did not have strong enough faith in the
Bishop’s powers.
The Bishop of Geneva had remarkable powers as his exorcism ’caused’ a
terribly destructive glacier to stop and retreat in 1644 somewhere in
France. Some 20 to 30 years later, he (by then a different human
being: it was the role that gave him the powers) was called in by the
people of Chamoix to stop a massive glacier destroying them. Once
again the Bishop triumphed.
Richard
No No No, it’s not the oceans. It’s Man on land. After all the oceans and seas only account for a little more than 2/3rds of the Globe. Man on the other had has developed all the land, with the exception of the vast deserts, mountain ranges, the south pole, tundra areas and those large lake areas. I mean that must account for something like say, um, perhaps 10% of the remaining third that’s not oceans. So what is 10% of 30%?? Ok, maybe we’ve developed 20% of the landmass, that must be causing catastrophic boiling of the planet, right?!? That’s got to be a huge chunk of the planet, right?
But surely, 10ºC in 20 years; that’s not climate, it’s just weather, ha ha.
Could the Bishop of Geneva be persuaded to exorcise the AGW crowd?
Large, abrupt climate changes do not occur only during glacial periods, though they are most common then.
Google “8.2 KA event” or “preboreal oscillation” for two cases during the present interglacial and “Late Eemian Aridity Pulse” or “intra-eemian cold event” for two during the previous (Eemian) interglacial.
Paul S (02:05:59) :
“It’s amazing how many people are not aware of this historical event and are genuinely shocked at the change. Education is the key!”
Well said – though I think many in the paleoclimate and geological community have perhaps been very aware of the complexity of the climate system for some time. I think a key issue is that they have typically been following the more traditional reserved, methodical, objective scientific method with no want to grab a soapbox (in my view that is what a scientist SHOULD do).
Meanwhile, the crafty marketers and salesman with pseudo theories and dogmatic political and social views have astutely leveraged the pieces of “science” that fit their view of the world and have been allowed to command with ease with very loud voices from the soapbox/pulpit.
Until the media and politicans learn to listen to objective science and not the guys with placards on the street corner claiming “the end is nigh”, the same problems will remain.
RobJM (22:27:21) has made the salient point. These events are identified in the N hemispheric records (particularly high latitudes), whereas the S hemisphere response has been muted and on detailed inspection clearly responds in an antiphase manner with respect to changes in the N. hemisphere. This phenomenon has been increasingly well-charactierised and has got its own designation: “the bipolar see saw”.
The evidence supports a scenario in which thresholds of meltwater from Northern ice sheets are periodically passed and the large dilution of the high latitude waters dilutes the salty surface waters of the Atlantic conveyer circulation, effectively and rapidly switching it off for a period. The high Northern latitudes cool abruptly while the reduced transfer of heat to the high Northern latitudes results in warming of the Southern oceans. In other words this is not a global warming/cooling phenomenon but is a massive and rapid change in the heat distribution of the Earth. The hemispheres respond in antiphase with a see-saw redistribution of heat due to large and rapid changes in ocean currents.
rather topically, a paper that describes good evidence for this scenario was published yesterday in Nature:
S. Barker et al (2009) Interhemispheric Atlantic seesaw response during the last deglaciation Nature 457, 1097-1102
http://www.nature.com/nature/journal/v457/n7233/full/nature07770.html
The link in my post just above may not work. This one should:
http://www.nature.com/nature/journal/v457/n7233/abs/nature07770.html
The finding that the climate has been very unstable in the past is hardly reassuring for assessing the current situation. Clearly, ocean currents are very important for global and region climates. It is not surprising that ocean currents can change on a relatively fast time scale and that they also can remain stable for long periods.
I need to read this article. It seems to me this idea of previous rapid temp. fluctuations is a deal-breaker for the alarmists. Not only has there been much higher average temp. and CO2 in the past, but fluctuations have been just as rapid. The alarmists always say that the crisis lies in the rapidity of the change. If the T has changed so rapidly in the past, and there is still life on earth…no need for alarm. It will be interesting to see if someone can identify ecological effects of these historical rapid fluctuations.
What are they protesting in D.C. on March 2nd?
http://www.wetter24.de/de/home/wetter/profikarten/gfs_popup/archiv/NAmerica/t2m/2009022706/nothumb/on/81/ch/18cf07517c.html