Ice Ages and Sea Level

Guest post by Dr. David Archibald

The Earth is currently in an interglacial period of an ice age that started about two and a half million years ago.  The Earth’s current ice age is primarily caused by Antarctica drifting over the South Pole 30 million years ago.  This meant that a large area of the Earth’s surface changed from being very low-albedo ocean to highly reflective ice and snow.  The first small glaciers were formed in Antarctica perhaps as long ago as 40 million years.  They expanded gradually until, about 20 million years ago, a permanent ice sheet covered the whole Antarctic continent.  About 10 million years later, glaciers appeared on the high mountains of Alaska, and about 3 million years ago, ice sheets developed on lower ground in high northerly latitudes.

Pacific Ocean bottom water temperatures started declining 40 million years ago, falling 10° C to the current 3° C.  The band of high ocean temperatures (above 25° C) also contracted towards the equator, from 45° latitude to 20°.  Eventually the oceans lost enough heat that the Earth’s orbital parameters started causing surges in ice formation.  There are three orbital parameters: eccentricity, precession and obliquity, shown in Figure 1.

eccentricity-precession-and-obliquity1

Figure 1:  Orbital Parameters:  Eccentricity, Precession and Obliquity- click for larger image

This figure is developed from A.L.Berger, 1978, Long Term Variations of Daily Insolation and Quaternary Climatic Changes, Journal of the Atmospheric Sciences, volume 35 (12), 2362-2367.

Eccentricity is caused by changes in the shape of the Earth’s orbit due to the gravitational attraction of other planets.  Precession is the change of direction of rotation.  Obliquity is the tilt of the axis.  When these effects aligned, their effect is reinforced.  From three million years ago to about 800,000 years ago, the dominant pattern of glaciation corresponded to the 41,000 year period of changes in the Earth’s obliquity.  Since then, a 100,000 year cycle has been dominant.

Ice ages occur because the summer sun in the northern hemisphere does not get hot enough to melt all the ice that accumulates over winter.  Ice has a much higher reflectivity than rocks or vegetation, and so reflects more sunlight into space and the cooling is reinforced.  Eventually the orbital parameters change back and warming occurs.  Glacial periods tend to cool slowly and warm abruptly.  Because the Earth’s orbital parameters can be calculated, the amount of sunlight in high northern latitudes can be calculated.

insolation-at-65-north

Figure 2:  June Mid-Month Insolation at 65° North – click for larger image

This figure is derived from M.F.Loutre and A.Berger, 2000, Future Climate Changes: Are we entering an exceptionally long interglacial?, Climatic Change 46, 61-90

Figure 2 shows how that translates to insolation (sunshine) at 65° North.  The recent peak in insolation was 11,000 years ago at the end of the last glacial period.  It has since declined by about 10% to 476 watts per square metre. Insolation will rise from here for the next 30,000 years, but it will still be low enough for the next glaciation to form.  This is shown by Figure 3 of Northern Hemisphere ice volume for the last 200,000 years and a projection for the next 130,000 years.  According to these calculations, the Earth is at the beginning of a 20,000 year plunge into the next ice age.

The reason why the Earth doesn’t respond more rapidly to changes in insolation is due to the retained heat in the oceans, which smoothes the whole process over thousands of years.  Over the short term, the oceans are very responsive to changes in solar activity.  Figure 5 shows the very strong correlation between the annual rate of sea level rise and solar cycles over the 20th century.  The sea level rise of the 20th century can largely be attributed to a more active Sun relative to the 19th century.  About 70% of the sea level rise of the 20th century was due to thermal expansion of the oceans, with the rest due to melting glaciers.

future-glacial-periods-9th-january-2008

Figure 3:  Future Glaciation – click for larger image

This figure is derived from M.F.Loutre and A.Berger, 2000, Future Climate Changes: Are we entering an exceptionally long interglacial?, Climatic Change 46, 61-90

sea-level-rise-and-solar-cycles-of-the-20th-century

Figure 4:  The Correlation between Sea Level Rise and Solar Cycles over the 20th Century. – click for larger image

The sea level data is derived from S.Holgate, Decadal rates of sea level change during the twentieth century, Proudman Oceanic Laboratory, Liverpool, UK.

About these ads

207 thoughts on “Ice Ages and Sea Level

    • No. I believe the sun’s irradiance is slowly increasing over geologic time scales.

      The temperature decline may be related to the earth entering one of the spiral arms of the Galaxy from a relatively less active region for GCR, but I don’t think anyone knows for sure.

      • I was wondering, since the time stamp is about the same, would we get enough energy when the supermassive black hole in the center of the milky way turns on to get us back to the temperatures that existed through most of the geological record with higher life forms?

        How much of the night sky be lit up with the two jets blasting out perpendicular from the center of the milky way from our vantage point in the galaxy?

        Maybe an event like this effects the output of the sun itself ….

        Being in and out of spiral arms may be a possibility.

      • Below someone reminds me of the time with water over the poles and Pangea the supercontinent girdling the globe. Perfect configuration to avoid Milankovitch cycles. Fortunately we still have one pole with water to avoid that other scenario … Snowball Earth. Although the theory that ever happened is not supported by a large amount of evidence from what I’ve seen.

    • Antarctica started drifting over the south pole as it separated from South America. As glaciers and an ice cap formed, sea levels dropped, and circumpolar winds started insulating antarctica from the rest of the planet. Then as the continent totally separated from SA, a circumpolar ocean current started up, that further isolated and insulated Antarctica from the rest of the global climate. This all made Antarctica a sort of refrigeration compressor.

      Since about 22 million y.a., the Antarctice ice caps have been stable during some periods of significantly greater warmth and higher CO2 levels than at present. Expeditions to the buried glaciers in the katabatic canyons have verified this, which has demolished the disasturbationist theory claims of imminent doom.

    • “The Earth’s current ice age is primarily caused by Antarctica drifting over the South Pole 30 million years ago. This meant that a large area of the Earth’s surface changed from being very low-albedo ocean to highly reflective ice and snow. “

    • Antarctica has been slowly drifting SE in a continental drift sense during the Tertiary. Starting 40 mya, the first edges of the continent were reaching latitudes greater than 85 South. During the last 40 million years, the drift has continued so that 90 S is located in the middle of the continent. If the spreading continues about 40 million years in the future, it will be mainly north of 85 degrees south.

      The importance is that as the land mass moved further south, ice could begin to accumulate on it and that started a cooling feed back loop.

  1. Interesting post.

    A couple of minor points:

    1. It is difficult to conceive of Pacific bottom waters’ ever having been 13 degrees Celsius. Are there other corroborations of this number?

    2. Figure 3 appears to be inverted.

    • Harold, read the scale again. The graph is correct…more ice is towards the bottom of the graph! :)

      • I understand that the scale increases toward the bottom, however I think the author made a mistake in formatting the graph that way. Many people will fail to notice that and misunderstand. They will think “He predicts the ice is melting!”

      • Thanks, I missed that 1st time through… I’d suggest changing the caption to “Future (inverse) Glaciation”.

    • Figure 3 indicates a potential emergency crisis.

      Buy bricks now! You can put them on your SUV’s fast pedal in the near future to protect the Earth from Climate Change.


    • 1. It is difficult to conceive of Pacific bottom waters’ ever having been 13 degrees Celsius.

      I agree. I was taught in elementary school that bottom waters always stay at 4 degrees (probably slightly different for salt water), since the density at this temperature is the highest. To reach 13 degrees I guess extreme currents would be necessary, so this figure sounds like nonsense.

      • Because the temperature of rocks increase with depth, it would also make sense for the deep ocean to be warm. But convection can remove that heat. The ocean bottom is kept cold by water from the poles. So all that’s needed to warm the ocean bottom is for the poles to warm, and we’re being told that it’s easy for the Arctic Ocean to warm. The south polar area is oddly isolated by the current flowing all the way around it, so to keep the Pacific bottom warm there would be competition between cold water from the Antarctic and the warming caused by upwellings such as off the coast of Peru.

    • Same question, 10C at the bottom?. Plain physics tells you that water under serious pressurte will tend to the temperature for which it has its smallest volume, which for water is about 4 degrees C. No matter how warm or cold the surface, the bottom of the oceans is always 4C everywhere, except near thermal vents, of course. Yet you mention 10C and I have seen similar numbers in connection with carbonate sediments. So, how come, and do you have references? Apart from that, good post, although I must mention that I was told about the Milankovitch cycles already at secundary school in the 1960-ies by an enthousiastic teacher.

      • Hello Ed,
        the heaviest water sinks to the bottom, regardless of its temperature. There may not even be any 4 C water if the overall average temperature is high enough. When you start heating your tea water there may be some 4 C just having come right out from the tap, but very soon the coldest water is close to 100 C.

  2. “Precession is the change of direction of rotation”

    It makes it sound like the sun rises in the west during the ice age. Maybe say the “Change in the direction of the AXIS of rotation” to be a bit more accurate.

    Also, the bottom waters of the pacific ocean at 13 C? Where does that information come from? It is pretty tough for me to swallow.

  3. Nice post David.

    Here is nice animatable graphic showing Antarctica continental drift over time.

    Between 50 million to 40 million years ago, the Australian plate separated from Antarctica and then Antarctica moved far enough away from the South American plate (while simultaneously drifting toward and over the South Pole) so that the southern ocean current could isolate it from warmer ocean patterns. ie. Glaciation.

    And CO2 is not involved in continental drift (although I’m sure some model could simulate it).

    http://www.exploratorium.edu/origins/antarctica/ideas/gondwana2.html

    • A little off topic but this change in the location of Antarctica reminds me of how long the penguins have occupied Antarctica and how long the Emperor penguins have been making the migration to breed!! Now that’s what I call adaptation!!

    • Please: “And CO2 is not involved in continental drift”. CD was Alfred Wegener’s theory, for which he was hooted out of polite scientific society. He actually had the correct idea, and the mechanism now known as “plate tectonics” explains how, for example, one can cut out maps of Africa and South America, put them together, and they fit very well. Today, he’s (posthumously) back in good standing.

      Geology is replete with many such great controversies. The latest of course is “global warming” var. “anthropogenic”. One camp is again trying to hoot another out of the fold. We should know better by now.

      • We should know better by now that man is insignificant when it comes to Solar scales.
        Epicycles met Ockham’s razor.
        So too will CO2 forcing. When going to great lengths to smash a square peg into a round hole, the first clue is the splinters and destroyed carpentry.

  4. it would have been helpful for the article to have referred to the third of the Milankovitch cycles – the variations in the elliptical orbit of the Earth. The three together (obliquity, changes in the precession), act like biorythms when they can reinforce or cancel each other in varying degrees.

    In any event, as a Geographer, my understanding that we are in the Fourth Great Ice Age of the earth’s history. It actually started nearly forty million years ago, became somewhat more intense about 16 million years and ago then worsened a lot 3 million years ago. The article is right in that there are alternating glacial / interglacial periods.

    For the record, the first was a possible snowball earth approx 2,500 million years ago, the second a probable snowball earth about 750 million years ago and the third (the Kerroo if memory serves) was about 380 million years ago (I stand to be corrected on the actual figures)

    As a counterpoint, we should be aware that the Cretaceous (160m years ago) was the total opposite – so hot that there was no ice anywhere on the planet. Since then it has been downhill all the way !

  5. Seems DA is marching thru his info with the Cana protocol, it just seems to get better at each turn. The simplicity of presentation here of something that has always humbled me in text is arresting.

    • Thanks to Anthony for posting this. I did write this as a simple summary. Lautre and Berger are loony warmers, but they left enough information in their papers to see what was going on. I turned their graphs around so that time marched to the right, as it should. The Holgate – solar cycle graphic came from a graphic that was originally posted on Climate Audit a couple of years ago. That relationship is worth a paper. Lautre and Berger dreamt up a 50,000 year Holocene and said we would have another glacial period after that. They weren’t going to be so completely loony as to say that we would never have another glacial.

      What is going to happen is that Mankind is going to burn through the rocks we can economically burn over the next couple of hundred years and the oceans are going to swallow 97% of that. The net result will be an increase in the biological productivity of the oceans. There will be no other discernible result.

      On the current minimum, in the absence of larger sunspot numbers to calculate it from, the month of solar minimum is likely to be put in the middle of the period of flatlined F 10.7 radio flux. On that basis, if activity ramped up tomorrow, the month of minimum would be November 2008. Otherwise, each extra two months of flatline adds another month. Each extra month of minimum takes 0.06 degrees C off the temperature of the mid-latitudes over Solar Cycle 24.

      For those of us amongst us in solar denial, I recommend Hoyt and Schatten’s “The Role of the Sun in Climate Change”. They note that the first person to discern a link between solar cycles and climate was in ancient Greece in 400 BC. That person was only equipped with an open mind.

      • The TSI bird is in it’s first solar cycle so what minimum looks like no-one knows.

        Just threw this together for a quick look. (taken from 6 hour data, lot of data points)

        Is it correct? Can’t be sure.

      • David, you say: “Lautre and Berger dreamt up a 50,000 year Holocene and said we would have another glacial period after that.” That is consistent with what I see in their paper, but your figure 3 above (which you say is from their paper) shows glaciation starting now, not in 50,000 years.

        Am I missing something here, or is there an error somewhere?

  6. “Why did temperatures start declining 40 million years ago? Is the sun cooling down?”

    The major portion of the cause lies with terrestrial continent formations. Beginning in the 60’s plate tectonics observed, as DA alludes, to Pangea formations with most all of the land in one continent lead to peak global temps.

    The reverse, ice ages recur with land ‘evenly’ distributed about the globe. While some have noted here that the NH and SH appear decoupled, the situation is worse with a Pangea configuration and one ocean of size.

    • Gary,
      If you take a globe of the world and take it out of it’s mount, turn the globe so as Antarctica is on the Equator all you can see is one big ocean, makes you wonder what is up and what is down, I myself think that the Northern Hemisphere with all the extra weight must be down, but as I have not traveled in space and found out what is up and what is down I remain ignorant.

      • Well, the Northern Hemisphere is probably not all that much heavier. This is because continental crust is lighter than oceanic crust (density-wise). This is why, for the most part, oceanic crust subducts under continental crust.

    • Thanks, I forgot about that.

      It think I ran into that discussion when looking at the ‘Snowball Earth’ theory. Pangea with water over the poles made us warmer and kept us out of the Milankovitch cycle …

      It would be nice if the Milky Way remains an abstraction and not an influence.

  7. David,

    Is it not true that although insolation will begin to increase in the near future (geological time) the current level of insolation will continue to decrease slightly before then?

    • The graphic says that insolation at 65 north will be higher than present for the next 50,000 years. Not enough to stop a glaciation though.

  8. Very nice and clear explanation of the orbital parameters. Some tectonic events also should be noted: 1) the separation of the Indian subcontinent from Antarctica and subsequent contact with Asia caused the uplift of the Himalayan plateau and changed circulation patterns between 40 and 10 million years ago (mya), 2) opening of the Drake passage between South America and Antarctica allowed a circumpolar current that limited the flow of warm water as far south as before, 3) uplift of the isthmus between North and South America caused more warm waters to flow poleward about 6 mya. The physical factors are given little acknowledgment in the media, yet are by far the greater contributors to the basic climate we have.

    • yes the start of the ice ages 2.5 mya corresponds to the formation of the gulf stream/THC. strangely nobody seem to realise that this should act like a car radiator and cool the earth by transporting heat and moisture from the tropics to the high latitudes where heat can escape easier and moisture forms more clouds increasing albedo. Of course people in the north atlantic think the gulfstream warms the entire world because it warms their own. However the system is a little bigger than the north atlantic
      cheers

    • Absolutely….. and one would have to admit, these tectonic processes are much more substantial than a molecule of CO2 gas….. and more believable in cause and effect.

      • Is it so difficult to believe that carbon dioxide is a greenhouse gas? Is it so difficult to understand that man has pumped billions of tons of CO2 into the atmosphere? Is it so difficult to believe that the amount of carbon dioxide in the atmosphere is steadily increasing and is it so difficult to believe that all this will have some effect on climate?

        Of course there are many other factors which affect our climate, from the sun to the inside of the earth but to blindly ignore any one of them is poor science.

      • Don’t forget the regulation and stabilizing effect of water and water vapor, which has kept the climate stable for about a billion years. I was taught this 35 years ago in high school. It is bizarre to me how this has been corrupted by modelers.

      • No one is blindly ignoring demon CO2. With Pangea formations comes interruption of the oceanic circulation of polar waters between hemispheres, the global average temperature has recurrently rising to 72 degrees F.

        CO2 follows temperature rising to roughly 10 times its crustal abundance as its solubility in the oceans decreases. Episodes of extreme volcanism, possibly induced by the odd asteroid hit serve to accelerate the process.

        Your piddling Gtons aren’t much against the background of natural fluctuations.

  9. Concerning fig.3 attributed to Loutre and Berger, there is a Science paper of the two authors from 2002, vol 297, p. 1287, which gives an almost constant (and close to zero) northern ice sheet volume over the next 50 ka, fitting to their title: ‘an exceptionally long interglacial ahead?’. Only a drop of CO2 concentration to 210 ppm would induce earlier glaciation, significant after 20 ka.

    However, my main concern is fig. 4, which does not really agree with the data from University of Colorado:http://sealevel.colorado.edu/current/sl_noib_global.jpg
    There are no hints given, how terrestric data, taken since 1900, can be of higher quality than the recent satellite data, which do not seem to indicate any signature of SC 23.

    • “Only a drop of CO2 concentration to 210 ppm would induce earlier glaciation”

      I believe your maths are open to question. First one needs to demonstrate that CO2 has ever changed the Earth’s temperature rather than being, in fact, the other way around.

  10. Anyone who wants to learn more about how Milankovitch was validated can read Imbries’ book. Its excellent.

    The position of the continents determines how excess heat or cold is distributed and how efficiently it is transported.

  11. The reason why the Earth doesn’t respond more rapidly to changes in insolation is due to the retained heat in the oceans, which smoothes the whole process over thousands of years. Over the short term, the oceans are very responsive to changes in solar activity.
    You can’t have both.

    Figure 5 shows the very strong correlation between the annual rate of sea level rise and solar cycles over the 20th century.
    The sea level even knew that cycle 19 was coming and started rising way before.

    The sea level rise of the 20th century can largely be attributed to a more active Sun relative to the 19th century.
    Except that the Sun was not more active during the 20th century.

    • There’s a much better correlation between solar cycles and ocean levels, than there is between CO2 and temperature.

    • The sea level even knew that cycle 19 was coming and started rising way before.

      Lol, I noticed that too. Such smart oceans we have! That or they’re so powerful they influence the sun! /sarcasm

      • Leif,

        Your Figure 7 goes back to 1750. Lee’s graph goes back to circa 1610. The portion of Lee’s graph from 1750 on is virtually identical to your Figure 7. Why is your graph correct and his wrong?

    • The sea level even knew that cycle 19 was coming and started rising way before.

      Remember that the PDO switched to a cool phase in 1945, so several changes in the ocean behavior are to be expected around that time.

    • “Except that the Sun was not more active during the 20th century.”

      Actually, it was. The solar cycles of the 20th have had far higher peak sunspot counts and higher 11 year running average sunspot counts than previous centuries. We are now entering an era more akin to the Dalton Minimum of the early 19th century.

      • They certainly spent a lot more time on the high side heating up the place than they did on the low side, which was short & elevated.
        Low cycles spend a lot of time at the bottom, freezing the heck out of things and barely manage to get themselves high enough to simply halt any more freezing.

  12. David,

    Your figure 3 seems to have time reversed from Berger et al (2002). That would explain the discrepency noted by Werner above.

    • Now that I look closer, my reversed time comment is not correct, but your figure is definitely different for future projection than Berger et al (2002).


  13. Spectrum of 100-kyr glacial cycle: Orbital inclination, not eccentricity

    http://www.pnas.org/content/94/16/8329.full

    ” The hypothesis that variations in inclination are responsible for the 100-kyr fluctuations cleanly solves three of the difficulties associated with the hypothesis that variations in eccentricity are responsible. First, the inclination shows a single narrow peak, in agreement with the spectrum of climate proxy records. Second, the variation in inclination does not show any peak at 400 kyr, again in agreement with observations. Third, the inclination hypothesis satisfactorily deals with the causality issue. “

    • That’s got to be due to all the SUVs concentrated in one hemisphere. Someone needs to move the tire weights around the rims. ;)

  14. The time scales mentioned are academic. CO2 is being taxed now.
    We are told there is only four years to save the planet.
    We have screwed the planet over 150 years and we will fix it in three!!!
    Okay. I can wait three years to see what happens.
    Where can I lay a bet on the outcome?

  15. Werner Weber (08:46:02)

    I have to say, I agree with you. In a paper published shortly before the data from which the curve in Figure 4 above was produced, Holgate published a paper on the rate of sea level rise since the mid-19th century in which a dominant effector was the stratospheric aerosolic depth (e.g from the effects of volcanic eruptions). See Figure 6 of

    S. Jevrejeva, A. Grinsted, J. C. Moore, S. Holgate (2006) Nonlinear trends and multiyear cycles in sea level records. J. Geophys. Res. 111, C09012.

    …and there is no indication of a solar cycle contribution in that analysis.

    In the Holgate’s paper from which the data in Figure 4 in the top post was drawn, Holgate selected a very small sub-group of 9 coastal tide guages (in N. America and Europe and 1 in Hawaii), and perhaps it is this subset of stations in shallow coastal waters that respond somewhat more quickly than the oceans as a whole to solar irradiation changes through the solar cycle, that give rise to a variation that seems to track (somewhat) the solar cycle. Of course that would require that the local sea levels in the subset were “out of equilibrium” with the oceans as a whole in terms of sea level….

    • Likely he selected coastal tide guages located in areas that did not experience significant subsidence or uplift/rebound that would possibly skew results, particularly given that tectonic processes are very erratic in their changes consistent with major earthquakes.

    • “and there is no indication of a solar cycle contribution in that analysis.”

      Because it wasn’t considered?

  16. Lord Nicholas Stern is at it again, predicting climate change will result in “extended world war.”

    http://www.foxnews.com/story/0,2933,498133,00.html

    “Stern, author of a major British government report detailing the cost of climate change, was one of a select group of two dozen — environment ministers, climate negotiators and experts from 16 nations — scheduled to fly to Antarctica to learn firsthand how global warming might melt its ice into the sea, raising ocean levels worldwide. . . .”

    “. . . If the world’s nations act responsibly, Stern said, they will achieve “zero-carbon” electricity production and zero-carbon road transport by 2050 — by replacing coal power plants with wind, solar or other energy sources that emit no carbon dioxide, and fossil fuel-burning vehicles with cars running on electric or other “clean” energy. Then warming could be contained to a 2-degree-Celsius (3.4-degree-Fahrenheit) rise this century, he said.”

    Yes, I think a 2 degree Celsius per century is an achievable goal. In fact, I’d bet we could even keep it down to 1.2 degrees.


    • Mike McMillan (10:36:56) :

      Lord Nicholas Stern is at it again, predicting climate change will result in “extended world war.”

      http://www.foxnews.com/story/0,2933,498133,00.html

      From the link above:
      “After he spoke, Norwegian organizers announced that the forecast looked good for Stern and the rest to fly south on Sunday to further ponder the future while meeting with scientists in the forbidding vastness of Antarctica.”

      Picture of Norwegian minister of the environment Erik Solheim in Antarctica

      http://www.aftenposten.no/nyheter/uriks/article2942300.ece

      “He leads an expedition consisting of environment ministers from China, the Czech Republic, Finland, Russia, Sweden, Great Britain, Algeria, as well as representatives of seven other countries, to visit Antarctica”

    • The much more likely trigger of world war would be a global famine caused by drought induced crop failures after a shift to a cooler regime with lower CO2 levels.

      WWII was partly about “living room” and the desire to control the Ukraine bread basket… The French Revolution was partly about the lack of wheat during a Little Ice Age crop failure. Hungry people start shooting.

      Crops grow well when it is warm, wet, and CO2 rich. They fail when it is cold, dry, and CO2 poor. Cold and Dry come together as a set. We are presently getting dryer and the PDO et. al. and Landscheidt hypothesis are pointing to colder. Now we are going to push for much less CO2. He may have his outcome right, but his drivers are backwards…

    • What, as distinct from an ‘unextended’ World War? Not only does he mouth a great deal of drivel, he expresses it poorly.

    • “extended world war.”?

      Modern force on force conflicts are likely to be short rather than extended as smart weapons and cruise missiles take out the major points of interest on both sides. Hence extremely expensive (another limiting factor) in terms of blood and treasure…

      ’nuff said – topic for another blog.

  17. I am inspired by Edward Morgan’s post to believe that the Antarctic Circumpolar Current in its modern path started forming about 40 million years ago. The current had earlier been forced by the near connection of Australia and Antarctica to travel far to the North along the Northern coast of Australia before dropping south to the pole again. This would have brought relatively warm water down to the South Pole and kept Antarctica uncovered by permanent ice. Perhaps the poleward plunge of Antarctica and a change in current path together account for the change in frequency of the ice ages. Gary, has this idea been looked into and discarded?

    It also looks to me that strong currents like these over millions of years can even help nudge continents along their paths. Relatively small forces summed over long periods can have important consequences. This is uninformed speculation on my part.

    • Ocean currents have little, if anything, to do with moving continents along on their journey around the earth. Mantle convection is what is thought to be the cause of continental drift.

      STOP CONTINENTAL DRIFT!!

      REUNITE GONDWANALAND!!

    • Ocean currents do not contribute to the motion of the plates. There is just no way to move that much material. Plates are more than just the crust; it’s the crust and upper rigid part of the mantle which forms a plate. These plates are many a kilometer thick and have an incredible amount of mass.

      Density is the driver of plate tectonics.

      Incidentally, since the title of this post mentions sea level, the rate of plate motion (more specifically the rate of production of new ocean floor) has the greatest control on large scale changes in global sea-level.

    • Um, need I point out that the stock market and futures markets offer all the real money betting options you could ever want?

      Bet on drought via grain futures or “MOO” “COW” “WOOD” “JJG” or “DBA” tickers (ag inputs, animals, trees, grain, and general ag basket; respectively). Bet on bad winter with road salt makers (ticker escapes me at the moment, though I own it… ). Bet on war with ‘aerospace & defense’ or bet on cold via heating oil (UHN) or natural gas (UNG) both up today, btw.

      Disclosure: I own JJG and some “MOO” along with some natural gas producers and oil. I don’t think my saying anything about them here is going to move the world grain or oil price, though 8-}

    • I worked at an outstation in the Andes during the 1980-s and we relied for the forecast on an “interpolation” between Santiago and Antofagasta. One day we found on the telex: today no weather (forecast) because of the weather. It was that bad. So
      if Al Gores disasters come fast and strong, then we will have to do without weather forecasts altogether, so that we can all stop worrying about it.

  18. Strike frequency and replace with severity in my post above.

    “About 70% of the sea level rise of the 20th century was due to thermal expansion of the oceans, with the rest due to melting glaciers.”

    Several times I’ve seen the 70% figure now. Is that also from Holgate?

    • John G. Bell,

      It should be kept in mind that glaciers always melt eventually. Glaciers move, and they always flow downhill, either entering the ocean or warmer lowlands, where they melt.

      It should also be remembered that glaciers grow and recede not because of the planet’s warming or cooling, but because of precipitation [or lack thereof] at higher altitudes.

      That makes the 30% sea level rise due to glacier melt appear highly questionable. It could just as well be argued that the [very minor] seal level rise of the past century was due to precipitation, leaving out the glacier middle man. There are other causes besides glaciers and sea density. Had they said that fraction of sea level rise was due to general South polar ice shrinkage, or a decrease in global humidity and precipitation, it might have been defensible. But melting glaciers alone? Not likely.

      The planet has been warming in fits and starts for ~11,000 years, ever since the end of the last great Ice Age — when Chicago was buried under a mile of ice. The sea level is still rising slightly as a direct result of the planet’s emergence from that Ice Age.

      AGW has nothing measurable to do with the sea level. What is being described is entirely natural.

      • John,

        Glacial ice can affect sea level. 35,000 years ago the sea level was hundreds of feet lower. Our current major sea ports would have been inland locations. But it is true that current glacial melt (for the ones that are retreating) is not going to cause a catastrophic increase in sea levels.

        BTW…. To your list of causes for glacial ice loss don’t forget to add wind and landuse.

        I addressed glaciers briefly in
        The Story Of Glaciers

        An excerpt..

        We have all heard about the catastrophic retreat of glaciers during the 20th century and supposedly increased rates of retreat during the late 1990s. Glaciers don’t just retreat geographically, they also thin. In most cases they, (being three dimensional), also narrow. Glaciers historically pointed to by the AGW crowd retreated at a faster rate in the past, and, lost most of their volume of ice long ago. Long before the use of fossil fuels. Long before the 20th century.

        The rest can be found here:

        http://penoflight.com/climatebuzz/?p=88

      • I agree Smokey. Re: precip increasing ocean levels, I have wondered about the volume of water we are pumping out of the land-based aquifiers adding to the ocean volume. We’re pumping faster than the aquifiers can refill, it has to go somewhere and it doesn’t appear to be in the atmosphere either.

      • We are emptying aquifers but that may be more than offset by the lakes and reservoirs we create.

    • I called the National Weather Service in Bismarck and was told the following two things:

      1. North Dakota remains fully frozen — no flowing water anywhere.

      2. They get noise from their instruments due to ice sometimes.

  19. I think you misunderstood or I misunderstand

    Steinar Midtskogen in his post said, “I was taught in elementary school” and then listed a fairly complex scientific concept.

    I don’t understand what was objectionable about my jokingly asking where he attended elementary school since it was obviously a pretty advanced one.

    • Is it really a complex concept for kids that water at 4 degrees sinks to the bottom? No need to know exactly why. Anyway, my point was that I was surprised to see this 13 degrees figure mentioned without any explanation, since it seems to contradict a well known fact even by those who haven’t studied science.

      The Pacific is deep and to have the bottom water at 13 degrees sounds as fantastic to me as if the Arctic ocean was frozen solid to the bottom during some ice age. So an explanation would be in place how this is possible, since, if it’s true, I must be missing something very important.

      • So much has been forgotten. A good study of the ice ages is a book written by Fred Hoyle entitled “Ice”. We know it is a good book because he dismisses CO2-related warming in about three lines of text. On pages 99 of that book is Figure 28 showing the bottom temperature of the Pacific Ocean over the last 40 million years, after from Emiliani, Scientific American, vol.198, 1958.

      • The references to ‘the bottom water of the Pacific’ might cover a wide range of situations. The depth of the Pacific bottom is highly (is that called a pun ?! – sorry-) variable. Perhaps the description just requires a more detailed explanation?

      • Water at 4C will sink to the bottom, yes, but I seriously doubt your conclusion that the bottom must therefore be at 4C. First, compression does not drive a fluid to its most compressed temperature. Adiabatic compression as in an air conditioner increases the temperature of a gas as it compresses, despite all gases expanding with temperature. Second, if you take a huge body of water, all of it hotter than 4C, then some of it must be at the bottom. If there is some process that drives the temperature from whatever it was to 4C, then heat would have to travel from cold water to hot, violating the second law of thermodynamics. I don’t guarantee this is correct, but my take on it says you are incorrect. If you see a flaw in my reasoning, I really want to have it explained to me.

  20. Scientists capture dramatic footage of Arctic glaciers melting in hours

    Scientists have captured dramatic footage of massive lakes in the Arctic melting away in a matter of hours.

    http://www.telegraph.co.uk/earth/environment/climatechange/4734859/Scientists-capture-dramatic-footage-of–Arctic-glaciers-melting-in-hours.html

    Glaciologist Jason Box has been testing a Moulin, a shaft that allows water to travel from the glacier’s surface to its bottom, in a glacier on the Greenland ice cap to find out how fast it is melting.

    He said: “There’s no escape from a Moulin. It’s just got danger written all over it. But the information is so important that we actually had to take that risk.”

    Dr Box said: “We’re in the midst of a climate catastrophe and glaciers are the epicentre of that problem.

    “Glaciers around the planted are decanting into the oceans at shocking rates and I want to stop that.”

    • He then should “insert” himself into the glacier and verify his theory.
      After all the glacier according to him will melt in a matter of hours so he will survive…

      • Wasn’t this the same experiment where they dropped little yellow bath duckies into the moulon expecting them to surface in the ocean but they have completely disappeared!!!!!

    • Also in that article: Greenland lost enough water in a year to cover Germany with 1 meter water. Since Greenland is 6 times the size of Germany, this implies that per unit area Greenland loses 17cm of water, i.e. 20 cm of ice per year. 20 cm in about 2000 meter ice (if not more) , 1 in 10000. So what’s the problem? One winter’s snowfall and it’s all back again.

      Dr Box’s “shocking rates” are actually pretty modest, but even so I am very curious how he intends to “stop that”. By shouting at the Sun, I guess.

    • I wonder if Jason Box is aware of the real global ice mass balance?

      I wonder if Jason Box realizes that if the fresh water influx to the oceans increase so does precipitation. A reduction in influx results in a reduction in evaportation and precipitation thus an increase in drought? Why does he want to increase drought?

      I spliced together some of John Cristy’s comments on Greenland made during his presentation while participating in debate with Schlesinger. (Global Warming Debate / William Schlesinger versus John Christy /John Locke Foundation / February 11, 2009)

      [video src="http://s247.photobucket.com/albums/gg136/BigLee57/?action=view&current=GreenlandMelt.flv" /]

    • What a load of old cobblers!

      This is pure gee whiz, boy’s own derring-do inconsequential rubbish.

      The first clue comes when the voice over states in a quietly awed voice that the scientists are out to see if they can save the planet.

      Then the talk is all of danger – ‘there’s no escape from a moulin’ etc etc.

      Finally, after many dangerous adventures in his crampons, the actor (surely this is not for real) provides an accurate (about 5 and a half miles per hour -I forget the exact figure and cannot bring myself to go back and look at it again) measurement of the flow velocity.

      Oh the precision! And then, without any measurement of the area of the flow, not even an estimate, we are told how many zillions of litres are going down the plug hole every day (or whatever). From the bare velocity information this clown (surely this is meant to be funny) can provide statements about volume rate of flow.

      And then we are told that there are ‘hundreds’ of these over the Greenland ice-cap. Alas and alarum! Oh woe for the planet! (@#^&!!**)

      And Dr Box wants to stop the glaciers decanting into the oceans at these ‘shocking rates’…….. For heaven sakes, why doesn’t he just jump in and block the plug-hole?

      But worst of all, there is not one scene, not even a still shot of any Arctic glacier or lake melting away “in hours”.

      Where do you get this unutterable rubbish?

    • It does seem as if the reporter/news outlet is unable to distinguish between the concept of “draining” and the of “melting”.

    • Greenland is losing enough water each year to cover Germany a metre deep.

      Germany is losing enough water each year to cover Germany a metre deep (approximately). That’s how much precipitation it has.

      What drivel.

      • I live 25km North of Hambur, Germany, It has rained, or snowed for 90% of the time I have lived here (5 years) a day of sun gets front page on the news! Contract about finish, moving to Italy, if that’s global warming.

  21. “The Earth’s current ice age is primarily caused by Antarctica drifting over the South Pole 30 million years ago.”

    So did it just drift there and stop or is it still moving. What happens when Antarctica moves off the south pole? Would the ice move back into the ocean like the north pole? Would that cause a rise in sea level or would the land rise as ice was removed and offset the weight of ice in water. Is anyone studying current continental drift. Seems to me there has been quite a bit of movement in the pacific and western united states plates lately, so hows Antartctica just sitting there?.

    I apologise if I seem dumb, but an object in motion and all that.

      • Jeez; it’s carnaval

        Atlantis (in Greek, Ἀτλαντὶς, “daughter of Atlas”) is a legendary island first mentioned in Plato’s dialogues Timaeus and Critias.
        wiki

        http://www.surfacestations.org project going

        Reply: I couldn’t think of a better response to my post Fernando. I intentionally left Rio before it got so loud I wouldn’t be able to sleep for a week ~ charles the moderator aka jeez

    • Continents drift at about the rate your fingernails grow. It isn’t something to worry about in our lifetimes.

      Heck, you could even make a case that we as a species evolve faster than the continents drift, so it isn’t an issue for our species… though it might be for what ever species we evolve into in a few more million years … ;-)

      BTW, there is a crack in Iceland where one can directly measure the rate of sea floor spreading and continental drift. One side is N. American plate, the other is Europe. It has ‘fresh’ rock in the bottom from old lava a few thousand years ago. I’ve seen film of a guy standing in the bottom of the crack describing the two sides…

    • Antarctica once was in the tropics, witnessed by its large coal reserves (in the places that have been explored). Yes, the Earth has iceages only if either one of the poles, or both, are occupied by a landmass. Indeed, they are shifted in and out of place by continental drift.

      The reason is simple: if the poles were covered by oceans, any ice formed would float on the water. Not only would that mean high sealevels, but also, little ice because the ice would not grow thicker than a few tens of meters at most. This is what we observe now at the North Pole; the ice thickness is determined by the cooling at the surface being balanced by the “heat” from water underneath, constantly replenish by ocean currents from warmer places.

      If, however, there is a landmass at the pole, much largere quantities of ice will accumulate and form gletchers at first and a thick ice shield eventually, containing
      much more ice than otherwise without land. Hence a lowering of sealevel.

    • pkatt (13:35:45) :

      “The Earth’s current ice age is primarily caused by Antarctica drifting over the South Pole 30 million years ago.”

      So did it just drift there and stop or is it still moving. What happens when Antarctica moves off the south pole?

      It’s more complicated than just having Antarctica at the South Pole. The Antarctic continent drifted to the antarctic circle and South Pole more than 20 million years before the latest great glaciatons commenced about 30 million years ago. Consequently, it was a combination of events including the location of Antarctica which caused the latest ice ages. Likewise, Antarctica will still be present at the South Pole when the ice ages decline during the next 50 million years. Yet, the glaciations will wane and wax on the Antarctic continent as the Atlantic Ocean basin stops expanding and begins to re-close following the subduction of the mid-Atlantic Ridge, bringing Australasia back into contact with Antarctica. Greenland and the North Pole will be free of glaciation, while the Antarctic retains lesser and greater glaciations as the continental configurations continue to shift and shift oceanic circulation patterns.

    • Continents move in response to plate tectonics, caused by convection in the mantle. Typical rates are on the order of a few (1-6) centimeters a year. Now assuming there is some mantle convection current impelling the Antarctic as a whole, it will take millions of years to move it substantially away from its present location.

  22. Ed,

    Perhaps Jason Box and his team could wedge themselves into the top of the moulin and stop some of the decanting, or go looking for epicentres at earthquakes :-)

  23. common cause
    As Mr. Svalgaard has kindly calculated the total tidal pull on the Sun’s surface is of order of 2mm. The graphic showing apparent correlation of see level and sunspot cycle shows tides of 2 to 3 mm around the central value. Therefore, it can be concluded that the sea level (even sometimes precedes the solar cycle) has noting to do with solar cycle but with planets’ tidal pull on the oceans volume.
    The apparent correlation (although not perfect) may lead us to conclude that planet’s influence is the common cause to both, the rise in sea level and the sunspot cycle, this Mr. Svalgaard bitterly opposes.

  24. Does anyone know if they use Chlorine36 to map sea water exchange? Looks like it ought to work…

    From the wiki:

    http://en.wikipedia.org/wiki/Chlorine-36

    “Additionally, large amounts of 36Cl were produced by irradiation of seawater during atmospheric detonations of nuclear weapons between 1952 and 1958. The residence time of 36Cl in the atmosphere is about 1 week. Thus, as an event marker of 1950s water in soil and ground water, 36Cl is also useful for dating waters less than 50 years before the present. 36Cl has seen use in other areas of the geological sciences, including dating ice and sediments.”

    So, Cl36 enters seawater at the surface, floats to poles, enters the THC plunge to the bottom … Or do you need the hydrophobic decay products to make this work?

  25. I don’t think a correlation between sea level rise and sunspot number necessarily suggest that the sea levels would not be rising without the current level of solar activity. Note that even weak cycles like solar cycle 16 coincided with an increase in sea levels. How small would the cycles have to be to not cause an increase in sea level? I’d think that the oceans would have caught up with the current level of solar radiation by now, and that sea level rising rates would vary around 0. The radiative imbalance in the system likely arrives from cloud cover changes.

  26. Ed, Reference to Glaciologist Jason Box and his Moulin suggest (?) something
    new about this. Not so. Lakes on glacier surfaces and their rapid disappearances, along with disappearing streams, through open shafts in the ice are as old as glaciers. The topography created underneath reveals, when the glacier is gone, where these flows once were. A Moulin makes a roar as did old grinding mills; thus, sounds like a mill = Moulin.

  27. We have recently discovered Antarctica isn’t a contiguous continent. Its more of an archipaeligo.

    Antarctica appears to be a contiguous continent because it’s icesheet is contiguous. I am unable to find an estimate of when that contiguous icesheet formed, but its creation would have had substantial effects on ocean currents and climate.

    The land area of Antarctica at current sea levels is about half of what is shown on maps.

      • Prior to the ice depressing the land, the sea level would have been higher (the water having become the icecap). The text of the Wikipedia article suggests that isostatic rebound would be “hundreds of meters” which is probably greater than the sea level decline. I suspect that it is probable that more of the depressed area was above sea level than is now.

  28. The formation of the Isthmus of Panama, about 3 million years ago, is one of the most important geologic events in the last 60 million years.It formation shut down the flow of water between the Atlantic and Pacific Oceans. Atlantic currents were forced northward, creating the Gulf Stream today. increasing the temperature of Europe by as much as 10 °C. The Atlantic, no longer mingling with the Pacific, grew saltier. This favors an ice free north pole.

    Secondly, about the 4 °C temp for water under pressure. This is true for pure water, which is extensively hydrogen bonded. However, salts ruin the tight packing, as cations have an outer aqueous sphere, and so do anions to a lessor extent. The smallest degree of packing depends on what salts are present. The best way to drop volume is to get rid of the salts, the easyest way to do this is for the formation of precipitants. Expect some very funky mineralization reactions; using precipitation of minerals many endothermic reactions would be rendered thermodynamically viable.

    • Umm, they do still mingle, Cape Horn, Northwest Passage, water does flow under the ice.

      The creation of the isthmus certainly altered important currents, and most likely affected global climate.

    • DocMartyn, are you suggesting precipitating minerals out of the oceans? Or are you just saying it’s ‘viable’?

      I’m not a climate scientist, so I wouldn’t know if totally upsetting the oceans’ balance would be a problem or not… [/s]

    • If I take a purely empiral approach, isn’t the fact that the temperature of the deep ocean now is everywhere near 4C proof that it also applies to salt water?

      Which still leaves me with the reported 10C.

  29. Is anyone aware of a discussion/study regarding volume changes of the oceanic basins due to crustal rebound as the crust returns to its pre-ice age shape, and filling due to river silts and dust sedimentation ?

    I would think that not only water volume due to temperature density changes, but the reductions in the volume of the container need to be considered, to evaluate the changes in sea level.

    Take for example the 2004 Indian ocean Tsunami that involved uplift of the ocean floor over large areas. That obviously changed the volume of the ocean basin. Was there a world wide step change in mean sea level some time after December 2004? Was this a net gain or loss to ocean basin volume?

    I can think of at least 5 mechanisms that should be constantly changing (reducing) the ocean basin volume.

    – Crustal rebound and seismic uplift ( subduction would obviously subtract some volume)
    – silt transport by major river deltas into the ocean basins.
    – silt build up in the deep ocean due to dust and organic “snow” as organisms in the upper layers fix material and carry it to the ocean floor as they die.
    – Volcanic intrusions due to undersea volcanic erruptioins.
    – volcanic dust that settles in the ocean basins

    I do not recall ever seeing any values being assigned to sea level change due to the volume of the container (the ocean basin) as it slowly fills up or changes shape due to these effects.

    Something like 500 million metric tons of dust fall into the Atlantic basin each year from North Africa alone. You add to that Dust from the Gobi desert and silt from the major rivers you must have displaced a fair amount of water storage capacity in the basin.

    http://www.space.com/scienceastronomy/planetearth/dust_storm_010514.html

    Mt Pinatubo ejected approximately 10 cubic kilometers of dust, most of which most likely fell into the South China Sea for example. In other areas of the world like the Persian Gulf and the Red Sea you also have large deposition rates of dust into the oceans due to sand storms in the region.

    So here is at least one other mechanism that should figure into world wide sea level change that is not driven by CO2 emissions. In fact warm most conditions might reduce the dust components, due to wind erosion.

    Larry

    • obviously I don’t know the orders of magnitude involved, but if you add dust you have to subtract all the fish we eat. No?

      That was probably a stupid statement, but then I’m not shy nor afraid of saying something stupid to be corrected.

    • Hotrod.

      I had wondered about the same thing, i.e. ocean basin volume. The Atlantic Ocean widens about 2-3 cm per year. Many other continental movements are even faster. Deep Ocean trenches get deeper or shallower depending on the rate of subduction of the ocean plate. Continental plates tilt one way or another.
      With ocean level changes of .13 mm quoted for last year, just normal tectonic movement could easily account for that. Everyone always assumes that any and all ocean level change is due to water volume change. I’m with you. There are several things that could account for such a small change.

      Bruce

    • hotrod: You mention a number of things that might affect ocean volumes. I can speak to some of them, and hazard an opinion at some others.

      Isostatic rebound: Land areas that were covered by glaciers were, to some extent, depressed. Now that the ice is gone, they are rising (see: Isostasy for the principle). Areas in Maine, Norway, etc. have risen amounts measured in meters. However, glaciers gone to sea float sooner or later. The ocean floor is little affected by glaciers.

      Seafloor spreading/subduction: The world is not, last I heard, increasing in diameter. Therefore, when new ocean seafloor is produced at the spreading ridges, seafloor somewhere else has to be consumed. This is “conservation of volume” (nothing is “new”, material is simply being recycled in the tectonic system). New seafloor material is relatively hot and so less dense, and stands up as a “ridge”. As it gets pushed away from the spreading ridge, it cools and becomes more dense and begins to sink (oceanic trenches result). Ultimately it is either subducted (taken back into the mantle) or obducted (thrust up onto the continental mass that it impinges on). Density – as a function of temperature and composition of rocks – more or less is the driver of the system.

      Volcanic ash, etc. – In terms of Pompeii, this stuff was bad news. But x cubic kilometers spread over 75% of the earth’s surface (the oceans) is inconsequential. Over 4 billion years, it adds up of course, but most of that goop has been accreted to (added to, pasted on, or turned into lava/ash on) the continental masses/island arc systems through the subduction/obduction process. The oldest ocean deposits are some tens of millions year old; the earth > 5 BY.

      River deltas: Some of these are big enough (Mississippi River, for one) to really affect local geology. They act like a glacier to some extent, depressing the materials beneath them or their own older deposits or finally the underlying mantle. As a result, older unconsolidated sediments are squeezed, forcing out water, shrinking open pore spaces, causing new denser minerals to form, etc. They are compacted and lose volume. In some cases (Miss. Delta for one), the underlying “rocks” are massive deposits of salt. These can flow like a magma under pressure, and rise to form salt domes (even occasionally “salt extrusions” like a lava flow). If finally the mantle is depressed, somewhere else something is pushed up (the mantle essentially is an incompressible material). The oldest ocean deposits are some tens of millions year old; the earth > 5 BY.

      Same for the tsunami. I haven’t read that there was a big uplift of seafloor or continental mass, but something happened that shifted billions of tons of material rapidly one way or another, probably along a line of weakness (fault). Maybe something went up or down 5 or 20 meters over a large area. The main product was an enormous shock wave (tap your wine glass with a knife and watch the ripples). That shock wave was transmitted to the sea, which exercised it in a way that physics explains nicely and that was hugely destructive of human beings and their constructs.

      Ultimately, we live in a very dangerous place. No one can guarantee our existence for the next five minutes, much less eons. Most of us don’t realize that, and so the AGW thing scares some badly. I am a geologist, so I realize (some of) the things that could happen. My retort to nature is: “Bring it on. We can handle it.” Man-made problems may however be a different ball of wax.

  30. correction should read:

    In fact warm moist conditions might reduce the dust components, due to wind erosion.

    Larry

  31. One thing to remember in talking about orbital cycles and changes in insolation is that the total amount of energy reaching the surface of the Earth over the period of a year does not change it is just distributed differently.

  32. Dr. Archibald,
    Many thanks for taking the time and trouble to produce your “Ice Ages and Sea Levels” article, which I read with great interest. The article has prompted a few questions — and please forgive the absence of citations other than Wikepedia.. I am simply too ancient to want to learn how to handle that sort of informatin from my browsing of Google.

    . Is the current series of glaciations the only known example of recurrent sequences of glaciation?
    2 Wikipedia reports that ocean bottom drilling indicates that there have been about 80 glaciations thus far in the current series. You state that the last four glacial periods have run about 100,000 years, and prior to that the cucles covered 41,000 years. Dividing 41,000 into 1,700,000 gives 41 plus a tad, which of course doesn’t fit. I have come across a paleoclimate article which indicates that the initial glacian-interglaciation periods only lasted 25,000 years. If that were the case, it would easily be possible to strike a balance between the two that would work. Or could the Wiki information be that far off?
    3. Do the orbital parameters provide an explanatory rationale for the 41,000 year long glacial cycles? My guess is that they don’t, and that they certainly wold not seem likely to explain 25,000 year cycles (assuming that they did occur).
    4. Has anyone provided an explanation for the sudden shift from 41,000 year cycles to 100,000 year cycles? That is one robust climate change!

    There is clearly a growing audience for reliable, unbiased information of the sort represented by your excellant and important article.

    • My 2c worth,

      Indeed, the glacial/interglacial cycles have been getting longer over the current Ice Age, although not smoothly. It’s more like they have a sudden jump from one period to another, eg 41k years to 100k years.

      Whatever the underlying cause of the glacial cycles, and my view is that it is currently unknown, is causing longer cycles. These cycles then synch with Milankovic cycles, which (by providing the insolation change) control the timing of the shift from warming to cooling and visaversa.

      So the glacial cycles would happen anyway, but their timing is governed by the Milankovic cycle closest to the glacial cycle’s natural period.

    • C.Colenaty (20:48:30)

      Yes, the orbital parameters provide an explanatory rationale for the 41,000 year glacial cycles. This arises from the axial obliquity of the Earth’s orbital variation which has a period of 41,000 years. A recent paper (abstract below) addresses your point about the switch in the glacial cycles from a dominant 41,000 year cycle to a 100,000 year “driver” (orbital eccentricity). It’s not “proven” but it does provide a rationale that is consistent with the evidence.

      The idea seems to be that the 41kyr cycle was represented in the high Northern latitudes by the waxing (cooling phases) and waning (warming phases) of the Eurasian ice sheet, but as time progressed the N. American ice sheet became progressively more significant. At some point around the time of the switch from 41kyr to 100kyr the combined ice sheets became sufficiently large that they were able to survive the insolation changes on the timescales of the obliquity (41 kyr) and precession suppressing the 41 kyr transition to full interglacials. In other words the glacial cycles “missed the pulse” and interglacials were only realized in line with the eccentricity variations.

      Bintanja R and van de Wal RSW (2008) North American ice-sheet dynamics and the onset of 100,000-year glacial cycles Nature 454 869-872

      Abstract: The onset of major glaciations in the Northern Hemisphere about 2.7 million years ago(1) was most probably induced by climate cooling during the late Pliocene epoch(2,3). These glaciations, during which the Northern Hemisphere ice sheets successively expanded and retreated, are superimposed on this long-term climate trend, and have been linked to variations in the Earth’s orbital parameters(4). One intriguing problem associated with orbitally driven glacial cycles is the transition from 41,000-year to 100,000-year climatic cycles that occurred without an apparent change in insolation forcing(5). Several hypotheses have been proposed to explain the transition, both including and excluding ice-sheet dynamics(6-10). Difficulties in finding a conclusive answer to this palaeoclimatic problem are related to the lack of sufficiently long records of ice-sheet volume or sea level. Here we use a comprehensive ice-sheet model and a simple ocean-temperature model(11) to extract three-million-year mutually consistent records of surface air temperature, ice volume and sea level from marine benthic oxygen isotopes(12). Although these records and their relative phasings are subject to considerable uncertainty owing to limited availability of palaeoclimate constraints, the results suggest that the gradual emergence of the 100,000-year cycles can be attributed to the increased ability of the merged North American ice sheets to survive insolation maxima and reach continental-scale size. The oversized, wet-based ice sheet probably responded to the subsequent insolation maximum by rapid thinning through increased basal-sliding(13,14), thereby initiating a glacial termination. Based on our assessment of the temporal changes in air temperature and ice volume during individual glacials, we demonstrate the importance of ice dynamics and ice-climate interactions in establishing the 100,000-year glacial cycles, with enhanced North American ice-sheet growth and the subsequent merging of the ice sheets being key elements.

  33. hotrod (18:46:16) :

    In fact warm moist conditions might reduce the dust components, due to wind erosion.

    In fact data supports this. Have a look at the icecore record as given in http://en.wikipedia.org/wiki/Ice_core ( not a hotbed of skeptics). The dust measures are high when it is very cold. This is explained as the result of most of the water tied up in ice and large areas open to wind erosion.

  34. Paul Hildebrandt (12:13:33) :
    Your Figure 7 goes back to 1750. Lee’s graph goes back to circa 1610. The portion of Lee’s graph from 1750 on is virtually identical to your Figure 7. Why is your graph correct and his wrong?
    Because it is not identical. The correct [see below] sunspot numbers are higher than on his graph before 1945.

    mikelorrey (13:04:50) :
    “Except that the Sun was not more active during the 20th century.”
    Actually, it was. The solar cycles of the 20th have had far higher peak sunspot counts and higher 11 year running average sunspot counts than previous centuries

    Recent work [summarized in http://www.leif.org/research/Napa%20Solar%20Cycle%2024.pdf ] shows why I make the statement that activity in the 19th century [and 18th for that matter] was comparable to that in the 20th.

  35. Thanks for the very interesting article about ice ages. It prompts a question which nobody here seems to be asking: shouldn’t we be more worried about the global cooling attendant upon returning to ice age conditions than about global warming? Or, isn’t concern about global warming short-term alarmism, and in the longer term our real problem is going to be global cooling?

    That said, I’ve yet to read anything anywhere which says exactly when the next ice age is going to start. In part that may be because ice ages gradually deepen, and so the start of the next ice age will likely be one of a gradual cooling rather than a sudden, overnight (in geological terms) return of deep freeze conditions.

    And if we’re currently thinking of ways of preventing AGW, shouldn’t we be thinking just as hard about ways of slowing or preventing a long cooling trend as a brief AGW warming trend? By adding CO2 to the atmosphere, for example. Assuming that CO2 does have some warming effect, might it not be argued that some global warming now will translate into a welcome delay in the start of the next ice age?

    And if we’re going to be sceptical about AGW, shouldn’t we be equally sceptical about Milankovitch cycles? It’s another relatively new idea (I think Milankovitch figured it out in the 1920s). And I’ve read that it doesn’t explain everything.

  36. Dr Archibald

    You said “This meant that a large area of the Earth’s surface changed from being very low-albedo ocean to highly reflective ice and snow.”

    Is that the case right up at the poles where angles of incidence are very shallow. Change of albedo should have only a marginal effect. If ice melt exposes open sea water, surely the incoming solar will still be largely reflected off the ocean surface at low angle of incidence?

    Also, Kirchoff’s law tells us that a darker surface will be a more efficient radiator. So there should always be a counter-acting response to ice retreat at very high lattitude.

    These should be good reasons to expect ice at the caps, regardless of the local topology. Just asking.

  37. I believe Dr. Archibald’s arguments should be taken very, very seriously by people who really want to get to the bottom of the climate change mess. His reasoning is so simple and unbiased that the dogma gang should have a lot to learn from his way of approaching things.

  38. My own pet theory is that the closing of the gap between the Americas stopped the direct oceanic connection between the Pacific and Atlantic oceans, forcing a long circuitous route for the deep ocean currents to transfer heat from the Pacific, which is low albedo water, to the Atlantic which is in the middle of the high albedo land hemisphere consisting of the americas and eurasian landmasses. Once the direct route was broken, most of the heat has to be transferred in deep ocean currents round Australia and Africa.

    Both the ice ages and the joining of the Americas occurs 3 million years ago. Coincidence? I think not.

  39. Above Wally said “One thing to remember in talking about orbital cycles and changes in insolation is that the total amount of energy reaching the surface of the Earth over the period of a year does not change it is just distributed differently.”

    Here is a plot of data from the SORCE satellite for earth distance, Total Solar Irradiance. Same timeline as the plot I put up last night showing we might already be past solar minimum, a plot of data for distance 1au.

    At earth distance irradiance varies over a year as shown here. (flats on the line is missing data, interpolation by hold)

    http://lasp.colorado.edu/sorce/index.htm

    • Your link does not address Wally’s statement at least if we interpret his “over the period of a year” to mean you integrate over such a period. And, indeed he is correct that changes in the mean annual irradiance are very small. It is just the distribution in time (of year) and location (in latitude) that changes. See Fig. (S3) in this publication by Hansen et al: http://pubs.giss.nasa.gov/abstracts/2008/Hansen_etal.html

  40. Tim Channon (06:08:06) :
    Above Wally said “One thing to remember in talking about orbital cycles and changes in insolation is that the total amount of energy reaching the surface of the Earth over the period of a year does not change it is just distributed differently.”

    He clearly means by ‘over the period of a year’ the ‘average over a year’ and that does, indeed, not vary [except the 0.1% solar cycle variation]

    Here is a plot of data from the SORCE satellite for earth distance, Total Solar Irradiance. Same timeline as the plot I put up last night showing we might already be past solar minimum, a plot of data for distance 1au.
    It has this variation every year, so no variation ‘over a period of a year’. I do agree that TSI shows we must be past minimum, F10.7 and cosmic rays show the same: http://www.leif.org/research/TSI-SORCE-2008-now.png
    P.S. this plot updates in real time.

    At earth distance irradiance varies over a year as shown here. (flats on the line is missing data, interpolation by hold)

  41. Jim F (22:19:05) :

    hotrod: You mention a number of things that might affect ocean volumes. I can speak to some of them, and hazard an opinion at some others.

    Seafloor spreading/subduction: The world is not, last I heard, increasing in diameter.
    Therefore, when new ocean seafloor is produced at the spreading ridges, seafloor somewhere else has to be consumed. This is “conservation of volume” (nothing is “new”, material is simply being recycled in the tectonic system).

    I understand that, and also recognize that what I am talking about is probably a relatively minor factor over all, but it is an effect that I don’t see accounted for when they talk about sea level rise due to thermal expansion.

    More specifically I am thinking about volume changes due to changes in shape of the basin, not volume changes in the earth.

    If you make a container of a certain amount of material in the shape of a hemisphere and make a flat pan shaped container from the same amount of material, the amount of water they can hold will be drastically different due to the geometry of the two containers.

    For example:
    The average depth of the Pacific basin is 4280 meters, while the average depth of the Atlantic basin is about 3600 meters.

    If the assumption is made, that for each unit of spreading of the Atlantic ,results in a similar unit of shrinkage of the width of the Pacific, that would imply that at least for those two oceans, sea floor spreading would reduce the total ocean basin volume as the deeper basin is shrinking in size, while the shallower basin in increasing in size.

    If you increase the size of the Atlantic basin by some slice of X width near the center of its basin and shrink the Pacific basin by the same width near the center of its basin, the difference in their average depth would amount to a reduction in volume of the combined basins of about 18% of the volume of the Atlantic slice.

    In a practical every day situation you can see this sort of thing if you fill a plastic sink liner used for washing dishes with water while it is resting on a flat surface. If you then pick it up, the center of the plastic basin sags under the weight of water it holds. Now the basin is no longer full to the brim since its geometry has changed. If you set it down on an uneven surface so the container distorts, it will overflow.

    Basically I am contending that there is an unspoken assumption implied in the sea level change due to temperature discussion, that the shape (and therefore volume) of the worlds ocean basins are constant (at least on short time scales like year to year or decade to decade).

    I am suggesting that that is not a valid assumption. At the very least, you have basin volume changes due to the differences in basin average depth and continental drift, as mentioned above. You also have continuous siltation which is constantly trying to fill the basins.

    At the outlets of all the major rivers, you have large silt deposits each flood season, plus the displaced volume of wind blown dust which falls into the oceans each year due to wind erosion, and the beach material washed into the margins of the oceans each year due to beach erosion.

    In even an entry level physical geography class when they discuss land changes they talk about the evolution of lakes as they gradually silt up, transition to wet lands and eventually turn into a meadow with a river running through it over time. Obviously the oceans will not “fill up”, but the shape of the ocean basin cannot be assumed to be static in my view.

    In the case of the Christmas 2004 Tsunami it has been reported that it was generated by very large uplifts of the sea floor in the quake epicenter area of 15-20 meters. The total volume displaced I have not been able to find a number for yet, although this web page mentions the 15-20 meter uplift and the length of the rupture was some 1200 km long.

    http://www.itc.nl/library/Papers_2005/tsunami/Earthquake.pdf

    In the Yangtze river, it carries enormous silt loads, estimated at 60% by weight in places. The best number I have found is about 1.4 billion tons are carried to the sea annually in this river alone. That would equate to something in the neighborhood of 6.4 x 10^9 cubic meters per year if my ball park calculations are accurate for this single river. If a 1 mm sea level rise is about 3.61 x 10^11m^3, then that would imply that siltation from the Yangtze river each year accounts for about 1% of the annual sea level rise of 1.8 mm per year.

    The above calculations were based on the silt having a density of 2.2 gm/cm^3 the same as silicon dioxide.

    Since I do not normally work with this sort of calculation, I welcome anyone to double check these back of the envelope calculations.

    Larry

    • The assumption that ice-cap melt volume divided by total ocean area gave sea-level rise would work in a metal bath tub, but the ocean ain’t like that. Hope to see more on this.

    • The idea of the conservation of volume would not necessarily apply in this case… as the Indian sub-continent continues to move north into the Asian plate, new ocean space is being created at the expense of the atmoshere…i.e. the Himalayas are growing at the same time the Indian Ocean expands ( or Bay of Bengal, Arabian Sea, etc.). The point being that new ocean volume can be created.

  42. Gripegut (10:53:21) :

    What role does accretion of mass from space do to the level of the oceans? Is the accretion significant enough to measurably affect seal level rise?

    It looks like accretion would only amount to about 1/18000 of the mass of the annual silt from the Yangtze river. So in and of itself over short time scales it appears to be of not concern.

    However if you sum up all these basin filling processes you might come up with a significant fraction of the annual sea level increase.

    There are 165 rivers in the world with lengths over 1000 km. The Yangtze is probably the dirtiest and only amounts to about 1% of the global sea level rise, but if you add up the siltation from all those rivers it could be more sizable.

    Just to grab a number out of the air, suppose those 165 rivers on average each had 15% of the silt load delivered to the ocean each year as the Yangtze did, you now have accounted for somewhere in the neighborhood of 25% of annual sea level change being accounted for by siltation. Obviously this is just a grab a number out of the air calculation, but it shows that it is not seem unreasonable to assign a fraction of annual sea level rise to ocean basin capacity changes due to siltation and dust accumulation in the oceans.

    Larry

  43. Thanks Larry. That does make sense. So, of the 3 mm or so annual rise of the sea level, about 70% is due to thermal expansion and that sedimentation (from all sources) and plate tectonics could account for a significant portion of the remaining 30%. Therefore it seems that the sea level increase brought about by about ice melt is hardly the man made disater that Al Gore et al would have us believe. Why does that not suprise me?

  44. Gripegut (14:42:13) :

    Thanks Larry. That does make sense. So, of the 3 mm or so annual rise of the sea level, about 70% is due to thermal expansion and that sedimentation (from all sources) and plate tectonics could account for a significant portion of the remaining 30%.

    I would not be willing to say that is a fact yet only that I have made a case for a proper analysis of that mechanism by someone who has access to the data and time to properly compute the annual contribution to sea level rise by mechanisms other than thermal expansion.

    I am simply stating that on a first blush examination it is not unreasonable to suppose that this is at least one other mechanism that could account for a percentage of the change, but my off the top of my head ball park calculations certainly do not in any way establish a value for that contribution, but only give me reason to speculate that it might be worth while to investigate.

    Larry

  45. Have you seen the pictures of the Titanic, Bismark or Hood?
    All three ships are being covered with gloop (a technical term), a mixture of organic material, derived from atmospheric CO2 and N2 and newly precipitated minerals. We know when these ships when down and we know how much gloop there is.

    Here is a pic of the Titanics out propeller, made of bronze and not subject to corrosion.
    This wing propeller is 23.5 feet (7 m) in diameter and weighs 38 tons (34 t).

    here in an anchor chain,

    Some idea of the size.

    http://www.titanic-model.com/articles/anchor/titanics_center_anchor.htm

    How much gloop is there in 90 years ?

    My guess is about 1 cm in 90 years. The Earth is biotic.

  46. Here are a few more figures I just found on ocean sedimentation.

    http://www2.ocean.washington.edu/oc540/lec02-2/

    The material deposited in marine sediments has its origin on the continents:

    * rivers
    o suspended load: 180 x 10^1^4 g/y
    o dissolved load: 40 x 10^1^4 g/y (corrected for cyclic salt component)
    * wind
    o atmospheric dust: 5 x 10^1^4 g/y

    http://www.ngdc.noaa.gov/mgg/sedthick/sedthick.html

    http://www.odp.usyd.edu.au/odp_CD/oceplat/opindex.html

    It looks like the data is out there but would take someone a considerable amount of time to digest and analyze.

    From:

    http://www.waterencyclopedia.com/Oc-Po/Ocean-Floor-Sediments.html

    The different combination’s of each process’ effectiveness result in a commensurate variety of sedimentation rates. Sediment can accumulate as slowly as 0.1 millimeter (0.04 inch) per 1,000 years (in the middle of the ocean where only wind-blown material is deposited) to as fast as 1 meter (3.25 feet) per year along continental margins. More typical deep-sea rates are on the order of several centimeters per 1,000 years.

    Larry

  47. hotrod: Whew, lotsa numbers there. But on a couple things:

    “…More specifically I am thinking about volume changes due to changes in shape of the basin, not volume changes in the earth….” Interesting, worth investigating. Years ago I had a speaker to a forum talking about the Cretaceous. He said it was a time of unparalleled rapidity of spreading (NAm was scooting away from Africa, and SAm had begun to move, too. Consequently or coincidentally the K was a time of great epicontinental seas covering big chunks of NAm, Africa and maybe elsewhere. The Mid-Atlantic Ridge must have been bulging, and Atlantic sea floor, at any given distance from the MAR would have subsided less than in a more ordinary rate of spreading. And presumably those rapidly westward-moving plates were overriding deeper Pacific oceanic sea floor.

    Long story short: yes I think it’s possible for plate tectonics to affect the sea basin volume and thus sea levels. Which way they’re working today, I couldn’t hazard a guess.

    On the Indian Ocean (IO) uplifts attendant on the tsunami-generating seism, let’s agree that it was 100 meters uplift by 5 KM wide by 1200 KM long. That gives us (0.1x5x1200) km^3 in volume = 600 KM^3. The IO has a volume of 292M KM^3 (wikipedia). So the delta volume is 600/292M = .0002%. Does this calculate to a measurable increase in sea level? And remember, in dealing with with faults, something is moving up – and something is moving down or being attenuated somewhere. Google “rift and graben”. There is no new volume created – just things adjusting up, down or laterally.

  48. hotrod – re “check the numbers”.

    “In the Yangtze river, it carries enormous silt loads, estimated at 60% by weight in places. The best number I have found is about 1.4 billion tons are carried to the sea annually in this river alone.”

    Let’s agree 1.4 x 10^9 tonnes of solid matter get carried to sea. This is deposited as grains of silt and flocculated clay particles and so on in an initially not very dense aggregate. Let’s say the deposits have a s.g. of 1.65 g/cc (2.3 g/cc solid, 1.0 g/cc H2O, 50:50).

    Then 1.4×10^9 tonnes x (1×10^6g/tonne) = 1.4×10^15 g x 1cc/1.65g = 8.5×10^14 cc. A kilometer cubed is 1×10^15 cc. So we get 8.5×10^14 cc x (1km^3/1×10^15cc) = .85 km^3 of new material deposited in the Yangtse delta annually. That’s not much, and it will get denser as time goes on as water is ultimately squeezed out.

    Please check my math!

  49. David Archibald has transferred the correlation of insolation changes with glacial change from his main reference source* and overlaid his own interpretation.

    * http://www.dvgu.ru/meteo/library/243887.pdf

    The originating source reflects mainstream understanding on the contribution of insolation changes to glacial change (triggering other processes like atmospheric changes and albedo). Dr Archibald has dismissed the findings of that paper, which are quite different from his own, but has not explained why he has done so.

    As Dr Archibald’s above thesis is purely correlative, and not in disagrement with this superficial part of the originating paper, there is a significant argument missing here.

    Specifically, Loutre and Berger posit that insolation changes are too weak by themselves alone to account for past glacial changes. This is entirely consistent with virtually all the modern literature on the matter (referenced in the study). Yet Dr Archibald seems to contend, with no references, meaningful calculations or descriptions, that insolation changes are alone strong enough to cause the glacial changes. His thesis is consistent with the scientific literature regarding correlation with orbital variaton/insolation changes. I cannot fathom why he ignores/dismisses the rest of the science on the subject of glacial change.

    I note with disappointment that Dr Archibald has referred to Berger and Loutre in the comments above as “loonies”. As this is an ad hominem remark (ie, a slur devoid of any argumentation to buttress it) I now wonder if Dr Archibald is a serious scientist qualified in the field he has undertaken to weigh in on.

  50. Jim F (20:11:23) :
    hotrod – re “check the numbers”.

    So we get 8.5×10^14 cc x (1km^3/1×10^15cc) = .85 km^3 of new material deposited in the Yangtse delta annually.

    Thanks for the check Jim! It has been a long time since I worked with scientific notation, and I think you are correct. It looks like I dropped a decimal place doing my quick calculation, and was off by a factor of ten using my assumptions.

    On reworking it with 2.2g/cc density as I did the original, I came up with 6.3636 x 10^8 cubic meters rounding to 6.4x 10^8 cubic meters, rather than my original value of 6.4 x 10^9 cubic meters, or about 0.00176278 of 1 mm sea level rise which would be about .1% , not 1% of an annual sea level rise of 1.8 mm which was the number I was working with.

    I must have dropped a decimal point some place. Thanks for the check!
    That change would drop the effect of sedimentation to a minor contributor to annual sea level rise.

    It just bothers me when no one even mentions a mechanism like this. I would much rather have them work the numbers and then state it was of negligible effect.

    Years ago I worked as an emergency planner and my job basically involved looking for the unstated assumptions or pointing to the 600 lb gorilla in the room no one wanted to talk about. As a result, my first instinct when looking at a problem, is to brain storm every possible other explanation and then start eliminating them one by one to see if one of them refuses to go away.

    Larry

  51. On the Indian Ocean (IO) uplifts attendant on the tsunami-generating seism, let’s agree that it was 100 meters uplift by 5 KM wide by 1200 KM long. That gives us (0.1×5×1200) km^3 in volume = 600 KM^3. The IO has a volume of 292M KM^3 (wikipedia). So the delta volume is 600/292M = .0002%. Does this calculate to a measurable increase in sea level? And remember, in dealing with with faults, something is moving up – and something is moving down or being attenuated somewhere. Google “rift and graben”. There is no new volume created – just things adjusting up, down or laterally.

    My understanding is this specific type of rebound of a stressed plate would result in the subsidence of the above sea level portion adjacent to the fault (the island of and the sudden upward thrust of the subsurface plate, as shown in the following video.

    http://www.iris.edu/hq/programs/education_and_outreach/aotm/5

    No single event like that probably would have a very large effect, although it would be interesting if there was a detectable step change in world wide sea surface height measurements. I was speculating on the over all stability of the shape of the basin, with this as an example of some of the distortions that might be taking place along the ring of fire due to thousands of small earth movements.

    In the case of the Good Friday 1964 earth quake in Alaska, they estimate total displacements underwater were on the order of 120 cubic kilometers.

    http://www.drgeorgepc.com/Earthquake1964Alaska.html

    It is not clear what the net change in undersea volume was, as some of the changes were uplift and some were subsidence, some areas effected were submerged and others were above sea level prior to the quake.

    As mentioned in my other post, I am just brainstorming about alternate mechanisms I have not seen discussed much in the context of world sea level changes.

    Larry

  52. Re Abuliam (12:23:52) :

    Sorry but it’s not that simple, as the Indian plate keeps moving north and ppushing up the Himalaya, the latter is being eroded and filling out the Indian ocean. The Ganges fan is the largest accumulation of submarine sediments on Earth.

  53. “David Archibald has transferred the correlation of insolation changes with glacial change from his main reference source* and overlaid his own interpretation.”

    I’m not allowed to use your data, possibly for another issue than that for which you gathered same, and come to a conclusion differing from yours?

    Whatever.

  54. One intriguing problem associated with orbitally driven glacial cycles is the transition from 41,000-year to 100,000-year climatic cycles that occurred without an apparent change in insolation forcing

    It didn’t. It changed from 1*41kyr to 2, 3 or 3*41kyr, probably caused by the connection of the Americas, bringing more moist (snow) to the high north.
    And the interglacials last 1 mill. years have never survived an obliquity minimum so why would it this time?

  55. gary gulrud says:

    I’m not allowed to use your data, possibly for another issue than that for which you gathered same, and come to a conclusion differing from yours?

    You are certainly allowed to, but it seems like the least you should do is explain clearly what the other person’s interpretation was and why you interpret it differently.

    barry says:

    I now wonder if Dr Archibald is a serious scientist qualified in the field he has undertaken to weigh in on.

    Here is one piece of information that I found on him ( http://www.sourcewatch.org/index.php?title=David_Archibald ):

    Archibald is a scientist operating in the fields of cancer research, climate science, and oil exploration. In oil exploration, he is operator of a number of exploration permits in the Canning Basin, Western Australia.

    Perhaps Dr. Archibald can fill us in with more detail on his qualifications and publications in the field.

  56. In the introduction to this thread, David mentioned that that bottom water temperature of the Pacific Ocean started declining 40 million years ago, falling by 10C from 13C to the current 3C level. A number of posters have queried this assertion; Harold Ambler (07:30:40); Steiner Midskogen (09:29:52) 23022009 & Ed Zuiderwijk (05:39:12) 24022009, but to date I don’t think that their concerns have been answered.

    Oxygen can only be produced by sunlight. At the bottom of the ocean there is no light source, other than the very faint bioluminescence powered by chemical reactions, and so no oxygen gas can be formed. In the ocean, oxygen is created in the surface waters, where sunlight allows marine algae to photosynthesise in the euphotic zone and storms, that produce breaking waves, permit atmospheric oxygen to mix in. The presence of oxygenated water at oceanic depths in the aphotic zone requires a process of gas transport and replenishment throughout the water column. Thermohaline circulation is the mechanism by which the world’s ocean waters overturn and the process by which oxygenated water reaches the ocean depths.

    Throughout millions of years of geological history, the overturn of the world’s oceans has operated in one of two modes, either the “Haline” mode of mid-latitude warm water oceans or the “Thermo” mode of polar cold water oceans. In the Jurassic and Cretaceous eras the haline mode of ocean water overturn dominated. The world was warm and so the bottom waters the oceans were warm also. During the Cenozoic era, since the Paleocene-Eocene Thermal maximum 55 million years ago, as the world has cooled and Antarctica has become an ice continent, the cold thermal mode of ocean water overturn has prevailed.

    Haline circulation is a warm world process, it relies on the creation of dense saline water in mid-latitude oceans where evaporation exceeds rainfall, it dominates today only in the waters of the Mediterranean. The Mediterranean Sea occupies an enclosed series of basins. Its waters experience high temperatures in summer and insufficient input of river water from Southern Europe and the Nile, to maintain the total seawater mass balance.

    Because of the loss of water to the atmosphere through evaporation, the Mediterranean Sea is more salty than the adjacent Atlantic Ocean. If it wasn’t for the continuous surface influx of new ocean water through the Gibraltar Strait, then the Mediterranean Sea would eventually dry out. In the past the Mediterranean, with an area of 2.5 million sq kms, did indeed greatly reduce in size, as the presence of deeply buried canyons of the ancient River Nile and River Rhone testify. In addition, seabed boreholes in the abyssal plains of this small ocean prove the presence of ancient thick salt layers. Think Dead Sea, but two and a half thousand times bigger.

    Today the Mediterranean Sea exports its salty water back into the Atlantic Ocean through the Gibraltar Strait as a dense bottom water counter-current. This warm saline-rich water falls under gravity to depth in the Atlantic, but does not now reach the abyssal ocean plain. Instead it floats at depth above the denser 3C, polar ocean derived, bottom waters of the modern cold water world.

  57. Doug Janeway (07:13:14) :

    “The Earth’s current ice age is primarily caused by Antarctica drifting over the South Pole 30 million years ago. This meant that a large area of the Earth’s surface changed from being very low-albedo ocean to highly reflective ice and snow. “

    Incorrect. Antarctica was already moving into the Antarctic circle some 125 million years ago, and it was at the South Pole during the Early Cretaceous about 120 million years ago. Although Antarctice experienced cool temperate conditions with winter snowfalls and icing and very limited periods of small permanent polar ice caps, much warmer conditions free of polar ice caps dominated from the Late Cretaceous 117mya to the onset of the latest ice ages about 30-32mya. In other words, Antarctica was located at the South Pole for tens of millions of years without causing an ice age and polar galciations to occur.

    There were species of of dinosaurs and flora adapted to nocturnal habits well suited to the six months of darkness prevalent in an Antarctic in the antarctic circle.

  58. foinavon (15:03:17)

    Thank you so much for your generous response to my post. I really appreciated your comments and the inclusion of the abstract. That said, I hope that you will not take it as ungracious of me if I pose a few questions.

    You describe the transition from a 41,000 cycle to the 100,000 cycle as beling something like missing a “pulse” while the abstract describes it as more of a gradual transition. Is this a situation where there isn’t enough good data available, so that a certain amount of speculation is necessarily involved in arriving at such conclusions? My limited reading on the subject has not included research findings that describe intermediate length cycles. I think that this is a key issue and that your “pulse” notion is more nearly correct. But on the other hand, I wonder if the growth of more extensive ice sheets isn’t more likely to be an effect of an X factor(s) rather than the cause of the sudden shift from a 41,000 cycle to a 100,000 cycle.

    Am I correct in recalling from my reading that interglacial periods have extended for of a failry similar time periods? If so, this would support the notion that the earth has been in a prolonged cool phase for the past 20 to 40 million years, with recurrent heat cycles being introduced (for largely unknown reasons) periodically. The coolness includes but is not necessarily dependent upon glacial conditions. For example, the Andrill project of a few years ago found that the earliest indication of a collapse of the Ross Ice Shelf in Antartica dates back about 17 million years. This seems like evidence of a ing phase occurring during a non-glacial period of the prolonged (still going) period of cold.

    From this “heat clcyes” notion I suggest that unknown factors might have pushed the 15.000 to 20,000 year recurring warm phase (which accounts for the interglacial periods) into a 100,000 cycle, and that in turn wouild have caused much increased growth of the ice sheets. These heat cycles that I propose also seem to regularly warm things up a bit beyond our current Antarctic regional (or possibly global) temperature, in that the Andrill pras reported in Science the Scott Ice Shelf has apparently been warmed to the point of collapsing some sixty times or so in the past 17 million years..

  59. ******
    barry (22:13:52) :

    Specifically, Loutre and Berger posit that insolation changes are too weak by themselves alone to account for past glacial changes. This is entirely consistent with virtually all the modern literature on the matter (referenced in the study). Yet Dr Archibald seems to contend, with no references, meaningful calculations or descriptions, that insolation changes are alone strong enough to cause the glacial changes. His thesis is consistent with the scientific literature regarding correlation with orbital variaton/insolation changes. I cannot fathom why he ignores/dismisses the rest of the science on the subject of glacial change.
    ******

    As you say, Loutre and Berger are running a model (BTW, it does seems interesting). For their model, they use a CO2 sensitivity of 2C for a doubling. Their results obviously depend on this sensitivity. This sensitivity is disputed by many. Empirical data suggests it is lower — as low as .5C or lower for a doubling.

    They should have run their model w/a range of CO2 sensitivities to compare the results.

  60. “Perhaps Dr. Archibald can fill us in with more detail on his qualifications and publications in the field.”

    How about your Curriculum Vitae Joel?

  61. Touche, Gary.

    Joel seems to be in the “kill the messenger” camp.

    I suspect there are many examples of discoveries made by people who don’t have Harvard Ph.D.s in whatever field is being illuminated. Arguing against the principle, not the man, seems to be a useful construct.

  62. Hmm

    Strong asymmetry of hemispheric climates during MIS-13 inferred from correlating China loess and Antarctica ice records

    Z. T. Guo, A. Berger, Q. Z. Yin, and L. Qin1,

    Abstract. We correlate the China loess and Antarctica ice records to address the inter-hemispheric climate link over the past 800 ka. The results show a broad coupling between Asian and Antarctic climates at the glacial-interglacial scale. However, a number of decoupled aspects are revealed, among which marine isotope stage (MIS) 13 exhibits a strong anomaly compared with the other interglacials. It is characterized by unusually positive benthic oxygen (δ18O) and carbon isotope (δ13C) values in the world oceans, cooler Antarctic temperature, lower summer sea surface temperature in the South Atlantic, lower CO2 and CH4 concentrations, but by extremely strong Asian, Indian and African summer monsoons, weakest Asian winter monsoon, and lowest Asian dust and iron fluxes. Pervasive warm conditions were also evidenced by the records from northern high-latitude regions. These consistently indicate a warmer Northern Hemisphere and a cooler Southern Hemisphere, and hence a strong asymmetry of hemispheric climates during MIS-13. Similar anomalies of lesser extents also occurred during MIS-11 and MIS-5e. Thus, MIS-13 provides a case that the Northern Hemisphere experienced a substantial warming under relatively low concentrations of greenhouse gases. It suggests that the global climate system possesses a natural variability that is not predictable from the simple response of northern summer insolation and atmospheric CO2 changes. During MIS-13, both hemispheres responded in different ways leading to anomalous continental, marine and atmospheric conditions at the global scale.

    The correlations also suggest that the marine δ18O record is not always a reliable indicator of the northern ice-volume changes, and that the asymmetry of hemispheric climates is one of the prominent factors controlling the strength of Asian, Indian and African monsoon circulations, most likely through modulating the position of the inter-tropical convergence zone (ITCZ) and land-sea thermal contrasts.

    Interesting extract.

    The correlation reveals a number of decoupled aspects between the loess and ice records. Among them, a strong anomaly is observed for MIS-13 compared with the other interglacials.Comprehensive examination of the relevant geological
    records consistently suggests a significantly cooler Southern Hemisphere, but an unusually warmer Northern Hemisphere with reduced northern ice volume, and hence, an enhanced asymmetry of hemispheric climates. During this interglacial, both hemispheres responded in different ways to the northern summer insolation and atmospheric CO2 changes.

    MIS-13 is therefore a real case of a substantial northern hemispheric warming under relatively low concentrations of greenhouse gases. Smaller northern ice-sheets would have also occurred during MIS-11 and MIS-5e, with apparently
    a lesser hemispheric asymmetry than for MIS-13. These also suggest that the coupling of hemispheric climates at the glacial-interglacial scales was significantly unstable in the Mid-Pleistocene and that marine 18O records may not
    be always reliable indicators of northern ice-volume. These findings may also have implications for the evolution of the climate system during other periods of the Quaternary.

    http://www.clim-past-discuss.net/5/635/2009/cpd-5-635-2009.html

Comments are closed.