I’ve been thinking further about this knotty problem, which has vexed climatologists and glaciologists for many years. Finally the light has come on. A little while ago the Hockey Schtick site reported a new paper which had found that the Arctic ocean between 50,000 and 11,000 years ago was warmer than it is now by 1-2C to a considerable depth. The authors think it is due to a reduced fresh water flux.
I think it’s due to the glacial period frozen-year-round Arctic ocean surface providing a skull cap of insulation over the bulk of the Arctic ocean preventing it from losing heat to space.
This would mean that the warmer water circulating up in to the Arctic from the equator and sub-tropical ocean would not be able to lose heat as quickly as it acquires it, leading to a gradual buildup of energy. If the heat can’t escape upwards it will build up downwards. The authors note that this warmer water was extending down from around 1000 to around 2500m depth. That’s a lot of excess energy.
So when the Milankovitch cycles bring the configuration of Earth’s orbital parameters to the point where increased summertime insolation at high latitudes in the Northern Hemisphere ablates the Arctic ocean’s surface ice to the point where the warmer ocean below melts through and starts radiating to the cold Arctic night-time atmosphere, there is going to be a lot of energy released. This will generally warm the atmophere, leading to further melting, increased exposure of the ocean, decreased albedo on the land surface, and a rapid positive feedback. This might explain the familiar non-linear rise in temperature from glacial to interglacial.
The standard explanation – increased co2, is a non starter. There is not enough energy from the forcing to explain the speed at which the shift from glacial to interglacial conditions proceeds. Only Earth’s oceans are capable of buffering the energy required. Sea ice melts predominantly from beneath not from above, as rolling icebergs neatly demonstrate.
On one of our previous ice age discussions, I posted a plot comparing the 100,000 year timescale temperature estimates with the decdal scale temperature measurements. Here’s the plot:
At the time, people pointed out that the change in forcing provided by the Milankovitch cycles weren’t enough to account for the glacial-interglacial rapidity of change. I think this finding on the extra heat stored in the Arctic ocean during the glacial period solves the problem. Just like an El NIno is fuelled by warm water from the subsurface Pacific Warm Pool which was previously hidden from the surface temperature record spreading out over the surface, so the Glacial-Interglacial transition is fuelled by the warm intermediate layer releasing energy into the newly uncovered Arctic ocean surface.
Given that co2 levels don’t start to rise at the end of glacial periods until 800-2800 years after the temperature starts to increase, and the unconvincing argument that the co2 increase then amplifies the temperature increase to give us the 6-9C lift estimated to occur, I think the warm ocean hypothesis is the best explanation.
I find the co2 argument unconvincing because there just isn’t enough energy to do the job. Mile thick continent wide ice sheets don’t melt from above in a couple of thousand years due to slighty elevated air temperature caused by any co2 driven effect. An ocean releasing a massive amount of energy into the arctic atmosphere to equilibriate with it after the insulative barrier is removed is a far more plausible explanation in my opinion.
Tallbloke's Talkshop 
Rog ,
Rog is also forcing volcanic!
Do you remember?
I think multiple factors.
Observe Volcanic Markers 13000BP – 11500BP very importants (green Line)
Click to access Ward2009SulfurDioxide.pdf
10. Conclusions
III. When “large” volcanic eruptions occur in quick succession at the rate of at least one each year for ten or more years, the oxidizing capacity of the atmosphere is severely impaired, greenhouse gases accumulate, causing global warming
Roger,
What you are suggesting seems to me to make good sense. When I was working on my post on the Milankovitch cycles:
I went in some depth into the period from circa. 30,000 to 10,000 bpa. in relation to the timing and magnitude of the Milankovitch cycle. The point at issue was the apparent disparity between the slowish rise of the M. cycle compared with the clearly abrupt rate of melt that started in the circa . 20,000 time slot. You may well be right about the type of mechanism involved; will add to thoughts tomorrow morning.
Michele: Multiple factors; of course! But which is the biggest factor? The whole atmosphere has the same heat capacity as 2m of ocean. The continental ice sheets were 3km thick! A lot of energy is needed to melt all this ice. Where does it come from? the air or the ocean?
Roy: Thanks for the encouragement. I’ll look forward to your further comments.
WUWT discussion on the paper:
Another possible contribution is tidal forcing, as explained by (of all people) Charles D. Keeling and Timothy P. Whorf in their 2000 PNAS paper:
The 1,800-year oceanic tidal cycle: A possible cause of rapid climate change
http://www.pnas.org/content/97/8/3814.full
“We have also calculated the effect on γ of varying eccentricity. First, we estimated the variation of γ with distance, R , of the earth from the sun by establishing the average seasonal cycle of γ derivable from the data of Wood (ref. 5, Table 16). We then assumed a dependence proportional to R3 for both the seasonal and secular rate of change in R. The 1,800-year cycle in γ remains almost exactly as at constant eccentricity, but a 100-kyr variation is introduced into γ that is several times as large as the amplitude of the 1,800-year cycle.”
It’s an interesting paper, probably worthy of a separate post.
Good to see Keeling has been investigating other possible causes of climate change beyond the co2 he has been measuring in Hawaii. 🙂
So are you saying that all that “heat” just sits there underneath the ice and do nothing to the underside of all that ice it is rising up against?
Something is not adding up here because ice will melt when water is above freezing point.
More snow is being added above and being compacted under its own weight into ice as the sea water melts the bottom of the ice from underneath. The water immediately beneath the ice is pretty cold anyway. According to the authors of the paper, the intermediate layer from 1000-2500m is where it was warmest. How the thermohaline profile is reorganised and how the heat heads up and out when the ice starts to melt in summer at the start of the interglacial are questions which need further study.
A fantastic Harvest moon this evening. Can’t understand why most ignore the gravity thing and varying orbits of the sphere.This is a powerful force.
sunsettommy says: September 29, 2012 at 8:12 pm
“Something is not adding up here because ice will melt when water is above freezing point.”
Are you forgetting that water begins to expand at ~4 centigrade? Without turbulence to force the mixing of water of differing temperature in this thermal region, a ‘temperature inversion’ exists that ‘caps’ convection and we know how good a thermal insulator water can be.
Thus, the melt rate would be set by turbulent advection (tidal flow etc.).
Best regards, Ray.
TB.
I find it hard to disagree with anything in this thread because all the parameters seem to conform with my last post in the ‘OLR’ thread (from which I divorced myself 😉 ).
There are many more factors that need to be fitted into this, tidal flows through the Arctic Basin under varying degrees of glaciation and geothermal activity to name but two of the obvious factors. 🙂
Best regards, Ray.
As stated, one still needs the Milankovitch cycles in the background to provide the initial variations in equatorial ocean warmth in the first place.
An interesting issue is that glaciations currently last 100,000 years or so compared to interglacials of around 10,000 years.
During a glaciation the Arctic ice cap would be present throughout the summer so given the length of that situation it doesn’t seem likely to me that any build up of warmth in the Arctic Ocean
would be the main cause of the ice age ending.
If it were, then ice ages would be much shorter because the process of warming the water under the ice would start as soon as the increasing cold of the air began to reduce the length of the summer ice melt. In that case one would never expect the Arctic Ocean to remain frozen throughout the summer in the first place because the less open water in the summer the warmer that water would get in a negative feedback process.
However the effect proposed might well be a contributory factor as regards timing in the sense that the precise moment of any switch from glaciation to deglaciation would always be modulated by an interaction between ocean and atmosphere.
I have previously suggested that the timing of the switch would most likely be governed by the interaction between solar cyles and ocean cycles superimposed on the Milankovitch variations such that the switch would normally occur when ocean and solar cycles are in phase supplementing each other’s effects on the climate system.
In fact I suggested that glaciations occur when solar and oceanic cycles are predominantly in phase causing wild swings in temperature that result in the polar ice not having time to melt in the subsequent summer whereas interglacials occur when the solar and ocean cycles predominantly offset one another so that the climate is more equable with less severe winter cold and the summers are then able to melt enough ice to keep glaciation at bay.
That reasoning was induced by the observation that the global climate is far more equable during interglacials.
It would then follow logically that the current landmass configuration results in the 90% glaciation / 10% deglaciation because the amount of ice that can form over winter outside the polar regions themselves is controlled by the size and location of the landmasses.
The more land there is near the poles upon which ice can accumulate in winter the harder it is for it all to melt in summer because of the speed at which the landmasses can cool at night and in winter.
So, I agree with the basic proposal but it needs to be placed in the wider context.
OK, it looks like I need to post the abstract, because people are getting the wrong end of the stick here:
In the Arctic Ocean, the cold and relatively fresh water beneath the sea ice is separated from the underlying warmer and saltier Atlantic Layer by a halocline. Ongoing sea ice loss and warming in the Arctic Ocean1, 2, 3, 4, 5, 6, 7 have demonstrated the instability of the halocline, with implications for further sea ice loss. The stability of the halocline through past climate variations8, 9, 10 is unclear. Here we estimate intermediate water temperatures over the past 50,000 years from the Mg/Ca and Sr/Ca values of ostracods from 31 Arctic sediment cores. From about 50 to 11 kyr ago, the central Arctic Basin from 1,000 to 2,500 m was occupied by a water mass we call Glacial Arctic Intermediate Water. This water mass was 1–2 °C warmer than modern Arctic Intermediate Water, with temperatures peaking during or just before millennial-scale Heinrich cold events and the Younger Dryas cold interval. We use numerical modelling to show that the intermediate depth warming could result from the expected decrease in the flux of fresh water to the Arctic Ocean during glacial conditions, which would cause the halocline to deepen and push the warm Atlantic Layer into intermediate depths. Although not modelled, the reduced formation of cold, deep waters due to the exposure of the Arctic continental shelf could also contribute to the intermediate depth warming.
My bold
Once the insolation at high latitudes increases (not the equator so much), due to changes in the Milankovitch cycles, and open water in the summer starts to appear, the fresh water can be blown by wind southwards and storms can mix the cold fresh and warmer brine. Then the 2C warmer intermediate layer can rise to the surface, releasing humungously enormous amounts of energy into the atmosphere.
2C warmer over a 1500m layer depth is an absolutely vast store of energy. People need to get their heads around just how much energy is stored in such a layer. Enough to melt continent wide mile thick ice sheets. It’s mind boggling.
I wrote this back in November 2009:
“If it be the case that solar and ocean effects can move out of phase and if they can do so for long periods of time then that could resolve the doubts entertained by some about whether orbital
changes are sufficient on their own to induce ice ages.
We can see from the Bond events of more than 10,000 years ago that ice age
conditions seem to occur when the global air temperatures swing more wildly
whereas inter glacial periods seem to be much more stable.
It may well be that during inter glacial periods the solar and oceanic effects
described above minimise extremes by offsetting one another.
Thus, during an inter glacial period:
When the oceans release energy to the air faster a more active sun is cooling
the stratosphere to reduce overheating. When the oceans release energy to
the air more slowly a less active sun is allowing the stratosphere to warm to
reduce overcooling.
The more evenly balanced the two effects are then the warmer the global air
temperatures can become because the winter cooling effects of the northern
land masses are minimised. In this connection I think the current landmass
distribution is critical in determining whether cooling occurs faster than
warming when the solar and oceanic cycles start drifting away from offsetting
one another and instead start supplementing one another.
The less balanced the solar and oceanic effects become the larger the climate
swings and during the northern summers ice takes longer to melt with the
current landmass distribution thus gradually skewing the global air
temperatures even more towards overall cooling of the air and continents.
When both solar and oceanic effects combine to supplement each other on a
regular basis the global air temperature swings become large enough to allow
accumulations of ice in the northern landmasses to survive the summer melts
over increasingly large areas.
I note that glacial periods have been much longer than inter glacial periods so
I suspect that inter glacial periods can currently (given existing land mass
distributions) only arise when the solar and oceanic effects are substantially
(rather than just partially) offsetting one another.”
I’ve never really got to grips with the explanations of the tidal bulge on the other side of the Earth from the Sun and the Moon. Most of them seem contradict each other and only leave more questions.
Is Adam Hart-Davis on the mark with the biscuit, a pickled onion and an orange explanation?
Makes sense to me 🙂
Caz, Adam Hart Davis does a pretty good job in 2 mins there. Try reading the Keeling-Whorf paper I linked for an in depth explanation of the longer cycles beyond the 18 year perigee/eclipse cycle.
http://www.pnas.org/content/97/8/3814.full
“2C warmer over a 1500m layer depth is an absolutely vast store of energy. People need to get their heads around just how much energy is stored in such a layer. Enough to melt continent wide mile thick ice sheets. It’s mind boggling.”
I don’t think anyone would dispute that that is part of the process once the Milankovitch cycles have done their work in causing some open water in summer in the first place.
But isn’t the pole the last region to experience Milankovitch warming.?
Wouldn’t warming occur more in lower but still ‘high’ latitudes nibbling the ice sheets away from the south first ?
A warmer Atlantic would fast reduce ice cover in the North East Atlantic for example long before any open water turned up around the pole in summer.
Hi Stephen. The whole northern hemisphere will get the effect of precession and eccentricity changes, but yes, you’d expect the southern edge of the ice to go first.
Also, I would expect tidal forcing changes that go with obliquity changes to affect the mixing of the warm intermediate layer under the ice cap.
Lots of research and modelling needed no doubt. 🙂
TB:
Sounds like a very plausible theory you have there.
Any chance something similar could be happening in the Antarctic?
On the subject of the Antarctic and Milankovitch cycles, here’s a plot of 18O versus 10Be at Taylor Dome. Taken at face value it suggests that that the recovery into the current interglacial was triggered 15 ky ago by an abrupt increase in solar activity that I don’t think can be related to Milankovitch cycles. But probably there’s something wrong with the data. Anyway, FWIW.
tallbloke says: September 30, 2012 at 12:20 am
“Hi Stephen. The whole northern hemisphere will get the effect of precession and eccentricity changes, but yes, you’d expect the southern edge of the ice to go first.”
I think you are both missing a point here. The Arctic Basin is a region that’s ‘oceanically’ regionalised by its tidal inlet/outlet configuration.
If you’ve a problem realising this, mail me TB. OK? 🙂
Best regards, Ray.
Hi Ray, yes, and the Fram strait was that little bit tighter when the sea level was lowered by the landlocked ice sheets.
Roger Andrews (September 30, 2012 at 1:31 am) “[…] abrupt increase in solar activity that I don’t think can be related to Milankovitch cycles. […] http://oi49.tinypic.com/f4jyw0.jpg “
10Be deposition is modulated by circulation/hydrology – not just sun (…so careful interpretation). Informative/interesting graph. Thanks for sharing.
—–
More general comment on article & discussion:
Air-sea coupling morphology – and anything that can short it giving rise to nonlinearity incl. mixing/turbulence & Milankovitch – appears key TB. Some good stuff. Thanks for sharing.
Sea with its capacity.
Air with its fluidity.
Not one or other,
But both together.
Looking at that graph from Roger Andrews, it appears that the Younger Dryas seems to show up there as well. Just as I was beginning to favour an impact event for the YD.
JM, beware the 10Be data, as Paul cautions above.
TB,
At the 48 degree latitude is when water changes directions. Water, rock and debris flow downstream but NEVER upstream. Snow compacts to ice but does not move. Ice can trap rock and debris but still they ALWAYS move down stream. Rocks even underwater are rounded and eroded(even in areas not known to have been in an Ice Age).
Massively more water on our planet was NEVER considered nor pressure from this source.
A better explanation for the end of ice ages
Posted: September 29, 2012 by tallbloke
A little while ago the Hockey Schtick site reported a new paper which had found that the Arctic ocean between 50,000 and 11,000 years ago was warmer than it is now by 1-2C to a considerable depth. The authors think it is due to a reduced fresh water flux. I think it’s due to the glacial period frozen-year-round Arctic ocean surface providing a skull cap of insulation over the bulk of the Arctic ocean preventing it from losing heat to space. This would mean that the warmer water circulating up in to the Arctic from the equator and sub-tropical ocean would not be able to lose heat as quickly as it acquires it, leading to a gradual buildup of energy. If the heat can’t escape upwards it will build up downwards. So when the Milankovitch cycles bring the configuration of Earth’s orbital parameters to the point where increased summertime insolation at high latitudes in the Northern Hemisphere ablates the Arctic ocean’s surface ice to the point where the warmer ocean below melts through and starts radiating to the cold Arctic night-time atmosphere, there is going to be a lot of energy released.
Taking the solar photon diffusion time of about ~190 ky from the inner Sun to the surface, mode resonances could be create a solar heat source pattern which is like the measured global temperatures, like the sample in Vostok, Antarctica.
Talking about the end of the Ice Ages we speak on global temperature shifts of about 8K in a short time and a relaxing rate of 15 ky per K or ~100 ky per 8K.
Whatever temperature proxies tell different, it is in contradiction to the well established global data.
As one can see the shape of the ice age cycles have saw tooth character, and have nothing to do with Milankovitch sinusoid functions.
s.a. http://www.volker-doormann.org/ghi_solar_s.pdf
V.
Hi tallbloke
Interesting concept. Thinking ahead a bit, if ocean heat breaks down the polar ice leading to an interglacial, why then does the process reverse so suddenly. The interglacials often seem to suddenly drop right after the inter-glacial has reached a temperature peak.
Does then the breakout of stored oceanic heat meet the colder conditions due to the cooling Milankovich cycle and bring a relatively slow descent into a glacial period. Or, is there a tipping point where the warmer polar oceanic conditions and the colder Milankovich cycle result in rapid precipitation and altered weather patterns bringing about a rapid refreeze.
If we imagine the Little Ice Age which coincided with low solar activity, we saw advancing sea ice and glaciers and increased precipitation. However, at that point polar ice was presumably still intact and more extensive in both area and thickness. Now the polar ice appears to have decreased yet further than LIA levels could we be approaching the reversal point where the downturn in temperature and subsequent build up of precipitation cannot be overcome by future warming periods.
The oceanic heat would thus feed the glaciation process until that heat was spent leaving Earth in deep freeze until the warming phase of the Milankovich cycle began the slow thaw.
TB,
Is not our atmosphere less than when the sun was very active?
I seem to remember reading a report on this.
Our poles have a very small atmospheric layering compared with the equator.
Volker:
“As one can see the shape of the ice age cycles have saw tooth character, and have nothing to do with Milankovitch sinusoid functions.”
I disagree. The ice core data looks like saw teeth, but the ice ages look more like a succession of big El Nino’s and weather in between. See my plots comparing the glacial/interglacial cycles and El Nino/La Nina cycles in the article at the top of the thread. The magenta curve in the lower plot follows the dark blue sinusoid quite closely. That sinusoid is the insolation at 65N determined by the Milankovitch cycles.
Volker:
“As one can see the shape of the ice age cycles have saw tooth character, and have nothing to do with Milankovitch sinusoid functions.”
I disagree.
OK Rog.
V.
Gray says:
September 30, 2012 at 12:16 pm
I am thinking along the same lines – the amount of energy required to evaporate enough water to drop sea-levels by 500 feet, and accumulate 40 million km^3 of ice on the northern continents must be colossal, and TB may well have identified the source of that energy.
We also have to consider the possibility that it is the dynamics of the ice sheets themselves which dictate the length of the ice ages, with the Milankovitch cycles perhaps only playing a secondary role.
Think of it like this : Covered with 3km of ice, NW Europe and North America would have similar climates to those found today in Antarctica and the heart of Greenland (think Summit Camp). Are Milankovitch forcings really enough, by themselves, to melt all that ice?
The big difference between the permanent ice sheets of Greenland and Antarctica and the “temporary” ice sheets which covered NW Europe and North America during the last glaciation, is that the former are constrained by being surrounded by water, while the latter were not, and this is why ice sheet dynamics play a pivotal role :
At the height of the last glaciation, the extreme cold probably starved the ice sheets of the precipitation needed to replenish them but, at the same time, the irresistible force of gravity would cause the ice sheets to both thin and continue to advance towards warmer lower latitudes, leading to the the rapid collapse which occurred at the end of the last glaciation.
Very little to do with CO2, OR Milankovitch……….
“I think this finding on the extra heat stored in the Arctic ocean during the glacial period solves the problem.”
Not to state the bleeding obvious, Roger, but the Arctic Ocean is a very special case as “oceans” go. It is a shallow basin, more of a puddle at the top of the world!
Average depth in feet …………………… Area in Million Sq Miles
Pacific ……. 15,215 ………………………………. 64 million
Atlantic ……12,881 ………………………………. 33 million
Indian ……..13,002 ………………………………. 28 million
Southern …15,000 ………………………………… 8 million
Arctic ………. 3,953 ………………………………… 5 million
The end of an ice age….
@tallbloke says:
September 29, 2012 at 11:33 pm
“OK, it looks like I need to post the abstract, because people are getting the wrong end of the stick here:
In the Arctic Ocean, the cold and relatively fresh water beneath the sea ice is separated from the underlying warmer and saltier Atlantic Layer by a halocline.”
I think you need to explore this Idea in greater detail. The Arctic Ocean layout is perfect to enhance this effect for trapping and then releasing energy due to its’ deep inlet from the Atlantic and shallow outlets around North America at Bering and Greenland. pg
Fen, inspired work my friend, the night of the sharpened turbine blades approaches.
Marchesarosa, good point. I think the authors of the paper must be considering a ‘paleo-arctic’ ocean which extends further south than the way it currently defined. Can’t see any other way to explain their ‘intermediate layer’ from 3000 to 7500 feet in a 4000 foot deep puddle anyway. Of course, as it expands south, it grows in area at an exponential rate, notwithstanding the land masses.
I’ll use my uni login to grab the paper and see if they define their geography. I suspect they are referring to the area under year-round ice during the last glacial, which extended down past Iceland I think. However, here’s the relevant potion of the Abstract:
“the central Arctic Basin from 1,000 to 2,500 m was occupied by a water mass we call Glacial Arctic Intermediate Water. This water mass was 1–2 °C warmer than modern Arctic Intermediate Water,”
Central Arctic Basin… 1,000-2,500m. Hmm, we have a mystery to solve.
I think Marchesa Rosa needs to tell us the date in the front of her atlas. 🙂
http://www.channelone.com/news/gal_north-pole/3/
This graphic released by the National Geographic Society Tuesday Jan. 14, 1997 is part of oceanographic study by the U.S. and Russia on the Arctic Ocean. This cross-section Arctic Ocean map, combining U.S. and Russian data, represents a transect of Arctic waters, red line, showing an area in Greenland, left, where warmer surface water is pulled in and cooled, forming a mass of deep ocean water. By releasing the information, both nations hope to help scientists around the world who are investigating environmental questions such as global warming.
http://encyclopedia2.thefreedictionary.com/East+Greenland+Rift+Basins
The Arctic Ocean has the widest continental shelf of all the oceans; it extends c.750 mi (1,210 km) seaward from Siberia. From the shelf rise numerous islands, including the Arctic Archipelago, Novaya Zemlya, the New Siberian Islands, and Wrangel Island. The continental shelf encloses a deep oval basin (average depth 12,000 ft/3,658 m) that stretches between Svalbard and Alaska; E of Greenland the ring of the continental shelf is broken by the Greenland Sea. The greatest depth (17,850 ft/5,441 m) in the Arctic Ocean is found just N of the Chukchi Sea. Since the Arctic’s connection with the Pacific Ocean is narrow and very shallow, its principal exchange of water is with the Atlantic Ocean through the Greenland Sea. Even there, though surface waters communicate freely and a strong subsurface current brings warm water from the Atlantic into the Arctic basin, exchange of deeper waters is barred by submarine ridges. Thus a near stagnant pool of very cold water is found at the bottom of the Arctic basin.
Canada Basin:
” Below the ice, the ocean floor is found at an average depth of 3600 metres, although the Lomonosov Ridge near the North Pole reaches up to a kilometre below the ocean’s surface.”
Wkipedia says:
Fram basin:
“The Nansen Basin (also Central Basin, formerly Fram Basin) is an abyssal plain with water-depths of around 3 km in the Arctic Ocean”
I wonder if the Lomonosov Ridge which connects Greenland to Siberia and passes near the North Pole that reaches up to a kilometre below the ocean’s surface is the cause of two separate circulations; the Beaufort Gyre above Western Canada, and the circulation north of Siberia.
Might this have anything to do with the bifurcated north magnetic pole?
Is this the cause of the mysterious correlation between rate of change in the north magnetic pole position and changes in global temperature? Is it because higher temperatures caused the the northern Gyres to speed up unevenly and the Antarctic circumpolar current to speed up as the tropic change the rate at which they shift heat towards the poles?
If that’s the case then the fact that multi-decadal changes in Length of Day also correlate suggests that the mass distribution of the ocean would partly be an effect of circulation changes due to temperature change, as well as changes in wind patterns.
Vuk? Paul?
TB. I feel a new thread coming on. 😉
Best regards, Ray.
TB, Are you sure about the amounts of heat and melting “mile thick” ice?
My quick and dirty calculation:
Taking the heat capacity of water at about 4.2 J/(g.K) and heat of fusion of ice at 333.55 J/g, at 273K, a column of water with 2K “excess heat” has sufficient heat to melt a multiple of 8.4/333.55 times it’s own mass of ice [at 273K]. For 1500m column of water this amounts to enough heat to melt about 41m of ice [to 38m of water]. I doubt the heat capacity of water varies strongly enough with depth/pressure to make much of a dent in that number.
Glaciers rot from within and the energy comes from gravity. You’ve seen glacial ponding and images of those ponds plummeting into glacial chasms. There’s not a lot of temperature difference between the melt water and the ice at the surface, but when those ponds cascade into the chasms much more than simple melting takes place. There is abrasion by shock waves formed as bubbles of air blast against immovable walls of ice, water droplets become grenades, cavitation and vortices carrying a slurry of water, ice, foam, and particulates chafe and grind and carry away tons of ice without melting a drop. The volume of slurry grows as gravity pulls it down, creating ever more havoc as it seeks out any opportunity to continue downward.
That crashing and swirling and conversion of gravity to energy does finally warm the slurry such that true melting occurs at lower levels. If it makes it out the bottom, which it will certainly do with time, it will form a lake if in a basin, or a river of white water that wears at the base of the ice. The wearing down is now happening above and below as well as through the rotting corps of ice.
A large glacial lake can remove thousands of square miles of ice in a matter of days.
It starts here:
And ends here:
http://www.iafi.org/
And we know this because it happens here with some regularity:
Michael, yes, I’ve been considering this since Marchesa Rosa’s timely reminder of the size of the Arctic ocean. I’m sure that Paul Vaughan is right that both ocean and atmosphere (and gravity as DP says) are involved, The atmosphere is much drier during the glacial. The release of the oceanic heat will increase humidity in a big way. That will increase cloud over the wintertime pole and have a warming/insulating effect.
@tallbloke (September 30, 2012 at 9:54 pm)
Wo.
Slow down there TB. [ :
One thread at a time!
(certainly not enough time to address all of that in one sitting, let alone a month’s worth of sittings!)
some good ideas for other threads for sure — looking forward to it…
I know, I know. I want it all, I want it now…
If not sooner. 🙂
“.. suggests that the mass distribution of the ocean would partly be an effect of circulation changes due to temperature change, as well as changes in wind patterns.”
Surely the gyres and circulation changes driven by the winds anyway?
And the winds are driven by…
Winds are driven by diurnal, seasonal, latitudinal and altitudinal etc temperature gradients. Both the daily wind anomalies (e.g. like Piers forecasts), and other scales of wind changes connected with medium and longer term weather and inter-annual climatic anomalies are solar driven. Everything other than the daily weather events, correlates particularly well to variations in the solar wind speed.
This is something that is seriously neglected in the Milankovitch theory relying solely on insolation variation, there are long solar magnetic cycles that are heavily modulating Earth’s orbital variations.
(I have no idea how accurate that is but it gives some idea)
http://en.wikipedia.org/wiki/Arctic_Ocean
I was beginning to think I had made a silly copying error mistaking feet for meters! But the ocean depths given in the little table I posted were average depths and since the Arctic has very extensive continental shelves the average of about 4,000 feet is probably correct. Average depth x surface area still gives a relatively small volume as oceans go and the Fram and Bering Straits are very much shallower than the basins according to the diagram in the wiki article here
http://en.wikipedia.org/w/index.php?title=File:BrnBld_BeringToFram.svg&page=1
These straits “contain” the Ocean to a considerable extent, even today. When sea level was much lower there may have been only a trickle getting in and out of the Arctic basin so that the relatively slowly overturning water was able to be warmed up by hydrothermal vents?
Sorry if this has already been mentioned or is too fanciful. (I’m a conspiracy theorist, you know!)
Thanks for that marchesarosa.
The graphics from your link show how the tidal influence on the Arctic Basin is off-set.
East of Greenland, the Atlantic oceanic connection is ~opposite its Pacific counterpart, and more open, than the ‘Fram Strait’, but to the ‘West of Greenland’ there are waterways that ~equal the flow of the Fram Strait.
Although the tidal influence between the ‘Fram Strait’ and ‘East of Greenland’ can be rationalised as self negating, what of the ‘West of Greenland’ tidal influence?
Best regards, Ray Dart.
BTW. My last post was in response to:
marchesarosa says: October 2, 2012 at 2:02 am
Best regards, Ray.
Marchesa Rosa,
Yes sea levels were lower, but the topology of the Earth’s crust was lower too, due to the weight of ice on the continents.
Wikipedia:
The formation of ice sheets can cause the Earth’s surface to sink. Conversely, isostatic post-glacial rebound is observed in areas once covered by ice sheets that have now melted, such as around the Baltic Sea and Hudson Bay. As the ice retreats, the load on the lithosphere and asthenosphere is reduced and they rebound back towards their equilibrium levels. In this way, it is possible to find former sea cliffs and associated wave-cut platforms hundreds of metres above present-day sea level. The rebound movements are so slow that the uplift caused by the ending of the last glacial period is still continuing.
So the continental shelves would also have been lower, and would have had deep water over them.
Michael Hart says:
My quick and dirty calculation:
Interesting point Michael. However, the water temperature of the column would presumably be constantly fed from the equator and be in the process of melting the polar cap to achieve the temperature difference.
TB,
Thanks for bringing our attention to a potential magnitude of energy that can be released from the artic sea. It has brought some very valuable discussion.
Consider a post on the process of energy accumulation. Another on energy release. And another on NH glacial effects.
The information from the comments are of major value!
I think the build up of ocean heat under the polar ice caps is a good explanation for why the transition from an ice age to an interglacial is so rapid, but it doesn’t really explain the timing. Ocean dynamics must somehow be involved in glacial cycles because they contribute about one third of the total heat transported to the poles. Obliqiuity cycles have a large effect on insolation at high latitudes, so we should really expect a glacial cycle of 42,000 years (as existed 3-1 million years ago) . No-one can explain why it switched to a 100,000 year eccentricity cycle 1 million years ago. An increase in insolation for one pole close to perihelion is offset by a diminished insolation for the other pole. The South pole is covered by Antarctica which may give an asymmetry. Overall the net annual effect of eccentricity on the Earth’s insolation is negligible. The main effect of ellipticity is to modulate the effect of the precession terms at 23,000 years. Indeed if the orbit was circular then the precession of the equinoxes would have no effect whatsoever. This is the paradox as to why regular glaciations and warm interglacials occur every 100,000 years in phase with the eccentricity.
Two other interesting effects:
1. During a glacial maximum there is shift of 4*10^19 kg of water transfered from the Oceans to Ice at high latitudes. This must change slightly the moment of inertia of the Earth making a day slightly shorter.
2. The lunar/solar tidal effect will increase during glacial periods at northern latitudes
The big question for the human race is just how long the current interglacial will last – what triggers the onset of a new ice age? Based on the last 10 ice ages, it seems highly probable that the next glacial period will start within about 1500 years. Global warming will be seen as having been a minor blip in the overall glacial cycle.
After a slow start Arctic temperatures are now falling faster than the mean. Perhaps the heat released from this Ocean after the early August storm which blew the ice into warmer waters has now dissipated?
http://ocean.dmi.dk/arctic/meant80n.uk.php
Joachim Seifert, a Dresdner climate researcher, sees one of the major cause of glaciation and thaw as Earth’s distance from the sun changing as it spirals around its elliptical orbit. These spirals change diameter and alter the amount of insolation the Earth receives.
The positions of the maximum extension are not fixed, but shift from year to year. You can be close to the sun or even just a long way from what a difference in the intensity of the incident solar radiation exposure. Currently, the two points are close to the maximum extent of the sun, which Seifert sees the sole reason for the increase in temperature.
Here’s a summary of how this, along with other climate drives touched on above, can work…
Click to access eoo_paper_summary.pdf
tallbloke (October 1, 2012 at 6:26 am) wrote:
“[…] both ocean and atmosphere (and gravity as DP says) are involved […]”
Gravitational (lunisolar) and thermal (insolation) tides in concert…
Current conventional “wisdom” about monsoons leaves way too much to be desired, but is there any outstanding tidbit of conventional monsoon wisdom that is largely ignored in the climate discussion? Yes…
Somali Current & Findlater Jet…
HALF of global northward boreal summer interhemispheric tropospheric mass transfer blasts through this narrow bottleneck (which spans only 10% of Earth’s circumference). This thing can switch on from nothing to nearly full blast in a matter of only a few weeks.
What happens to an ice cube suddenly blasted by a firehose? Lots to discuss moving forward…
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Recommended resources:
http://www.ecmwf.int/research/era/ERA-40_Atlas/docs/index.html
http://ds.data.jma.go.jp/gmd/jra/atlas/eng/atlas-tope.htm
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