What Causes Ice Ages?

[William Astley]

There is recent research that supports the assertion that the start of an ice age epoch is initiated by an increase in Galactic Cosmic Rays (GCR) and that the ice age glacial/interglacial cycle is controlled by processes that periodically modulate the amount of GCR that penetrates the solar large scale magnetic field and the geomagnetic field, and hence penetrates the Earth's atmosphere.


The following is a link to a paper that provides data and an explanation for the mechanisms, to support that GCR hypothesis.

From Kirby, Mangini, and Muller's 2004 Paper "The Glacial Cycles and Cosmic Rays"

"The cause of the glacial cycles remains a mystery. The origins is widely accepted to be astronomical ...(however) ... high precision paleoclimatic data revealed serious discrepancies with the Milankovitch model that fundamental challenges its validity and re-open the question of what causes the glacial cycles. We propose that the ice ages are not driven by insolation cycles but by cosmic ray changes ..."

The Glacial Cycles and Cosmic Rays

http://arxiv.org/pdf/physics/0407005

Comment:
GCR creates ions in the atmosphere which recent papers show affects the amount of low level cloud cover. The data shows a decrease in GCR results in a decrease in low level clouds which will warm the planet and an increase in GCR results in an increase in low level clouds. See the thread Clouds and Albedo for details.

 

[Andre]

Hi William,

Thanks for your posts and most welcome here. That's indeed an excellent paper, not entirely unexpected. But very helpful to convincing others that our current explanation for ice ages is a mess. I glanced over it and will study more in detail later. So the next comments are not very well founded and I may be forced to withdraw them but anyway.

I know about the struggle of Rich Muller to solve the ice ages (inclination cycle and dustband). But the more ideas you have the more you risk of getting falsified. It doesn't seem to harm him.

The idea appears to be that long term cosmic ray activity perhaps regulated by the magnetic field causes the dramatic climate changes. The sun rather than the Earth being the driver of the geo magnetic field

First of all, the overwhelming preassumption of ice ages is the warm - cold waxing/ waning ice sheet idea. Considering the "warm" mammoth steppe in Siberia (>3 degrees warmer than today) during the Last Glacial Maximum, any 'solution' that ignores this, cannot be a solution. To me it appears that the ice ages is much more about arid - moist due to a certain pet idea,

I would think that the registration of the paleo magnetic field in benthic stacks at the sea floor would register the Earth generated part of the magnetic field, rather than the solar part. This would suggest that the main driver might be terra firma itself. Years ago I discussed the apparent ~30-50ka lag of glacial terminations to paleomagnetic excursions with Prof Langereis, who supervised Sint800. result: could be, could not be.

Moreover, comparing the frequency bands of 10Be with Karners Benthic stack (deep ocean foraminifera) one should still wonder why the stacks don't show any inertia or millenium scale delay due to water mixing between surface events and deep ocean events.

BTW, Karners stack is outdated, they should have used Lisiecky and Raymo's LR05 stack but of course it's tempting to stick with own work.

Oh sorry this is not a peer review of course.

 

[William Astley]

Unstable Geomagnetic Field? Affects on Climate.

Hi Andre,

In reply to this excerpt from your comment:

"The idea (my comment, Kirby's paper Glacial Cycles and Ice Ages, see above for details) is that the Ice age appears to be driven by changes in the cosmic ray activity which are regulated by the geomagnetic field. The large changes in the GCR flux it is hypothesized causes the observed dramatic climate changes, that are observed (glacial/interglacial cycle.) The sun rather than the Earth being the driver of the geo magnetic field."

Yes, something certainly is triggering a massive drop in the geomagnetic field. There is new data that indicates that the geomagnetic field, spends 20% of its time in a low state (5 to 10 times less than the current geomagnetic field intensity and unstable.) The question is what causes the geomagnetic field to drop and to become unstable? Changes happen for a reason.

From Zang and Gubbin's attached paper "Is the geodynamo Unstable?"

http://eprints.whiterose.ac.uk/archive/00000416/01/gubbinsd4.pdf

Recent palaemagnetic studies suggest that excursions of the geomagnetic field, during which the intensity drops by a factor of 5-10... The 'normal' state of the geomagnetic field dominated by an axial dipole, seems to interrupted every 30-100 kyrs: it may not be as stable as we once thought."

"These important results paint a rather different picture of the long term behavior of the field from the conventional one of a steady dipole reversing at random intervals; instead, the field appears to spend up to 20% of its time in a weak, non-dipole state (Lund et al 1998). ... This raises a number of important but difficult questions for geodynamo theory. How can the geomagnetic field change, so rapidly and dramatically? Can slight variations of the geomagnetic field affect the dynamics of core convection significantly? If so, is the geomagnetic process intrinsically unstable?

 

[Andre]

problem here is that the paper ignores Earth orbital pertubations. Earth precession does have a big impact on Earth Core dynamics (see Jim Vanyo). Aparantly, this is not recognised by Gubbins.

I'm time pressed, Sorry, more later.

 

[William Astley]

When did Ice Sheets Start to Form In North America?

For those who are not familiar with the glacial/interglacial cycle, attached is a link to a lecture that provides planetary temperature temperatures over the last 100 kyrs.

John Stone, Climatic Record the Last 100,000 years

http://www.washington.edu/research/or/symposium/stone.pdf [Broken]


A couple of comments concerning this ice age epoch.

The ice sheets started to form in the Northern Hemisphere roughly 2.5Ma years ago. The Quaternary Ice Age has a cyclic pattern. Ice sheets have formed and then retreated, roughly 25 times, in the last 2.5 Ma. At the beginning of the Quaternary ice age 2.5 Ma yrs ago, the glacial/interglacial cycle period was 41kyr. 700 kyrs ago the glacial/interglacial cycle changed to a 100 kyr cycle, where the interglacial period is less than 20 kyrs and the glacial cycle is roughly 80 kyrs. Specifically why the glacial/interglacial cycle changed from a 41kyr cycle to a 100 kyr cycle is not known.

The last glacial period is known as the Wisconsin Glacial period. During the coldest period of the last glacial period, all of Canada, portions of the Northern USA States, and large portions of Europe and Russia were covered with a ice sheet that was 3000 Meters to 4000 Meters thick. (Roughly 2 miles thick).

Attached is a paper by Raymo that discusses the scientific problems with explaining the 41 kyr cycle, using an insolation based theory. As Raymo notes in the paper, the 21th century climate models cannot model the 41 kyr pattern.

The 41 kyr World: Milankovitch’s Other Unsolved Mystery

http://www.agu.org/pubs/sample_articles/cr/2002PA000791/2002PA000791.pdf

Comment:
Proxy evidence shows that the geomagnetic field changes with a 41 ky and 100 kyr cycle. An increase in the geomagnetic field reduces Galactic Cosmic Rays (GCR) that strike the atmosphere. GCR atmosphere strikes, is inversally correlated with low level cloud cover. An increase in GCR cause a decrease in low level clouds and vice versa. As the noted in the paper linked above, cyclic changes in amount of planetary low level clouds is hypothesized to be the cause of ice ages and the glacial/interglacial cycle.

 

[William Astley]

Abrupt Climate Change

From Broecker’s famous Angry Beast article (see attached link for details) in which he discussions macroclimate models and extreme climate changes:

http://www.soest.hawaii.edu/GG/FACULTY/POPP/Broecker 1999 GSA Today.pdf

“Models to the Rescue?”

“…No one understands what is required to cool Greenland by 16C and the tropics by 4 +/-1C, to lower the mountain snowlines by 900m, to create an ice sheet covering much of North America, to reduce…CO2 by 30%, or to raise the dust rain… by an order of magnitude. If these changes were not documented in the climate record, they would never have entered the minds of the climate dynamics community.

Models that purportedly simulate glacial climates do so only because key boundary conditions are prescribed (the size and elevation of ice sheets, sea ice extent, sea surface temperature, CO2 content, etc;)”

The current climate models do not explain and cannot reproduce the sever and abrupt climate changes in the proxy climatic record.

Comments:
1) In the Angry Beast article Broecker postulates that the Younger Dryas (Youger Dryas is the name for the sever cooling event that occur during the start of this interglacial) was caused by a fresh water pulse, from Lake Agassiz (Lake Agassiz was a massive glacial lake in the Province of Manitoba) Subsequent data has shown that the fresh water pulse hypothesis is likely not correct, as the fresh water pulse occurred a 1000 years before the Younger Dryas. See attached paper below for the data and another hypothesis.

2) An alternative hypothesis to Broecker’s non-linear knife edge hypothesis (Small natural or anthropogenic changes can force the macroclimate from one mode to another mode and hence create the massive ice sheets and so forth.) is the hypothesis there is a massive semi-periodic external forcing, that forces the macroclimate from one mode to another.

Link: Reduced solar activity as a trigger for the start of the Younger Dryas?

http://scholar.google.com/url?sa=U&q=http://dept.kent.edu/geography/GEC/Reduced_solar_activity_as_a_trig.pdf [Broken]

 

[Andre]

From Broecker’s famous Angry Beast article (see attached link for details) in which he discussions macroclimate models and extreme climate changes:

The current climate models do not explain and cannot reproduce the sever and abrupt climate changes in the proxy climatic record.

Comments:
1) In the Angry Beast article Broecker postulates that the Younger Dryas (Youger Dryas is the name for the sever cooling event that occur during the start of this interglacial) was caused by a fresh water pulse, from Lake Agassiz

That's a fairly general paradigm, but it's hard to see how a mouse can lead the charge of an angry herd of elephants.

[edit: added:

http://www.americanscientist.org/template/AssetDetail/assetid/51963?fulltext=true&print=yes#52137

(the whole article is highly recommended reading but here the focus is on:

For many years, the leading theory for what caused the Younger Dryas was a release of water from glacial Lake Agassiz, a huge, ice-dammed lake that was once situated near Lake Superior. This sudden outwash of glacial meltwater flooded into the North Atlantic, it was said, lowering the salinity and density of surface waters enough to prevent them from sinking, thus switching off the conveyor. The North Atlantic Drift then ceased flowing north, and, consequently, the northward transport of heat in the ocean diminished. The North Atlantic region was then plunged back into near-glacial conditions. Or so the prevailing reasoning went.

Recently, however, evidence has emerged that the Younger Dryas began long before the breach that allowed freshwater to flood the North Atlantic. What is more, the temperature changes induced by a shutdown in the conveyor are too small to explain what went on during the Younger Dryas.

Sorry William, if I'm disturbing your lesson material but the story seems to be completely different. In many proxies there is clear evidence that the average Younger Dryas temperature was not that low, although the seasonality extremes were much greater compared to the adjacent periods


Now Am I insane or? Since textbook lesson one, A sub 1 about the Quartenary is that the Younger Dryas was a bitterly cold interval with massive glacier advance..NOT!

So why that misconception? The main reason for this are the problems with carbon dating. In the early 70-80ies when carbon dating matured, little was known about the variability of Atmospheric delta14C. So they found a lot of glacial activity both around 11,000 and 10,000 carbon years ago, the Younger Dryas. Then the Greenland ice cores showed massive Younger dryas changes between 12,800 and 11,600 layer counted years and independetly from other proxies it became slowly clear that the carbon dating underestimated the age by 1000-2000 years in that range.

Nowadays carbon dating and calibration is much more accurate and the glacial features are found to be typically something like 10,010 +/- 50 or 10,970 +/- 50 carbon years. These dates would calibrate to 11.500 +/- 100 calendar years and 12005 +/- 25, calendar years using the INTCAL04 conversion table:
http://www.radiocarbon.org/IntCal04.htm

But that's outside the Younger Dryas in the Greenland Summit ice cores, actually at its transitions. So there you are looking at the reason of the widespread misconception. The 'massive' glaciations took place just prior and after the Younger Dryas in outbursts of extremely wet climates of the Allerod and the Preboreal, not during the event itself.

Then what was the Younger Dryas? A hyper arid period, likely due to a greatly reduced water cycle, due to very low sea surface temperatures. Note that the last Siberian refuge of Mammoths during the Younger Dryas was northernmost Taimyr Peninsula, currently high arctic tundra, then a productive grassy steppe with horses, reindeer, aurox etc.

See also these thread for some substantiation:

https://www.physicsforums.com/showthread.php?t=125669
https://www.physicsforums.com/showthread.php?t=73130

 

[William Astley]

Effect of Stoppage of Gulf Stream?

Hi Andre,

I agree with your above comment “it's hard to see how a mouse can lead the charge of an angry herd of elephants.”

Andre's above comment provides a link to Richard Seager’s article in American Scientist “Is the Gulf Stream responsible for Europe’s Warm Winters” which debunks the myth that a sudden stoppage of the Thermal Haline Conveyor (THC) for what ever reason, would result in a sudden drop in European temperatures.

The Gulf Stream myth has been spread in the popular press, movies, and so forth. Seager’s paper also questions the assertion that THC stoppage could have been the forcing function for the multitude of sudden cooling events that occur in the proxy climate record.

The following is an excerpt from Seager's article. (See the link for details and a graph that shows, based on analysis and data that is widely accepted, that the atmosphere rather than ocean currents is responsible for the majority of heat transfer equater to mid latitudes.)

But from what specialists have long known, I would expect that any slowdown in thermohaline circulation would have a noticeable but not catastrophic effect on climate. The temperature difference between Europe and Labrador should remain. Temperatures will not drop to ice-age levels, not even to the levels of the Little Ice Age, the relatively cold period that Europe suffered a few centuries ago. The North Atlantic will not freeze over, and English Channel ferries will not have to plow their way through sea ice. A slowdown in thermohaline circulation should bring on a cooling tendency of at most a few degrees across the North Atlantic …. When Battisti and I had finished our study of the influence of the Gulf Stream, we were left with a certain sense of deflation: Pretty much everything we had found could have been concluded on the basis of results that were already available. Ngar-Cheung Lau of the National Atmospheric … Their modeled climate cooled by a few degrees on both sides of the Atlantic and left the much larger difference in temperature across the ocean unchanged. Other published model experiments went on to show the same thing. … What is more, by the late 1990s satellite data, and analyses of numerical models into which those data had been assimilated as part of the weather-forecasting process, had shown that in mid-latitudes the poleward transport of heat by the atmosphere exceeds that by the ocean several-fold.

All Battisti and I did was put these pieces of evidence together and add in a few more illustrative numerical experiments. Why hadn't anyone done that before? Why had these collective studies not already led to the demise of claims in the media and scientific papers alike that the Gulf Stream keeps Europe's climate just this side of glaciation? It seems this particular myth has grown to such a massive size that it exerts a great deal of pull on the minds of otherwise discerning people.

 

[BillJx]

In March 2004, a geological team from the University of Wisconsin found evidence of cyclical changes in cosmic ray bombardment of rocks. They didn't assume from that, that the rate of bombardment was cyclical. Since cosmic rays don't penetrate very far, they took it as evidence that the rocks were intermittently covered by ice. Their work showed that ice ages are globally simultaneous, rather than local, events.

http://www.news.wisc.edu/9557.html [Broken]

I know you're familiar with the CHRONOS PROJECT:
http://www.universetoday.com/am/publish/geologists_use_particles_earth_surface.html [Broken]

Kirkby and Mangini analyzed ocean sediments rather than surface rock. Is it possible that the variation they found is due to changes here on Earth, rather than in the rate of cosmic ray bombardment? i.e. changes in dust levels in the atmosphere, or in the rate of erosion by wind and/or water?

 

[William Astley]

Galactic Cosmic Rays

Hi BillJx,

In reply to your comments:

A) Evidence that shows simultaneous planetary temperature changes glacial/interglacial. If the evidence which you provide a link to is correct, then there must be a mechanism that could cause simultaneous planetary temperature changes.

B) Galactic Cosmic Rays
Galactic Cosmic Rays (GCR), which are mostly protons, travel at about 150,000 km/s to just less than 300,000 km/s the speed of light. A portion of the GCR flux penetrates the sun’s and earth’s magnetic field, and through secondary reactions with molecules in the earth’s atmosphere, create charged nuclei, which affect cloud formation.

GCR protons have a typical energy of range of 100 Mev to 10 Gev. The solar system is currently traveling through the spiral arms of the galaxy, a region where the GCR more than doubles in magnitude. It is hypothesized that the increase in GCR is the reason (trigger) why the Earth is currently in an ice epoch.

GCR is modulated by changes in the earth’s magnetic field and by changes in the sun’s large scale magnetic field. (Stronger field less GCR. Less GCR, less clouds and as clouds reflect the sun, less clouds would result in an increase in the planet's temperature.)

B) Proxy Data to determine Past GCR Levels
GCR create isotopes which do not occur naturally. The researchers can isolate the cosmogenic isotopes in sea floor sediment and in the ice cores. By measuring the relative abundance of the cosmogenic isotopes, researches can make determine an estimate of past GCR level.

Attached is a link to Shaviv and Vezier’s paper that shows there is correlation between the start and end of the glacial epoch with increases and decreases of Galactic Cosmic Ray (GCR). Shaviv examines meteorites (GCR creates isotopes in the meteoriods) to find how the GCR varied over time, over 300 million years. Shaviv believes his analysis shows, that the increase and decrease of GCR correlates with the passage of the solar system through the spiral arms of the galaxy. GCR intensity is higher in the spiral arms as there is higher formation of stars in the arms.

http://www.phys.huji.ac.il/~shaviv/Ice-ages/GSAToday.pdf

Also attached is Shaviv and Vezier’s response to criticism concerning their paper.

http://www.phys.huji.ac.il/~shaviv/ClimateDebate/RahmstorfDebate.pdf

See the thread in this forum "Clouds and Reflectivity" for how it is hypothesized that GCR changes and solar changes affect low level cloud intensity.

 

[Andre]

But don't forget that several mammoth mummies found(Jarkov, Fishhook, Yukagir, Mol et al 2006), dated around the onset of the Last Glacial Maximum, confirm that there was a productive (hence not too cold) grassy steppe in what is now the high arctic tundra of Siberia with very little grass. This disdains a global character of the cooling. Also there are good signs that there was no ice age going on in the lower lattitudes (Colinvaux et al 2000, Kastner & Goñi 2003,).

That's why I invented the pulsating equator.

Refs:

Colinvaux P.A., P.E. De Oliveira, M.B. Bush, 2000, Amazonian and neotropical plant communities on glacial time-scales: The failure of the aridity and refuge hypotheses, Quaternary Science Reviews 19 (2000) pp 141-169

Kastner, TP., Goñi, MA 2003 Constancy in the vegetation of the Amazon Basin during the late Pleistocene: Evidence from the organic matter composition of Amazon deep sea fan sediments, Geology,Volume: 31 Issue: 4 Pages: 291-294

Mol, D., Tikhonov A., van der Plicht J., Kahlke R-D., Debruyne R., van Geel B., van Reenen G., Pals J. P., de Marliave C., Reumer J.W.F., 2006. Results of the CERPOLEX/Mammuthus Expeditions on the Taimyr Peninsula, Arctic Siberia. Russian Federation Quaternary International, January volumes 142-143 pp. 186-202.

 

[William Astley]

Pulsating Equator Hypothesis

Hi Andre:

Re: "This disdains a global character of the cooling. Also there are good signs that there was no ice age going on in the lower lattitudes (Colinvaux et al 2000, Kastner & Goñi 2003,). That's why I invented the pulsating equator."

Why don't you start a new thread, to discuss the Pulsating Equator Hypothesis hypothesis. I would be interested to discuss, but I need a better base from which to start the discussion. What is the hypothesized mechanism? What drives it? Is it periodic?

As to significantly warmer temperatures, at LGM. Does the sea level reflect higher or lower temperatures, at the LGM? i.e. Is there data that does not support significantly warmer temperatures? Does other data support the hypthosis? If not why not?

See the attached link to a paper that discusses sea level last 350 kyrs.

http://www.geol.ucsb.edu/faculty/lea/pdfs/Lea%20QSR%202002.pdf [Broken]

As to the high latitudes being warm during the LGM, can you provide a link to a full paper rather than to an abstract? Without data and analysis there is nothing to discuss.

 

[Andre]

Dear William, thanks for your interest, let's go over all this.

Hi Andre:

Why don't you start a new thread, to discuss the Pulsating Equator Hypothesis. I would be interested to discuss,

We could revive this thread:

https://www.physicsforums.com/showthread.php?t=153634

but I need a better base from which to start the discussion. What is the hypothesized mechanism? What drives it? Is it periodic?

I know the part of the scientific method saying that the hypothesis requires a physically sound mechanism. We know that the Earth has a pulsating equator now, albeit in millimeters. Why can't it be ~100 meters order of magnitude on a millenium time scale on an equatorial bulge of 21 km. But a mechanism, is far from understood. To explain the ice ages it would have to be the cause of the 100,000 years cycle, which cannot be explained as a Milankovitch wobble.

Since the milankovitch cycles are fairly stable on a multi million years time scale and the 100,000 years cycle emerged only 900,000 years ago, the only factor I can think of such a behavior, is the solid inner core of the earth, which is assumed to be growing under the pressure and the cooling. 900,000 years ago it may have exceeded a critical size to break the physical stability of the core spin axis. The resultant misaligment of core and mantle spin axis would have caused turbulence, excess heat, which reduced the core size again, which could have permitted the spin axes to realign eventually, starting a new cycle of cooling and core growing. I know there is an old publication that assumes that the size of the equatorial bulge is also a function of the total fluidity of planet (haven't found it back yet). Perhaps it is. But surely that's all highly speculative.

Point is that it seems physically not impossible to have a pulsating equator and we have one now.

http://www.space.com/scienceastronomy/equator_bulge_020801.html [Broken]

Others have thought about it:
http://adsabs.harvard.edu/abs/1982Prir...46M

As to significantly warmer temperatures, at LGM. Does the sea level reflect higher or lower temperatures, at the LGM? i.e. Is there data that does not support significantly warmer temperatures?

There is an abundance of proxy data considering paleo sea surface temperatures (Mg/Ca Ca/Sr, d18O, alkenones etc). The problem is however the dependence of those data on assumed chemical conditions. Ion ratios and biota activity are sentitive to pH, the biota producing the proxies may have reacted on changing conditions and you bet that the oceans reacted vigourously on the moving of the ocean bottom, amplified by massive methane hydrate decomposition events on record (Bryn et al 2005, Evans et al 2005, Maslin et al 2005, Mienert et al 2005) Refs here:

http://home.wanadoo.nl/bijkerk/ext-refs-new.pdf [Broken]

Does other data support the hypthosis? If not why not?

Perhaps have a look at that ref list and realize that there must be a common denominator that fits for all of those phenomenons. There is the puzzle of the Pleistocene.

Sea levels is perhaps the most important evidence. We know that there are many anomalies actually refuting the common paradigm. We also know that there was not nearly enough ice during the LGM (due to the alleged but missing ice on Siberia) to cause the 127 meters sea level rise for instance. We also know that there is no source for melt water pulse 1A. See:

https://www.physicsforums.com/showthread.php?t=113807

however a moving equatorial bulge would be a splendid explanation instead.

See the attached link to a paper that discusses sea level last 350 kyrs.

http://www.geol.ucsb.edu/faculty/lea/pdfs/Lea%20QSR%202002.pdf [Broken]

As usual papers like that fill in the blanks with assumptions based on the current paradigms, ignoring the anomalies. There are only a few areas from where sea level proxies are used notably the corals of Barbados and the mangroves of the Indonesian Sunda shelf, both on rather low lattitudes. A pulsating equator is probably explaning the sea level changes much better.

As to the high latitudes being warm during the LGM, can you provide a link to a full paper rather than to an abstract? Without data and analysis there is nothing to discuss.

Interesting warm indicator are insect assemblages for instance in my ref list:
Alfimov et al 2003, Kuzmuni 2001, Schirrmeister et al 2002, Sher et al 2002

Most of the papers are behind bars and not directly assessable online. Sometimes reports of conferences help. Dig into this one for instance:

http://www.yukonmuseums.ca/mammoth/progabst.htm [Broken]

Click the abstracts on the bottom of the page for a wealth of information, for instance:

http://www.yukonmuseums.ca/mammoth/abstrmol-mor.htm [Broken] containing basically the same information of Mol et al 2006.

Furthermore, my pdf library is a few gigs, containing most, if not all of those listed publications. Not free papers have been accumulated by visiting homepages of authors, and/or mailing them with requests for papers (works very well. Sometimes, you get more than you ask for) or asking around. My study partner is very good at that. You could PM me an email address.

 

[William Astley]

Periodic Ocean Level Fluctuations - Heinrich Events

Hi Andre,

The Heinrich events are simultaneous ice sheet discharges from three ice sheets. The Laurentine, Greenland, and the Scandianvian ice sheets. As noted in the following review paper, there is a periodic rapid accumulation of ice (which is hypothesized to be due to a periodic increase in solar activity) that is followed by a very cold period, during which the ice sheets discharges ice into the ocean and stabilize.

Review Article: "Sea Level Change through the Last Glacial Cycle" by Lambeck and Chappell

http://geochemistry.usask.ca/bill/courses/International Field Studies/Sea level.pdf

“… the pre-Last Glacial Maximum (pre-LGM) is characterized by substantial fluctuations in sea level of 10 to 15 m about every 6000 years. The timing of these rapid change events during oxygen isotope stage 3 (OIS-3) apparently coincides with Heinrich ice-rafting events recorded in North Atlantic sediments (61), which suggest that they reflect major ice discharges from continent-based or shelf grounded ice sheets (62). Of note is that sea level falls during this period occur in similarly short time intervals and the ice accumulation also appears to have been a rapid process (39).

 

[Andre]

Thanks William, I included the Heinrich events in this little presentation here:

http://home.wanadoo.nl/bijkerk/Pulsating-ice-age.pdf [Broken]

#17 on page 7.

The article is a good example of filling in the wide wide gap between data and blanks with scholar assumptions. The most important is the oceanic isotope - ice sheet volume hypothesis of Rutherford I believe. However when you check the numbers and the calculations, you're short a massive Siberian ice sheet, which did not exist at all.

Sea levels are much more complicated in the pulsating equator setting.

 

[William Astley]

Abrupt Planetary Cooling?

Is the abrupt cooling event that occurred 8200 years ago, after a period of very high solar activity, an analogue for the current solar macro cycle changes? (See Astrophysics in this forum: Thread “Solar Cycle Changes” for details concerning recent anomalous solar changes.)

The following is data and analysis that shows there was an abrupt planetary cooling event 8200 years ago, at a time when global temperatures were similar to or warmer than current temperatures. The paleo data indicates that the cooling event was wide spread; simultaneously affecting the Northern Hemisphere and tropical seas. The 8200 yr cooling event was the most sever temperature change in this interglacial period. There is also evidence of a concurrent drop in solar activity with the 8200 yr cooling event.

http://www.geo.arizona.edu/palynology/geos462/8200yrevent.html

This figure shows snow accumulation and isotopically inferred temperature records in the Greenland GISP2 ice core and a temperature record derived from oxygen isotope measurements of fossil shells in the sediments of Lake Ammersee, southern Germany. These records all show a major climatic instability event which occurred around 8200 years ago, during the Holocene. The event was large both in magnitude, as reflected by a temperature signal in Greenland of order 5 °C, and in its geographical extent, as indicated by the close correlation of the signal in these two locations. The dramatic event is also seen in the methane record from Greenland (not shown here) indicating possible major shifts in hydrology and land cover in lower latitudes. source: Von Grafenstein et al (1998) Climate Dynamics, 14, 73-81.

Abrupt tropical cooling ~8,000 years ago
M.K. Gagan, L.K. Ayliffe*, H. Scott-Gagan, W.S. Hantoro, B.W. Suwargadi, D. Prayudi, M.T. McCulloch


http://wwwrses.anu.edu.au/enproc/EP/ep_annrep/gagan.html [Broken]

"We drilled a sequence of exceptionally large, well-preserved Porites corals within an uplifted palaeo-reef in Alor, Indonesia, with Th-230 ages spanning the period 8400 to 7600 calendar years before present (Figure 2). The corals lie within the Western Pacific Warm Pool, which at present has the highest mean annual temperature in the world's ocean. Measurements of coral Sr/Ca and oxygen 18 isotopes at 5-year sampling increments for five of the fossil corals (310 annual growth increments) have yielded a semi-continuous record spanning the 8.2 ka event. The measurements (Figure 2) show that sea-surface temperatures were essentially the same as today from 8400 to 8100 years ago, followed by an abrupt ~3°C cooling over a period of ~100 years, reaching a minimum ~8000 years ago. The cooling calculated from coral oxygen 18 isotopes is similar to that derived from Sr/Ca. The exact timing of the termination of the cooling event is not yet known, but a coral dated as 7600 years shows sea-surface temperatures similar to those of today."

Comments:
1) Recent changes in the Sun
As noted in the astrophysics section of this forum (See thread: “Solar Cycle Changes”) the sun is currently spotless. Solar observers have noted a significant asymmetrical reduction in the solar meridian deep polar flow. The deep meridian flow is believed to control the solar magnetic cycle. There has been an abrupt drop in the velocity of the solar wind which is expected as the solar magnetic cycle appears to have been interrupted.

2) There is evidence that 20th century changes in solar wind caused the planet to warm and cool. See thread “Clouds and reflectivity”, for satellite data and Earth'shine data that shows there is direct correlation with 20th century changes in the solar wind and low level clouds. Also included in that thread is data that shows there is correlation with the solar parameter Ak (Ak is a measure of the solar parameters that affect the magnetic field about the earth) and the pattern of the 20th century temperature changes.

3) An increase in the geomagnetic field reduces the amount of Galactic Cosmic Rays (GCR) that strike the Earth's atmosphere. Satellite data and Earth'shine data shows that an decrease in GCR causes a decrease in low level clouds and an increase in GCR causes an increase low level clouds. Data also indicates that high speed solar winds causes an increase in the Global Electric Current, which through the process of "electroscavenging" removes cloud forming ions. From 1974 on, solar coronal holes started to appear at the end of the solar cycle which created very high speed solar winds. Through the process of electroscavenging it is believed that the high speed solar winds caused a significant reduction in low level clouds.

 

[Peter Lloyd]

Milankovitch 100k cycle

I am mystified by the comments in earlier postings on this thread, that there was no known mechanism by which the Milankovitch 100k cycle can influence glacials/interglacials.

Maybe I am simplistic (not maybe, I know I am!) but I have always understood the following to be the cause and mechanism.

The cause is the orbital periodicities of Earth and the gas giant planets and resulting planetary positions relative to the Sun. These cause Earth's orbit to oscillate between circular and elliptic, with a period of between about 94,000 and 114,000 yrs and an amplitude of 5% to 7%, depending on the precise planetary configuration. The Sun, of course, stays at one focus of the ellipse of Earth's orbit.

I have often read that this small change in eccentricity cannot explain ice ages, but to me, the opposite is very clear. It is easy to explain with a diagram, but I will try with words.

First, although the eccentricity is low, the effect is large because of the inverse square law. With a minimum (circular) orbit radius of
1.471 x 10e8 km, an eccentricity of 7% at max. aphelion gives max. radius of 1.574 x 10e8 km. The inverse square relationship results in Earth at max. aphelion receiving only 87.3% of the solar energy received at perihelon or circular orbit.

A NASA website:

http://earthobservatory.nasa.gov/Library/Giants/Milankovitch/milankovitch_2.html

- says that Earth receives 20-30% less insolation at max. eccentricity, with no explanation, but I cannot see how that is worked out - if they are right, my point is more strongly made. If anyone can explain this conflict, I would be grateful.

Now the tricky part. It takes 50,000yr to get from circular orbit to max. eccentricity. Therefore, for about 20,000yr (10,000 before and after max.), Earth receives only 90% of max. insolation for 3 months of every year. Both poles, by the way. And in that 20,000yr, almost a complete precession cycle occurs, so the effect is well distributed. That is surely an effective trigger for an ice age. As Earth approaches circular orbit, it heats rapidly as it increasingly gets almost maximum insolation all year round; as it leaves circular orbit and appoaches max. eccentricity, it radiates heat slowly; thus we get the sawtooth temperature profile seen in ice cores.

In between these two extremes, the 21,000yr precession cycle can induce minor ice ages alternately between the two poles when orbital eccentriciy is high, but not when it is low or circular.

This view also gives us a timing for peak of this interglacial. Orbital eccentricity is currently about 3%. Depending on the orbital eccentricity at the nadir of the last ice age (5% or 7%) we are just before or just after halfway to the peak of the interglacial - 30k or 20k yrs to go! Given the minimum temperature recorded in the Vostok core at 28k yrs ago, I would guess at 7% eccentricity at the last max. aphelion, about 20k years to go to mid-interglacial and crisping up nicely.

I would be very interested to read any critique of this - always ready to learn.

For some reason I cannot get this site to accept the full NASA website URL - after .gov/ it is Library/Giants/Milankovitch/milankovitch_2.html. See if this works!

 

[Peter Lloyd]

PS - I am not proposing this is the only forcing mechanism - only that it is mechanism behind the obvious approx. 100k cycle seen in ice cores, etc.

There are many minor cyclic influences, many of which I suggest we know nothing about!

 

[Andre]

You did quite some digging, Peter.

First of all, the 8200years event as well as the Younger Dryas "cooling" etc is almost solely based on water isotopes, d18O, dD which has been declared temperature proxies in 1997 by Jouzel et al. They are NOT!

d18O in precipitation is depending on temperature during consensation and rain out effect. If we assume the latter constant, then the condensation temperature is a measurement of the relative humidity of the air. Low when it is dry, high when it is humid. And that fits exactly with what we see in the ice cores and other proxies. Non calor sed umor.

See also:
http://home.wanadoo.nl/bijkerk/refuting%20the%20Greenland%20paleo%20thermometer1.pdf [Broken]

This would make the cold nature of the 8200y event suspect.

The 100 ky cycle is indeed not related to Milankovitch and for two reasons it doesn't make sense. Why did it suddenly start about 900,000 years ago while the milankovitch cycles linger on for millions of years with only very small variation:

http://home.wanadoo.nl/bijkerk/41-100k-world-milankovitch.GIF [Broken]

How could a Milankovitch minimum variation around 420,000 year ago trigger the largest "deglacitation spike"

http://home.wanadoo.nl/bijkerk/milanko3.GIF [Broken]

See also some problems around 200,000 years ago.

For a completely different idea, see the pulsating equator thread.

 

[William Astley]

Ice Age's and Milankovitch's 100k cycle.

Hi Peter Lloyde

In response to your comments.

I am mystified by the comments in earlier postings on this thread, that there was no known mechanism by which the Milankovitch 100k cycle can influence glacials/interglacials.

Maybe I am simplistic but I have always understood the following to be the cause and mechanism.

The cause is the orbital periodicities of Earth and the gas giant planets and resulting planetary positions relative to the Sun. These cause Earth's orbit to oscillate between circular and elliptic, with a period of between about 94,000 and 114,000 yrs and amplitude of 5% to 7%, depending on the precise planetary configuration. The Sun, of course, stays at one focus of the ellipse of Earth's orbit.

1. First the Earth is currently at perihelion during the Northern Hemisphere winter (around December 25) and at aphelion during the Northern Hemisphere summer. Due to the seasonal difference, of the distance of the earth, from the sun, the Northern Hemisphere winters are roughly 4C warmer and the Northern Hemisphere summer's are roughly 4C colder due to the orbital effect. Note however that the opposite is true for the Southern Hemisphere. Cold Northern Hemisphere summers are according to the Milankovitch hypothesis, the reason why the glacial cycle begins.

Comments:
Another interesting question is why do the ice age epochs begin and end? This ice age epoch began roughly 17 MM years ago with ice sheets forming in the Antarctic. (The Antarctic has been polar centric for roughly 100 MM years. No ice sheets on the Antarctic continent prior to roughly 20 MM years and a climate warm enough to support reptiles.) Then roughly 1.7 MM years ago ice sheets began to form in the Northern Hemisphere. The general population is not concerned by the glacial period because they believe it be a gradual change.

Some have stated that the next glacial period will not occur for 20 k years which is not correct, based on the proxy paleo climatic data and the competing hypothesis as to what causes the glacial/interglacial cycle. The past interglacial periods have all been shorter than the Holecene. Based on the pale data this interglacial period will end abruptly.

It is interesting to note that the sun appears to be moving to a super Maunder type state in which the sun spot cycle stops. The Maunder minimum (Little Ice Age) lasted for 70 years.

2. Northern hemisphere insolation is currently the same as during the last glacial maximum. Why are we not in an ice age? i.e. The opposite was true when the glacial period ended.

3. When an ice age begins (based on the paleo data) the entire planet simultaneously cools, which does not make sense from the stand point of the insolation hypothesis. Also the cooling is very rapid. There is evidence of periodic abrupt climatic changes. Abrupt climate changes cannot be explained by the insolation hypothesis.

4. The insolation hypothesis does not explain why the ice ages prior to 700 kyears ago followed a 41 k year cycle and then starting 700 k years started to follow a 100 kyear cycle.

 

[Andre]

Check out the latest work of Lisiecky and Raymo here

http://www.moraymo.us/2007_Lisiecki+Raymo.pdf [Broken]
http://www.moraymo.us/2006_Tzipermanetal.pdf [Broken]

and notice that the 100 ky cycle is not explained whatsoever as I keep trying to tell.

But this work invokes some question marks too.

 

[Peter Lloyd]

Andre,

I want to address the interesting questions raised by you and WA and it would be easier to use a couple of graphs - but I have not been able to import images on to either the Quick or Advanced reply panels. (I told you I was simple!) I've tried the conventional Cut and Paste on both .xms and .jpg files, but only the text under the image transfers, Any advice?

Otherwise I shall have to struggle with words, which will be very tiring for you.

 

[Andre]

Unfortunately, Peter, the Board of Directors of this enterprise has disabled the function in these divisions here. It only works in the general chat area. Sometimes I use that to show graphs.

In this area you can upload files and imgs. But then you have to hit the "New reply" button instead of typing into the quick reply box.

Below the edit box you will find "additional options" where you can "manage attachments". That should be self explanatory for uploading pics and graphs like I did here for instance:

[url]https://www.physicsforums.com/showthread.php?t=162192[/url]

:smile:

 

[William Astley]

Evidence that Contradicts Milankovitch's Hypothesis

The data and analysis from the paper referenced in the attached link contradicts Milankovitch's hypothesis. The data shows that a planet wide forcing function is simultaneously affecting both the Northern and Southern Hemispheres. The data and analysis shows that the Northern and Southern hemisphere glacial and interglacial cycle is synchronized. (i.e. The Northern hemisphere and Southern Hemisphere cool and warm at the same time.) The Milankovitch orbital change mechanism is not capable of simultaneously affecting both the Northern and Southern Hemispheres. The insolation changes due to the orbital changes are asymmetrical comparing their affect on the Northern as opposed to the South Hemisphere. i.e. If summers are warmer in the Northern hemisphere due to orbital changes they are colder in the Southern hemisphere. (See comment for details.)


http://www.news.wisc.edu/9557.html [Broken]

The following are quotes from the link that discusses the paper and quotes from the author’s paper.

What's more, the group found evidence that the last major glacial period prior to the last ice age, from a time dating to 150,000 years ago, mirrored North American climate for the same period.

"During the last two times in Earth's history when glaciation occurred in North America, the Andes also had major glacial periods," says Kaplan.

The results address a major debate in the scientific community, according to Singer and Kaplan, because they seem to undermine a widely held idea that global redistribution of heat through the oceans is the primary mechanism that drove major climate shifts of the past. The implications of the new work, say the authors of the study, support a different hypothesis: that rapid cooling of the Earth's atmosphere synchronized climate change around the globe during each of the last two glacial epochs.

"Because the Earth is oriented in space in such a way that the hemispheres are out of phase in terms of the amount of solar radiation they receive, it is surprising to find that the climate in the Southern Hemisphere cooled off repeatedly during a period when it received its largest dose of solar radiation," says Singer. "Moreover, this rapid synchronization of atmospheric temperature between the polar hemispheres appears to have occurred during both of the last major ice ages that gripped the Earth."

Comments:
1) It should be noted that a number of scientists have questioned Milankovitch's hypothesis and there is other evidence that indicates that Milankovitch'e hypothesis is incorrect.

2) The Milankovitch orbital changes, determine whether summer is relatively colder and winter is relatively warmer or visa versa in a hemisphere. As stated above the orbital effect is opposite when comparing hemisphere to hemisphere.

3) As the Earth is 70% covered by water and the ocean has a 1000 times more heat capacity than the atmosphere, the ocean and atmosphere should smooth out the Milankovitch seasonal change in insolation. i.e. The total amount of energy received by the Earth is the same. The only difference due the orbital changes is how much energy is received in which season.

 

[William Astley]

Abrupt Climate Changes

Periodic rapid climate changes (drops in regional and planetary temperature of as much as 2C in less than a decade) were discovered in the 1990s when the Greenland ice sheet cores were drilled and analyzed. The rapid climate changes are periodic. Paleoclimatologists at first thought the Greenland ice sheet indication of very rapid changes might be incorrect, however sea floor sediment data, two additional core samples from Greenland, Southern Hemisphere ice cores from Andes’ ice sheets, and other proxy data has confirmed that the changes are real, widespread (affects both hemispheres and tropics), and that the rapid climatic change events are periodic.

This is an overview of the data and the first attempts to explain what could be causing “Rickeys”, Rapid Climatic Change Events, RCCE.

Sudden climate transitions during the Quaternary

http://www.esd.ornl.gov/projects/qen/transit.html [Broken]

Until a few decades ago it was generally thought that all large-scale global and regional climate changes occurred gradually over a timescale of many centuries or millennia, scarcely perceptible during a human lifetime. The tendency of climate to change relatively suddenly has been one of the most surprising outcomes of the study of Earth history, specifically the last 150,000 years (e.g., Taylor et al., 1993). Some and possibly most large climate changes (involving, for example, a regional change in mean annual temperature of several degrees Celsius) occurred at most on a timescale of a few centuries, sometimes decades, and perhaps even just a few years.

According to the marine records, the Eemian interglacial (My comment, Eemian is the name for the last interglacial cycle. There has been roughly 22 interglacial/glacial cycles, in the last 1.8 MMyears. The interglacial cycles last around 12 kyrs, the glacial cycles around 90 kyears.) ended with a rapid cooling event about 110,000 years ago (e.g., Imbrie et al., 1984; Martinson et al., 1987), which also shows up in ice cores and pollen records from across Eurasia. From a relatively high resolution core in the North Atlantic. Adkins et al. (1997) suggested that the final cooling event took less than 400 years, and it might have been much more rapid.

Based on the Paleoclimatic data, the current interglacial period will end abruptly. The next comment provides data and analysis concerning what could be causing abrupt periodic changes in the planetary temperature.

 

[Andre]

problem though is that the interpretation of proxies is almost a comedy of errors.

 

[William Astley]

What Causes Abrupt Planetary Temperature Changes?

The paleoclimatic data shows that there have been regular periodic abrupt changes in planetary temperature. It appears that the short term increases and drops in planetary temperature are due to changes in the solar cycle (Increases similar to the 20th century warming which it is hypothesized was primarily caused by high solar activity and a drop in temperature due to a solar cycle change to a Maunder Minimum or to a Super Maunder Minimum). It appears that the long term drops in planetary temperature are due to abrupt and long term drops in the geomagnetic field.

Both the solar changes and geomagnetic field changes modulate the amount of planetary cloud cover. As low level clouds reflect short and long wave radiation back into space, an increase in low level cloud cover cools the planet and a decrease warms the planet.

Is there data that supports the hypothesis that cloud levels are modulated by changes in the solar cycle and geomagnetic field changes?

Attached is a link to Enric Palle’s (2003) paper that provides data and analysis that supports at a 99.5% confidence level that low level planetary cloud cover, tracks changes in Galactic Cosmic Rays (GCR) 1983 to 1993. For the period 1993 to 2001 planetary cloud cover continues to track GCR changes except for a persistent reduction in cloud cover. The reduction in cloud cover is believed to be due to the “electroscavenging” process.

See copy of Palle's satellite paper. (See figure 2. Note low level clouds are reduced by minus 0.065% per year, starting in about 1993.)

http://solar.njit.edu/preprints/palle1264.pdf

Comment: Planetary cloud cover is believed to modulated by two processes: 1)Changes in the number and strength of the Galactic Cosmic Rays that strike the Earth's atmosphere and create cloud forming ions (The geomagnetic and Solar large scale magnetic fields, partially block GCR) and 2)Changes to the Earth's global electric circuit which removes cloud forming ions. Data and analysis indicates that changes to the global electric circuit are caused by high speed solar winds, that are caused by solar coronal holes that started to appear near the solar equator 1993 and on.) The next comment provides a link to Yu & Tinsley's paper that describes how both processes affect cloud formation and physical properties.

Some climatologists stated that the satellite analysis of cloud cover could be incorrect. (There was a paper published that ridiculed Svensmark’s paper which had analyzed the satellite data.) Palle's paper re-examined the satellite data, using a different analytical technique than Svensmark had used, which addressed others complaints concerning Svensmark's paper. Palle’s analysis of the satellite data confirmed Svensmark’s original finding. As climatologists were still skeptical, Palle measured the change in planetary cloud cover using a completely different observation technique.

Attached below is a link to a second Palle paper that provides data from observing the shine of the Earth on the moon, to measure planetary albedo. The Earth'shine data, confirms that planetary cloud cover tracks GCR and that planetary cloud cover was reduced in the 1993 to 2001 period, which completely supports the satellite data and analysis.

http://solar.njit.edu/preprints/palle1266.pdf

Palle’s Earth'shine analysis found that the 1994 to 2001 reduction in cloud cover warmed the planet by 7.5 W/m2 +/- 2.4 W/m2 which is three times greater than the total estimated greenhouse gas estimated warming for the 20th century. (Note the 20th century very high solar activity is over. Will the planet cool? If so, how much and how quickly?)

From Palle's Earth'shine data paper:

Our observations of the Earth'shine take the ratio of the Earth'shine to moonshine, so they are insensitive variations of the solar irradiance. The 5 +/-2% change in our observed reflectance translates to …. Solar and terrestrial changes are in phase and contribute to a greater power going into the climate system at activity maximum. However, the effect of the albedo is more than an order of magnitude greater. Our simulations suggest a surface average forcing at the top of the atmosphere, coming only from changes in the albedo from 1994/1995 to 1999/2001, of 2.7 +/- 1.4 W/m2 Pall e et al., 2003), while observations give 7.5 +/-2.4 W/m2. The Intergovernmental Panel on Climate Change (IPCC, 1995) argues for a comparably sized 2.4 W/m2 increase in forcing, which is attributed to greenhouse gas forcing since 1850.

Still, whether the Earth’s reflectance varies with the solar cycle is a matter of controversy, but regardless of its origin, if it were real, such a change in the net sunlight reaching the Earth would be very significant for the climate system.

 

[William Astley]

Periodic Planetary Temperature Drop?

Evidence that both Northern and Southern hemispheres cool in response to periodic solar changes?

This paper provides data that shows that the well known and discussed periodic cooling events in the Northern Hemisphere appear to have occurred concurrently with Southern Hemisphere cooling events. Both the Northern and Southern Hemisphere periodic cooling events appear to coincide with solar activity minimums.

"Solar modulation of Little Ice Age climate in the tropical Andes"

http://www.pnas.org/cgi/reprint/0603118103v1.pdf

Quoted from the above paper.

The underlying causes of late-Holocene climate variability in the tropics are incompletely understood. Here we report a 1,500-year reconstruction of climate history and glaciation in the Venezuelan Andes using lake sediments. Four glacial advances occurred between anno Domini (A.D.) 1250 and 1810, coincident with solar activity minima. Temperature declines of approx. 3.2 +/- 1.4°C and precipitation increases of approx. 20% are required to produce the observed glacial responses.