From the “things Earth does without our help” department:
Study: 100,000 square miles of Ross Ice Shelf disappeared in 1,500 years
From RICE UNIVERSITY
HOUSTON — (Feb. 18, 2016) — In a new study that provides clues about how Antarctica’s nation-sized Ross Ice Shelf might respond to a warming climate, U.S. and Japanese oceanographers have shown that a 100,000-square-mile section of the ice shelf broke apart within 1,500 years during a warming period after the last ice age.
The Ross Ice Shelf is the world’s largest ice shelf, a vast floating extension of the West Antarctic Ice Sheet that is about the size of France. But at the end of the last ice age, it extended much farther north and covered the entire Ross Sea.
A study in this week’s Proceedings of the National Academy of Sciences details how the ice shelf shrank during a period of climate warming following the ice age. The paper was co-authored by Rice University oceanographer John Anderson, postdoctoral research associate Lauren Simkins, graduate student Lindsay Prothro and colleagues at the University of Tokyo.
“At the height of the last ice age, we know that the sheet of ice covering the Antarctic continent was larger and thicker than it is today,” said Anderson, Rice’s Maurice Ewing Professor of Oceanography and professor of Earth science. “This continent-enveloping ice sheet extended all the way to the continental shelf, and in western Antarctica it filled the entire Ross Sea basin.”
While people typically think of continents as landmasses that rise above the sea, the margins of all continents, including Antarctica, extend well beyond their shores to include continental shelves, subsea aprons that are far more shallow than the deep ocean abysses that mark the continental boundary.
In western Antarctica, the Ross Sea is characterized by a continental shelf that extends nearly 1,000 miles from the coast and is as much as 3,500 feet deep. Anderson said the geologic record shows that as recently as 18,000 years ago the entire Ross basin was filled with ice that was so thick and heavy it was grounded on the seafloor all the way to the edge of the continental shelf.
“We found that about 10,000 years ago, this thick, grounded ice sheet broke apart in dramatic fashion,” Anderson said. “The evidence shows that an armada of icebergs — each at least twice as tall as the Empire State Building — was pushed out en masse. We know this because this part of the Ross Sea is about 550 meters (1,804 feet) deep, and the icebergs were so large and so tightly packed that they gouged huge furrows into the seafloor as they moved north.”
Researchers measured the furrows using a seafloor mapping system — the most sensitive ever employed in the Antarctic — during a 2015 cruise by the U.S. research vessel Nathaniel B. Palmer, which is operated by the National Science Foundation.
Simkins, who helped gather data during the 56-day cruise, said other features preserved on the seafloor, formed by the retreating ice, showed that the margin of the grounded ice sheet retreated rapidly after the initial collapse and fell back hundreds of miles in stair-step fashion.
The Ross Ice Shelf appeared after the breakup of the ice sheet. An ice shelf is the floating, seaward extension of an ice sheet and marks the point at which the ice is thin enough to float.
“The grounding line is the location where the ice actually sits on the seafloor,” Simkins said. “Following ice-shelf break up, the grounding line is left exposed to marine processes, such as ocean warming, which can erode the grounding line and cause it to move back toward the shore.”
The retreat was halted when the grounding line reached a series of shallow banks that acted as anchors and stabilized the ice shelf for about 5,000 years.
Anderson said, “Throughout this period, the ice shelf was pinned atop these shallow banks. On the surface, ice still covered large portions of the Ross Sea, but there was open water beneath the ice shelf.”
The researchers know the times when the seafloor was partially or fully ice-covered, thanks to painstaking geochemical analyses of seafloor sediments that were overseen by study lead author Yusuke Yokoyama, a professor at the University of Tokyo who was also a Wiess Visiting Professor in Rice’s Department of Earth Science in 2014-2015. The geochemical analyses also relied on evidence gathered by the Palmer, which is capable of drilling and recovering sediment cores from the seafloor. Such cores contain a geological record that can extend thousands of years, and Yokoyama’s team used Ross Sea core samples that were recovered during a 1999 Palmer cruise as well as 2015 cores and seafloor imagery to pinpoint the timing of the ice-shelf breakup.
“The really big breakup began around 3000 B.C.,” Anderson said. “We believe it was similar, in many respects, to the breakup of the Larsen B Ice Shelf in 2002. The Larsen is far smaller than the Ross Ice Shelf, but satellite imagery that year showed the Larsen dramatically breaking apart in just a few weeks. We believe the large breakup of the Ross Ice Shelf occurred at roughly this same pace, but the area involved was so much larger — about the size of the state of Colorado — that it took several centuries to complete.”
By 1500 B.C. the breakup had exposed about 100,000 square miles of the Ross Sea that had been either wholly or largely ice-covered for many millennia, Anderson said.
To pinpoint the timing, Yokoyama’s team used two novel geochemical approaches: measurement of the isotope beryllium 10, which forms in the atmosphere and does not fall to the seafloor beneath ice shelves, and “compound-specific radiocarbon dating,” a painstaking technique that involves identifying and ascertaining the age of specific organic molecules in sediments. Yokoyama said each compound-specific radiocarbon dating measurement took several weeks to perform, and more than a dozen were needed for the study, which marked the first systematic use of the technique in Antarctic science.
“Our radiocarbon dating work alone took more than a year to complete,” Yokoyama said. “The results of those tests, as well as the beryllium tests, provided conclusive evidence that the main breakup of the ice shelf occurred between 5,000 and 3,500 years ago.”
Anderson said knowledge about the past behavior of the ice sheet and ice shelf, in particular their rate of response to atmospheric and oceanic warming, informs scientists about how present-day ice sheets and ice shelves may respond to future warming.
“There are similarities to what we see the modern Ross Ice Shelf doing,” Anderson said. “The farthest boundary of the ice shelf extends nearly 1,000 kilometers (621 miles) from the grounding line, where the ice sheet is grounded in about 800 meters (2,625 feet) of water. That’s a condition that most glaciologists consider unstable, and it is not unlike the situation that existed prior to the big breakup that began 5,000 years ago.”
The present Ross Ice Shelf is about 500 miles wide and several hundred feet thick. Because the ice shelf is already floating, its breakup and melting would not, by itself, pose a risk of raising global sea level, Anderson said. However, he pointed out that the ice shelf acts as a brake to dozens of Antarctic ice streams and outlet glaciers, and ice flowing into the ocean from those would contribute to global sea level rise.
“The ice shelf slows the flow of grounded ice from the glaciers, and as we saw after the Larsen B breakup, once you pull the stopper out of the bottle, the glaciers move much faster, in some cases about 10 times faster,” Anderson said.
###
I presume that somewhere in the study the following statement is made:
” These findings should not, however, be taken to indicate that the comparatively minor diminution of Arctic Sea Ice during the 1990s could be at all natural, since it is the approved consensus of IPCC climate scientists that major climate variations of this this kind no longer take place naturally, and are instead driven by human capitalist greed creating consumer items which Gaia would be better off without. Much more research on this subject (and much higher grants) are recommended…
I think that Gaia would be better off without the fanatical AGW believers. You probably don’t realize it but the capitalist consumer items allowed you to make this stupid post here.
I sugggest you look up ‘irony’ in your dictionary..
Or sarcasm
Woosh!
Some time ago, when the Larsen B ice sheet collapsed and broke up, a chap named Svend (can’t remember the last name) with the Danish Environmental people, a glaciologist who actually lives on Greenland, sent me a picture of the collapse part of the Larsen B and next to the broken up part, there was a brand new ice sheet attached to the whole continent, and that piece was as big as the newly broken part, but was shallower, so there was a cliff, where you went from that sheet, and climbed up onto Antarctica.
From the height of that cliff, they deduced that the mainland had 50 years more ice than the new sheet, so that part of the Larsen B had broken up just 50 years ago, and was simply growing back as has been going on for eons. since there are satellites going more or less north south polar orbits, Svend can take pictures of ice and glaciers anywhere, from his igloo on Greenland.
G
If it is concensus it isn’t science.
Precisely.
It was a gravitational wave that took the anthropogenic CO2 from the twentieth century back 3,500 years to the Ross ice shelf. The break up was due to man made warming.
As far as Arctic warming is concerned, its cause is a rearrangement of the North Atlantic current system at the turn of the twentieth century that caused an increase in the amount of warm water carried north by the Gulf Stream. The warming was not uniform but was interrupted by a thirty year cold spell in mid-century. Warming resumed in 1970 and almost all temperature measurements you see start later than that. These people have no idea that prior to the twentieth century there was nothing but two thousand years of slow cooling in the Arctic. Read E&E 22(8):1069-1083 (2011).
I just had the unfortunate situation of being forced by having nothing better to watch and watching a documentary titled ‘Antarctica Edge: 70 Degrees South. A group of narcissistic, group thinking, motivated by political ideology and tax payer money, made a movie full of so much BS that I almost puked my dinner up on the carpet. Everything they claim is so full of holes and outright lies it is sickening. The dramatic music and claims of doom and gloom while talking themselves up as heroes and at the same time complaining like babies about how hard they work and the extreme sextent they “have” to go through to do what they do.
Amongst all the other BS, they seem to begin their observations of climate from the time when they were born. Make unconfirmed statements as if it was fact and truth, try to impress the viewers with statements such as ‘we turned photographs into DATA’, as if data were a new phenomenon they had just invented, made up on the spot by ‘The Team’.
They claimed that over the last decades the Antarctic sea ice has been reduced by over 70%… If anyone else has watched this, please give me your impressions of this production by these obviously group think idiots who suck their existences out of tax payer funding for studies, that if we had a real problem, wouldn’t go to them but to fixing the real problems..
If my rusty maths skills have not completely deserted me, isn’t that approximately 67 square miles per year ?
Doesn’t sound nearly as threatening when put that way, does it ?
They should convert it into Hiroshima bombs for better effect?
‘They should convert it into Hiroshima bombs for better effect?”
Mouse farts would produce really scary numbers!
Or Olympic swimming pools.
Would going to square feet be better? It would be a much larger number!
Or 3 Manhattans a year?
Or Olympic-size swimming pools (frozen of course).
The exterior surface of ice will melt if the temperature of the air or water in contact with the external surface of said ice is greater than 32F STP.
Ice will not bend, twist or warp regardless of how much pressure is applied to the external surface of said ice.
Non-entrapped (confined) ice will fracture and/or break apart if there is sufficient external force (pressure) applied to one (1) of the external surfaces of said ice.
The forces caused by gravity, floatation, winds, waves and tides result in the calving of glaciers and the “fracturing” of sea-ice from its grounded source.
While I think this is from England, you should visit the Appalachian mountains some day.
http://pages.geo.wvu.edu/~jtoro/geol101/mountains/fold.jpg
http://www.geoexpro.com/articles/2015/01/folds-and-folding-part-ii
@ Ric Werme – February 19, 2016 at 6:34 am
Rick W, … I was born, reared and educated here … and have spent all but 20 years of my life (1963-83) here in the Appalachian Mountains of central WV and I can surely tell you more about them than you could possibly want to know.
My commentary was in reference to SURFACE ICE formations, …… not the geology of rock layers or the multi-colored layers of Christmas candy.
=================
I suggest you take a look at http://aroundtheworldwithjeeves.blogspot.com/
Being we are talking about the Ross Ice Shelf, where the ice shelf has to bend around Ross Island it produces spectacular pressure ridges. Toward the bottom of that page, the author takes a tour of the area (normally off limits to USAP personell) and has some very good pictures. Including a couple that plainly show the bending of the layers in the ice.
@Bruce – February 19, 2016 at 9:16 am
Bruce, and just what is/was that “magical” force that caused the ice to “bend around” Ross Island? A curious mind would like to know.
========================
Samuel C Cogar:
You say,
All solid rocks – including ice – do “bend, twist or warp” in response to a sufficient sustained force. The distortions occur slowly but are permanent.
Richard
“All solid rocks – including ice – do “bend, twist or warp” in response to a sufficient sustained force. The distortions occur slowly but are permanent.”
My impression also. On top of which, ice has the unusual(?) characteristic of possibly melting and later resolidifying when put under pressure. see https://en.wikipedia.org/wiki/Regelation
Don K:
You say
All solid rocks – including ice – do “bend, twist or warp” in response to a sufficient sustained force. ….. The distortions occur slowly but are permanent.
________________________________________
Neither is true.
Ice sheets flow like water over rocks, or a stable airflow over mountains. The layers flow, bend, reform, and continue flowing down to the sea. With patterns and forms, like rotor, that any glider pilot will instantly recognise.
http://www.antarctica.gov.au/__data/assets/image/0003/142824/varieties/antarctic.png
ralfellis
February 19, 2016 at 6:40 am
richardscourtney is correct. The force here in your example is roughly horizontal and is a sustained force. The same thing happens with rock formations in large sheets, pushed from behind (assisted by gravity if the fault dips in the direction of motion) riding on very shallow dipping faults. These shallow dipping to horizontal fault surfaces, often extending for many miles, are called thrust faults and the formations riding on them are called nappes. Essentially it results in older rocks riding up on top of younger rocks. The common feature above the fault surface is a recumbent fold, in cross-section shaped like a hair pin. Scroll down to the bottom photo of a recumbent fold that has been thrust over younger rocks in Sierra de Juarez, Mexico.
http://blogs.agu.org/mountainbeltway/2012/02/13/recumbent-fold-in-sierra-de-juarez-mexico/
Air is too fluid to compare with ice and rocks. In large sheets with confining pressures over long periods of time, both can bend and fold. They are “plastic” under such conditions. Small pieces of ice and rock are brittle to a quickly applied force. It is tempting to surmise the type of connection you made with air currents. I’ve marvelled at the structures one can see in clouds, particularly from the air where long straight “faults” can be seen and other forms. However, you should refrain from calling others wrong because of your a priori thoughts and conclusions.
Gary.
I think you misinterprest that glacial cross section. The ice in that image is not static and being folded, it is dynamic and flowing very slowly downhill into the sea (greatly assisted by pressure from above). The ice-fold here is not static, it is directly analogous to water or air flowing over an obstruction in the underlying topography.
Think of a glacier flowing down a valley, which behaves like a river, but just 30,000 times slower. Ice sheets do the same. They act like layers of plasticine being squeezed through a nozzle by pressure from above. The layers will remain distinct, but thin and bend as they flow through the nozzle. Think of the extrusion process that allows a stick of rock (candy) to retain the name of the resort, despite being squeezed 100 times smaller than it was before. The ice layers in an ice sheet, are the same as the lettering in the stick of rock – much thinner, able to be bent in any shape, but still distinct.
http://f.tqn.com/y/gouk/1/W/b/I/0/-/GettyImages-10193578.jpg
ralfellis:
I wrote the correct statement:
The effect is the material property of solids known as ‘creep’ (considering the name of this material property, I would have thought you and MarkW would have known of it).
But, with your usual desire to broadcast your ignorant arrogance, you replied
Gary Pearse gave a clear explanation that your assertions were wrong, and you have replied to him saying
In other words, you are now saying as I said,
“All solid rocks – including ice – do “bend, twist or warp” in response to a sufficient sustained force. The distortions occur slowly but are permanent”
but – as is your usual behaviour – you are not admitting you were plain wrong.
Richard
Richard: You said:
>>The distortions occur slowly but are permanent
They are not permanent. The distortions in the ice layers flow and bend, and can be reformed with every underlying topographic feature under the glacier or ice sheet. Just like water flowing over rocks or an airmass flowing over mountains. So you were wrong. There is no ‘permanence’ to the folds at the base of an ice sheet, as if it were a monolithic slab of rock, it continues to flex and flow as much as any river, except slower.
You also forget the principle of lithic fabrication by deliberate distortion and internalised deception – a principle that you really should be quite familiar with.
Ralph
ralfellis:
I see you are conducting your usual wriggling instead of admitting that – as usual – you are plain wrong.
You wrote to dispute my clear, true and accurate statement that
Your dispute said
Your response was so wrong as to be risible and Gary Pearse explained your error beginning his explanation saying to you
You responded to him with silly twaddle about extrusion which you claimed was rebuttal of my original comment but actually supported what I had said! Therefore, I provided you with this link to an explanation of the material property called ‘creep’. And I said
Were you content with that? No, you could not stop yourself from digging your hole deeper and replied
Yes, that is because,
“All solid rocks – including ice – do “bend, twist or warp” in response to a sufficient sustained force. The distortions occur slowly but are permanent.”
An imposed creep distortion is permanent and a subsequent creep distortion (that may conceal previous creep distortion) results from application of another sufficient sustained force.
It seems you are unaware that ice has weight which applies force. Consider the case of aluminium which has high creep rate and distorts under its own weight much more rapidly than ice. Aluminium wires are used as high tension cables because aluminium has high electrical conductivity but the cables are coextruded with a steel core: creep of pure aluminium cables would cause them to sag down to the ground but the steel core holds a coextruded cable up.
Richard
>>The distortions occur slowly but are permanent.
What part of ‘not permanent’ do you not understand Richard? Ice layers in a glacier or ice sheet are plastic, not solid and permanent. That is why glaciers can flow in curves around hillsides, and ice sheets can flow over buried mountains. They behave as a malleable viscous fluid, not a solid crystal. As do iron and steel, if you get them under enough pressure and temperature. Or do you think that crystaline iron is always solid and immutable, as Gary Pearse seems to think?
BTW, it is February. Are you not due back at the kindergarten by now? You should really check with them.
Ralph.
ralfellis:
YOU ARE – AS YOU USUALLY ARE – PLAIN WRONG!
Creep distortion is permanent deformation: read the link I have twice provided for you.
Strewth! I even explained about the composite construction of high tension cables in hope that you would be able to learn about creep, but – as usual and with everything – you prefer to think your arrogant ignorance is bliss.
And your usual temper tantrums – including silly comments about kindergartens – do you no good.
Richard
@ richardscourtney – February 19, 2016 at 5:09 am
Richard S, my commentary was in reference to SURFACE ICE formations (glaciers and sea ice), …. NOT entrapped (confined) ice. And ps, given the fact that glaciers originate due to “snowfall” …. you can not prove that the bent or warped ice layers comprising said glacier ice was not the result of the un-even depositing of the snowfall.
You all need to “stay-on-subject” ……. And the subject of the above published commentary is, to wit:
Ice is the “crystal” form of H2O ………… and crystals do not easily bend, twist or warp.
Try bending a hunk of diamond, …… the crystal form of C (carbon).
Samuel C Cogar:
You said
I pointed out that your statement is wrong explaining
You now say
It seems you are as consistent as ralfellis and – like him – you don’t admit when you are shown to be plain wrong but pretend you did not say what you did.
Richard
ralfellis
February 20, 2016 at 12:39 pm
Samuel C Cogar
February 20, 2016 at 6:34 am
Yes you can get differential compaction of layers of rocks, too, but surely you are not imagining ice under pressure NOT responding plastically and NOT flowing away from the pressure. Your mention of diamonds is a good departure for understanding the phenomenon of folding and extending of large sheets of matter under pressure and directional forces. I don’t suppose I could convince you that although an ice cube and a diamond are brittle to short term stresses adequate to break them, diamonds are surprisingly quite elastic. If you drop a diamond on a hard surface (stone tile floor) it bounces like a super rubber ball. If you drop a small box full, they will bound and rebound until they are from one end the room to the other. This means it is capable of being distorted by the impact and rebounds by flexing back to its shape.
If you had a diamond layer like a glacier you would be surprised that it would bend and flex. Scale and time matter in the behavior of materials. Anyone who has made taffy (toffee? do people still pull taffy these days?) will remember that you can stretch the rope of taffy easily while you are pulling it. However, if you give it a yank, it snaps square across the “rope” like it was made out of glass. After it is worked, you can bend it, but if you strike it a blow with hammer it shatters into shards! Ice and rock behave in these ways depending on time and scale.
A priori reasoning is the kind your smart teenager uses on you because they lack empirical experience. It isn’t a very good tool to rely on with most things you want to understand. Vehemently arguing using this tool with experienced knowledgeable people is …well… juvenile.
@ richardscourtney – February 20, 2016 at 11:47 am
Sure you did, Richard S, you sure did point out my statement was wrong.
Now Richard, …. maybe you would be so kind as to point out to me just how in ell it is possible for the “calving” of glaciers to occur …… and/or just how in ell it is possible for the sea-ice to break-off and float away from its grounding point …. when said ice will “bend, twist or warp” in response to a sufficient sustained force.
Richard, how’s come that “calving” glacier ice just doesn’t “bend, twist or warp” downward when it reaches the shoreline and continue its flowing into the deep ocean water?
HA, is not the “calving” of glaciers proof-positive that …… your above quoted statement is wrong?
(I can play the “game” by your out-of-context-rules … if that is what turns your crank)
Cheers
Samuel C Cogar:
You say to me
There is no need for me to repeat information merely because you have refused to read it.
Please read the item I have repeatedly linked concerning creep.
Your diamond example summarises your ignorance. According to you, because diamonds can creep they cannot be cut! Therefore, please read the post by Gary Pearse which told you e.g.
Those two items have already explained these matters which you don’t understand so please read them and try to understand them.
Also, I suggest you do a search to learn how ‘work hardening’ occurs by crystal entanglement.
Richard
@ richardscourtney February 21, 2016 at 5:36 am
Richard, this was excerpted from your cited hyperlink concerning “creep”, to wit:
—————————–
Yup, high temperature and an increase in length ….. sure sounds like normal glacier movement to me ….. as a result of the force of gravity acing upon the ice.
Richardscourtney, I really don’t think that your miseducation in/of the Physical Sciences qualifies you for rendering judgement on the extent of my ignorance in/of the science of the natural world.
And “according to me”, ….. HUH, … Richard?
Obfuscate much and often, …. do you Richard? A “PP” CYA is better than no CYA, …. Right?
By the way, I shure would like to see a picture of one of them thar “creepy” diamonds.
Are all the diamonds that DeBeers employs recover from deep deep deep deep underground the “creepy” elongated (increased in length) type?
And Richard, which direction was the Late Wisconsin Glacier “creeping” when its mile-high mass was situate over what is now New York City and Long Island?
Samuel C Cogar :
Stop clutching at worthless straws!
“Generally” does NOT mean “uniquely”. Creep can and does occur at all temperatures but is accelerated at “high” temperatures.
Importantly, for water ice “high temperature” means any temperature above -33°C (water ice becomes liquid at 0°C).
Now, for your benefit, return to the link and try to learn from it because you are making a fool of yourself with your silly posts.
Richard
Richard, I accept defeat due to your greater science intelligence ……. even though I am fairly certain that I was awarded my AB (Teaching) Degrees in both Biological and Physical Science (1962) long time before you were ever “potty” trained ….. so best you cease with your “smoke-blowing” science mimicry in your silly attempt to impress me with your self-perceived nurtured beliefs in/of the science of the natural world around you.
Claiming that the same physical forces responsible for the creation of the crystal form of carbon (diamond) ….. are the same physical forces that are responsible for the malformation (lengthening “creep”) of the crystal form of carbon (diamond) ….. is a highly questionable claim to say the least.
But whatta I know, …. I was never educated in the neo-sciences that are being taught in the public schools during the past 30 years.
Richard, the extent of one’s nurtured knowledge of his/her environment …. is prerequisite to ….. the extent that him/her is capable of being nurtured with the mental attributes of common sense thinking, logical reasoning and/or intelligent deductions.
And both of the aforementioned “nurtured mental attributes” are highly dependent upon one’s nurtured mental ability of “association “triggered” recall of stored memory data/info”.
NO association “triggered” recall = NO thinking, reasoning or deducing of the subject matter being discussed.
Samuel C Cogar:
OK, so you are saying that you are yet another example of ‘those who can’t teach’. That explains much.
And your statements say my involvement in material science research was clearly much more and three decades longer than yours, but so what? Penis length does not demonstrate which if either of us is right.
I have cited and linked to explanations of reality and evidence which you have tried to refute with your mistaken beliefs. I provide you with the following explanation in one final attempt to get you to understand the reality which your mistaken beliefs are rejecting.
Metals and glacial water ice obtain their ductilities from their polycrystaline structures. They consists of ‘grains’ which are microcrystals that form a 3-dimensional ‘jigsaw puzzle’.
Glaciers form by consolidation of ice crystals that fall (as snowflakes) on glacier surface. The crystals settle in random orientations. When they consolidate they form ‘grains’ with random crystal orientation.
Ductility in metals and in glacial ice is provided by movement of crystal dislocations which provide work hardening when they entangle. Additional ductility is provided to glacial ice by a layer of liquid water on grain surfaces (this strange property of water ice is why ice is slippery).
The above should enable onlookers to search for all the information you are denying (but I doubt you will). Key search words; creep, crystal, dislocations, polycrystaline, ductility.
Richard
richardscourtney said:
Richard, my teaching ability is not in question, ….. but what is in serious question is your “reading comprehension” abilities … which is a direct result of you limited education in/of the earth sciences. And your “involvement in material science research” does not compensate for said “lack of education”.
richardscourtney also said:
Sure you did, Richard, sure you did. …. But just what the hell does any of your “cited and linked explanations of reality and evidence” have to do with, to wit:
The following quoted text was excerpted from the above published commentary about a scientific study that was conducted specifically for the purpose as defined in the following first (1st) sentence of the first (1st) paragraph, to wit:
So, I ask you again, Richard, just what the hell does any of your posted commentary have to do with the growth and/or break-up of the Ross Ice Shelf ….. or the “calving” or “sliding” of Antarctica glaciers during any part of the past 30,000 years? And the answer is, ….. “NOT A DAMN THING”.
1500 BC was when the Minoan Warm Period was so very warm and deliciously wonderful. This was thanks to the super warming that went on before that time. I swear, these ‘scientists’ complaining about it being slightly warmer than the Little ICE Age want us to be in another Ice Age.
As a note; I was under the impression that we were in an ice age now.
From the warmest wikipedia:
How did life survive prior to 2.6 million years ago when there were no ice sheets?
(or maybe there was no life at all till 2.6 million years ago — need to get the Southern Baptists on that one)
~ Mark
There has been an ice-shelf here on and off for the past 33.6 million years.
The sea floor will have gouges in it and ice-rafted debris from most of the 50 advances and retreats of the shelf that have occurred over that time period.
There were ice sheets prior to 2.6 mill years ago, they were just much smaller. Greenland is very prone to keeping ice sheets, as the underlying topography is bowl-shaped, which stops the ice sheet flowing away, and prevents the Atlantic from warming its base.
http://i.livescience.com/images/i/000/056/407/i02/Greenland3.jpg
@MarkStoval:
Proper usage is as you stated. We ARE presently in an Ice Age, but having an interglacial warm period.
Common usage is to call the glacial periods an ice age, but they are properly called a glacial period.
I compromise, for clarity, and use the phrase “ice age glacial” for the glacial period, and “interglacial” or sometimes “warm interglacial” for the warm periods in our present ice age.
Attempting to correct others generally results in rejection and resentment. The penalty for being more accurate and correct.
Perhaps we need to consult the Pope. Oh Wait – they are still coming to grips with those nasty theories of Galileo!
My questions are why was there so much ice to begin with? What were the CO2 levels before, during and after this? What caused the breakup of the ice.. was it the campfires of the early humans?
According to the article, the burrows were left by ginormous icebergs being pushed north. Where did these things go before they melted? Did they cause a permanent La Niña in the tropical Pacific for a millennia causing misery for what humans were on the earth at the time?
So many unanswered questions..
The most logical answer is that the climate is more stable in an ice age confuguration, cooled by the huge albedo of the ice sheets. The long duration of ice ages, in comparison to the short interglacials, demonstrates this proposal very well.
So to produce an interglacial, Gaia needs to disrupt the dominance of the high albedo caused by ice-sheets. It does this by trapping so much CO2 that concentrations plummet and there is a wholesale die-back of plant life. This lack of plant-life causes desertification and dust storms, which settles on the ice and reduces the albedo of the ice sheets, and allows rapid warming. And yes, it just so happens that every interglacial is preceded by thousands of years of dust storms.
If true, this rather suggests that albedo is the primary control knob of glaciation and of climate. Ice sheet albedo controls long term ice age glaciation, while Willis’ cloud albedo feedback controls short term climate. While Co2 does not very much, bar holding a noose around the neck of all plant-life and therefore all animal life too.
https://www.academia.edu/20051643/Modulation_of_Ice_Ages_via_Precession_and_Dust-Albedo_Feedbacks
.
No matter how broadly you define glacial periods, the five or so episodes of glaciation since the Proterozoic occupy far less earth time than warmer periods. Seemingly warm is more stable.
Surely it is reasonable to suspect that whatever forces drive these macro scale changes play at least some role in the micro scale glacial/interglacial fibrillations that seem to ocurred in all macro glacial periods.
Ralph, I like your dust on ice hypothesis for helping to trigger the end of each glacial period. Do you have any favorite hypotheses for what factors end the interglacial periods?
Also, with increasing CO2 causing increasing greening of the globe, this could potentially have an albedo effect by allowing absorption of more sunlight as compared to less vegetation. Any thoughts on this aspect of a greening earth?
>>what factors end the interglacial periods?
The standard reason is that the Great Summer turns into a Great Winter, and NH insolation reduces by up to 90 wm2. Which is a large reduction, and allows the ice sheets to regrow. So you end up with 5,000 years of warming, and then straight back into cooling, because the cool climate is the most stable mode in normal circumstances.
The only time the interglacial is extended, is when the Great Winter is very weak (ie, with low eccentricity). The climate appears to be bi-stable, and the transition between the warm and cool modes is quite finely balanced. So if there is no Great Winter, and if the obliquity remains high, then the interglacial can continue almost indefinitely, as it has during the Holocene.
Will our present increased CO2 maintain the Holocene for longer? Probably. But as you say the CO2 albedo forcing will be greater than the Co2 radiation forcing. We happen to be in a very low eccentricity period, with very weak precessional Great Summers and Winters, and the next decisive cool period is not due for another 100 kyrs or more. So with any luck we should evade any ice age for the forceable future. And even when the next Great Winter does come along, this new albedo theory means we can easily geo-engineer our way around it. All we need to do is spray the northern ice sheets with soot every spring, and presto – no ice age.
So the alarmists were right, carbon is the key to maintaining a stable climate – but carbon in the form of graphite, not CO2.
R
Such interesting paper – I wonder how important was the very sudden increase in eustatic sealevel, from 120 metres below the present, in only a few thousand years. I visualise the sea covering the grounded ice – and freezing solid immediately.
AndyE, your thoughts about the sea covering the grounded ice assumes one detail which was not mentioned. This paper only says that the ice was deep enough to be on the sea floor out to the end of the continental shelf. This does not say how high the ice was. It might have been a glacial sheet which rose far above sea level.
“In western Antarctica, the Ross Sea is characterized by a continental shelf that extends nearly 1,000 miles from the coast and is as much as 3,500 feet deep.”
So the glacial sea level, 120 meters below the present, when it rose it only rose by about 10% of the depth of the ice. That is not an obviously overwhelming amount, but the increased flotation forces were undoubtedly impressive over such a huge area.
” This does not say how high the ice was. It might have been a glacial sheet which rose far above sea level.”
Indeed. Glacier ice has a density of c. 0.9, so it will rest on the seabottom as long as the depth of water at the glacier front is less than about 90% of the ice thickness.
“The really big breakup began around 3000 B.C.,”
==============================
Amazing. How was this possible without man-made CO2? The IPCC has already stated that climate doesn’t change naturally, so this must have been due to human activity somewhere. Were the Egyptians riding around in fossil fuel chariots? Were to pyramids coal powered? What was the cause? Surely climate doesn’t change naturally. It can’t be possible.
The ice breakup was triggered by CO2 from Egyptians burning torches while they dug tombs. We know that beyond a shadow of a doubt because we have found both the tombs and the torches. You can’t argue with SCIENCE.
Actually, it was caused by Moses. What do you think he was doing up on the mountain for those 40 days? Eating chicken soup? He was creating CO2! Then God handed him the Tablets!
Of course, the Rice University researchers avoid speaking about the elephant in room;
“What caused the warming, 3500 to 1500 years ago , that caused these ice sheets to collapse?”
Was it the burning of / use of gasoline, oil and natural gas?
Was it the abundance of automobiles, in particular just way too many SUVs?
Too many diesel trucks?
Maybe the burning of too much wood for heating and cooking?
Maybe the Egyptian Pyramids were too tall, which shifted micro region wind patterns in Egypt, and due to the “butterfly affect,” caused the global warming.
Presumably, the rise in CO2 caused this warming.
Fine.
What caused the rise in CO2??
Yes folks, the science is settled.
JohnT
I appreciate your take on this, very much.
I have inveighed against the Ancient Greeks keeping their hypocausts [Or were they the Roman equivalents?] warm with heavy oil-fired heating.
And [because I hugely appreciate the work of our Mods.] I do sometimes help them with sargastic cuidance.
Auto
Yes – more than a fistful of salt in this one!
The analogy to Larsen B is faulty. There, there are two true glaciers the feed the ice shelf. With its mass removed, the glaciers were able to flow much faster to the sea. The Andrill program found that the massive grounded portion of Ross is anchored by many intruding sea mounts. It can still creep, but does not behave like a glacier. It also found that the Ross grounding line has been stationary for about 4000-5000 years. So the subsequent loss of this portion of the ice shelf did not affect the grounded ice flow, newly confirming the ANDRILL anchoring. Another piece of evidence that Ross is not some CAGW SLR tipping point.
The present ice-front in the Ross Sea is pinned by Ross Island and Roosevelt Island and ANDRILL 1B showed that it has never receded south of this line for more than a million years.
Nothing unexpected here. We know from ice cores in Antarctica and Greenland that 10,000 years ago the Pleistocene Ice Age came to an abrupt, screeching halt. Temperatures went from full glacial to warming at incredible rates (20 F in 40-100 years in Greenland) and thousands of feet of the huge ice sheets all over the world melted suddenly. So it should be no surprise that Antarctica participated in this dramatic global event–it’s what one would expect.
However, in this story, there are some subtle inferences–I get the impression that we are supposed to infer that this could happen today, The climate swings we have seen in the past several thousand years are miniscule compared to incredibly sudden end of the last Ice Age 10,000 years ago. There is a fundamental flaw in Anderson’s view. He says “the ice shelf acts as a brake to dozens of Antarctic ice streams and outlet glaciers, and ice flowing into the ocean from those would contribute to global sea level rise. “The ice shelf slows the flow of grounded ice from the glaciers, and as we saw after the Larsen B breakup, once you pull the stopper out of the bottle, the glaciers move much faster, in some cases about 10 times faster,” The notion that ice shelves act as ‘ice dams holding back the upper part of glaciers’ so if they are removed, the glacier essentially slides into the sea, is total nonsense, propagated by the people who are pushing ‘unstoppable catastrophic collapse of the West Antarctic Ice Sheet. Every glaciologist knows that glacier termini are not controlled by ‘ice dams’ at their margin, but by the mass balance (ratio of accumulation of new ice and snow to melting and calving) of the entire glacier.
So the subtle inference that what happened 10,000 could happen today by reduction in shelf ice is total nonsense. The underlying notion of the collapse pushers is that reduction of ice shelves today will ‘unstopper’ the West Antarctic Ice Sheet and cause it to collapse. That is an incredibly flawed notion to any glaciologist who understands glacial dynamics.
Every day we hear about ‘accelerating melting of the Antarctic Ice Sheet’ despite the fact that satellite and surface temperature measurements show that the East Antarctic Ice Sheet is growing, not shrinking and Antarctic temperatures have actually been cooling since about 2000. Satellite and surface temperature records and sea surface temperatures show that both the East Antarctic Ice Sheet and the West Antarctic Ice Sheet are cooling, not warming, invalidating the Steig et al. and news media assertion of warming of all of Antarctica. Satellite and surface temperature measurements of the southern polar area show no warming over the past 37 years. The Southern Ocean around Antarctica has been getting sharply colder since 2006.
Surface temperatures at 13 stations on or near the Antarctic Peninsula have been sharply cooling since 2000, including the Larson ice shelf. I’ve documented all of this with satellite and surface data and will be publishing it soon.
I appreciate what you are saying Dr Easterbrook, but the paper reflects the same dynamics of the shelves that I have read about in numerous publications. This is not an outlier.
What I want to know is, where are all the glaciologists who hold the same view as you? Shame on them for not coming forward if this is poor science.
Classic back handed compliment, insult framed as negative support.
‘argumentum ad verecundiam’ also called ‘argument from authority’ uses the appeal to authority as if that alone rebuts the science.
It does not.
Dr. Easterbrook introduced observations and research, not models and suppositions. Perhaps you missed that little sentence,
A result that only surprises the alarmists trying to build and base their careers and credibility on Antarctic ice disasters. Steig et al. papers have a hard time surviving honest scientific review.
Consider your own attempt at ‘argumentum ad verecundiam’.
What science did you offer in contrast to Dr. Easterbrook’s? None.
The paper described above has a number of issues that require further discussion. One of which is how did the sea level rise since the beginning of this inter glacial affect the allegedly ‘grounded’ sea ice shelve?
Another is how does rapid sea ice shelf replacement in literally blinks of geological time affect their estimates?
This little statement if the foundation for all of their claims!
“…compound-specific radiocarbon dating measurement took several weeks to perform, and more than a dozen were needed for the study…”
From this little it of observation couple with one older borehole and perhaps some newer tests in 2015, these researchers have revealed the sea ice breakup secrets for over 100,000 square miles of Ross Sea?
Where are the validations? Where did they establish scientific certainty for their ‘model’? Or are we left to assume that alarmists do not need proof? Just like all of those outlier “…same dynamics of the shelves that I have read about in numerous publications…” research published results; proof is not in the science, only belief for the devout?
cerescokid did have one point: “where are all the glaciologists….”. We see a lot of scientific carp and legions of experts who must know better do not tend to come forward. Especially the tree ring, glaciologist, ocean pH and the like types.
Right on Dr. Easterbrook.
Take for instance the following link from CNRS http://www.insu.cnrs.fr/node/5663
in which they conveniently forget to mention that the largest tabular iceberg measured off Scott Island
was observed by the USS Glacier during the international polar year November 12, 1956 and it measured 31,000 km2 is 335 km x 97 km, compared to Ross Shelf B-15 which was only 295 km by 37 km in 2000.
One suspects that, before the satellite era, other, probably larger and smaller must have gone their way, un-witnessed.
“One suspects that, before the satellite era, other, probably larger and smaller must have gone their way, un-witnessed.”
They certainly did, and not always un-witnessed. There were actually more ships in the Southern Ocean during the nineteenth century when sailing ships used the strong western winds at high latitudes. They recorded at least two huge outbreaks of icebergs in 1853-58 and the 1890’s. These were probably caused by large unrecorded shelf breakups. One berg sighted off Cape Horn in the nineties was roughly triangular with each side of the triangle 40 miles long.
Thank you Dr. Easterbrook for a welcome sense of reality. I’m looking forward to reading your paper when it is published.
Interesting that is took some 10,000 years before the Ross Ice Shelf responded to the Holocene interglacial warming.
Part of the reason for this, is that interglacial warming is precipitated by the precession of the equinox, combined with orbital eccentricity, which causes long term seasonal changes (by long term, I mean summer and winter seasons that last 5,000 years each). And just like normal annual seasons, these long term season effect only one hemisphere.
The warming that initiated the current interglacial warming was precipitated 50% by precession (which was warming the northern hemisphere and cooling the southern hemisphere), and 50% by obliquity (which was warming both polar regions). The result is that the northern hemisphere warmed first, while Antarctica could only follow its lead.
And I imagine that the Ross Ice Shelf can be quite stable, as long as it is grounded and the sea cannot warm its base. In that grounded mode it is like the insulated base of Greenland. And they also report the Ross ice sheet stuck on some low ridges, which stabilised it. This is again similar to the Greenland sheet, which is firmly stuck upon and surrounded by substantial hills, which have maintained a ‘fossilised’ ice sheet in a position it could not be in otherwise.
R
The key bit to remember is number of summer days in the north.
We have an interglacial when the N.H. points at the sun during the perigee of greatest eccentricity. It adds several days more melt from a longer summer.
The incease in solar heat from more W/m^2 is helpful, but the key bit is getting it for more days, and less days of winter to add ice. Less added, more leaving, the mass balance line shifts and albedo feedback begins to take a toll. Then more rain and less snow increases the melt rate.
Actually the main factor governing the size of the Antarctic icecap is the amount of ice in the northern hemisphere. When the ice in the north melts the higher sea level causes the ice-edge in the Atarctic to retreat since for purely mechanical strength reasons ice is unstable in deeper water than c. 500 meters. This equates to a glacier “freeboard” of about 50 meters and at that point the ice start breaking apart spontaneously.
.
However this decrease at the edges is partially countered by more precipitation inland during interglacials, causing the ice in inland East Antarctica to actually grow thicker during interglacials. There have been many recent studies of changes in ice-levels at various nunataks in Antarctica and it seems that Antarctica has actually contributed at most about 10% of the 120-130 m sea-level rise since 20,000 BP.
Remember that hardly any ice ever melts in Antarctica (except on the northern Peninsula). It either calves into the ocean along the edges or sublimates (very slowly) inland.
The key element is not the number of days, but the increased intensity of the summer insolation. During the precessional summer (a Great Summer) the insolation in the NH can rise by 90 wm2, in comparison to the Great Winter. And that is a large change. The same happens in the SH during their Great Summer, but because there are no great landmasses in the south the warming effect is not so noticable.
E.M.Smith
We have an interglacial when the N.H. points at the sun during the perigee of greatest eccentricity. It adds several days more melt from a longer summer.
Thanks, a very helpful explanation of current Milankovich pacing of interglacials.
How and why in your view did the MPR (mid Pleistocene revolution) happen 1 million years ago, when interglacial frequency changed from obliquity paced (41 kyrs) to eccentricity (100 kyrs)?
ralfellis
The result is that the northern hemisphere warmed first, while Antarctica could only follow its lead.
Wrong. Antarctica started warming 20+ kya, the NH continued cooling till ~14 kya at the start of the BA. Only then did NH warming begin. See the paper by Weaver et al.:
http://home.sandiego.edu/~sgray/MARS350/deglaciation.pdf
I was wondering if this break-up could have been causal of the Black Sea flood, which is commonly dated to 8000 years ago, rather than 5000 years ago. It also depends on how much of this Ross Shelf break up was previously water-displacing and how much had been above sea level.
In short, probably not connected. But I have always wondered if there was an ice-melt event that precipitated the Bosphorus breach, or whether sea levels gradually reached the highest point on the coastal plain and flowed in with the smallest of trickles.
Take a look at
8 to 7 kya was a hugh rate of rise. Ice was melting in lots of places and oceans rising fast.
There was an abrupt cooling 8,200 years ago that only lasted a couple hundred years, but is very evident in ice cores. Might be interesting to speculate about the rapid warming coming out of that cool period.
I read – might even have, still, in a pile – a book [1980s??] that explicitly put he Black Sea flooding back about 7,500 years ago.
AND the origin of most of the ‘Noah-type’ stories, of many cultures . . .
I still wonder how much there was in he book
Auto – no /sarc here. But not sure how much belief, either.
Interesting, for sure.
But the rapid warming actually began some 20,000 years BP, to wit:
One side effect of more sea ice would be a cooler ocean, over time, which would cool the atmosphere over time, which would (?) expand glaciers,, including perhaps in the Antarctic.
That cooling would occur not by heat loss but by dilution and mixing. The oceans gained a great deal more water.
Roger – that also made me think of the impact of all that ice moving “north”. I wonder how long the “Cool Blob” lasted and how it affected the weather. Maybe an inverse model of the RRR and the Warm Blob could be used. Grant Money for future Climatologists. (I know, the ocean volume is large, but we are now talking about local climate models, right?)
Only half kidding. Someone may have the math to say or the gift of writing grant apps.
What if the massive iceberg breaking off and then moving to lower latitudes was the cause of the sharp cooling around 8200 years ago? That could have lead to instant air conditioning as surface winds cooled, and then moved inland to cool continents. When the main mass of the sea ice finally melted, then the warming trend reasserted itself.
I enjoyed the report because it involved new techniques and information (for me). The data produced came from field research – a real plus. Beyond that I find it sad that scholars seemingly have to say that they applied techniques never used before (cutting edge?), that it was very demanding, took 50 whole days in a ship, took two weeks to analyze some samples, and that they had 12 whole samples to test. Publish or perish and grant-dependency must necessitate such verbiage that draws the attention of the media but adds nothing to the science.
Why the title to this post? Title should be, Ross Sea Breakup 2000 years following the Holocene Temperature Maximum 5000 years ago, and not after “last ice age”, hell, anything that has happened the last 10-12 k years could be framed in that statement. As Trump would say, big fn deal. The Holocene temperature maximum had nothing to do with “elevated” CO2, so why the concern?
Rob,
We proved ‘gravity waves’ after the last Ice Age.
Hey – you are bang on dead centre!
Magic – and plus lots.
Auto.
Don, looking forward to your paper. The stopper out of the bottle motif was of course prominent in the May 2014 Science magazine studies of the Thwaites Glacier by Joughin et al. and Rignot et al. Hope your paper is published soon and comments on those studies. For the curious, I challenged the media hype in this post: http://www.globalwarming.org/2014/05/23/the-west-antarctic-ice-sheet-is-doomed-but-dont-sell-the-beach-house/
The ‘stopper’ concept is prominent in the Rigot and Joughin papers and in comments to the news media. Rigot is an electrical engineer, not a glaciologist, which may explain his strange views. Both papers totally ignore readily available satellite and surface temperature measurements showing that all of
Antarctica, including the West Antarctic Ice Sheet, has been cooling since 2000. Both papers also ignore the BedMap ice thickness and depth below sea level maps that clearly indicate that the ice thickness is greater than the depth below sea level of the glacier base–i.e., when the ice thickness exceeds the depth below sea level, the ice won’t float. They also ignore isostatic rebound, which would amount to several thousand feet if you remove the present 10,000 feet of ice.
The only way a marine ice-sheet can become dynamically unstable is if the water depth at the ice-front is >90% of the ice thickness and the bedrock under the glacier sinks monotonously upglacier at a rate than the thickness of the glacier increases.
Alarmists also love to talk about how seawater will penetrate below the glaciers and melt and/or lubricate them. This is however physically impossible since the pressure underneath a glacier resting on the seabottom is necessarily higher than the water pressure in front. Otherwise the glacier wouldn´t be resting on the bottom. Water does not move against a pressure gradient.
It is instructive to have a look at the glacial landforms called “eskers” formed during the retreat of the ice near the end of the last ice-age. These are long sinuous ridges of sand and gravel, often stretching for hundreds of miles. They were caused by subglacial rivers debouching underneath the icecaps. Once the water came out into the sea it lost speed and dropped the sediment it had been carrying along. How could those subglacial rivers run fast enough to carry uncounted trillions of tons of sand and gravel out into the sea if the sea was actually moving in under the ice at the same time?
What is also a little unusual about the Ross Ice-shelf is that at least the top third of the glacier that it is composed of, has really been formed in place by thousands of years of snow falling on it. It takes 30 years to 75 years of snow accumulating on top and being compressed from above before the snow turns into ice. The Ross is not just fed by up-stream glacial flow, but also by snow falling on it (and no melting in the summer).
http://blogs.ei.columbia.edu/wp-content/uploads/2015/11/F005_SIR_20151116_124907_3_QCB1.png
Don, also, the ice “upstream” from the “stoppers” is at higher elevation and would continue to push the coastal ice outward. It would move easily over the grounding offshore because it is already buoyed up partially by the seawater. Moreover, with winds and tides the pressure on the grounding portion would oscillate, ‘wiggling’ the ice over its grounding a bit more quickly. It the ice was truly stoppered, with a wall of rock, the ice would buckle up and flow over the stopper. I believe a proper engineering analysis of this type of behavior is doable.
Second, surely the rapid sea level rise during the meltback of the last glacial period had to be the mechanical cause of the Ross Ice Shelf break up. How could the shelf hold up against a 120m of sea level rise only to be massively broken apart by lesser mechanical forces a few thousand years later. I think I would look for evidence that the breakup was earlier than the authors think.
Interesting picture. The “original” ice seems to be pretty heavily crevassed, so I imagine it has come down the Beardmore glacier or some other valley glacier in the Transantarctic Mountains.
Incidentally that thick snow cover would seem to preclude melt/refreeze wedging of crevasses which was apparently the main mechanism in the Larsen breakup (not that there is ever much melting on the Ross shelf).
TTY – Yes at last someone explian that completely.
Don Easterbrook – Also bravo to give a lot of info for all these alarmists that knew nothing about the reality of glaciers.
“The results of those tests, as well as the beryllium tests, provided conclusive evidence that the main breakup of the ice shelf occurred between 5,000 and 3,500 years ago.”
Since tidal effects are known to be important for the breakup om ice-shelves it is worth noting that a major peak in tidal force occurred 4239 BP, which would also fit in nicely with the major cooling and drying of global climate known as “the 4.2 KA event”.
This Antarctic ice sheet collapse is of course well known already for a long time. It triggered the Bolling-Allerod NH warming spike which was followed, in a series of connected events oceanographically driven by inter hemispheric bipolar seesawing, by the Younger Dryas and eventually the Holocene.
Holocene inception began about 22 kYa (thousand years ago) with Antarctica starting warming. The NH at the same time slightly cooled. However at about 14 kYa the “Bolling-Allerod” (BA) happened, i.e. the NH abruptly warmed, as evidenced by Greenland cores. This was initiated by the Antarctic ice sheet collapse – we’ll return to this. This caused a reciprocal pause and slight reversal in the (already long established) gradual Antarctic warming – the bipolar seesaw. In opposition to the BA, Antarctica went into cooling – the much studied “Antarctic reversal”. At the time of the BA there was a sharp rise in global sea level – 20 meters in 500 years. Weaver et al 2003 (link below) show that this was caused by a collapse of the gradually warming Antarctic ice sheet. The pulse of fresh meltwater from Antarctica had the effect of speeding up the AMOC and the gulf stream in the NH, bringing rapid warming to the NH and the BA.
A basic oceanographic feature comparing the NH with the SH in the palaeo record is more fluctuation and instability in the NH and more stable, gradual changes in the SH. The nonlinear instability of the AMOC is the root of this. It is driven by the salinity positive feedback in the AMOC. Also, there is a clear signature of interhemispheric bipolar seesawing, whereby when the NH moves in one direction, the SH moves in another.
The bipolar seesaw continued – the BA warming was shortlived. Down in the deep ocean, interactions between cold bottom water formed in the Antarctic and Arctic caused – about a thousand years later – an abrupt stoppage of the AMOC and the gulf stream. This ended the BA. In fact the cuplrit was Antarctic Intermediate water (AAIW) – see again Weaver et al. With the interruption of the gulf stream the NH went cold again – the Younger Dryas. In response – by now you get the picture – the Antarctic did the opposite and turned to gradual warming. After about 1000 years of NH cold with no gulf stream, the effect of the Antarctic collapse subsided allowing the AMOC and the gulf stream to resume. By now the gradual Antarctic warming was more or less complete, around 12 kYa. Warming at in the NH was completed at the same time by abrupt warming which terminated the YD. This marked the final end of the last glacial and the Beginning of the Holocene.
http://rockbox.rutgers.edu/~jdwright/GlobalChange/Weaveretal_Science_2007.pdf
http://epic.awi.de/15280/1/Lam2004a.pdf
http://onlinelibrary.wiley.com/doi/10.1029/97GL02658/pdf
Here’s a better link for Weaver et al 2003:
http://science.sciencemag.org/content/299/5613/1709.short
Better yet (no paywall)
http://home.sandiego.edu/~sgray/MARS350/deglaciation.pdf
Actually it would make sense for some of the MWP-1A to have a NH location, since it had the effect of promptly kickstarting the AMOC and thence the BA (sorry – don’t know what else to call it).
The above is reply to tty – wrong place.
No. MWP-1A was larger than the entire ice loss from Antarctica from LGM up to the present day, so wherever it came from it wasn’t mainly Antarctica.
Incidentally the term “Bölling” is questionable since the interstadial recorded at Bölling Sö is not really the ‘traditional’ “Bölling” but only the later part of it.
tty
Thanks. When I read the above article more closely – the Ross Sea ice collapse occured only 5000-3500 years ago, I realised that the much earlier pre-Holocene collapse triggering the BA-YD, which I referred to, is separate and irrelevant to the above article.
I thought that BA is just a name for the spike before the YD.
BTW if it took a whole 1500 years for ice to clear out of the Ross Sea that sounds gradual, not catastrophic.