Guest essay by Jim Steele
Director emeritus Sierra Nevada Field Campus, San Francisco State University and author of Landscapes & Cycles: An Environmentalist’s Journey to Climate Skepticism
Dansgaard Oeschger Events and the Arctic Iris Effect
During the last Ice Age, Greenland’s average temperatures dramatically rose on average every 1500 years by 10°C +/- 5°C in a just matter of one or two decades, and then more gradually cooled as illustrated in Figure 1 below (8 of the 25 D-O events are numbered in red on upper graph; from Ahn 2008). These extreme temperature fluctuations between cold “stadials” that lasted about a thousand years and warm “interstadials” lasting decades are dubbed Dansgaard-Oeschger events (D-O events). These rapid temperature fluctuations not only rivaled the 100,000‑year fluctuations between maximum glacial cold and warm interglacial temperatures but D‑O warm events coincided with expanding Eurasian forests (Sánchez Goñi 2008, Jimenez-Moreno 2009), northward shifts of subtropical currents along the California coast (Hendy 2000), and shifts in belts of precipitation in northern South America (Peterson 2001).
Just 25 years ago most climate researchers were hesitant to accept initial Greenland ice core evidence suggesting such abrupt D‑O warming events (Dansgaard 1985). But as other Greenland ice cores verified their reality, it was clear that the only mechanism realistically capable of producing such abrupt warming was the sudden removal of insulating sea ice that allowed ventilation of heat previously stored in the Arctic as Dansgaard (1985) had first proposed. Still that begged the question ‘what caused the sudden loss of insulating sea ice’?
Changes in CO2 concentration are unlikely to have had much impact on D‑O events (3rd graph from the top in Figure 1). CO2 concentrations did fluctuate by about 20 ppm during a third of the D-O events (red numbers), but could contribute directly to no more than 0.4°C to only 30% of the largest warming events. In contrast during 68% of the other D-O events (not numbered), abrupt warming occurred while CO2 was declining. Thus rapid warming and cooling seems independent of any CO2 forcing.
Abrupt D‑O warming and cooling suggested to researchers (Broecker 1985) that the Atlantic Meridonal Overturning Circulation (AMOC) turned “on” and “off”. Based on the misleading belief in the existence of a simplistic “ocean conveyor belt” (Wunsch 2007), researchers incorrectly interpreted a lack of deep-water formation as evidence of a lack of warm water flowing into the Arctic. However based on increasing proxy evidence (Rasmussen 2004, Ezat 2014), it is now understood that the inflow of warm Atlantic Waters never “shut off” but continued to enter the Arctic and warmed the subsurface layers. As seen in Figure 2 (from Itkin 2015) the upper layer of fresh water and the halocline insulate the warm Atlantic water from the overlying ice. Together the thick sea ice and polar mixed layer simply “turn off“ any heat flux from the ocean to the air, thus maintaining cold stadial air temperatures. Furthermore if the salty Atlantic Water cannot be cooled by the cold Arctic air, then North Atlantic Deep Water is shut off as well.
Although climate models have failed to simulate D‑O events, models were manipulated to shut off poleward heat transport by prescribing ad hoc floods of freshwater. As long as freshwater “hosing” was applied, the models prevented the cooling and sinking of North Atlantic waters, which shutoff the deep water formation and thus “ocean conveyor belt” resulting in contrived cooling. That interpretation became the reigning paradigm and researchers began searching for evidence of a flood of freshwater, while nearly every model engaged in “hosing” experiments to explain abrupt climate change. But evidence of the required freshwater flooding has yet to be found and a growing wealth of proxy evidence suggested there was as much freshwater during stadials as there was during interstadials. Even the notion of freshwater floods from an armada of melting icebergs was not consistent with the timing of D‑O events (Barker 2015). Freshwater shutdown of the Atlantic Meridonal Overturning Circulation is most likely just a figment of the models’ configuration.
Other researchers suggested drivers of past and present rapid temperature change were likely to be very similar (Bond 2001, 2005), and recent findings are now supporting that notion. More recent explanatory hypotheses for D‑O events are gaining widespread critical acceptance and do not require any massive floods of freshwater nor a shutdown of the AMOC (Rasmussen 2004, Li 2010, Peterson 2013, Dokken 2013, Hewitt 2015). When sea ice prevents heat ventilation, the inflow of warm and dense Atlantic Waters continues to store heat in the subsurface layers. As heat accumulated, the warm Atlantic Waters became more buoyant, upwelled and melted the insulating ice cover. The loss of an insulating ice cover “turns on” the heat flux causing a dramatic rise in surface temperatures to begin the D‑O interstadial. Although details of hypothesized D‑O mechanisms vary slightly, they all agree on the ability of growing and shrinking sea ice to affect the heating and cooling of the northern hemisphere. I refer to this sea ice control of heat ventilation the Arctic Iris Effect.
The signature of an Arctic Iris Effect is the opposing temperature trends in the ocean versus atmosphere: when ice is removed, warmer air temperatures coincide with cooler ocean temperatures. When ice returns cooler air temperatures coincide with a warmer ocean. The thicker the sea ice, as during the last Ice Age, the longer the period between ventilations such as the D‑O events. Thick sea ice is less sensitive to small changes in insolation and/or natural variations of inflowing Atlantic Waters. As discussed in Hewitt 2015 decreases in the freshwater layer that separates sea ice from the warm Atlantic Waters are also likely critical contributors to D‑O events. For example as the Laurentide Ice Sheet grew, sea levels fell shutting of the inflow of fresher Pacific water through the Bering Strait, coinciding with an increased frequency between D‑O events from 8 thousand to 1.5 thousand years.
Peterson 2013 suggested that in addition to thick multiyear sea ice, ice shelves were critical for maintaining the longer cold stadials by better resisting small oscillations of increased inflow of Atlantic Water. Likewise with the current reduction of Arctic ice shelves and reduced multiyear sea ice during our present interglacial, much smaller changes in insolation and/or Atlantic inflow could more easily initiate ventilation events. With smaller time spans between each ventilation event, less heat accumulates and warm spikes are more muted (1°C to 2°C) compared to 10°C +/- 5°C during the D‑O interstadials. Over the past 6000 years, decades of rapid ice loss resulted in 2°C to 6°C air temperatures warmer than today quickly followed by centuries of colder temperatures and more sea ice (Mudie 2005).
The 20th century ventilation events produced only a 1°C to 2°C increase yet the signature of the Arctic Iris Effect is still observed. In 2001, Dr. Vinje of the Norwegian Polar Institute reported on the opposing temperature effects as ice retreated in the Nordic Seas. Between 1850 and 1900 there was a rapid warming of 0.5°C ocean temperatures between 1850 and 1900 with very little change in atmospheric temperature. Then they reported, “The warming event during the first decades of this century is characterized by a significant decrease in the Nordic Seas’ April ice extent, an increase of ~3°C in the Arctic surface winter temperature, averaged over the circumpolar zone between 72.5° and 87.5°N, and an increase in the Spitsbergen mean winter temperature of as much ~9°C. During this warming event the temperature in the ocean was lower than normal.
An increasing preponderance of positive ice extent anomalies, with an optimum in the 1960s, is observed during the period 1949–66, concurrent with a cooling in the circumpolar zone of ~1°C, a fall in the Spitsbergen mean winter temperature of ~3°C, and an increase in the mean winter air pressure in the western Barents Sea of ~6 hPa. During this cooling event the temperature in the ocean was higher than normal.” [Emphasis Added]
Similarly the most recent Arctic warming again reveals the fingerprint of the Arctic Iris Effect. There was no atmospheric warming in Arctic when there was an insulating cover of multiyear sea ice. Measurements between 1950 and 1990 reported a cooling Arctic atmosphere prompting researchers to publish, “Absence Of Evidence For Greenhouse Warming Over The Arctic Ocean In The Past 40 Years”. They concluded, “This discrepancy suggests that present climate models do not adequately incorporate the physical processes that affect the Polar Regions.”
Abruptly rapid Arctic warming began in the 1990s with an initial loss and thinning of Arctic sea ice when the Arctic Oscillation’s shifted wind directions and below‑freezing winds from Siberia pushed multiyear ice out of the Arctic. Rigor 2002 correctly pointed out, “One could ask, did the warming of SAT [Surface Air Temperatures] act to thin and decrease the area of sea ice, or did the thinner and less expansive area of sea ice allow more heat to flux from the ocean to warm the atmosphere?” They concluded, “Intuitively, one might have expected the warming trends in SAT to cause the thinning of sea ice, but the results presented in this study imply the inverse causality; that is, that the thinning ice has warmed SAT by increasing the heat flux from the ocean.” [Emphasis Added] That conclusion has been further supported by recent analyses of ocean heat content by Wunsch and Heimbach 2014, two of the world’s premiere ocean scientists from Harvard and MIT. They reported the deep oceans are cooling suggesting the oceans and atmosphere are still not in equilibrium and oceans are still ventilating heat from below 2000 meters that was stored long ago. Also in their map illustrating changes in the upper 700 meters of the world’s oceans (their Figure shown below), we see the entire Arctic Ocean has cooled between 1993 and 2011, as would be expected from the Arctic Iris Effect. Keep in mind that the warm layer of Atlantic water on average occupies the depths between 100 and 900 meters.
The Earth’s Energy Budget
The Earth’s energy budget depends on a balance between absorbed solar radiation and outgoing infrared radiation. While some atmospheric scientists have focused on a possible energy imbalance created by 2 watts/m2 generated by rising CO2, widespread regions of the ocean absorb and ventilate over 200 watts/m2 of heat each year. As illustrated in Figure 3 (from Liang 2015), the oceans absorb heat (blue shades, in watts/m2) along the equator and over the upwelling zones along the continents’ west coast. Intense tropical insolation and evaporation creates warm dense salty waters that sink below the surface storing heat at depth. Changes in insolation, tropical cloud cover, and ocean oscillations like El Nino affect how much heat the oceans absorb or ventilate. Excess heat absorbed in the tropics is transported poleward. To gain a proper perspective on the importance of heat transport from the tropics to the poles, currently Polar Regions average 30°C colder than the equator. If there was no heat transport, the poles would be 110°C colder than the tropics (Gill 1982, Lozier 2012).
On average, the greatest ventilation of ocean heat happens where heat transportation is most concentrated: along the east coast of Asia over the Kuroshio Current and along east coast of North America along the Gulf Stream. Additionally large amounts of heat are also ventilated over Arctic’s Nordic Seas region, a focal point of the Arctic Iris Effect. A comparison of the temperature changes at varying ice core locations from southeast to northwest Greenland, points to this North Atlantic region as the main source of heat ventilated during each D‑O event (Buizert 2014). Likewise modeling work (Li 2010) shows that reduced ice extent in this region exerts the greatest impact on Greenland temperatures and snow accumulation rates. And it is in this same region that Vinje 2001 reports the greatest reduction in ice cover coinciding with the rapid changes in Greenland’s instrumental data. While CO2 warming would predict the greatest rate of Greenland warming in the most recent decades, the Arctic Iris effect would predict a greater rate of warming in the 1920s because thick sea ice from the Little Ice Age would have caused a greater accumulation of heat. Indeed Chylek 2005 reported, “the rate of warming in 1920–1930 was about 50% higher than that in 1995–2005.”
Climate Model Shortcomings
In 2008 leading climate scientists at the University of East Anglia’s Climatic Research Unit published Attribution Of Polar Warming To Human Influence. As seen in their graph below, their models completely failed to account for the 2°C Arctic warming event observed from 1920 to the 1940s, (illustrated by the black line labeled “Obs” for observed). This was a warming event that climate scientists called “the most spectacular event of the century” (Bengtsson 2004). Their modeled results of natural climate change grossly underestimated the 40s peak warming by ~0.8° C, and simulated a flat temperature trend throughout the 20th century as illustrated by the blue line labeled “NAT” for natural. More striking when the models added CO2 and sulfates, the modeled results (red line labeled all) cooled the observed warming event further. Despite their failure to model natural events they concluded, “We find that the observed changes in Arctic and Antarctic temperatures are not consistent with internal climate variability or natural climate drivers alone, and are directly attributable to human influence.”
However their results only demonstrated that their models failed to account for natural climate change, the Arctic Iris Effect and ventilation of ocean heat during the 1930s and 40s. By all accounts the recent warming of the 1990s and 2000 was likewise a ventilation event that also cooled the upper layers of the Arctic Ocean. The failure to model ventilated heat events led to incorrectly attributing that warming to increasing concentrations of CO2. That failed modeling further led to explanations that reduced albedo effect allowed greater absorption of summer insolation, warming the Arctic Ocean and amplifying temperatures. But observations show the ocean has cooled. Like the 40s peak, it is likely 1990s/2000s ventilation similarly contributed a minimum of ~0.8° C to the recent rise in Arctic temperatures, and probably much more as the greater reduction in sea ice extent has allowed for much more ventilation.
If climates models are correctly configured, they should be able to reproduce both D‑O events and the 1940s ventilation events. We don’t expect model perfection, but turning a massive warming event into a below average cool period is unacceptable. When the modeling community simulates the Arctic Iris Effect more accurately, only then will their attribution of polar warming to human vs. natural factors be trustworthy! Until then all the natural factors – lower insolation with reduced Atlantic inflow, cooler oceans, negative North Atlantic Oscillation, and increasing multiyear ice – all suggest the current ventilation event will soon come to a close. But the return to cooler surface temperatures and more sea ice has always been much slower than the abrupt warming. When sea ice is reduced, the winds are suddenly able to mix the ocean’s fresher upper layer with the saltier lower Atlantic Waters disrupting the halocline. But once the halocline and upper layers of freshwater are restored, the cooling is rapid.
In contrast, those who attribute Arctic warming to rising CO2 predict a continued sea ice death spiral. And those who also suggest global warming is slowing down the poleward flow of Atlantic Water, also argue CO2 warming will offset any cooling effects of that slowdown (Rhamstorf and Mann 2015). Within the next 2 decades, nature should demonstrate how well these competing models and competing interpretations extrapolate into the future. Good scientists always embrace 2 or more working hypotheses. But with the politicization of science, I sincerely doubt President Obama is travelling to the Arctic to advise the world to be good scientists!
Jim Steele is author of Landscapes & Cycles: An Environmentalist’s Journey to Climate Skepticism
Models and the observation temperature
Natural variability and the observation temperature
http://www.vukcevic.talktalk.net/AT-GMF.gif
more info HERE
“Climate scientists are better prepared than ever with prediction models and data on El Nino patterns, but the impact of this El Nino in the northern hemisphere is hard to forecast because there is also an Arctic warming effect at work on the Atlantic JETSTREAM current.
‘The truth is we don’t know what will happen. Will the two patterns reinforce each other? Will they cancel each other? Are they going to act in sequence? Are they going to be regional? We really don’t know,’ said David Carlson, the director of the World Climate Research Programme.”
http://www.dailymail.co.uk/sciencetech/article-3218747/Look-Forecasters-warn-El-Nino-strongest-recorded-January.html
Changes in temperature over the polar circle depend on solar activity.
http://cosmicrays.oulu.fi/webform/query.cgi?startday=01&startmonth=09&startyear=2014&starttime=00%3A00&endday=01&endmonth=09&endyear=2015&endtime=00%3A00&resolution=Automatic+choice&picture=on
This is a great article and the sea ice thickness as a modulator(through the ventilation process of warm sub-surface ocean water to atmosphere) of the atmospheric temperatures in the high latitudes makes sense.
This is as good an explanation, as I have come across for D/O events.
Both from article. It looks like the article ‘s conclusion is that a threshold of accumulated sub- surface warm Atlantic water must be reached which then is able to start to overcome the sea ice thickness. This in turn allows heat to escape from oceans to atmosphere. This is quite good.
Although details of hypothesized D‑O mechanisms vary slightly, they all agree on the ability of growing and shrinking sea ice to affect the heating and cooling of the northern hemisphere. I refer to this sea ice control of heat ventilation the Arctic Iris Effect.
Together the thick sea ice and polar mixed layer simply “turn off“ any heat flux from the ocean to the air, thus maintaining cold stadial air temperatures. Furthermore if the salty Atlantic
l have a hard time believing that the swings in temp in Greenland during the ice age were down changes in the ocean currents without the weather allowing it to happened. Because these changes happened often and they were fast. l think its more likely that it was down to the weather patterns over the northern Atlantic during the ice age. What l believed happened during the ice age was that the weather patterns become bigger and much slower moving.lf this was so then the large swings in temp in Greenland during the ice age l believe were due to changes in the high pressure weather pattern that l believed often settled between Greenland and NW Russia. Because at times it was likely that the highs would settled more over towards Greenland then at other times. When this happened then Greenland would have been on the “warm side of the high with warm air pushing up over Greenland from the mid Atlantic. While over northern europe low pressure would have been able to move in bringing cold and heavy snowfall across northern europe and a increase in rainfall in southern europe. So with this increased rainfall it allowed the forests in southern europe to extend.
The Arctic Iris Effect does not exclude those changes in weather systems andthe jet stream and those effects are clearly seen today. For example the Arctic Oscillation shifted the winds that removed thick ice from the Arctic allowing heat to ventilate. Warmer waters ventilating in the Barents Sea create low pressure system that creates greater inflow of atmospheric and oceanic heat. Indeed the glacial ice sheets are believed to have forced the jet stream further south and minimize poleward heat flow. But by themselves those weather events can not explain the 10C abrupt warming or the subsequent abrupt cooling. But all those natural weather dynamics work hand and hand with the Iris Effect.
Jim its because these swings were so abrupt is what makes my think it was down the the weather.
For example look what happened in the winters of 2009/10 and 2010/11, when there was blocking over the Greenland/ northern Atlantic area. lt brought bitter cold to Europe but record warmth in the NE Canada area.
taxed I am in full agreement that blocking high pressure systems cause abrupt extreme weather. Again the Iris Effect does not exclude those weather effects.
Agreed.
Top down solar effects causing a bottom up oceanic response and both involving the proposed Iris Effect from changing Arctic ice concentrations.
THOUGHTS AND QUESTIONS
The trigger point for climatic changes is the North Atlantic area of the globe as this article demonstrates. That is certain. Another possible trigger point could be Antarctic Sea Ice extent? Is there a SEA ICE threshold down in that part of the globe?
In the large climatic picture it is still ocean/land arrangements, geo magnetic strength, Milankovitch Cycles , with solar variability superimposed upon these slow moving gradual cycles(which is moderated by those three moving gradual cycles) that bring the earth toward or away from a glacial /inter- glacial period, in my opinion.
Then depending on the ice dynamic, initial state of the climate this makes the abrupt climatic changes more dramatic or less dramatic as this article shows.
I think this is the correct path and will be proven to be so. I think how severe the quote ice age may or may not be with D/O events superimposed upon the ice age itself, is again depended upon how land/ocean arrangements, Milankovitch Cycles, geo magnetic field strength combined with solar variability phase with one another.
In the big picture since the Holocene Optimum we are still in an overall cooling trend due to the above climate parameters.
What is challenging for me is to now try to reconcile the lower solar insolation factor(post 2005) as a consequence of what is mentioned above to the resultant sea ice growth or lack of it in the Arctic , with a amplified climatic result being the result of the sea ice dynamic changing.
I for one will be monitoring even more closely the Arctic Sea Ice Extent going forward and see how this ties into prolonged solar minimum effects ,despite the fact as the article says until recently or maybe still the Arctic Ocean has been cooling keeping the ventilation process intact raising the Arctic temperatures.
The other item I want to monitor is the oceanic temperatures in general and atmospheric circulation changes as we move forward into this decade. I want to see how this contrast to very prolonged minimum solar conditions and how it plays out.
Also the wild cards have to be taken into consideration which is a super volcanic eruption or extra terrestrial impact which can throw things upside down in the climate world and must happen from time to time in earth’s historical past.
As far as ENSO,PDO,AMO, run of the mill Volcanic Activity they are transient climatic factors in my opinion and just refine the present climatic regime the climate may be in.
As far as the tropic thermostat effect keeping the climate stable ,stable is in the eyes of the beholder and if one wants to say the climate is stable because it is bounded by an upper and lower temperature range that is fine, but on the other hand there is nothing stable about the climate going from a glacial state to an inter-glacial state or having D/O events superimposed upon those climatic states and those D/O events being very dramatic during glacial times.
Salvatore wrote, “What is challenging for me is to now try to reconcile the lower solar insolation factor(post 2005) as a consequence of what is mentioned above to the resultant sea ice growth or lack of it in the Arctic , with a amplified climatic result being the result of the sea ice dynamic changing.”
If changes in insolation reduce the inflow of warm Atlantic Waters as evidenced during the Little Ice Age, it suggests the there will be a trend to cooler subsurface waters in the Arctic. However the connection with insolation must include lag periods. Warm water is pumped into the subtropical gyre and may have a residency of about 20 years. LIke a capacitor it stores and releases warm water years after the source has cooled. Similarly NAO can determine both the spin up of the gyres and the width of the sub polar gyre and how much warm water it allows to enter the Arctic. Furthermore the reduction of the halocline due to wind mixing when the loss of sea ice re-connects the surface winds with subsurface waters, requires time to be reinstated.
So I think looking for any linear correlation with insolation over relatively short time spans of less than 50 years will never present significant statistical correlations.However on longer time scale that reduced insolation that began after 2005 predicts less warm water inflow and recovering sea ice. I suspect this will be obvious by 2030, but it may take a few more decades. On the other hand when insolation dropped after its 1950s peak, sea ice recovered substantially within a decade. But the background state of how much thick multiyear sea ice is present also determines how quickly the Arctic will respond, so due to progressive 20th century thinning, it will likely take a tad longer to recover now than it did in the 1960s.
Thanks for the input Jim.
Your article is the best explanation thus far for D/O events.
Salvatore
Here is an explanation for some of the D-O events
http://onlinelibrary.wiley.com/doi/10.1029/1999PA000468/pdf
Agreed, but note that insolation drops due to more clouds and not changes in raw TSI.
I find the Svensmark idea, involving cosmic rays,unconvincing and much prefer increased cloudiness from more meriodional jet stream tracks when the sun is less active.
Salvatore Del Prete
THOUGHTS AND QUESTIONS
The trigger point for climatic changes is the North Atlantic area of the globe as this article demonstrates.
[IF THE TRIGGER POINT FOR CLIMATIC CHANGES LIE IN THE NORHT ATLANTIC, THEN THERE SHOULD BE A LAG EFFECT IN THE SOUTHERN HEMISPHERE–BUT THERE ISN’T–THE CLIMATE CHANGES ARE SYNCHRONOUS IN BOTH HEMISPHERES. THAT’S WHY THIS EFFECT DOESNT’ EXPLAIN D/O EVENTS]
That is certain. Another possible trigger point could be Antarctic Sea Ice extent? Is there a SEA ICE threshold down in that part of the globe?
In the large climatic picture it is still ocean/land arrangements, geo magnetic strength, Milankovitch Cycles , with solar variability superimposed upon these slow moving gradual cycles(which is moderated by those three moving gradual cycles) that bring the earth toward or away from a glacial /inter- glacial period, in my opinion.
Then depending on the ice dynamic, initial state of the climate this makes the abrupt climatic changes more dramatic or less dramatic as this article shows.
I think this is the correct path and will be proven to be so. I think how severe the quote ice age may or may not be with D/O events superimposed upon the ice age itself, is again depended upon how land/ocean arrangements, Milankovitch Cycles, geo magnetic field strength combined with solar variability phase with one another.
[THIS IS WHAT BROECKER TRIED TO DO BUT IT DOESN’T WORK BECAUSE OF THE SYNCHRONOUS CLIMATE CHANGES IN BOTH HEMISPHERES]
In the big picture since the Holocene Optimum we are still in an overall cooling trend due to the above climate parameters.
What is challenging for me is to now try to reconcile the lower solar insolation factor(post 2005) as a consequence of what is mentioned above to the resultant sea ice growth or lack of it in the Arctic , with a amplified climatic result being the result of the sea ice dynamic changing.
I for one will be monitoring even more closely the Arctic Sea Ice Extent going forward and see how this ties into prolonged solar minimum effects ,despite the fact as the article says until recently or maybe still the Arctic Ocean has been cooling keeping the ventilation process intact raising the Arctic temperatures.
The other item I want to monitor is the oceanic temperatures in general and atmospheric circulation changes as we move forward into this decade. I want to see how this contrast to very prolonged minimum solar conditions and how it plays out.
Also the wild cards have to be taken into consideration which is a super volcanic eruption or extra terrestrial impact which can throw things upside down in the climate world and must happen from time to time in earth’s historical past.
[VOLCANIC ERUPTIONS ARE NOT A FACTOR BECAUSE THEIR EFFECT LAST ONLY A COUPE OF YEARS]
As far as ENSO,PDO,AMO, run of the mill Volcanic Activity they are transient climatic factors in my opinion and just refine the present climatic regime the climate may be in.
As far as the tropic thermostat effect keeping the climate stable ,stable is in the eyes of the beholder and if one wants to say the climate is stable because it is bounded by an upper and lower temperature range that is fine, but on the other hand there is nothing stable about the climate going from a glacial state to an inter-glacial state or having D/O events superimposed upon those climatic states and those D/O events being very dramatic during glacial times.
“By all accounts the recent warming of the 1990s and 2000 was likewise a ventilation event that also cooled the upper layers of the Arctic Ocean. The failure to model ventilated heat events led to incorrectly attributing that warming to increasing concentrations of CO2.”
The accelerated warming of the AMO and Arctic from the mid 1990’s was due to increasing negative NAO episodes, caused by the decline in solar plasma strength since then.
http://snag.gy/HxdKY.jpg
Nuclear warheads may be useful ordinance in the future for destroying ice shelves threatening to disrupt the AMOC.
Persisting in pedant mode, you mean “ordnance”.
Correct thank you.
Sturgis, you’re slipping. How could you miss “meridonal” (more than once) in the post? I hereby challenge your claim to Pedant in Chief…
: > )
Juan,
You may claim the crown, but IMO “meridonal” was a typo, lacking an “i”, while “ordinance”, with an extra “i”, being another word, wasn’t.
Quality thinking Jim, and the reader’s comments also, thanks both.
A few things for all of you to ponder:
1. The abrupt termination of the late Pleistocene and the YD proved that you can go from full glacial to interglacial conditions, back into full glacial conditions, and finally the abrupt end of the Pleistocene in very short periods of time. These abrupt swings in glacial/interglacial conditions are far too rapid to have been caused by Milankovitch orbital changes and effectively spelled the demise of the Milankovitch theory. If you can produce abrupt full glacial/interglacial conditions without Milankovitch, then there must be some other cause of glaciations and interglaciations.
2. Broecker attempt to explain these abrupt climate changes with interruptions to his global ocean conveyor belt system, but his explanation requires a lag in glacial/nonglacial conditions between the Northern and Southern Hemispheres. New isotope dates on the YD, Inter-allerod cool period, and preceding cold period show very clearly that even short term climate changes were highly synchronous in both hemispheres. The ‘iris effect’ suffers from the same problem.
3. 10Be and 14C variations are a measure of cosmic radiation, which show interesting correlations with climate changes, suggesting possible cause-and-effect relationships. These relationships need additional study, but the correlation of multiple events is too good to be simply random.
4. Whatever is the cause of the D/O events, it must be capable of producing what D&O called the ‘flickering’ of late Pleistocene climate changes. So far we have no good explanation of this phenomena, but we do know what it can’t be.
When you say highly synchronous, what is your time constraint decades, centuries?
Jim — it depends on the dating method. For 14C-dated moraines it’s +/- 40 -80 years (for 19 ka) and for 10Be it’s about 0.2-0.4 ka (for -13 ka)
That range of uncertainty is why I ask, The 200 to 400 year uncertainty in 10Be can be used as proof of lag effects and a see saw effect OR a more synchronous behavior. I agree with you that the ultimate driver is most likely associated with solar effects but there are likely lag effects that determine how that solar forcing is detected.I do suggest there is a lag effect between the poles due to the way thick multiyear ice in the Arctic and thinner annual Antarctic ice respond to poleward transport of heat. While you see the Iris Effect as contrary to a synchronous driver, I am suggesting the Iris Effect supports a synchronous behavior while also explaining a perceived 200 year lag suggested by the recent WAIS paper, because it all happens within the bounds of dating uncertainty.
Don, How would you explain the difference in the Antarctic and Arctic warming presented in the graph from Ahn 2008 which I used as my first figure and it commonly agreed upon as being representative of the observed changes. It suggests a steady warming in the Antarctic but in the Arctic that warming trend has cyclic warming and cooling events superimposed. I suggest the Iris Effect explains the rapid changes in the B_A and D and YD events experienced mostly in the Arctic that are superimposed on a synchronous warming.
http://wattsupwiththat.files.wordpress.com/2015/09/clip_image002_thumb.jpg?w=598&h=403
Don I am not sure why you argue synchronous behavior between the poles is a problem for the Arctic Iris effect. Te new WAIS paper suggests a stong synchronous behavior with the Antarctic lagging the Arctic by about 208 years. However if you examine their idealized relationship as their illustration suggests, and consider the Arctic Iris effect, the changes are even more synchronous
http://www.nature.com/nature/journal/v520/n7549/images/520630a-f1.jpg
The gradual warming in the Antarctic is readily observed because the thin annual ice does not isolate heat or cause it to accumulate. The Arctic expresses a more “digital” on off mode suddenly warming and suddenly cooling as predicted by an iris effect. What the WAIS team calls a lag effect, can easily be seen as a sudden warming in the Arctic that began in synchrony with Antarctic warming but was not observed until the heat was ventilated.
“The 200 to 400 year uncertainty in 10Be can be used as proof of lag effects and a see saw effect OR a more synchronous behavior.” YOU LOST ME HERE–HOW DOES 200-400 YEAR UNCERTAINTY HAVE ANYTHING TO DO WITH LAG EFFECTS AND SEE-SAW EFFECT? THE 10BE POSSIBLE RANGE OF VALUES DOEN’T PROVE ANYTHING–ALL IT MIGHT DO IS LEAVE THE QUESTION OPEN. THE SEVERAL HUNDRED TO 1000 YEARS LAG TIME MAKES A PRETTY BIG TARGET TO HIT. LOTS OF 14C DATES IN BOTH HEMISPHERES ON 10BE-DATED MORAINES ALSO HAVE 14C AGES THAT PROVIDE BETTER ACCURACY AND CONFIRM THAT THE MORAINES ARE SYNCHRONOUS.
.I do suggest there is a lag effect between the poles due to the way thick multiyear ice in the Arctic and thinner annual Antarctic ice respond to poleward transport of heat. I DON’T SEE HOW THAT COULD IN ANY WAY SHOW THAT THE 10BE AND 14C DATES ARE WRONG.
While you see the Iris Effect as contrary to a synchronous driver, I am suggesting the Iris Effect supports a synchronous behavior while also explaining a perceived 200 year lag suggested by the recent WAIS paper, because it all happens within the bounds of dating uncertainty. YOU LOST ME HERE–EVEN IF THE IRIS EFFECT WERE TRUE, YOU ARE STILL LEFT WITH THE 200-1000 YEAR LAG IN THE S. HEMISPHERE. THE IRIS EFFECT CERTAINLY DOESN’T DEMONSTRATE SYNCHRONOUS BEHAVIOR AND THERE IS NO 200 YEAR LAG.
Don Easterbrook,
A question for you.
It appears that you mean ’abrupt’ change from interglacial conditions to full glacial conditions only in context of a minimum approximate geologic timescale of at least a few thousands of years. So, my question is, looking at a period of the next decade up to the next century, if we were right now in a beginning part of an ’abrupt’ change from our current interglacial towards the next full glacial period then what change in temp would we expect in the next 10 years to next 100 years? Over the next 10 to 100 years, would the ‘abrupt’ change appear ‘abrupt’ to us while it was happening or would it only appear ‘abrupt’ in a ~1000+ year period?
I would appreciate putting in context what such ‘abrupt’ change would look like to us on the short timescale of 10 to 100 years. I wonder if the ’abrupt’ it would look significant to us over that non-geological timespan.
John
WHAT WE KNOW IS THAT WARMING AND COOLING EVENTS OF ~20 F OCCURRED IN A CENTURY OR LESS, ENOUGH TO PLUNGE THE EARTH INTO FULL GLACIAL OR INTERGLAIAL MODE.
Interglacial mode doesn’t occur until ice sheet melt is well under way.
IMO you mean interstadial rather than interglacial. There aren’t interglacials until most of the NH ice sheets have melted. Then, a few thousand years at most into interglacials, they melt back about to present limits, ie mainly just on Greenland, with patches here and there in the Arctic.
Don J. Easterbrook,
Thanks for responding.
Are you aware of anyone in your field who has a hypothesis that we are currently in a period of a swing toward glacial conditions of a D/O-like event? I am curious about what would be the claimed evidence supporting such a person’s hypothesis if there is anyone with such a hypothesis? NOTE: I am not suggesting there is anyone with such hypothesis or that there is any claimed evidence, just trying to understand the state of inquiry.
John
Gloria Swansong,
I do not know which person you are addressing, if anyone.
Does using a pseudonym in this dialog create a self-perceived tactic? NOTE: I ask only because of my interest for many years on the problems of an epistemological nature created through anonymous commenting.
John
Don Easterbrook says:
I disagree with this.
1. This rapid changes do not have enough time to re-build the ice sheets, so you are assuming that it was back to full glacial conditions just based on a proxy for temperature. Have you checked sea levels to see if they went back down to -120 m during the YD? It did become cold but it did not become full glacial.
2. You are making the common mistake of assuming that Greenland Ice Cores reflect a global situation. They do not. While full glacial conditions affect the entire planet very drastically, the YD affected drastically the Arctic region, importantly the Northern Hemisphere areas around it, noticeably South East Asia, barely South America and was completely absent in Australia and other regions of the Southern Hemisphere.
As the saying goes, the rumors of the demise of the Milankovitch theory have been greatly exaggerated.
1. This rapid changes do not have enough time to re-build the ice sheets, so you are assuming that it was back to full glacial conditions just based on a proxy for temperature. Have you checked sea levels to see if they went back down to -120 m during the YD? It did become cold but it did not become full glacial.
[OF COURSE THE ICE SHEETS DIDN’T REBUILD! YOU MISS THE POINT–WE’RE TALKING ABOUT RETURN TO GLACIAL CONDITIONS–IT TAKES TIMETO BUILD ICE SHEETS.]
2. You are making the common mistake of assuming that Greenland Ice Cores reflect a global situation. They do not.
[YOU’RE DEAD WRONG HERE–THE CORRELATION BETWEEN GLOBAL GLACIATIONS AND THE ICE CORE TEMPS ARE EXCELLENT. THE MAGNITUDE OF THE TEMP CHANES VARIES WITH LATIUTDE, BUT THE TIMING OF CHANGES IN THE CORES WITH PERIODS OF MORAINE BUILDING IS ALMOST EXACT]
While full glacial conditions affect the entire planet very drastically, the YD affected drastically the Arctic region, importantly the Northern Hemisphere areas around it, noticeably South East Asia, barely South America and was completely absent in Australia and other regions of the Southern Hemisphere.
[YOU’RE ALSO DEAD WRONG HERE–THE YD WAS NOT JUST REGIONAL, IT WAS GLOBAL (AS SHOWN BY MORE THAN 3,000 PUBLICATIONS]
As the saying goes, the rumors of the demise of the Milankovitch theory have been greatly exaggerated.
[AS THE SAYING GOES–SYNCHRONEITY OF GLACIATIONS IN BOTH HEMISPHERES IS THE FLY IN THE MILANKOVITCH OINTMENT]
Don,
Synchronicity, such as it is, isn’t a fly in the ointment. There is no reason to suppose it is any such thing.
Don,
Nothing you say has the least affect on the fact of Milankovitch Cycles, especially on the formation of NH ice sheets.
Abrupt switches are visible in all glacial terminations. They result from the effect of meltwater pulses. The melting behind these rapid changes is driven by orbital and rotational mechanics, but the ups and downs during deglaciations need not be caused primarily directly by Milankovitch parameters.
Neither do D/O events and Bond cycles in any way invalidate Milankovitch mechanics on insolation, hence on glaciation and deglaciation.
OF COURSE THEY DO! THE ABRUPTNESS OF D/O EVENTS PROVE THAT THEY CAN’T BE CAUSED BY MILANKOVITCH CYCLES AND THE MAGNITUDE OF D/O EVENTS SHOWS THAT FULL GLACIAL CONDITIONS CAN BE CREATED IN A CENTURY OR TWO
[We request you avoid all capital letters. .mod]
Don,
No, of course they don’t show any such thing.
Milankovitch cycles are responsible for the big swings between glacial and interglacial conditions.
D/O events occur within glacial conditions, so need not be caused by Milankovitch cycles. I don’t see why this fact is hard to grasp.
Interglacial conditions do not occur within glacials, even during interstadials. This should be obvious, since the ice sheets are still largely intact then. Interglacial conditions means the spread of forests and grasslands into previously glaciated areas. Clearly, this can’t happen with the ice sheets still there, and periglacial conditions around their edges. The periglacial steppe-tundra biome doesn’t exist once interglacials are established.
By interglacial conditions, do you mean temperatures rather than ecosystems? If so, that’s still not the case.
Asserting your easily shown false conjecture in all caps doesn’t make your case more persuasive.
Thanks, Jim good thoughtful article.
Referring to Fig. 2, the polynya illustrated appears to be related to a katabatic winds with sinking water. Do all polynyas ventilate heat as an iris or does it depend on their origin ?
most polynyas are “latent heat” polynya due to the release of heat when new ice is formed in addition to any upwelling heat. Rigor 2002 concluded that the lack of ice was the cause of atmospheric warming due to observations such as:
“the exchange of heat between the Arctic Ocean and atmosphere is strongly moderated by the thickness of sea ice. For example, during winter the sensible and latent heat flux into the atmosphere from a refreezing open lead is ~700 W/m2, as compared to ~10 W m2 into the ocean over 3 m thick”
Something extraordinary is currently happening to the sun. We are going to see an abrupt switch to the cold phase of a Dansgaard-Oeschger cycle followed it appears by what causes a Heinrich event.
It is fact that the paleo data shows evidence of cyclic rapid immense climate changes (cyclic changes require a cyclic forcing function rather than massive positive feedback to amplify tiny changes which would create a random oscillating pattern). The last event of this type is called the 8200 year before present event which is a 2C cooling event that lasted for 200 years. The Younger Dryas is the super large example of the cyclic abrupt forcing function. During the Younger Dryas abrupt cooling event the planet went from interglacial warm to glacial cold with 70% of the cooling occurring in less than a decade at a time when summer insolation at 65N was maximum. The YD abrupt cooling lasted for 1200 years. The massive YD forcing mechanism is capable of and does terminate interglacial periods.
This is the Greenland Ice sheet temperature data for the last 100,000 years. Can you see the cyclic abrupt changes?
http://oceanservice.noaa.gov/education/pd/tidescurrents/media/effect_influences_3.gif
The climate does not ‘tip’ or ‘jump’ from one ‘state’ to another without a physical cause, a physical reason for the observed change. Euphemisms and analogues are used when there is no scientific basis for a claim. There is no magical, ‘smart’ amplification mechanism that can when required amplify tiny forcing changes to create what is observed. There are no peer reviewed papers that support the assertion of a massive ‘smart’ amplification mechanism. The ‘tip’ or ‘jump’ zombie theory stops people from looking for the physical reason for what is observed. Makes it impossible to solve the problem.
You would not accept the assertion that now and then rocks jump up hill. There is no analytical data to support the assertion that planetary climate can or does have massive cyclic changes without a forcing function, a physical reason for what is observed. There is no evidence for a ‘smart’ amplification mechanism that appears when required to create for example the Younger Dryas abrupt climate change event. The Younger Dryas is an immense climate change which is an example of cyclic, abrupt, immense climate change.
Meanwhile back to climate Urban Myths/Zombie Theories
ClimateMyth/Zombie Theory 1- An interruption to the discrete Gulf Stream (a discrete deep water return for the North Atlantic Drift Current (aka The ‘Gulf Stream’) does not exist, see below, but even if it did so a melt pulse could interrupt it) would not result in significant cooling of Europe. The Gulf stream myth has been perpetuated for almost 20 years.
http://www.americanscientist.org/issues/feature/2006/4/the-source-of-europes-mild-climate
William,
The 8200 B.P. event is not the only cooling event in the Holocene. Please look at the second figure at the following blog post:
http://astroclimateconnection.blogspot.com.au/2013/06/are-dansgaard-oeschger-d-o-warm-events.html
William, First I am not sure why you are repeating lengthy posts about the myth of the conveyor belt. But I agree that there is no such thing and it has supported bad hypotheses. Poleward transport of heat is the integration of several dynamics. That said heat transport does vary, and impacts the iris effect.
2nd I disagree with your earlier statement that “The cyclic abrupt cooling events require a massive forcing function to cause the cyclic abrupt cooling.” The oceans have cooled over the past 35 million years into the icebox state such that the default condition of the arctic is to freeze unless there is sufficient heat transport. In all D-O events as well as glacial-interglacial events the initial cooling happens slowly as heat transport is reduced and ventilation begins to exhaust the stored heat. When enough ice forms to prevent further ventilation, the final cooling to the stadial condition is rapid.Abrupt warming, slow cooling followed by fast cooling is the shape of all D-O and deglacial events.
3rd the iris effect does not dismiss contributions from solar forcing. As Don mentions the correlations with cosmogenic nuclides is too strong. I strongly suspect that changes in irradiance is part of the forcing that amplifies poleward heat transport to both hemispheres and increases the inflow of warm Atlantic Water by affecting both temperature and volume. But any solar forcing by itself can not explain the abrupt warming of 10C in just a decade based on how long it takes to heat the ocean.The impact of solar forcing provides too little energy over the short term. But if stored in the subsurface ocean can provide enough heat to explain the periodic warm events. I see solar forcing and the iris effect working in tandem.
In addition to irradiance, the Milankovitch forcing helps tip the balance during deglacial periods by increasing the summer ablation of arctic ice. But Milankovitch forcing can not explain D-O events. Also there is a debate about which is more important, the ~21 thousand year precessional forcing vs ~45 thousand obliquity forcing. Although there was an abrupt change in the glacial cycles from about 45 thousand to 100,000 thousand years, no one believes the 100,000 eccentricity forcing have enough power to affect glacial cycles and the observed 100,000 is a function of multiple precessional and obliquity forcing. Here again the iris effect would support that notion as the thickness of the arctic ice determines how sensitive it is to solar forcing. As the planet continues to descend into the ice box condition, greater accumulation of heat is required to tip us into an interglacial.
Jim is making sense here.
Some of my Milankovitch Cycle thoughts
One other point is the SH. and N.H. are not created equally when it comes to their response to Milankovitch Cycles.
The S.H. is set up as such , that it does not really matter if summer time insolation increases or decreases because the area of land that is entrenched in snow/ice is going to remain the same regardless of summer time insolation changes , in contrast to the N.H. where a difference in summer time insolation can cause a significant difference in the land area covered by snow/ice, thus effecting the albedo of the entire planet.
S.H. albedo remaining steady while N.H. albedo increasing due to favorable Milankovich Cycles.
Jim said:
“I see solar forcing and the iris effect working in tandem.”
Agreed, with ocean oscillations in various ocean basins interacting to mediate the speed and severity of the Iris effect.
Latitudinal climate zone shifting and global cloudiness variations being the leading indicator of what is to come.
William
The physical reason for a flip in climate, the mighty forcing that moves heaven and earth by several degrees centigrade and a trillion petajoules, is the flap of a butterfly’s wing.
I probably didn’t read the article carefully enough, but I don’t understand what keeps the warm saline layer under the cold one. Is it more saline, and thus denser even though it is warmer?
The Gulf Stream experiences heavy evaporation thus making the Atlantic water extremely saline and dense. In a simplified version of the Arctic vertical structure, Atlantic Water occupies a middle zone between fresher but colder surface waters and the deepest cold salty bottom layer from brine rejection. The halocline is cold and salty but not saltier than the Atlantic Waters.
So that’s a yes? The warm water is more saline, and thus denser?
Wonderful article. It actually describes the science. 🙂
thermogeddonites beware.
Jim here is what my thinking was at one time. Your article however has changed my mind to a degree although some of what is said below may still have some merit.
I have two questions and a statement. How accurate are the Arctic Ocean temperature measurements from 1993-2011 showing the cooling trend in the Arctic Ocean?
What is the Arctic Ocean doing temperature wise post 2011?
Statement
Let me say the synchronous argument in no way diminishes the Arctic Iris Effect. Remember D/O events are short warm spells within Ice Age conditions. The globe overall is still overall in an Ice Age State as opposed to an inter-glacial state when D/O events take place.
The D/O events to my way of thinking is strictly a function of the North Atlantic and Ice Coverage changes in the Arctic which gives these abrupt temperature changes but when happening during an Ice Age it is still within the ice Age. The D/O events during an Ice Age are not inter- glacial events which last some 10 to 20 thousand years.
Thinking at one time below.
Solar/Thermohaline Circulation/1470 year climate cycle connection – Southwest Weather, Inc. supports the theory that states the superposition of the DE VRIES – SUESS 210 year solar cycle, and the Gleissberg 87 year old solar cycle creates a solar variability every 1470 years, that impacts the fresh water concentrations put into the North Atlantic, which in turn either weakens or strengthens the Thermohaline Circulation. The effects, depending on the initial state of the climate; that being glacial or interglacial. Since we are currently in an interglacial period, we will examine the Solar/Thermohaline circulation possible connection for this initial state of the climate when solar activity is in a minimum state.
OVERVIEW
The connection between the Thermohaline Circulation and the Solar Cycle is if solar activity should reach a certain level of activity, it could through a modulating effect of the atmospheric circulation, either amplify or reduce the amount of sea ice entering the subpolar North Atlantic. This would then change the fresh water concentration of the subpolar North Atlantic, leading to a change in the North Atlantic Deep Water (NADW) production, which would either enhance or decrease the Thermohaline Circulation.
FOR EXAMPLE:
If solar activity were to reach a certain minimum magnitude (every 1470 years), it could modulate the atmospheric circulation, resulting in a negative Atlantic Oscillation (NAO), which in turn would amplify the transport (due to a stronger northerly wind flow over the North Sea to the Sub Polar North Atlantic, in response to a negative NAO) of drift ice into the Sub Polar North Atlantic, causing the salinity concentrations and the temperature of the Sub Polar North Atlantic waters to decrease. (Density decreases overall despite colder water temperatures)
This would cause a reduction in NADW formation, which would lead to a weakening of the Thermohaline Circulation. The result would be a further cooling in the higher latitudes, due to less northward transport of heat via the Thermohaline Circulation.
This would then have a PROFOUND EFFECT on the temperatures of the Northern Hemisphere much MORE, then what the solar reduction in activity itself would suggest.
The present arrangement of the continents, versus oceans is conductive for glacial conditions presently. The reason is that most of the land mass in both hemispheres is located in high latitudes, with water exerting a modulation effect on both the land mass in the Northern Hemisphere, as well as the Southern Hemisphere.
I agree with your statement ” the synchronous argument in no way diminishes the Arctic Iris Effect” See my response to Easterbrook above with the graph from the recent WAIS paper.
2nd I would be careful linking NADW formation with inflows of warm water. That linkage is a vestige of conveyor belt thinking. As Lozier 2010 wrote “the conveyor-belt model no longer serves the community well—not because it is a gross oversimplification but because it ignores crucial structure and mechanics of the ocean’s intricate global overturning”
For example warm water still intrudes the Arctic during stadial conditions but no NADW is formed because the ice prevents contact with cold air that is needed to cool the water enough to sink to the bottom. Poleward ocean heat transport is driven by the winds not loss of buoyancy in the polar regions. There is no Pacific Deep water formed yet there is still poleward heat transport.
I do see a solar connection based on observed changes in ocean heat content. During the LIttle ICe Age there both the Atlantic subtropical gyre (Keigwin 1997) and the Western Pacific Warm Pool (Roenthal 2014) cooled below todays temperatures , and conversely both warmed during the Medieval Warm Period. Furthermore there was less heat transport in the Gulf Stream during the LIA, and during the deglacial at peak insulation there was greater inflows of warm water.
Thus I suspect that due to the correlations with cosmogenic nuclides, solar irradiance can modulate the poleward flow of heat.
jim said:
“due to the correlations with cosmogenic nuclides, solar irradiance can modulate the poleward flow of heat.”
That would be the Svensmark hypothesis then.
May I suggest my alternative hypothesis of increased cloudiness from longer lines of air mass mixing when jet streams become more meridional ?
Stephen said “That would be the Svensmark hypothesis then. May I suggest my alternative hypothesis of increased cloudiness from longer lines of air mass mixing when jet streams become more meridional ?”
I was not invoking Svensmark.
Higher solar irradiance suggested for the MWP created a La NIna like zonal temperature gradient condition while lower irradiance during the LIA is associated with El Nino-like gradient.
I see a La Nina-lke gradient creating less cloud cover over the eastern Pacfic and more upwelled water that absorb more heat. A spin up of the subtropical gyre and the northward shift of the ITCZ would help increase poleward heat transport.
Jim said:
“Higher solar irradiance suggested for the MWP created a La NIna like zonal temperature gradient.”
Later in this thread you said this:
” El Nino years would diminish the HIgh allowing for more zonal flow.”
I can respond more intelligently if you resolve the discrepancy 🙂
My view is that in the MWP solar top down effects caused a positive AO which pulled the climate zones poleward so as to allow a more zonal flow whereas in the LIA solar top down effects caused a negative AO which pushed the climate zones equatorward to cause a more meridional flow.
Stephen said ““Higher solar irradiance suggested for the MWP created a La NIna like zonal temperature gradient.”
Later in this thread you said this:
” El Nino years would diminish the HIgh allowing for more zonal flow.”
I can respond more intelligently if you resolve the discrepancy :)”
There is no discrepancy. La Nina creates a colder eastern Pacific and a warmer western warm pool, hence a stronger zonal temperature gradient. The temperature gradients creates a stronger pressure gradient with a stronger HIgh over the cooler eastern Pacific that amplifies the Trade winds via the Walker Circulation and that HIgh directs the westerlies, jet stream and rains northward. Subtropical Highs block moisture carrying zonal westerlies to create the dry summer Mediterranean climate for California, Chile, and west Africa. However in the winter the temperature difference between land and oceans reverses, weakening the High and allowing winter rains. But in LA NIna years a much colder ocean helps maintain the High pressure system causing winter droughts as it forces the winds northward.
In El Nino years the warm water that floods the eastern Pacific amplifies the weakening of the HIgh so that moire moisture bearing westerlies maintain their zonal flow, bring rains to California and the southwest
OK,
Then are you suggesting that both La Nina and El Nino create a zonal flow but at different latitudes / locations ?
If so, then that would not matter for my proposition that globally an active sun shifts everything poleward on average with a more zonal global flow whereas a quiet sun allows an equatorward shift and more meridional global flows.
Your description would then be of regional / local significance only.
Stephen says, “Then are you suggesting that both La Nina and El Nino create a zonal flow but at different latitudes / locations ?
If so, then that would not matter for my proposition ”
No I am saying La Nina events force add a more meridonal vector causing a more wavy flow and El Nino events by virtue of minimizing the HIgh allow a more zonal flow.
I am not arguing against your proposition, I am simply arguing that there are other bottom of dynamics that cause a wavier jet stream. I just dont know to what degree your top down dynamics contributes.
Some confusion was present but I think you have now clarified it.
You previously said:
“Higher solar irradiance suggested for the MWP created a La NIna like zonal temperature gradient.”
and now you say:
“No I am saying La Nina events force add a more meridonal vector causing a more wavy flow”
I do accept that bottom up processes can also cause a wavier more meridional flow.
It is all a matter of the net interaction between top down and bottom up processes but I think we can agree that zonality is greater when the sun is nore active and meridionality when the sun is less active.
No doubt the ENSO process then modulates the top down solar influences from below.
I only mentioned Svensmark because you referred to cosmogenic nucleides.
I use the term zonal only to refer to east-west coordinates vs meridonal referring to north-south.
La NIna’s create a greater zonal temperature gradient meaning a cooler eastern tropical Pacific and a warmer western. Because La Ninas enhance the HIgh in the eastern Pacific, it blocks the zonal flow of westerly winds and directs winds and moisture northward, thus promoting a more wavy jet stream.
In contrast El Ninos minimize the tropical Pacific’s zonal temperature gradient, weaken the HIgh pressure in the eastern Pacific thus allowing a more zonal flow of westerly winds and moisture.
I have also maintained for years that a warmish Arctic is the prelude to a colder climate going forward. This is in line with what this article is suggesting.
Salvatore,
I greatly appreciate your questions and keeping the discussion alive. I need to step out but will reply when I return. For now regards your first question the cooling of the Arctic’s 700 meters is from Heimbach and Wunsch 2014. Their paper did not focus on the Arctic but provided their analyses of changes in global ocean heat at various depths. Wunsch’s attention to detail and careful identification of uncertainties, in my eyes makes him more trustworthy than most. In Wunsch and Heimbach (2014) the humbly admit that their “results differ in detail and in numerical values from other estimates, but the determining whether any are “correct” is probably not possible with the existing data sets.”
I am looking forward to more discussion. Thanks.
Jim my question is how does this train of thought get promoted? This is where it is at and it is so OBVIOUSLY sensible.
This combined with Milankovitch Cycles, Solar Variability ,Geo Magnetic Strength for the big picture etc is by far and away the best explanation for why/how the climate changes!
Well I started promoting the idea here at WUWT. I believe many eyes that visit this website are better than a few pal reviewers. I hope Judith Curry might give it some play. I tweeted her and she is swamped but she said she will try to post a comment on the Arctic Iris Effect. Based on peer reviewed papers from which evidence for this essay was gleaned, I also suspect there is a growing appreciation for the iris dynamics even though it has yet to be “officially” dubbed the Arctic Iris Effect. John Muir published in the popular press initially greeted with much push back but as academics began to embrace the validity of his observations, his ideas became a focus of discussion, despite being labeled by Whitney as just an “ignorant shepherd”. If this train of thought adequately synthesizes most observations, it will get promoted as well.
What is so good about this Arctic Iris Effect is it gets away from the rigid 1470 year climate cycle, it gets away from the fresh water rapid release scenario and slowing down of the AMOC ,it shows how a cycle leading to an abrupt climate change can take place and start the process over again, and it explains why the abrupt climate changes during an inter- glacial may not be as great in degree of magnitude as during a glacial.
And these dramatic temperature changes never lead to polar bear extinction either.
Jim says below which is correct. The 1470 year cyclic or semi cyclic climate oscillation never really held up and I thought was pretty much wrong.
Javier, Rhamstorf is wrong. There is no precise clock for D-O events. Their recurrence happened from 8 to 1.5 thousand years. Rhamstorf is also wrong about ocean conveyor belts and changes in the AMOC. While scientists have been increasingly abandinging the conveyor belt idea, Rhamstorf continues to defend it because his decades of publications are based on assuming the conveyor belt is a reality.
That said there are rather good clocks found in nature. Most extratropical plants can determine change in seasons. The biological clocks are determined by the amount of time required to build or degrade a certain concentration of chemicals. Similarly the Arctic subsurface can have a “clock” determined by the build up of subsurface heat and its ability to contribute to basal melting.
My queston to you is How would you determine oscillation determined by astronomical forcings versus oscillations due to internal variability?
The only way to get the 1470 cyclic cycle would be if the sun had a 1500 year cycle, or
the superposition of the DE VRIES – SUESS 210 year solar cycle, and the Gleissberg 87 year old solar cycle creates a solar variability every 1470 years, that impacts the fresh water concentrations put into the North Atlantic, which in turn either weakens or strengthens the Thermohaline Circulation.
This at one time I thought had a possibility but just that a possibility which I tried to reconcile to some degree.
RIGOR – info. last paragraph is in conflict with findings of first two paragraphs on AO phase /sea level pressure relationship in Arctic which I think is correct.
According to RIGOR as the AO went from a negative phase toward a more positive phase from 1979-1998 mean sea level pressure over the central Arctic Ocean drops which I think is opposite of what should happen when the AO is becoming more positive and supported by the paragraph just below which was from the Dec. 2009 Arctic Sea Ice report.
These regional contrasts in temperature anomalies resulted from a strongly negative phase of the Arctic Oscillation (AO). The AO is a natural pattern of climate variability. It consists of opposing patterns of atmospheric pressure between the polar regions and middle latitudes. The positive phase of the AO exists when pressures are lower than normal over the Arctic, and higher than normal in middle latitude. In the negative phase, the opposite is true; pressures are higher than normal over the Arctic and lower than normal in middle latitudes. The negative and positive phases of the AO set up opposing temperature patterns. With the AO in its negative phase this season, the Arctic is warmer than average, while parts of the middle latitudes are colder than normal. .
The phase of the AO is described in terms of an index value. In December 2009 the AO index value was -3.41, the most negative value since at least 1950, according to data from the NOAA Climate Prediction Center.
The phase of the AO also affects patterns of precipitation, especially over Europe.Data collected by the International Arctic Buoy Programme from 1979 to 1998 are analyzed to obtain statistics of sea level pressure (SLP) and sea ice motion (SIM). The annual and seasonal mean fields agree with those obtained in previous studies of Arctic climatology. The data show a 3-hPa decrease in decadal mean SLP over the central Arctic Ocean between 1979–88 and 1989–98. This decrease in SLP drives a cyclonic trend in SIM, which resembles the structure of the Arctic Oscillation (AO).
http://nsidc.org/arcticseaicenews/2009/12/low-ice-extent-in-barents-sea-and-hudson-bay/
http://nsidc.org/arcticseaicenews/2010/01/extreme-negative-phase-of-the-arctic-oscillation-yields-a-warm-arctic/
I meant to send this one not the above one.
. The data show a 3-hPa decrease in decadal mean SLP over the central Arctic Ocean between 1979–88 and 1989–98. This decrease in SLP drives a cyclonic trend in SIM, which resembles the structure of the Arctic Oscillation (AO)
Now to think about it he may be correct neg. AO 1979-1988 then more positive 1989-1998, pressure becomes lower.
-ao equates to high slp and vice versa.
I just wasted my time.
No you didn’t. You cleared up your own misunderstanding. Give yourself a pat on the back for digging deeper until you gained clarity. Most people do not.
Hey, Salvatore, you had me worried for a moment there.
Positive AO involves a tall polar vortex with a small surface footprint and the climate zones shift poleward. Low SLP at the poles. Less clouds globally for more solar energy penetrating the oceans.
Negative AO involves a less tall, flabby, polar vortex with a larger surface footprint and the climate zones are pushed equatorward. High SLP. at the poles. More clouds globally for less solar energy penetrating the oceans.
The thing is that the polar vortices are unlike surface pressure cells. They involve columns of descending air in the mesosphere and stratosphere (not the troposphere) and are caused by the Earth’s rotation rather than surface pressure differentials.
When the sun is quiet, more ozone is created higher up which warms the stratosphere and pushes the tropopause down which causes higher pressure in the troposphere and at the surface. Negative AO.
When the sun is active less ozone is created higher up which cools the stratosphere and allows the tropopause to rise which causes lower pressure in the tropopause and at the surface. Positive AO.
The thing is that that is precisely the opposite of standard climatology which focuses on ozone changes above the equator and at lower levels which are of opposite sign as regards the ozone creation / destruction process.
In order to achieve the right sign of ozone changes and latitudinal climate zone shifting in conjunction with solar variability to explain the MWP, LIA and late 20th century observations of stratospheric ozone decline at the poles one needs the reverse sign ozone response that I have been putting forward since 2010.
An Arctic Iris Effect fits in neatly and potentially resolves the nonsense of the AGW theory whereby albedo variations from changes in ice area somehow outweight the ability of open water to release more heat to cold air. That concept always struck me as daft because, being bald, I know just how fast one’s entire body can cool when going out in the cold without a hat 🙂
Stephen I read your links and will need to do so again to make sure I understand them correctly. As you have noted I have been lookiing at natural climate change from primarily a bottom up perspective while believing small changes in insolation (orbital or irradiance and resulting cloud cover change). So your perspective holds great interest as complimenting my perspective. But I have a fee questions.
1) I was not aware of the different solar impacts on equatorial and polar ozone. I always thought stronger sun causes more ozone creation. Is the difference that there is greater destruction at the poles? Are there other published papers.
2) I am a little dubious about attributing changes in a wavy jet stream simply to changes in the polar vortex but do not dismiss its contribution. Looking from the bottom up I first see a wavy jet stream as a predisposition due to the Rocky Mountains. Second the quasi permanent HIgh Pressure system in the northeastern Pacific also exerts a powerful influence. And third La Nina years would strengthen that High causing greater waviness while El Nino years would diminish the HIgh allowing for more zonal flow. I see those dynamics as more powerful determinants of the jet stream path, yet I still allow for the polar vortex influence of which I admittedly have only a marginal understanding.
I appreciate your comments
Hi Jim,
1) Conventional climatology does indeed suggest that a more active sun creates more ozone above equatorial regions which forces the equatorial tropopause down to create more zonal poleward jets and decrease cloudiness thereby allowing more sunlight into the oceans for a warming climate system. The problem with that is that when the sun was more active during the late 20th century warming spell stratospheric ozone actually declined which is why CFCs were blamed for the reducing ozone above the poles.
I noted that if ozone declined above the poles when the sun was more active then it was more likely that the tropopause was being pulled up at the poles rather than being pushed down above the equator and that since that was happening at a time of more active sun there was something wrong with the conventional viewpoint. I formed that opinion around 2008.
Then in 2010 I saw this:
http://www.nature.com/nature/journal/v467/n7316/full/nature09426.html
” Here we show that these spectral changes appear to have led to a significant decline from 2004 to 2007 in stratospheric ozone below an altitude of 45 km, with an increase above this altitude”.
Hence my hypothesis which I have already linked you to.
2) The Rocky Mountains certainly contribute to the waviness of the northern hemisphere jets but I am more interested in the changes in the degree of waviness over time which are mirrored although to a lesser extent in the southern hemisphere.
I’m not sure that we are in disagreement over the effect of changes in the high pressure cell over the north eastern Pacific. Presumably, like the Azores high pressure cell in the Atlantic it would respond to the net interaction between the top down solar influence and the bottom up oceanic influence. La Nina years would be associated with more jet stream waviness because the cooler equatorial oceans would allow greater incursions of polar air towards the equator and El Nino years would push equatorial air more poleward and reduce polar incursions towards the equator which would manifest in a more zonal poleward flow.
I think point 1 above is the more fundamental issue.
The reduction of ozone above 45km and especially towards the poles via a change in the level of solar activity is the feature required to account for both observations of reducing stratospheric temperatures at a time of active sun AND poleward migration of climate zones at a time of active sun.
If conventional climatology were correct then we would have seen an INCREASE in stratospheric ozone when the sun was more active.
That is pretty much the peg upon which my hypothesis hangs so unless there is recent data contradicting the findings reported by Jo Haigh from 2004 to 2007 then I may well be correct. I doubt that such contradictory data exists since it is becoming accepted that stratospheric cooling has ceased and there has recently been some stratospheric warming. That would be impossible at a time of less active sun under the conventional climatology.
Your Arctic Iris Effect remains intact under my hypothesis and for the reason stated previously in this thread I agree with it. Heat loss from open water is bound to be far more influential than any decline of albedo allowing more solar absorption at such high latitudes, contrary to AGW theory.
You have made a very good point which could well account for another layer of variability within the hypothesis which I have presented.
Stephen I was rushing and getting myself confused. Trying to equate to many variables at the same time.
At any rate I realized it. Thanks.
Salvatore,
We’ve all done it 🙂
The great thing about these blogs is that those of us who are honest and unbiased seekers of truth leave an uncensored and unalterable trail of our thought processes.
Thanks Jim. I am going to try to push this Arctic Iris Effect as much as possible each time the subject of abrupt climate change comes up.
In-fact I just sent this Arctic Iris Effect theory to the article that just came out on WUWT in regards to an ancient cold period.
http://www.snopes.com/politics/science/globalwarming1922.asp
VERY intersting article!!! curious to read part 2