Guest Post by Willis Eschenbach
A WUWT commenter emailed me with a curious claim. I have described various emergent phenomena that regulate the surface temperature. These operate on time scales ranging from minutes to hours (e.g. dust devils, thunderstorms) to multi-decadal (e.g. Atlantic Multidecadal Oscillation, Pacific Decadal Oscillation). He suggested that there is also a much slower thermostatic mechanism at play over thousands of years and longer. Here’s how I understand it.
He said that when it gets warmer, the atmosphere is more moist, so there is more snow on Antarctica. This translates into more ice on the ice cap, which puts increased pressure on the ice below. Now, the ice gain at the surface and the ice loss in the calving of the Antarctic glaciers is in some kind of long-term very slow-moving steady state. Pressure at the top squeezes out the ice on all sides. So increasing the ice mass over time would lead to more calving, which in turn would cool the surrounding ocean. He said this slow process shown below functioned as a long-term factor promoting thermal stability.
Warming –> increased Antarctic snowfall –> thicker ice cap –> increased iceberg calving –> cooling
He suggested I should look into the rate at which the ice has historically accumulated at the Vostok ice core location in Antarctica. He thought that the ice accumulation rate was a function of temperature. His idea was that Vostok shows that increased temperatures lead to increased antarctic snowfall, which in turn increases the rate at which the ice accumulates on Antarctica. So I took a look.
The ice core from Vostok is a technological marvel. They drilled 3.3 kilometers (two miles) straight down into the ice, and extracted a core of undisturbed ice. Then they analyzed it one metre by one metre, along the entire length of the core. The variations in temperature calculated from the core are well-known, they show the history of the last four ice ages:
Figure 1. Temperature record from the Vostok ice core. The zero point on the temperature scale is modern-day temperature. Temperature is calculated from the variations in the 18O oxygen isotope as recorded in the ice core. Present-day values are at the left of the graph. DATA SOURCE: NOAA Paleoclimate
Here, you can see the ice ages, interrupted by short periods of warming … well, short by geological scales at any rate. The most recent warm period, on the left, has lasted about 10,000 year (10 kya). (As an aside, for me the mystery is not what it was that slowly and gradually pushed us into each ice age with lots of fits and starts. The thing that perplexes me is what it was that abruptly yanked us out of each ice age in one extremely fast period of great warming. But I digress …)
Although I had seen that before, I’d never looked at the ice accumulation rates. Figure 2 shows the annual rate of accumulation of ice at Vostok.
Figure 2. Ice accumulation rate record from the Vostok ice core. Since the measurements are taken every metre along the ice core, the accumulation rate is calculated as the reciprocal of the age differences from one measurement to the next. Present-day values are at the left of the graph.
Urg. That was not too appealing. Clearly, what we are seeing is the progressive compression of the ice layers as we drill deeper and deeper into the ice cap. Millions of tonnes of ice on top have progressively flattened the deeper layers. Makes it hard to see any relationship. I considered various ways to model the compression of the layers and remove it … and discarded them all.
What I did notice, though, was that as we see at the left hand end of the graphic above, new snow is fairly bulky. But it gets compressed quite rapidly at first. After that initial rapid compression of the snow into ice, however, the compression is somewhat linear from that time onwards. So I decided to omit that first part of the data, which is about five thousand years. I then plotted up the remaining ice accumulation data, and I included the temperature data on the same graph so I could compare them.
Figure 3. Ice accumulation rate record (blue) and temperature record (red) from the Vostok ice core. Both records start a 5000 years before present. Recent values are at the left of the graph.
Dang … surprisingly, his claim was looking much, much better. So I took a first cut at modeling the ice accumulation rate from the temperature data. I’ve included the depth as a second explanatory variable. Here is the result of the estimation of the ice accumulation rate as a function of depth and temperature:
Figure 4. Ice accumulation rate record (blue), temperature record (red), and estimated ice accumulation rate based on temperature and age (black) from the Vostok ice core. All records start at 5000 years before present. Recent values are at the left of the graph.
Now we’re getting somewhere, but there is still a problem. Because the layers are progressively flattened with depth, the response of the ice accumulation rate to temperature is also progressively flattened with depth. To allow for this, I included the product of the two variables (depth and temperature) in the analysis, giving the following result:
Figure 5. Ice accumulation rate record (blue), temperature record (red), and estimated ice accumulation rate based on temperature, age, and age*temperature (black) from the Vostok ice core. All records start at 5000 years before present. Recent values are at the left of the graph.
Well, there you have it. Ice accumulation in Antarctica is assuredly a function of temperature. What’s not to like? His hypothesis is obviously correct. Done and dusted, right?
Well … in a word, no. I didn’t like it at all.
The problem that I had with the good fit is an odd one … the fit is too darn good. Nothing in nature fits that well, down to the tiny wiggles in the blue and black lines at the right of the graphic. Correlations that good make my nose twitch, they set off my bad number detector..
I had started with the raw data and no preconceptions. Now I knew what I was looking at and looking for, so I went off to research what might explain it. To do that, I looked at the various methods for dating an ice core. Turns out there are four of them—count the annual rings, align to known events, radioactive dating, and use a “flow model”. Problem is that the first three methods only get us back about 80,000 years into the past. Beyond that, it’s all flow models. Which is OK, and they are likely fairly accurate. The problem lies elsewhere, in the input variables to the various flow models. Here’s the list of what goes into the models:
- Temperature
- Ice thickness
- Flow patterns
- Gross accumulation rates
- Ice rheology, the study of how much ice deforms and moves in response to pressure.
I’m sure you can see the problem. In my calculations, the net accumulation rate shown in blue above is a function of the age change per metre of ice core. Makes perfect sense, that’s how you calculate it. If it takes a hundred years to add a metre of ice, the accumulation rate is equal to 1 metre / 100 years = 10 mm/year.
The problem is that in their model, the age change per metre in turn is very much a function of the temperature. And that means that we expect the net accumulation rate to be a function of the temperature. It is inherent in the calculation—accumulation is a function of age, and age is a function of temperature, so accumulation is a function of temperature.
As a result, the graphs that I have shown above have very little inherent meaning. It’s like showing that one equals one. The commenter was correct that he found a correlation … it just didn’t prove anything.
This also means we cannot use the correlation above to support the commenter’s theory that increased temperature leads to increased accumulation rates.
However, all is not lost. This analysis does point out one important thing—the best judgement of the scientists studying the question is that indeed, ice accumulation rates in Antarctica are strongly positively correlated with temperature. They say that counterintuitively, a warmer world indeed means more Antarctic ice.
So … IF the scientists are indeed right, then this analysis also allows for a couple more deductions. One is that near the surface, which is to say near the present, the depth and depth*temperature terms of the estimate are small. This means that the recent annual addition of snowfall to the icecap is about 20 mm (of ice equivalent) per year. The change in that accumulation rate per degree of warming is about 1.25 mm/year This implies that for each additional °C of warming, the accumulation rate goes up/down by about 6%.
The graph also shows that during the end of the most recent ice age, the annual accumulation rate was only about half of the current rate.
All of which would suggest that the change is large enough to support the idea of a slow restorative force opposing any change in temperature. Since at the start of an ice age the annual addition to the icecap drops rapidly to as low as 50-60% of its previous value, surely that much of a decrease in ice accumulation must result in a correspondingly reduced amount of iceberg calving at the ocean.
How much energy is involved in the change? Well, to first melt and then evaporate a cubic metre of ice takes about 90 watt-years of energy. The change in accumulation rate between ice age and interglacial is about 10 mm/year, which is about a metre per century difference.
This means that the change in energy between ice age and interglacial due to the variation in ice buildup is about 0.9 watts per square metre constant change over the surface of Antarctica. This is a fairly small effect.
However, in contemplating this situation, I realized that one oddity of this method of moving latent heat around in the form of ice is that the ice is added over two dimensions, over the surface area of Antarctica. But at the other end of the process, the ice is squeezed out in one dimension, along the coastline. Given the relative area (11.1E+6 km^2) and the coastline length (18.0E+3 km) of Antarctica, this is a concentration of about six hundred to one. This means the 0.9 W/m2 across the continent becomes about 0.9 * 618 ≈ 550 watts of heating or cooling per metre of coastline. This variation in iceberg calving rate represents a strong local change immediately adjacent to the coastline.
Next, let’s consider what this variation in ice calving rate along the Antarctic coastline does. The key underlying concept to keep in mind is that vast amounts of heat are being exported constantly from the tropics to the poles, where the heat is radiated into space. The transportation is done by both the ocean and the atmosphere, both of which move heat polewards 24/7.
As a result, the rate at which the planet can lose energy is constrained by the speed of the oceanic and atmospheric circulation. The general rule is, anything that speeds up oceanic circulation will cool the planet down, and vice versa.
The circulation around Antarctica is shown below.
Figure 6. Circulation patterns around Antarctica (right side of drawing).
Setting the details aside, the takeaway message from this graphic is that when the Antarctic coastline gets more ice input from the glaciers, the speed of the circulation increases because more cold water is sinking downwards around the continent.
And on the other hand, when there is less ice around the Antarctic coast the circulation will slow down. There will be less cold water to drive the downwelling leg of the thermal circulation.
So the entire feedback loop looks like this:
Warmer southern ocean –> wetter atmosphere –> more snow on Antarctic interior –> more glacier calving around Antarctic perimeter –> increased oceanic circulation –> increased global cooling.
Anyhow, that’s what I found out today. Of course, your conclusions from the same facts may be totally different …
Regards to everyone,
w.
My Usual Request: If you disagree with me or anyone, please quote the exact words you disagree with. I can defend my own words. I cannot defend someone else’s interpretation of some unidentified words of mine.
My Other Request: If you think that e.g. I’m using the wrong method on the wrong dataset, please educate me and others by demonstrating the proper use of the right method on the right dataset. Simply claiming I’m wrong doesn’t advance the discussion.
EDIT: Willis accidentally left figure 6 out of the body of the text, but made it the featured image for the post from the set of images he uploaded. I’ve corrected that problem – Anthony
Missing Figure 6 ?
Figure 6 has been restored, see note at end of essay
The warming of the Arctic (and large ice-free areas) would also provide the humidity necessary to form over one-mile-thick ice sheets to cover all of what is now Canada. An ice-free Canada is apparently an unusual state during the current ice age, the past 2.6 million years.
Indeed, for the last million years or more, most of Canada has been buried under a mile of ice. Pretending that Ice Ages will never happen again is part of the global warming dogma. It is also quite unbelievable since we still don’t know what there is causing this ticking clock of severe Ice Ages/sudden dramatic warmups/severe ice Ages.
“Pretending that Ice Ages will never happen again is part of the global warming dogma.” Even worse, it is common knowledge the Earth is in an Ice Age, we are living it now, but they ignore that fact. Part of the confusion they rely on comes from improper use of the term “ice age” when “glacial period” is actually meant. What CAGW theory amounts to is an end to the Ice Age, melting of the Arctic sea ice, Greenland ice sheet and, the biggy, all the ice at the South Pole. And beyond that, whatever ginormous forces of Nature have caused the steady cooling of the planet since the Eocene resulting in the present Ice Age…humans are now cancelling that out and reversing it by burning fossil fuels. Extraordinary claims require extraordinary proof.
Tick, tock, tick, tock, tick, tock … BOOOM! For the average plebe especially one living somewhere with crummy distribution “Boom” would mean … “you die.”
@Robert:
Yes, we are presently in an ice age, having a short interglacial.
W. used the term ‘ice age’ as it is commonly, but innacurately, used.
I usually say “ice age glacial” as a kind of compromise between the two modes of speech.
It is very important, though, to remember that a few thousand years of warm interglacial is NOT the end of an ice age, just a natural and expected warm excursion. Real climate change, all natural.
We WILL drop back into an ice age glacial, and very soon in geologic time. No more than about 2000 years (so about as much time as since Rome ruled Judea and that Christian thing started) or perhaps as short as about 300 years (think founding of North American British colonies). It is also remotely possible we entered the process in the Little Ice Age and are just having a tiny wobble to warm on our way down already. (It isn’t a linear process, and has large excursions, but is so slow we don’t notice much in any one lifetime)
Those warm spikes have a name too. Interstadial. Lots of them have happened.
https://en.m.wikipedia.org/wiki/Stadial
The null hypothsis ought to be that the present warm is just a natural Interstadial, the LIA was a stadial, and the pattern is towards more cold in each stadial, where they mark our decent into the modern glacial in our present ice age.
All that insight lost when one forgets we ARE in an ice age wobble of very brief warmth.
Hi Willis, thanks for this post. I had earlier received this comment from an Australian paleontologist, currently looking for fossils on Vega Island next to the Antarctic peninsula, an AGW believer:
“Steve Salisbury: The increase in sea ice around Antarctica is most likely a direct consequence of the warming Tom Harley. Tightening of the Circum Antarctic currents in the Southern Ocean due to warmer termperate waters in the Pacific, Atlantic and Indian oceans amplify the colder sea surface temps close Anarctica (similar to a positive phase of the Southern Annual Mode), combined with melting of continental and glacial ice that then feeds into the cooler surface waters… thereby increase the amount of sea ice. We’ve been monitoring this situation closely for the last five years.”
I had suggested he was wrong about warming and asked why Antarctic ice was at very high levels!
“Tightening of the Circum Antarctic currents in the Southern Ocean due to warmer termperate waters in the Pacific, Atlantic and Indian oceans amplify the colder sea surface temps close Anarctica.”
It take it that it wasn’t thought out too well. Apart from the typos (and what’s a Tom Harley), it suggests that being in contact with a warmer substance will make something colder. I take it is merely the cold waters are mixing less with the warmer waters.
I think a Tom Harley is a cross between a Tom Collins and a Harley (Harvey) Wallbanger.
Cheers.
So can you run the flow models without temperature? That might be interesting.
And yes, the real interesting bit is the discontinuity at the end of the ice age. Why is it so sharp?
The catastrophic and very sudden fall in temperatures is the entire point: NO ONE knows, exactly, what is going on and why this happens over and over and over again, the same way. I would suggest our local star isn’t as reliable as we want.
You raised a good point and did the start of a calculation on glacier calving in the Antarctic that was raised in a recent WUWT post:
http://wattsupwiththat.com/2016/02/19/colossal-antarctic-ice-shelf-collapse-followed-last-ice-age/
So, 100,000 square miles of ice 1500+ metre thick disappeared over 1500 years meaning 100,000 square miles of ice 1 metre thick melted every year for 1500 years. So what amount of cooling and what disruption to the ocean currents and atmospheric circulaton would that have caused? Rhetoric question perhaps.
There didn’t seem to be any discussion of that in the post but it certainly made me wonder where all that latent heat went – though as I commented in the post, the ocean volume is large. But that volume of ice melt must have had some effect on the atmospheric and ocean circulations. I just don’t have the skill to imagine or calculate it.
Just wondering since you commented on that aspect here:
Thanks for the comments on something I have wondered about for a long time. So many variables to think about. The climate is Gordian knot waiting for Alexander to come along.
There is the comment above from Tom Harley about the ocean currents and how the warmer world means colder waters around Antarctica. Slower mixing of warmer sub-tropical waters with the colder waters means more transport of latent heat from the tropics to the atmosphere, then to the poles. There would not only be larger energy loss to space as it condenses but also more snow/rain. There could also be a larger current flow into the Arctic ocean causing it to warm (the sea-ice extents seem to be oscillating between the two poles) and this is supposed to increase precipitation over N. America.
Gradually, the oceans cool but the ice sheet remaining keeps the planet cool (and dry) through a large albedo.
The glacial period ending suddenly is the difficult part. Maybe its not as simple as currents through the Drake Passage being blocked. It could be the winter sea-ice extent in the SH causing circumpolar current to deviate north, push warm tropical water towards the Arctic ice sheet. If it coincides with greater insolation in summer above 60N, you get a lot of rain, lakes of water in summer and eventually a rapid loss of the ice.
There is evidence of very dry places like the Sahara and deserts in the Levant having periods of high monsoonal rainfall at the end of the last two glacial periods. Probably need evidence of warmer seas in the south-eastern parts of the oceans in cooler waters in south western parts just for a short period at the end of the last glacial period.
You mean – since the ice melted – “where did all of the latent heat come from”.
If the warm waters closer to the tropics don’t mix with the colder water, then they don’t cool down by mixing but by evaporation. The latent heat in the evaporated water is then transported to the polar regions via the atmosphere where it condenses (freezes) and warms the troposphere plus emits LWIR. Mixing distributes the heat and reduces LWIR loss of energy from Earth. Evap distributes the heat to the colder waters but via a mechanism where more is lost to space.
Oops. Misread the units. It was 1800 feet thick, not 1500 metres, so it was 100,000 square miles 1 foot thick melting every year for 1500 years (rounding off the article’s 1800 feet to 1500 to get the one foot per year.) Apologies
There is no Figure 6 in my browser (Firefox).
Interesting discussion Willis. I caught the “self correlated” part fairly early, so proud of myself 🙂
Figure 6 is missing.
Peter
“Setting the details aside, the takeaway message from this graphic is that when the Antarctic coastline gets more ice input from the glaciers, the speed of the circulation increases because more cold water is sinking downwards around the continent.”
Willis, would not the cold water, being fresh, tend to sit atop the salty ocean?
Cheers,
Dave
@Dave,
“Willis, would not the cold water, being fresh, tend to sit atop the salty ocean?”
If I may, actually, no, because that cold water isn’t fresh: it’s saltier than normal. This is due to the higher concentration of dissolved minerals which are forced out by the freezing of sea water. That cold, salty water then sinks & runs along the bottom back towards the tropics, completing the heat loop.
It is true that glaciers deposit large chunks of solid fresh water into the ocean as they calve, but those take time to melt. In so doing, they (generally) restore some of the saline balance to the pole-ward flowing subtropical surface water (which would otherwise have an increased concentration of minerals, thanks to solar evaporation instead of freezing). As such that surface water becomes “fresher” than it otherwise would be, and remains both warmer and less dense/saline than the water which drops to the abyss & flows away from the poles as the sea ice freezes out.
smokey writes
As far as I can see the process Willis is writing about is increased calving at the coastline due to increased snow accumulation in the interior. And when that calved ice melts, it is fresher than the surrounding water because it had the salt forced out but also because it was fresh when it originally fell as snow if you look at the whole of the argument he’s making. Willis then appears to go on to suggest this “colder water” increases circulation but that’s not the accepted norm.
Perhaps I’m misunderstanding your argument. Do you see it differently?
Yet another self regulating thermostat!
ps. I don’t see figure 6?
Willis
As per Dave above, I think the general consensus around melted ice is that it stratifies the ocean rather than increases circulation. That assumption could be wrong…but you’re flying in the face of the commonly accepted mechanism.
Also I’m not quite sure what you’re getting at with the 55W at the coastline equivalent you mentioned. Can you please explain what you mean?
What janked us out of the iceage, it was falling CO2 levels, until a point is reached where vegetation dies off, and countries are turned inot a dust bowl, the dust is blown onto the ice sheets and reduces albedo.
I think the ice cores show the dust layers.
“What janked us out of the iceage, it was falling CO2 levels…”
Could it be that the ice age caused falling CO2 levels? If I recall correctly, cooling starts when CO2 is at a peak levels?
I hold to the theory that the so called last ‘Ice age’ was caused by wandering poles and had nothing to do with global climate change apart from modifying local conditions. The last ‘Ice Age’ ended when the pole migrated over the sea off the North American landmass in the northern hemisphere and onto the Antarctic continental landmass off the sea in the southern hemisphere. Siberia had no glaciation or permanent ice of any kind in the last ‘Ice Age’ and this can only be explained by the north pole migrating in an arc over Europe and North America to its present position.
Colder water holds more CO2. The challenge with climate science IMO is “which came first, the chicken or the egg?” According to Antarctic ice cores changes in temperature occur before changes on CO2 There is lots of “what” but not enough “why.”
“The thing that perplexes me is what it was that abruptly yanked us out of each ice age in one extremely fast period of great warming. But I digress …)”
You do not digress. The default state is clearly warmer. When the das boot of glaciation falters…
It is chilly in antarctica these days and warmer at the North Pole. Is ice accumulating faster up here?
Uncertain, but life isn’t fair. The south pole has been able to sequester continents for all of tectonic history as we know it. The north pole, never.
“The south pole has been able to sequester continents for all of tectonic history as we know it. The north pole, never.”
That’s because the North Pole is at the top and the South Pole is at the bottom. 🙂
Using your numbers for heat – 90 watt-years per cubic metre – 100,000 square miles is roughly 2.6e11 square metres by 0.3 metres thick so 7.8e10 times 90 watts or 7e12 watts per year for 1500 years. The “coast line” would have been longer but using your number of 18e3 for comparison gives 390 watts per metre or 7 times the rate you calculated using ice accumulation alone. Is that correct and if so is it significant? I have no idea.
But thanks for the information.
An excellent post. I was particularly impressed by the fact that the results obtained in fig 4 or 5 were not accepted at face value and the underlying assumptions were sought out and questioned. If I were still teaching environmental science at UEA I would strongly recommend my students to read it as an example of how to do real science.
Please keep this up Willis
Alan Kendall
alan kendall. i think many here would wish you were still teaching environmental science at uea. your successors appear to be failing miserably.
This link on how low CO2 induced stress on high altitude forest and consequent dust impact on ice sheet albedo may have triggered sudden melting of ice caps may be of interest.
https://www.academia.edu/20051643/Modulation_of_Ice_Ages_via_Precession_and_Dust-Albedo_Feedbacks
Pablo
Yes l also think that the sudden increase in dust over the ice sheets is a interesting and important point.
Because what it suggests to me that there was a major shift in wind/weather patterns taking place over the ice sheets during this time. Where l think the paper is wrong is that they think there was a sudden increase in the amount dust in the air. What l think happened is that there was a major change in where this dust was going. Look at a map of the temperature change during the ice age and you will see that the ice age was largely confined to NE North America and NE Europe/NW Russia. This to me has all the hall marks of the set up of a persistent blocking in the weather patterns that was driving cold Polar air down across these areas. What this sudden increase in dust on the ice sheets suggests to me that there was a break down of these weather patterns. And that during this time there was a large increase in warmer air coming up from the south over the ice sheets and a big drop in the flow of cold Polar air. lts this major change in weather patterns aided by this dust is what l think lead to the rapid melting of the ice sheets.
This is no ‘explanation’ since ALL ice ages end the same way and begin the same way and last roughly the same length. Only something that turns this process on and off could cause this. Normally, if one heats up something using flames of some sort, it causes melting, etc. and if one turns off the heat, it cools off to ambient temperatures.
This is why we must first look at a heat source if we wish to know why it gets colder. Namely, our star system called the ‘sun’.
emsnews
lts all very well saying “its the sun” that did it. But unless you explain in detail how the sun affected the earths climate to cause the ice age. Then you are no better off then these who claim that its all down to CO2 levels.
>>Only something that turns this process on and off could cause this.
Not so.
The perennial problem that has plagued palaeoclimatology for decades, is that the response to solar insolation variability is itself variable. Sometimes an insolation maximum causes an interglacial, but many times it does not. That selective response to insolation requires an explanation, and that is what this paper does.
It so happens that successful interglacials always follow dust epochs, lasting about 10,000 years. So it would appear that dust is important in this selective temperature response. But how? Well, this paper give the reason.
R
I agree with this thought. If it gets very cold, plants die and deserts grow. The wind then picks up the dry dirt and vast dust clouds help block the sun. So the acceleration cooling with combo of high ice/snow reflection during calm days and dust cloudsduring windy. A Model for that? Nope.
OT, But
[snip, no buts, that’s what our tips and notes section is for -mod]
……LOL
I’ll offer this thought. The weight of ice over Antarctica is such that it has depressed much of the continent below sea-level (isostasy). The more that accumulates, the greater the depression and, at least for a while, the less gets to the edges and floats away as icebergs.
Why not. One mile of ice sheet presses the continent 300 meters down, which is probably enough to let sea currents calve now grounded shelves. The same should happen in Canada and Northern Europe.
The theory that warmer air holds more water maybe true in the laboratory but history shows that it is the cooler periods that produce the greater number of storms, greater rainfall etc.
Thanks, John. I’ve shown that in the tropics warmer is indeed wetter. See Figure 2 here.
So if you have evidence to the contrary, please link to it.
w.
johnmarshall – more storm, yes. but more rainfall ???
I don’t believe this is true. More heat must put more moisture into the atmosphere. It will fall when it finds cooler air to condense in. This may mean it rains or snows more where it is cooler but that is confusing cause and effect. Where i live it rarely snows when it is below minus 30C. It may clearly be cold enough to condense but there is no moisture in the air.
more warmth => greater snowfall
Willis
Compliments on interesting exploration, especially the ice flow/calving rate.
That brings to mind the advances in quantitative modeling of the ocean:
Marshall, John, and Kevin Speer. Closure of the meridional overturning circulation through Southern Ocean upwelling Nature Geoscience 5, no. 3 (2012): 171-180.
Note 168 citations
e.g., Evidence for link between modelled trends in Antarctic sea ice and underestimated westerly wind changes
Quote:
To do that, I looked at the various methods for dating an ice core. Turns out there are four of them—count the annual rings, align to known events, radioactive dating, and use a “flow model”. Problem is that the first three methods only get us back about 80,000 years into the past.
______________________________
There is another method, which is tuning the ice temperature record to Milankovitch cycles. And just about every ice core record out there has some kind of orbital tuning included in the dating, some more than others. And they also contain the Mont-Berlin ash layer from 92 kyr ago, and the B-M magnetic reversal 778 kyr ago, which are two fairly accurately dated chronological pegs to hang the chronology on. So the beginning and end of the ice age chronology are well known, while the bits in the middle are uncertain.
According to Professor Huybers, when I contacted him, the only ice age chronology that does not contain ‘orbital tuning’ is the sea-silt core record he made, which was deliberately separated from Milankovitch cycles. But in doing so, the vast majority of his record has to depend on silt-depth and flow model ‘guesswork’, much as Willis points out. So instead of having multiple orbital (Milankovitch) date-fixing throughout the core, Huybers ended up with just two fixed points – the age of the Holocene warming and the B-M magnetic reversal 778 kyr ago, which is why his chronology comes back into line with orbitally tuned ice core chronologies at that time.
So the ice core chronologies are pretty accurate, but only if you believe and understand that interglacials and the smaller ‘failed interglacials’ warming events are all orbitally driven – mostly by the precession of the equinox.
The Prof Huybers ocean silt chronology (not orbitally tuned).
https://www.researchgate.net/publication/222422233_Huybers_P_Glacial_variability_over_the_last_two_million_years_An_extended_depth-derived_age_model_continuous_obliquity_pacing_and_the_Pleistocene_progression_Quat_Sci_Rev_26_37-55
Ralph
P.S. Willis – are your figures 4 and 5 reversed?
.
Thanks, Ralph. you say:
Mmm … citation?
w.
Perhaps the best paper on ice core dating is Parrenin et al, The EDC3 chronology for the EPICA Dome C ice core:
http://www.clim-past.net/3/485/2007/cp-3-485-2007.pdf
This pertains to the EPICA core, which is one of the latest drilled, and which has verified much of the chronology work done on the previous cores. But they do quite a lot of comparison work – make of that what you will. The chronology techniques they use include:
2.1 Dated volcanic eruptions during the last millenium
2.2 Synchronisation onto GICC05 with 10Be (6 kyr)
2.3 CH4 during the last deglaciation
2.4 The Laschamp event
2.5 The Mont Berlin ash layer
2.6 Timing of termination II
2.7 Air content age markers 0–440 kyr BP (orbitally tuned)
2.8 18Oatm age markers for stages 300–800 kyr BP (orbitally tuned)
2.9 The Brunhes-Matuyama reversal
Here are some relevant quotes for you:
(Note: Specmap is the most orbitally tuned chronology of all of them…)
Ice flow modelling has been historically used to date ice cores from Greenland and Antarctica. A one-dimensional flow model was first applied to Camp Century (Dansgaard and Johnsen, 1969), and later to GRIP (Johnsen and Dansgaard, 1992; Johnsen et al., 2001). The Camp Century, Dye-3 and GISP2 cores were also interpreted by matching the oxygen 18 isotope record of ice or air bubbles to the SPECMAP stack (Dansgaard et al., 1985; Bender et al., 1994), which is itself orbitally tuned.
The Vostok ice core has also been dated by matching to the orbital SPECMAP scale (Bender et al.,
1994), or directly to insolation variations (Waelbroeck et al., 1995; Shackleton, 2000).
Comparison of paleoclimatic records to insolation variations (so-called orbital tuning methods) are generally applicable to a whole ice core, as long as the stratigraphy is preserved (e.g., Martinson et al., 1987; Dreyfus et al., 2007).
A relationship between the isotopic composition of atmospheric oxygen (18O of O2, noted 18Oatm) and daily northern hemisphere summer insolation has been observed at Vostok for the youngest four climate cycles. This property has been exploited to construct various orbital age scales for Vostok (Petit et al., 1999; Shackleton, 2000). Dreyfus et al. (2007) used a similar approach to derive an age scale for the bottom part of the EDC ice core (300–800 kyr BP) by assuming that 18Oatm lags the summer-solstice precession variations by 5 kyr with an estimated uncertainty of 6 kyr. The selected age markers are placed at each mid-transition of 18Oatm (see Dreyfus et al., 2007, for more details).
Ralph
The close correlation between interglacials (and failed interglacials) and the precessional cycle can be seen in my Fig 2 (reproduced below), which was kindly created by Prof Palmer. However, although the basic profile of the temperature here is ‘accurate’, its precise correlation with each precessional maximum is achieved through ‘orbital tuning’. Otherwise there would be differences of a few thousand years here and there.
However, since the temperature spikes in this record match the precessional cycle very well anyway, and the precessional varies hugely from 15 kyr to 27 kyr, I think they are quite justified in ‘tightening up’ the correlation to make them match perfectly. It makes sense to me.
Orbital data is taken from Laskar 2004:
The Institut de mecanique celeste et de calcul des ephemerides.
http://vo.imcce.fr/insola/earth/online/earth/online/index.php
Graph and explantaions from my paper (which is in peer-review):
https://www.academia.edu/20051643/Modulation_of_Ice_Ages_via_Precession_and_Dust-Albedo_Feedbacks
Temperature vs precessional insolation at 65ºN, courtesy Prof Palmer.
http://s27.postimg.org/b5rt8k4ab/temps_insolation_Page_1.jpg
Just a few thoughts?
What about the Weather?
Is its severity in the polar regions a function of temperature or ice cover or both?
Increased/decreased albedo?
If the severity of storms and winds decreased, would that allow the ice sheets to extend further and reinforce a feedback loop there?
If the severity of storms decreased, would that decrease the mechanical pressures that help calving?
Interesting theory Willis, but I think you have one error.
You say:
This is correct, about 11 watt-years for melting, 72 watt-years for evaporation, and the rest for heating.
However, the cooling effect at the rim of the Antarctic ice shelf would only come from the melting part. The heating and the evaporation needed to create the precipitation occurs on the entire southern hemisphere.
If I am correct here, the cooling per meter of the coastline will therefore be only be 12% of what you have calculated.
/Jan
Thanks, Jan. The true answer is likely in between the two answers. However, remember that the evaporation which is driving the addition of ice to Antarctica happens preferentially around the coastline, which is why I included the evaporative cooling in the calculation.
w.
Well, I would imagine that most of the evaporation happens in the much warmer sea further from the Antarctica than in the ice-cold water close to the ice-shelf.
But I agree that some evaporation will also happen around the coastline, so the truth will likely be somewere between the two answers as you say.
Jan
The Antarctic Katabatic wind suggests that the initial evaporation could occur at any distance from Antarctica?.
Hi Willis
I was thinking about this again, and I realize now that you cannot include the evaporation energy at all because the evaporation and condensation occurs at virtually the same point in time.
That is unlike the freezing and melting which occurs thousands of years apart.
It is therefore only the freezing and melting that causes energy transport over time. Evaporation and condensation causes energy transport between ocean and atmosphere, but it does not play as a mechanism over thousands of years.
Jan
Jan Kjetil Andersen February 26, 2016 at 10:53 pm
Jan, thanks as always for your interesting comments.
The freezing and melting are both going on constantly. So the interval between them is not a factor. What is important is the rate of calving. When that increases, more cold is being transferred from the continent to the coast, and vice versa.
And curiously, despite the freezing and melting occurring thousands of years apart, there is no such lag between increased accumulation and increased calving.
This is because the calving rate depends on the pressure on the cap, and the pressure is transmitted instantaneously from the surface to the base and everywhere. As a result, as soon as the accumulation rate increases, so does the calving rate.
So both the evaporation on the one hand, and the changes in accumulation rate and the resulting changes in calving rate on the other hand, are all going on today, regardless of the interval between freezing and melting.
And as a result, we need to include both the melting and the evaporation in the changes under discussion.
At least that’s how I see it,
w.
I see your point Willis, but I think there are two problems with it.
Firstly, the time from freezing to melting.
Consider two simplified models of a 1000 meter thick shelf where it is 10, 000 years between freezing and melting. Each year the some snow are added on the top, and the same amount are melting/ calving away.
What happens if the precipitation doubles and all other factors are held constant?
One model could be that the calving/melting remained unchanged for the next 9999 years. This would lead to a doubling of the ice volume.
A second model could be that the melting calving immediately doubled from year one because of higher internal pressure. This would give constant ice volume, independent of the precipitation level.
The true answer lies between these two models. The ice shelf would grow in the beginning because the calving/ melting would be unchanged for several years. Then the calving / melting would gradually increase as the internal pressure grew.
I would guess that it the ice shelf would grow considerably before the melting / calving reached the same level as the precipitation.
That means that it has to be a lag, and I would guess that lag to be at last several centuries if not millennia’s.
Then I come to the second problem: I thought that lag was the whole point of the story.
Because if you consider that the second model is the most correct, i.e. that the ice-volume is more or less constant and independent of the precipitation level, then there would be no transport of energy from one time period to another either.
And the theory falls apart, doesn’t it?
True, higher precipitation give higher energy transport between the ocean and the atmosphere, but you do not need to go to Antarctica to find that.
Jan
Quite apart from the rate of evaporation off the surrounding ocean there is also a cycle in the latitudinal insolation gradient. If you look at the relative difference in insolation between 40S and 70S and its impact on atmospheric heating you get a cycle in the meridional temperature gradient. This is what ultimately is what drives much of the change in the position of the southern westerly wind belt. It has a big impact on the delivery of heat and moisture into the Antarctic interior. The pattern closely mimics the temperature fluctuations at Vostok. In other words the changes in the insolatiuon gradient are likely responsible for a large component of the Vostok temperature cycle and the Vostok ice accumultation cycle.
This reduces the extent to which one needs to rely on changes in atmospheric CO2 content to explain the Vostok temperature cycle. Basically the heat is blown in on the wind rather than trapped over Antarctica by CO2. Given that increased CO2 over Antarctica probably actually cools the surface the likelyhood that one can imply much from the CO2 variation over Antarctica was probably always rather low. Note that the Atmospheric CO2 cycle over Antarctica is the primary mechanism used to explain the temperature fluctuation by James Hanson and many others. It is a fundamental cornerstone of the whole IPCC enterprise.
Quote:
As an aside, for me the mystery is not what it was that slowly and gradually pushed us into each ice age with lots of fits and starts. The thing that perplexes me is what it was that abruptly yanked us out of each ice age in one extremely fast period of great warming. But I digress …
_____________________________
My take on this is that the primary forcing agent for interglacial warming is dust.
World temperatures on glacial scales are governed by albedo, not CO2. The preferred state for the climate (over the last million years) is the glacial ice age mode. World temperatures are driven down by increasing ice sheets and therefore increasing albedo, which greatly reduces the net energy absorbed by the Earth, especially during the all-important northern summer. However, there are two elements that can combat the supremacy of ice-sheet albedo and they are: precessional cycles and dust.
Precession can increase the insolation hitting the northern ice sheets by 90 wm2 each summer, during the precessional maximum (which lasts for 5,000 years). Conversely, dust can lower the ice-sheet albedo by a substantial amount. Just 400 ppm of dust on the surface of the ice sheets can lower the albedo by 0.45, and thereby increase the absorption of insolation by another 90 wm2.
The combination of these two elements will give a total increase of 180 wm2. So this is not the paltry 4 wm2 said to result from a doubling of Co2, but a massive 180 wm2, directed regionally and seasonally upon the ice sheets themselves. So just as the normal annual summer melts the snow-pack in the northern hemisphere, precession plus dust can melt the ice age ice sheets. And all interglacials happen to be preceded by massive dust storms, just as the ice record confirms. Note also that most interglacials only last for 5,000 years – the length of a precessional maximum in the northern hemisphere.
And voila, the result of these interactions explains the entire ice age record for the last million years. And Co2 does play a role in all this, but not in a fashion that the Greens would like. Interestingly, Co2 plays the role of the evil stepmother, trying to destroy the world but inadvertently saving the world from becoming an complete snowball.
https://www.academia.edu/20051643/Modulation_of_Ice_Ages_via_Precession_and_Dust-Albedo_Feedbacks
Ralph
Most likely these massive dust storms happened because…the warming ALREADY is beginning but is masked by these dust storms. That is, our atmosphere is warming up first, no? Something is shining in the sky making it warmer all of a sudden.
Actually, the warming dust storms began about 10,000 years before the interglacial warming. See fig 4 in the paper.
ralfellis
l don’t think that dust is the cause of the warming but rather it aided the warming and its because the melting was so quick it what makes me think this.
Why? because l think a large part of the cause of the ice age, was blocking weather pattern bringing cold Polar air down across the areas where the ice sheets were. Now if this was the case as l believe then this air mass would have had low dust content. Because the dust would have to have come from somewhere that was mostly to the south of the ice sheets. So with a Polar air flow over the ice sheets for most of the time. This dust would have to have taken a very indirect route to get onto the ice sheets. As most of the dust would have dropped by the time it got there. But if these blocking weather patterns broke down and this lead to a large increase in winds coming up somewhere from the south. Then this would have lead to a more direct route for the dust to land on the ice sheets. So l believe it was the large increase in a warmer airflow aided by this dust is what lead to the rapid melting of the ice sheets.
Yes, but that descending polar air flowing off the ice sheet is simply one component in a massive ‘sea breeze front’ circulation. If there is a wind flowing off the ice sheets, then it is being replenished by upper air flowing onto the ice sheets at higher levels. And this circulation has been demonstrated in modern Greenland, where that exact flow-pattern has been observed. So the dust can easily get onto the ice sheets, whenever there is dust in the local atmosphere.
ralfrllis
Thanks for the reply. lf that is the case then would it not cast doubt about the idea that the dust is the cause of the rapid warming at the end of the ice age.? As you stated to emsnews that the dust storms started 10,000 years before the rapid warming.
l myself don’t believe that dust was the cause of the end of the ice age.lts just that l understand how it could have been a aid to the rapid warming. Myself l think the main cause of the warming was the shutting down of what was at the time the prevailing northerly winds of the ice sheets areas.
lf that is the case then would it not cast doubt about the idea that the dust is the cause of the rapid warming at the end of the ice age.? As you stated to emsnews that the dust storms started 10,000 years before the rapid warming.
_______________________________
Not so.
As the paper cleary explains, dust (and its albedo reduction) is not powerful enough on its own to create an interglacial – because each dust layer is covered by another year of snow the next year. What is required, is the assistance of increasing insolation during a precessional maximum (a Great Summer), which can increase by 90 wm2.
Only then is there enough insolation and absorption, to begin a melting process. But once the melting starts, the dust from previous years concentrates on the surface of the ice sheets and the albedo falls almost exponentially. And this results in much greater absorption and rapid melting.
It is all explained. Give it a read, and see for youself.
Ralph
This is what ice sheets look like, when dust starts to concentrate on the surface. Note how low the albedo can go, in comparison with pristine snow and ice.
Incidentally, it may well be that the early melt and retreat of Arctic ice in recent years has been caused by Chinese soot and dust, in a very similar fashion. Which would certainly explain the great difference between the Arctic sea ice retreat and the Antarctic sea ice growth. A paper was written a few years ago, explaining that all the Alpine glacial retreat since the 19th century was caused by industrial soot.
http://www-tc.pbs.org/prod-media/newshour/photos/2013/01/30/IMG_4154_slideshow.jpg
Thanks for the interesting post.
Yes l can see how the dust would have help with the melting when the right conditions come along. But am rather more convinced that the reason for the warming was due to the change in the weather patterns over the ice sheets to the sort we have today. Here in europe the ice sheet extended as far as SW Ireland.
When you understand the present climate in Ireland you understand how even during a cooling climate it still would have been a serious challenge to have got the ice sheet to extend over there. Had the weather patterns been of the same type as they are today. Yet that is just what happened, and it was that what started to convince me that reason for the ice sheet growth in europe was largely due to the change in the weather patterns.
Ralfellis,
That picture is worth a thousand words. Where is it from?
Don’t forget algae forms under the ice, and then ice gets broken and flipped, and some “blackened” ice is not due to mankind’s soot or volcanic ash. (Just to add another variable.)
Various polar cameras have pictured some amazingly blackened ice.
Caleb:
It is in Greenland.
I took it from the Dark Snow Project, which is (was) trying to prove that recent ice sheet retreat has been caused by wildfires or industrial pollution. I think they concentrated on wildfires, because they could then cite ‘climate change’ and get funding. But because they mentioned pollution, they did not get any. Typical of the current funding bandwagon, which only rewards conformist believers.
So despite this being a very promising field of climate research, they had no grants, and were trying to fund their expeditions by public crowd-funding. And politicians wonder why scientists have become prostltutes, who will say yes to anything to get grants.
Dark Snow Project.
http://darksnowproject.org
Ralph
Ralph,
A worthwhile project. I hope you can get your results published.
“This means the 0.9 W/m2 across the continent becomes about 0.9 * 618 = 55 watts of heating or cooling per metre of coastline.”
Should that be 556 watts of heating or cooling per metre of coastline?
True dat, good catch. I’ve fixed it.
w.
“Clearly, what we are seeing is the progressive compression of the ice layers as we drill deeper and deeper into the ice cap.”
It certainly looks that way. And that looks plausible near the surface as trapped gases are squeezed and loose piles of snow are converted into more compact ice with some gas bubbles and presumably a lot of the gases escape. But. Water and ice are notoriously uncompressible. I’m having a little trouble envisioning layers of ice hundreds of meters below the surface flatenning to the degree suggested by your charts. They can compress a bit vertically as gases are squeezed into ever smaller space. And they will certainly try to push out horizontally. Probably with considerable success near the edges of the ice, But in the interior of the continent, the adjacent ice is presumably trying to expand into their space just as vigorously as they are trying to expand outwards.
Seems like an awful lot of flattening to be accounted for
I suppose the alternative is that the accumulation rate really is increasing over time.
The “Rate this” stars seem to be gone.
Willis
Nature fails to follow CMIP5 models! CMIP5 models get sea ice backwards – predicting a decline vs actual increasing Antarctic ice.
Wind may be one of the missing/underestimated feedbacks.
Evidence for link between modelled trends in Antarctic sea ice and underestimated westerly wind changes Ariaan Purich et al., Nature Communications 7, Article number: 10409 doi:10.1038/ncomms10409.
Willis –
“This implies that for each additional °C of warming, the accumulation rate goes up/down by about 6%.”
A 1% change in water temperature produces a 16% change in the specific humidity of the air above it; 16/2.73 = ~6. You may simply be looking at someone’s assumption that air circulation and *relative* humidity around Antarctica don’t vary with temperature.
Give thanks for “the pause” and clouds. A Limerick.
The cause for the Climate change pause:
The CO2 increase; because
there’s more clouds in the sky
make more snow, that is why
the climate is stable. Applause! lenbilen.com/2016/02/24/4697/
What would cause a large circulating mixed ocean to layer up, leaving all the warm water on top to be evaporated away? The Easterly winds would have to relax. Suddenly and for a long time.
A grand El Nino.
When this grand El Nino windless, cloudy epic period results in enough ocean energy depletion, the atmospheric/oceanic teleconnection kicks up the Easterly winds again and the other epic period begins: primarily a long period of mainly clear cloudless days (with necessary wind) which allows the Sun to extensively penetrate and build ocean stored energy. Windy mixing at the surface would keep that energy from rising to the surface and coming back out, though an occasional diminution in wind will let some evaporation occur resulting in this jagged step down in temperature.
I note that after the jagged step down, there appears to be a floor related to the oceans having absorbed all the heat they can (instead of being evaporated out to heat the Earth) and Earth’s global temperature is as cold as it can be.
At the floor, the winds rather suddenly stop, the stored energy begins to concentrate at the surface, clouds build from evaporation, and net heat loss from the oceans begins. That heat should evaporate fairly quickly leading to sudden changes in global temperatures.
During that sudden and sharp upswing in global temperature, there would likely be windless and very cloudy conditions in important ocean areas, resulting in constant ocean heat exchange to the atmosphere to the point that there is no more warm layer to evaporate away because the Sun can’t replace what is evaporated due to clouds and water vapor blocking solar irradiance. Evaporation continues till what appears to be a ceiling where oceans are depleted and Earth’s temperature has peaked.
Then the skies clear of water cycle clouds and the oceans begin to absorb solar energy once again. The wind also picks up leaving little of that energy to escape and warm the Earth through the process of cloudy greenhouse conditions. So back down we go again into freezing temperatures.
This pattern of sudden rise, jagged fall, and a ceiling and floor may be physically related to the size of the Earth and its surface area and volume of water. The epically long term solar to ocean recharge/discharge imbalance set up by the water cycle speed up then diminution supplies the drive that leads to the shape of the plus-to-minus, then minus-to-plus imbalance while top of the atmosphere solar irradiance remains stable for all intent and purposes.
One small quibble, Pamela:
From my jaundiced view of the temperature graphs, The pattern is sudden abrupt rise and a sudden abrupt drop.
From a peak temperature, there is a quick drop of 2°C with perhaps some bouncing around that drop and then a further plummet of five to seven degrees Celsius.
Remember the sheer scale of years crammed into a very small graph. Points immediately adjacent to each other are not very adjacent, time wise.
This is before one gets into discussions about temperature estimations from annular ice layers a mile deep.
A 2°C drop in temperatures is enough to seriously affect calendar length and overall depth of ice/snow cover.
Agreed Theo. The time scale is huge. That said, the kiss principle must still be our first theory before considering more exotic theories. Which makes me think of something we measure all the time, something that unusually arrives a bit sluggishly (lagged) but then spreads like a calming balm, relatively uninterrupted and stable, before it switches back to its normal state, greatly sluggish and jagged with interruptions. I am therefore reminded of the unusual, not normal, steady El Nino interspersed between the normal back and forth episodes of jagged neutral La Nada and super La Nina patterns that we see at finer scale. Now let that pattern run on a gross scale. I wonder if we need to look at anything at all beyond the imbalanced oscillation patterns that are everywhere in the oceans and land surfaces.
Shouldn’t figure 6 show the South Atlantic rather than the North? (apologies if someone else pointed this out)
Don K @ 4;54 AM
The thinning of successive layers would be due to extrusion of the ice along the path
of least resistance.
As for trapped gasses, I believe Dr. Jaworowski has the right of it. Until I see experimental
evidence to the contrary,I do not believe gasses below a very recent level are reliable .
http://www.21stcenturysciencetech.com/Articles%202007/20_1-2_CO2_Scandal.pdf
So roughly every 100,000 years the temperature anomaly spikes up 2C+ and slowly lowers? Perhaps the 2C target meme has some fundamental failsafes instilled in it and was not picked out of thin air…..
What could possibly provide enough energy to produce that consistent spike in temperature?
The 2C target meme comes from a 1970’s paper by Economist William Nordhaus estimating (guestimating?) the economic cost of warming. Not good @2C, worse@3C etc, The 2C has been endlessly repeated because it makes catastrophe seem more immenent. Action is needed now!
Makes sense, 2015 was the warmest year on record also the most ice on record.
Willis
Very thought provoking discussion.
While looking at the Vostok Ice Core Figure 1, I imagined the graph minus all the little bits and pieces, and was left with the relatively periodic shape, which is comprised of a slow change period in basically one direction, followed by an abrupt “reset”, etc. Lots of simple physical examples come to mind…filling a bucket with a tipping point, charging a capacitor, etc. Nothing magical/original. I then imagined a process that was NOT explicitly driven by any periodic external sources (ie ignore variations in orbit, sun output, CO2, politics (:)), etc. What we have left is a large ball covered with water (and ice and air). Perhaps not too interesting…but one item in your Figure 6 (Circulation Patterns around Antarctica) triggered a thought…the ridge. Now, again ignoring any specifics, just follow the basic periodic circulation you show in Figure 6, and imagine a relatively stable period of circulation…that is resulting in the gradual cooling, then, due to the inherent physical features of the ocean/land masses gross solar insolation (ie due to the tilt of the earth), interesting ocean ridges, etc, this circulation reaches a relative tipping point, bang, big change (bucket empties ) and we start again. This kind of grossly simplistic model would then infer that all of the indicators (CO2, forest cover, atmospheric temperature, ad nauseam), we love to collect analyse and argue about are just meek followers, causing all of the little bumps and sub oscillations that appear to drive current climate analysis. This type of physically constrained mega cycle would then have a gross period, but the specific amplitudes and periodicity would be the result of chaotic behavior…which invariable become targets of our pattern seeking brains (previous subject posted thank you).
Some of my background is in root cause/accident analysis. One observation I have made in both studying hundred of accidents, and investigating a relative few, is that although specific accidents have specific chains of events, what is often lost, is that there is really nothing special about THAT specific chain of events. Take the shuttle Challenger accident. The space craft is lost because the huge energy in the propulsion system was explosively expended. The “root” cause was o ring material temperature related. The analysis then goes into detail of how, what when, etc. Everything from group think to basic design was indited. For real world events and learning, this is important. It can demonstrably result in safer high risk activities. What is lost however, is that the basic driver of this kind of event is much larger. It was comprised of huge energy sources (boosters and fuel tanks) coupled with physical constructs (the craft itself) which will always, practically speaking, have some limit whereby bad things are going to happen. We attempt to ameliorate the probability of reaching that limit by studying the system and making changes to reduce our approach to those limits. The key here is that the physical system is something we make and can significantly control. We then gravitate to sorting out large phenomena with the same mindset. My point is that we have a strong tendency to of searching for something at a scale we can comprehend, and ultimately control (an obvious evolutionary advantage).
Now, going back to my climate “model”: Many (most?) of the arguments discussed here (WUWT) are rooted in discerning external drivers, orbital, solar, man made (CO2, deforestation), etc, etc. Willis makes very compelling observations, that intrinsic physical phenomena, ie T storms, ocean circulation, etc, comprise a huge, but relatively stable thermostatic behavior. I am drawn to the simplicity of a physically constrained climate system, the overall (but still chaotic) boundaries and behavior) driven not by above mentioned cyclical or man made forcing, but just by rock, water, ice and air.
So what does this lead me to? Perhaps a climate model which builds on Willis Figure 6. I hypothesize a model which is comprised of the basic physical shape and contents of the present earth. Big features matter (huge ridges, continents, etc). Add water, salt, air. Then the big inputs (but forget any periodicity), solar, orbital effects on solar (big, not little). Spin the ball. Start by configuring the model with the basic present earth parameters and starting points. Run it at a gross time scale per Figure 1. Do you observe a phenomena similar to Figure 1? If not only change big things…and only within actually observed reality. Forget adding variables. The oft discussed inherent pitfalls of too many variables is, I think, an inherent behavior. If my above thought experiment has any validity, then the observed phenomena of Figure 1 would grossly manifest itself, and be generally immune to input and physical constraints WITHIN a reasonable period of time (ie a few million years.).
The above train of thought has a basic premise. Look for the simplest explanation involving the largest energy sources and physical shape/constraints. An often held view is that the Earth is some delicate flower, only existing in its present state (Vostok time scale state, not today or yesterday) due to an incredibly rare and unstable confluence of very specific physical and or periodic external forces. The tiniest change (CO2, parking lots, a few more less solar flares) then can result in some huge variation in the climate. I think not. I surmise these things can have chaotic effects (like changing the color of my tipping bucket), but have relatively little/no effect on the basic behavior. This last is based on an obvious observation…the earth is neither a ball of ice, nor a barren desert (ie Mars).
The simplest explanation is definitely not always the most basic explanation, but I would strongly argue that it is far more likely to match reality than most humans would like.
Thank you Willis for an interesting morning.
Ethan Brand
Has anyone tried to run a computer simulation based on this kind of model? Not to try to replicate every feature of the climate record, but to capture the periodicity?
Very interesting comment by Ethan Brand.
2015 was the warmest year on record only in the imaginations of certain bureaucrats.
Most Antarctic ice = total of recent accumulation.
This is a very complicated see on meshing processes. We might not have identified all of them. Some points to note include the near absence of liquid water on the Antarctic plateau; the conceptual difficulty of plastic flow or compression compaction to give thinner layers with depth; the reported presence of large lakes in the basement rocks; the dating resolution down hole and possible upsets in it if prior melting removed ice and created iunconformities; the less than full understanding of the gas age/ice age difference; the effects on isotopes used to derive past temperature profiles through precipitation, sublimation and surface wind scour/ mixing at the depositional surface; the distinctions between temperature at ice formation and any impressed temperature printed on deep ice from geothermal heat ….
Just when you are getting into a synthesis accompanying these, along come more aspects like the paper this year that noted that surface ice was the coldest part of the vertical profile affecting its atmosphere, so that cooling gradients resulted from higher atmospheric CO2.
The effort to collect quality ice cores is commendable. The difficulty seems to stop confirmation exercises like drilling and cross matching of several holes close to each other to show conformity of layers for ageing. The cost is very high, so points of diminishing return from further holes set in early.
There are lessons from older attempts to gather stratigraphic info from sedimentary rocks. At least you sometimes crack a pleasant location for your collar for rock work.
Geoff.
Geoff: Thank you for questioning and being curious about impacts.
Some pictures I dredged up this morning looking for more information regarding Antarctic ice cores.
http://www.montana.edu/priscu/images/presentations/AAASFeb01/Vostok%20Ice%20Core%20Schematic.JPG
What are they drilling with?
http://weather.thisconnect.com/wp-content/uploads/2010/06/drillinguk_505.png
Antarctica ice core sites
http://cdn.antarcticglaciers.org/wp-content/uploads/2013/10/fig6.jpg
Antarctica altitude
http://cdiac.esd.ornl.gov/trends/co2/graphics/antartica_ice_core_stations.jpg
Drilling at Antarctica, Vostok I believe.
http://icecores.org/graphics/drilling_4inch-drill-01_joseph-souney.jpg
Ice drilling at Shallow Dome C.
http://icedrill.org/7th-international-workshop-on-ice-drilling-technology/graphics/drill_BAS-shallow-Dome-C_BAS-Robert-Mulvaney_350px.jpg
More ice drilling at Camp Plateau.
http://paleoglaciology.org/userfiles/image/caucasus/Ice%20Core%20Drilling/camp-plateau-and-Shtavler.gif
FIRN density at Law Dome C.
http://i90.photobucket.com/albums/k247/dhm1353/DE08_Geo_1969.png
Vostok team taking extreme care with ice cores. “French, Russian, and American scientists in the Vostok team photo with unprocessed ice cores.”
A paleo time reference chart so we can visualize just how much geological history we’re discussing with 460,000 years of ice cores.
http://img.docstoccdn.com/thumb/orig/12900337.png
There are several physical changes that occur to ice cores. A key transition is the change from ice crystals to solidified ice.
A second change is laminar ice flow away from ice buildup to areas where ice is less. When ice is no longer compressible, than pressure from above causes ice to flow.
Flow where from where? Pointing towards a pole and stating that the glaciers came from that direction is not the same as standing on top of several miles of ice and wondering how much ice has flowed in which directions. It is easy to take a straight flow of a glacier, point to how laminar ice flows over and around obstacles, but where is the testing for how ice flows when pressure is nearly equal from many directions?
Above, Willis has strengthened our current perception that
What I didn’t see in the data Willis used were any information about how droughts would be represented in ice layers. Or what impact does sublimation have on remaining ice?
I was curious about how many years were attributed to/by depth for the data Willis used. As Willis notes above, my BS meter is buzzing.
ATheoK
Thank you for this informative comment.
Willis,
Looking at the red Ice core chart… My first thought is, why does ANYBODY believe that this interglacial period that was caused by global warming, is man made, and therefore very different that the first 4 interglacial periods that were obviously caused by global warming that could not have possible been man made?
One problem with this theory as recent decadal observations show it not getting any warmer in Antarctica and its surrounding ocean, so increasing sea ice has not been caused by any warming.
http://i772.photobucket.com/albums/yy8/SciMattG/UAH_AntarcticTemps1978_zpsd4yjaujj.png
http://i772.photobucket.com/albums/yy8/SciMattG/UAH_AntarcticOceanTemps_zpsyk6tsbmm.png
Whereas the Arctic has been warming so sea ice has decreased mainly due to strengthening of the AMOC with positive AMO.
http://i772.photobucket.com/albums/yy8/SciMattG/UAH_ArcticTemps1979_zpstf88xnmu.png
Removing the AMO just shows how much a huge influence it has on global and Arctic temperatures.
http://i772.photobucket.com/albums/yy8/SciMattG/RSS%20Global_v_RemovedAMO2_zpsssrgab0r.png
The main reason for the difference between Arctic and Antartica / northern hemisphere and southern hemisphere is down to the AMOC with no equivalent in the latter. If a periodic warmer ocean current was able to penetrate the Antarctic land mass then there would be warming here too.
Matt G – As I understand it, the warming that leads to more precipitation over the Antarctic can occur in oceans that are remote from Antarctica. The water vapour then travels through the troposphere, arrives over Antarctica, then descends in the Katabatic wind and dumps as snow. So the correlation of ice accumulation rate with temperature shouldn’t use Antarctic temperature but global ocean temperature (or a subset). In your example, that’s RSS not RSS-AMO.
The ERA-40 shows decline in precipitation and moisture from the 1950’s to early 2000’s between 50-60S, but an increase between 60-90S. Between 80-90S there is only a very slight increase. Therefore it is doubtful the more remote ocean between 50-60S provided more water vapor over the Antarctic when this band declined itself.
http://onlinelibrary.wiley.com/doi/10.1002/joc.1684/epdf
Anyway this is less relevant to the topic in question because this deals with ice cores on the Antarctic land mass, so the temperatures trends in Antarctic and surrounding ocean implies more so here.
And, as far as I know at present, there is no observational evidence that the atmosphere is becoming more moist at present.
The warmists say that sea surface temps are higher and air temps are higher. That necessarily means higher absolute humidity in the atmosphere. I believe agw theory predicts slight increases in precipitation but I don’t know if that has been observed. There is certainly evidence of higher snowfall in Antarctica.
Willis – Thanks for yet another interesting and thought-provoking post. You say “the first three methods only get us back about 80,000 years into the past”. Well, to my mind, 80,000 years is still quite a decent slice of time. So, how about showing a larger-scale graph from -5,000 to -80,000? I’m assuming that the first three dating methods (count the annual rings, align to known events, radioactive dating) dominate in the latest 80,000 years, so this graph would not suffer from the built-in temperature expectations..
I think that Joe Bastardi pointed out that during cool phased PDOs (more la ninas) the SST around Antarctica should be warmer. If we had another 30 year long cool PDO like the 1945 to 1975 period temps should warm slightly around Antarctica.
The OZ east coast has warmer SST during a la nina, more evap and thus more rain and those warmer SSt eventually move much further south as well. Especially over say a 30 year period that produces more la ninas. What do others think, because I’m very much an uneducated layman lurker most of the time.
Another feedback for you to consider Willis, that has been previously discussed at WUWT, ocean fertilization from icebergs.
http://wattsupwiththat.com/2016/01/11/inconvenient-iceberg-calving-helps-carbon-sequestration-and-is-helping-to-slow-global-warming/
Don K
February 26, 2016 at 4:54 am
“Clearly, what we are seeing is the progressive compression of the ice layers as we drill deeper and deeper into the ice cap.”
Don, the “flattening” is not from the compressibility of ice, but rather a measure of how much ice has flowed away from that locality. Indeed, one could take the the difference and calculate how much ice has been squeezed coastward. The difference is indeed the volume of ice that has been squeezed out and melted in the ocean over hundreds of thousands of years.
Willis, this, too, would be an additional interesting calculation of the sustained cooling of the antarctic waters over 400,000 years attributable to the ice that was squeezed outward and into the ocean as icebergs.
Thanks, Gary and Don.
I referred earlier to the calculation that the area of Antarctic (in sq. km.) is about 600 times the coastline length. Better numbers put it nearer 700 times the coastline. Assume equal squeezing of the ice in all directions (not true, but work with me, this is a first cut). This means that the addition of one additional metre of ice on the surface (well, to be more precise, one metre after squeezing snow into ice) leads to the extrusion of 700 cubic metres of ice for each metre along the coastline. In practice, of course, this would mean something like a 100-metre-thick glacial tongue moving outward at about 7 metres per year.
In any case, here’s an oddity. It appears that the Vostok site is drier than average for Antarctica. It puts annual accumulation of ice at 20 mm per year.
However, the total volume of antarctic iceberg calving each year is on the order of 1000 – 2000 cubic km. To generate this much ice, the continent must be getting about 150 – 300 mm of ice accumulation per year …
w.
Thanks Gary. Actually I understood that flow was assumed. And the the pressure of a column of ice a couple of km thick is very large — 10^6 kg/m^2/km roughly, right? But the pressure differential at any given depth at/near Vostok between the ice you are looking at and the adjacent ice is going to be very small. A few grams/meter^2? If there is any friction at all in the system, is ice going to flow? Well … OK … maybe. What do I know about the behavior of ice under a couple of hundred atmospheres of pressure?
Also I forgot that Vostok is at 3400 meters elevation, so gravity is presumably helping things along.
Beyond my pay grade.
ancient maps show antarctica ice free, try reading Immanual Velikofsky’s books.
“Warmer southern ocean –> wetter atmosphere –> more snow on Antarctic interior –> more glacier calving around Antarctic perimeter –> increased oceanic circulation –> increased global cooling.”
It seems to me that the greater global cooling would not necessarily mean greater loss of heat to space because of calving, but rather simply an enthalpy change from melting the glaciers. The heat loss to space has already occurred at the time the atmospheric water became snow and fell to the glacier.
Willis,
Dating ice core deposition times by radioactive dating is not necessarily truncated near 80 kyr. That is about the oldest age that carbon-14 can date. However, occasional volcanic eruptions deposit ash on the snow-ice surface. This often can be dated by potassium-argon methods, which has no upper limit for ice cores. I don’t know if any Vostok ice was so dated.
Thanks, Willis, and thanks, commentators.
Now that I’m getting gray I can’t raise hell the way I used to on Friday nights, and life would be dull, (and perhaps killingly so), if there was nothing to interest me. Posts like this one remind me that life can still be interesting. Now, when I get arrested, it is my attention. Thanks again.
No-one has mentioned sea level.
If it were true that a warmer climate system means more, not less snow, then ice ages with the least snow accumulation should have the highest sea levels. Vice versa for interglacials.
So we would expect for instance in our current interglacial for extreme low sea level to mean dry land between Britain and France. An English channel a couple of hundred meters deep, plus a North Sea, would be expected only during glacial maxima.
Except that, like most climate modelling, this is nonsense. Last time I drove from France to England, there was this big sea in the way and we crossed by ferry.
Myopic focus on failed models stops people seeing the bigger picture. The earth is gradually cooling over a timescale of tend of millions of years. It began 30-50 million years ago. A major cause is tectonics and changing continental configuration. In particular as has been elegantly explained many times here by Bill Illis, it is the isolation of Antarctica and the formation of the Southern ocean with its circum polar current that is responsible. Also other continental changes like the cut off of the Pacific from the Atlantic.
Glaciation continues to deepen. The gradual cooling reached the level 3 million years ago where the glacial-interglacial cycle started. First with shallow glaciations and frequent interglacials with 41 kyr obliquity Milankovich pacing. Glaciation gradually deepened till the Mid Pleistocene Revolution (MPR) one million years ago when both the depth and length of glaciations abruptly increased. After the MPR interglacial pacing changed (increased) to 100 kyrs corresponding with the eccentricity Milankovich cycle.
Such deep glaciations occur periodically (but not regularly) in earth’s history. There was the Huronian glaciation 2.1 billion years ago. Then the Cryogenian and Marinoan glaciations between 750 and 600 million years ago – setting the stage for the Cambrian explosion of multicellular life. More recently the Saharan-Andean glaciation beginning at the end Ordovician.
Now, it appears, we are sliding down into another similar major glaciation tens to hundreds of million years in duration, which may approach global or near-global “snowball earth” proportions for a while.
Note that these large earlier glaciations tool place with atmospheric CO2 levels of thousands to hubdres of thousands of ppm. What makes people imagine that a few tens of extra ppm of CO2 this time will change the Earth’s glaciation behaviour as seem over billions of years? Some pathology of arrogance, confusion and wishful thinking.
belousov February 26, 2016 at 10:41 pm
An interesting thought, belousov. However, let me add a few points.
First, all we’ve been talking about to date is what happens in Antarctica, not the globe.
Next, the ice cap over Antarctica is in somewhat of a steady state, where more additions are matched by more calving. There’s no indication that during the ice ages Antarctica added two miles of ice like say Chicago did.
Next, the decrease in global sea levels was not (as I understand it) from changes of a millimetre per year in Antarctic ice accumulation rates. Instead, the sea level fall was from the creation of massive Northern Hemisphere glaciers covering huge areas of Eurasia and North America.
Finally, the mechanism of creation of these Northern Hemisphere glaciers is generally thought to be the result, not of an increase in winter snow, but of a decrease in summer melting due to reduced northern hemisphere summer insolation. It was this decreased summer melting, and the resulting increase in albedo, that allowed the growth of the glaciers—not a difference in snowfall.
So the fall in sea level was related to a different, and much stronger mechanism than the one discussed here regarding the Antarctic ice cap.
Regards,
w.
Thank you for a very interesting article, Willis.
I think you have isolated at least part of what makes the 100,000 year periodicity. If you take the ±15 mm/year which is roughly the accumulation rate you have calculated for the last glacial period and apply it to the northern hemisphere ice sheets, which (I’ve read somewhere and I think it’s based on the drop in sea level, but I can’t find it now that I need it, of course) averaged about 1200 metres thick, it would take about 80,000 years for those ice sheets to fully accumulate. We know that it took about 10,000 years to melt the NH ice sheets (deglaciation is fairly well documented), and that’s probably as quick as it could be – there’s an awful lot of latent heat used up in melting all that ice.
You can sort of visualize that when the NH ice sheet reached its maximum, it set off something (change in ocean circulation? – not my original idea, it’s been batted around quite a bit) that caused global temperature to rise and set off the melting phase. Melting phase is followed by an interglacial, but we know from the same ice cores that a slow cooling has taken place throughout the present interglacial (with the 1,000-year cycle and the 60-year cycle superimposed), and sooner or later that will trigger the start of another cold phase.
There’s your 100,000 year cycle. It takes 80,000 years for the NH ice sheets to reach their maximum and trigger a warm phase, 10,000 years for those sheets to melt and then another cooling phase starts but it takes 10,000 years before there’s any serious ice accumulation. This crude analysis would suggest that it’s not so much a cyclic phenomenon as a bimodal situation – it’s either cooling or warming, and the duration of those periods is determined by the time it takes for the northern hemisphere ice sheets to form and to melt. Again (and it’s all speculative, but it FEELS right) the interglacials are just a sort of 10,000-year grace period at the beginning of a cooling phase before it starts to get really cold.
May be all speculation, but it explains that saw-tooth temperature pattern.
belousov…well said, I must agree. Ice Age = Sick Earth. Ice does nothing and no one any good with the possible exception of re-mineralization as ice sheets/glaciers grind rocks to powder. Could be done as well with technology.
ralfellis, you know I cannot resist an interesting idea. Here’s what I find:
No question that it is interesting. What it means is another question.
w.
Interesting indeed. So you get a dust bowl at glacial maxima. But I don’t think that makes the dust bowl causative, per se, of glacial termination – although it might be a factor in megafauna extinctions especially at the Wisconsin glaciation maximum.
The Vostok dust concentration is largley a response to combined sealevel and wind-strength change. Low sea level extends the land area on the continental shelf to the east of Argentina. Change in the strength and position of the Southern Westerly wind belt then causes regularly arid conditions to the east of the axial montain chain down southern Sth America, This periodically kills off vast areas of pampas vegetation due to mega droughts and has a huge impact on the dust content of the Southern Hemispheric atmosphere. The dust is transported as far as central Antarctica. Its origin has been fingerprinted by geochemical testing.
ralfellis, thanks for the link to the Dark Snow project you referred to. I saw they are claiming a decrease in Greenland albedo. So I took a look at the CERES satellite data for Greenland. I got the following:
I don’t find any decrease there.
Upon closer examination I find that the Dark Snow graph is a comparison of a historical average albedo with a five-day! period in July, noting small variations of a few percent over the majority of the ice cap.
But an examination of the CERES data shows that Greenland July albedo varies about the July mean with a 95%CI of ± 4% … so a difference of a couple percent from the mean is historically meaningless, that happens all the time.
w.
As a marine meteorologist I have been arguing for some time that global warming means increased evaporation in the equatorial regions with the additional water vapour transferred to the poles by the global weather system where increase in ice cap up can be expected. This is opposite to the AGW alarmist view and indeed many climatologists who tell us global warming means the poles will reduce through melting. It is gratifying to see someone with a lot more qualifications than me shares the same opinion. Moreover, I have come to the conclusion the so called ‘Ice Ages’ were not caused by climate change but polar wandering that induced local climate change effects while global climate remained relatively un-altered. Siberia remained without ice cover during the last ice age while North America had ice sheet to several kilometres and this has raised questions for me.
Willis
The one important fact that you did not include is that during the warm periods there is a greater volume of atmospheric transport to Antarctic therefore more snow. There is a direct relationship.
Kiwikid. From another Kiwi, have a look at my comment above.
@ Willis Eschenbach February 27, 2016 at 12:29 am
That graphic is very interesting. Dust in ice cores followed by temp increase and then temp plunge and on a ~100k year interval.
Of course it would all depend on the interpretation of the data from the ice cores being that the data is interpreted in the correct sign (positive or negative).
Could the earth/solar system be passing through come sort of cosmic belts of dust as it cruises around through the Milky Way? If so what could be other cosmic factors occurring at the same intervals?
Anyway these threads always seem to mix long term (~100k year) with shorter term cycles and changes. It does lead to interesting discussion.
Almost like playing poker and black jack in the same game with the same deck of cards.
Second problem although minor is regarding a possible thicker ice cap.
Antarctica has already it’s largest possible ice cap for the majority of the continent. Maybe only the Peninsula where if it become colder would increase the ice mass here. The much drier parts of eastern Antarctica may be able to sustain further increase. The height of the glacier is ultimately restricted by the pressure/mass balance over the surface area. This is why the cores only go back to 800,000+ years due to pressure/mass balance forces older ice into the ocean over the long term as iceberg calving.
Therefore for future declines in sea level to be possible, Antarctica would hardly contribute and ultimately the northern hemisphere is required for glaciers to build and reduce sea levels back down to Ice age levels.
Someone commented above that iceberg calving would not increase the downwelling circulation, because the fresh water is lighter than the salty ocean. They pointed out that the main pump driving the downwelling cold-water currents was the high-salinity water that forms when sea water freezes … but the Antarctic glaciers are fresh water from the start. So I got to thinking about that.
First off, we need to consider the full cycle, from ocean to land and back to ocean. What comes down must go up. So the water in the snow falling on Antarctica must have come from the surrounding ocean … making the surrounding ocean both colder and saltier in the process. The more ice that accretes on Antarctica, the colder and saltier the oceans around it must become.
Of course this is counteracted by the return of the same amount of water (roughly) every year to the surrounding oceans in the form of ice. Net change in salinity? …
Well, this has an odd effect on salinity. Overall it is neutral, of course. But most of the melting doesn’t happen immediately adjacent to Antarctica. The bergs mostly melt in the somewhat warmer waters somewhat further north. This export of fresh water equator-wards increases the salinity of the area around Antarctica, increasing downwards circulation.
Next, while it is true that fresh water from melting ice increases stratification in most places, the melting of glacier ice in the waters around Antarctica has a curious effect. Let me run through the concepts.
When a cube of ice melts it has a strong cooling effect, of about 333 megajoules per tonne of ice melted. Since 4 megajoules of energy are required to warm or cool a tonne of seawater by 1°C, this means that a tonne of ice will cool about 84 tonnes of seawater by 1°C.
And what this does is that it moves the seawater closer to freezing. As an example, suppose we mix one tonne of ice at 0°C (actually warmer than Antarctic glacier ice) with 24 tonnes of seawater at a chilly 2°C. The temperature of this mix will be about -1.3°C, about half a degree above the freezing point of the mixture.
As a result, it will take less cooling to freeze the mixture of melted ice and seawater. This means that in the situation described above,because the water starts out cooler, for the same amount of annual external cooling you will get about 4% more sea ice formed … which in turn will increase the amplitude of the annual variation in sea ice, and thus increase the downwelling cold salty water.
Anyhow, that was my conclusion, although of course YMMV. To do the calculations I used the R package “gsw”, which calculates a wide variety of variable for seawater based on salinity, temperature, and pressure (density, freezing point, specific heat, latent heat of fusion, etc.)
w.
Whilst I dont necessarily agree with what I consider to be a simplistic view of the consensus stratification argument, I dont find your argument against it particularly convincing, Willis.
There is one enormous hole in your argument and that is that the majority of the iceberg melting occurs during the summer months when the solar energy is added to the ocean. During Winter there is net freezing of the water surrounding Antarctica. No, the ice doesn’t need to drift North for that melting to happen.
In fact the whole raft of ice must melt pretty much in-situ and freshen (at least to some extent) the whole top of the ocean around Antarctica. Calving will only add to that.
A net freezing in the winter. OK, where does the salt go?
As per Willis’ original comments, there is little to no net change in salt content over say a full year. Any “freshening” is temporary at the top of the ocean and as per the general consensus, is during summer.
Again…I dont necessarily agree with the consensus on this and it strikes me as being far too simplistic and idealistic but I dont think Willis has successfully argued against it, either.
TimTheToolMan February 28, 2016 at 3:29 pm
Mmm … as usual, nature is complex. Here’s where the Antarctic icebergs can be found, which according to freshwater distribution is also where they melt:
Finally, my basic theory is this:
Cooling of the southern ocean around Antarctica will increase the amount of ice that forms in the winter. This will increase the downwelling currents.
What do you see as being wrong with this?
w.
Icebergs are big, really big sometimes! And they’re going to take a while to melt… What you see as “drifting North”, I see as floating around in the cold Antarctic Circumpolar Current.
https://en.wikipedia.org/wiki/Antarctic_Circumpolar_Current
There is nothing wrong with “Cooling of the southern ocean around Antarctica will increase the amount of ice that forms in the winter. This will increase the downwelling currents.”
As I understand it, the downwelling currents are strongest when the ice is forming, the water has cooled and salinity is rising. Thats the “simplistic” consensus view and whilst I think its worth challenging, I dont think your argument is strong as it stands.
TimTheToolMan
February 29, 2016 at 2:41 am
“Icebergs are big, really big sometimes! And they’re going to take a while to melt… What you see as “drifting North”, I see as floating around in the cold Antarctic Circumpolar Current.”
==============
Tim, any icebergs that originate from Antarctica and drift north will show a higher density closer to the source (per Willis’ illustration) as they must pass through that region as they radiate outward/north. It doesn’t necessarily mean that is where they stay and/or melt. But one thing can be said with certainty is that those further north had to pass through the “middle ground” to get there. Consider a little geometry with regards to the area of an expanding circle.
Willis –
“Cooling of the southern ocean around Antarctica will increase the amount of ice that forms in the winter. This will increase the downwelling currents.”
Suppose a current with a 1kt N component. In a melt season, your meltwater will average some 2000 nm (your diagram icebergs go about 1500 nm N). I think your coolth will be long gone. Also, as ice has roughly the thermal conductivity of glass, the seasonal freeze + downwelling is probably self-limiting.
However, if you point out that more icebergs = more seasonal ice piled up and more polynyas opened for additional freezing (= increased ice *thickness*) while the icebergs are *not* melting, you may have something. 🙂
Thanks Willis. I’m glad I checked back on the comments before this post fell too far in the past.
A cooling ratio of 84:1 per degree C and considering that ratio is from 0 degree C ice which in reality is surely colder to begin with. That is huge!
This could lead to an enormous volume of downwellling cold salty water before any ice is even melted.
Antarctica can be described as the “Grand Central Station” of the THC – global oceanic thermo haline circulation. A nice image illustrating this is here:
http://www.nat.vu.nl/environmentalphysics/SIMULATION%20Experiments/newpage/Two-Dimensional%20Oceans%20Model_old/general/3D%20ocean%20circulation/scan100dpi.jpg
It comes from this reference:
http://www.nat.vu.nl/environmentalphysics/SIMULATION%20Experiments/newpage/Two-Dimensional%20Oceans%20Model_old/#reference
The accumulation graphs appear to be an inversion of what we would expect. The high plateau is usually described as a desert, and the reason for this is the elevation. So accumulation would have been highest at the bottom and reduced steadily. –AGF
Of course they choosing boring sites where the least flow and greatest age is hoped for.
Willis,
The apparent correlation between Pleistocene temperatures and ice accumulation, as well as the reversal of that correlation at the beginning of the Holocene is visible in the Greenland ice core data employed by Alley (2004) as well.
See:
#Greenland temperatures estimated via stable isotope data
#GISP2 Ice Core Temperature and Accumulation Data
#———————————————————————
# NOAA Paleoclimatology Program
# and
# World Data Center for Paleoclimatology, Boulder
#———————————————————————
#NOTE: PLEASE CITE ORIGINAL REFERENCE WHEN USING THIS DATA!!!!!
#
#
#NAME OF DATA SET: GISP2 Ice Core Temperature and Accumulation Data
#LAST UPDATE: 3/2004 (Original Receipt by WDC Paleo)
#
#
#CONTRIBUTOR: Richard Alley, Pennsylvania State University.
#IGBP PAGES/WDCA CONTRIBUTION SERIES NUMBER: 2004-013
“the fit is too darn good. Nothing in nature fits that well, down to the tiny wiggles in the blue and black lines at the right of the graphic. Correlations that good make my nose twitch, they set off my bad number detector..”
Bingo! Thank you, Willis, for a marvelous example of critical thinking, by a scientific mind.