Arctic Flushing and Interglacial Melt Pulses

In several other threads I’ve looked at lunar influence on ocean depth and currents and speculated that the cycles in lunar tidal forces might account for the periodic swings in our long term weather, ( Sometimes called ‘climate’, which IMHO, is not correct. The California Redwood Forest is still a redwood forest [and the California northern pines are still in a boreal forest] even if the State has a 900 year long drought. That, BTW, is a real example.) This notion of a lunar metronome on our weather and ‘climate cycles’ was picked up by Clive Best and expanded when he mixed it in with his ideas on drivers for interglacial timing. Well, what goes around comes around… Clive got me thinking about how this might reflect in the Arctic Melt, that got me looking at the ‘melt pulses’. That, then landed me on some Arctic maps. One thing leads to another, and now we have a new speculation. My speculation is just this:

During the deep glaciations, Arctic Ice goes very deep, and the ocean level drops. So much so that the Bering Strait closes, the Canadian islands and all their channels close, and the Arctic Ocean reduces to a small puddle in the middle (compared to what we have today), almost completely isolated from the warming ocean currents. As that reverses, as the ice melts some and water rises; those processes reverse at specific depths and there is a new “flushing step” as a current can now re-establish and flow under newly ungrounded ice. At particularly high tide intervals, when lunar tidal force is greatest, will be the moment when that (barely) grounded ice first lifts off the bottom, or when that (barely) closed channel first opens. Once that melt starts in a warming trend, it continues in a ‘pulse’ as the thinned bottom is no longer closed.

I’d further speculate that in a cooling cycle, the Arctic stays liquid until a very modest tide cycle, then it has time to thicken just enough to NOT lift off or melt in the next, colder, heavy tides cycle. Essentially, at the marginal state in a warming or cooling cycle, the lunar tidal metronome will kick off the exact moment of the pulse. It will flip the switch on the hysteresis of ocean currents and ice grounding.

Some links on Lunar Tidal influences:

http://www.pnas.org/content/97/8/3814.full

The foundation for a lot of the ‘The Moon Did It’ speculation / thesis.

http://clivebest.com/blog/ Does the Moon trigger interglacials?

Clive Best does an interesting look at things here.

https://tallbloke.wordpress.com/2014/01/10/clive-best-does-the-moon-trigger-interglacials/

Links to the Clive Best article, but has interesting commentary.

http://wattsupwiththat.com/2014/01/14/do-super-tides-kick-start-interglacials/

The ‘pick up’ at WUWT.

Then a bunch of my articles in retrospective:

https://chiefio.wordpress.com/2014/01/24/the-moons-orbit-is-wrong-it-can-change-a-lot-and-tides-will-too/

https://chiefio.wordpress.com/2014/02/16/tides-vectors-scalars-arctic-flushing-and-resonance/

https://chiefio.wordpress.com/2014/01/25/a-remarkable-lunar-paper-and-numbers-on-major-standstill/

https://chiefio.wordpress.com/2014/01/23/of-interstadials-a-fondness-of-beetles-and-warmer-than-now/

https://chiefio.wordpress.com/2013/01/24/why-weather-has-a-60-year-lunar-beat/

Essentially points out that the 18.x year cycle lines up with the same ‘face’ of the Earth on an ‘about 55’ year basis and that this is close to the ‘about 60’ year cycle of PDO et. al.

https://chiefio.wordpress.com/2013/01/04/lunar-cycles-more-than-one/

A sort of descriptive catalog of some of the lunar cycles as an attempt to put some order into the cycle-mania.

https://chiefio.wordpress.com/2011/11/03/lunar-resonance-and-taurid-storms/

Since “orbital resonance” dominates orbital cycles, and the moon orbits, it can also have correlations with other orbital stuff. Perhaps even cometary remnants that whack into us periodically.

https://chiefio.wordpress.com/2012/12/15/d-o-ride-my-see-saw-mr-bond/

A look at periodic failures of the Thermohaline Circulation (and how Florida gets summery weather then ;-) along with where we are in the cycle. Next ‘Little Ice Age’ you want to be in Florida, not England. This is periodic, not random, and not driven by atmospheric gasses.

https://chiefio.wordpress.com/2010/12/22/drakes-passage/

An ‘unfinished bit’ would be integrating circulation changes with depth at the Southern Ocean where I think Drake Passage is key.

Some evidence

Here is a nice image of the surface currents of the Arctic:

Beaufort Gyre

From: http://nsidc.org/cryosphere/seaice/processes/circulation.html

First thing to notice is that the Arctic Ocean circulates. ( I can hear someone saying “Well Duh.” Remember that it is important to notice all things, even the obvious. Like bilateral symmetry in a fish – there is a story behind that example…)

So why does circulation matter? Two reasons. First off, you can see warm water entering on the Pacific and Atlantic connections and cold water leaving via Canada and Greenland / Fram Strait. During a Glacial, that circulation stops. With a mile of ice over Canada, that exit is closed. With ocean levels 100 meters lower, folks can walk from Russia to Alaska. (Well, they do it sometimes now over the ice, but it will be easier and less seasonal during a Glacial ;-)

So look again. No Bering Sea warm intrusion. No Canadian cold drain. No Beaufort Gyre when the ice is deep, since there will be no wind driven circulation under the ice. The Asian current toward the Bering Sea will end. The entire Asian warm river drain into the Arctic likely freezes up and doesn’t happen – which raises the interesting question of where does it go then? But that is for another day. Like asking where the Alaskan rivers drain then, or are they just glaciers at that point?

In short, what is left is just the North Atlantic Drift (aka Gulf Stream for Americans) warming a small patch near Europe and some cold water near Greenland. As Scotland was under ice in the last Glacial, even that North Atlantic Drift circulation likely didn’t get very far north.

But is there more to this? What about layers of depth?

A deeper look

A bit further down, we see that the North Atlantic Drift skirts along the Asian side as is washes under the Arctic Ice. There it mixes with warm fresh water from Asian rivers and helps keep that side more melted. The Canadian side is colder, and that IMHO likely explains why the Glacial Shield tends to build up over Canada and northern USA. Less melt means more snow and precipitation needs to pile up and spread as glacial ice.

Arctic Ocean Circulation at depth

Image from: http://www.windows2universe.org/earth/polar/arctic_currents.html

Who state it is from Jack Cook from Woods Hole Oceanographic Institute.

We can also see that at the deeper level, a bit of cold current is flowing at the bottom layers of the Bering Straight. Block that off, and block off the Labrador Current and those various Canadian circulations, all that cold water has to leave via the place where the North Atlantic Drift is trying to enter. All in the context of a lower ocean level, so less total channel volume. That will tend to block warm intrusion and drive the process toward freeze-up. Ever less circulation and flushing in the Beaufort Gyer area, stunting of the warm intrusion, more cold and ice blocking flow out via Greenland / Iceland.

Now look even deeper…

Arctic bathymetry: Notice the depths

Arctic Ocean Bathymetry

Arctic Ocean Bathymetry

Arctic Bathymetry very large original

Most of the Arctic Ocean is a shallow Europe / Asian margin or shallow Canadian shelf. When ocean levels drop, that becomes land. Ice covered land, but still, not ocean and without circulation. The “drop” in ocean depth is somewhere over 100 meters. That is the first 4 or 5 blue color bands. Essentially, the Arctic Ocean reduces to that dark pit in the center and the narrow dark channel leading into it past Greenland. The ‘North Atlantic Drift’ (or whatever is left of it) and the cold exit water must churn past each other in whatever little space remains under the ice there. IMHO, not much is going to happen in terms of ice melt in the Arctic under those conditions. Thank God for Sea Level Rise! (And pray that Iceland spreading does not close that trench or we will not exit the next Glacial after closure, IMHO.)

Now, play it backwards

At some point in the melt / deglaciation process, ocean levels rise just enough that warm water CAN start to circulate under that ice in those light blue areas. How deep is that? About 100 meters. At some point ocean levels rise just enough that warm water can start to enter via the Bering Strait. How deep is that? About 50 meters (more on that in a minute). At those times, an exceptional tide can be the trigger that lifts that ‘grounded ice’ just enough to unground it and start melting from below. Starting the bending / tidal surge / melt / ocean rise cycle and letting it run to the point of the next shelf of depth.

Bering Strait depths

Bering Strait depths

It looks like those depths are in meters, as the Wiki says: “The Bering Strait is approximately 82 kilometres (51 mi; 44 nmi) wide at its narrowest point, with depth varying between 98 feet (30 m) and 160 feet (49 m)” and that reflects the numbers in the image.

So at about 50 m of ocean drop, the strait no longer exists at all, but above that point, ever more Pacific Ocean (relatively) warm surface waters can go north, and ever more salt dense cold Arctic water can drain out into the deeper Oceans. In essence, the Thermohaline Circulation as we know it today can form, as can the Transpolar Drift and some of that Asian cold water draining out to the oceans and letting more of the Northern Drift into the Arctic through an ever increasing Fram Strait in the Norwegian Greenland sea. Prior to that point, the Bering Sea will have gone from ice to melt. That depth is likely the point where the melt begins, but then the opening of the Strait lets it continue on into the Arctic Ocean basin.

Melt Pulses. Notice the depth.

Post Glacial Sea Level Rise

There are two “knees” in this chart that are of particular interest. One is at “pulse 1A” at about 110 m of depth. At that point, the Asian shelf glaciers of the Arctic starts to float and the North Atlantic Drift can scour a much larger flatter part of the Arctic Ocean margin. It is no longer constrained to nibbling at a tiny channel edge at the narrow deep bits of what is now the Fram Strait.

At about 80 and 60 meters we get the opening of the Canadian drainage (and melt of the ice over it) along with the opening of the Bering Sea and eventually the Bering Straight (and that ice melting). Once a new level of depth opens a new bottom water level, then melt from below can proceed until all the overlaying ice is gone. This process would be hindered by heavy ice above, but enhanced when there was a larger than typical tidal surge / flushing event. Once the melt of the ice above begins, the event proceeds to a new stability point at shallower bottom depth. As we reach modernity, there isn’t much more ice left to raise any sea level, and the whole process stops in that long flattish area at the end. Essentially, the Arctic contribution to sea level rise is over and the process stops.

It would be more complete to have an actual ocean bottom (global) model with computation of the water level at each point, and couple it all to a tidal model based on the long term 1800 year tidal surges; but until I get a grant to do that, someone else will need to ‘run with the idea’. Footnotes of attribution always appreciated ;-)

I would also assert that the time of greatest “risk” of a re-freeze is when ice is accumulating in the Antarctic. Why? That lowers sea level just enough that a low tidal surge ‘moment’ can let the Arctic start into a lowering / freezing feedback cycle. It can’t do it on its own (as it is melting from below due to warm water and stirred by winds). It needs an external event to get it into the refreeze cycle. That, IMHO, is a build up of ice. But where? The Polar See Saw would have that be Antarctica, then with a couple of years of low tidal flushing the Arctic ice cap starts to build a lot of ‘multi year ice’ and ocean level drop can start the feedback loop. The next half of the polar see saw builds more Arctic ice. When the next polar see saw or high tidal surge cycle arrives, it is too late to cause the melt, and we proceed directly to a long glacial period.

In short, the Millankovitch Cycle is the long slow driver of conditions, but it is the lunar tidal flushing cycle perhaps with a Polar see saw ‘kicker’ that throws the switch at each end of an interglacial. It provides the hysteresis that leads to switching.

How deep does the ice go during Arctic Glacials?

One “confounder” for this thesis is just how deep Arctic glacial ice went. It’s all well and good to say that the Bering Strait opens at 50 m of ocean depth, but what if the ice is grounded 1000 m down on each side of it? I’ve glossed over that “issue”, but it can easily explain the error bands on things like 60 m where the melt pulse starts vs 50 m for the strait depth. (or perhaps that 60 m was really the 100 m of bottom depth point, but with grounded ice needing 40 m more ‘lift’ to get off the shelf). All that is ‘in the details’ that would need a lot of work to sort out. Here’s an interesting link, though, to get the thoughts moving on that point:

http://www.academia.edu/4175556/Glacial_geomorphology_of_the_Central_Arctic_Ocean_the_Chukchi_Borderland_and_the_Lomonosov_Ridge

Abstract:

The last decade of geophysical seafloor mapping in the Arctic Ocean from nuclear sub-marines and icebreakers reveals a wide variety of glaciogenic geomorphic features at waterdepths reaching 1000m. These findings provide new and intriguing insights into the Quatern-ary glacial history of the Northern Hemisphere. Here we integrate multi- and single beambathymetric data, chirp sonar profiles and sidescan images from the Chukchi Borderlandand Lomonosov Ridge to perform a comparative morphological seafloor study. This invest-igation aims to elucidate the nature and provenance of ice masses that impacted the ArcticOcean sea floor during the Quaternary. Mapped glaciogenic bedforms include iceberg keelscours, most abundant at water depths shallower than ~350–400m, flutes and megascaleglacial lineations extending as deep as ~1000m below the present sea level, small drumlin-like features and morainic ridges and grounding-zone wedges. The combination of thesefeatures indicates that very large glacial ice masses extended into the central Arctic Oceanfrom surrounding North American and Eurasian ice sheets several times during the Quaternary.Ice shelves occupied large parts of the Arctic Ocean during glacial maxima and ice rises wereformed over the Chukchi Borderland and portions of the Lomonosov Ridge.

So don’t fret the 1’s to 10’s of meters. We’ve got 1000 m of ice below the present surface and who knows how much above to confound the small bits.

But what this says to me is that clearly the 100 m level around that Asian margin was grounded ice, the Bering Strait was closed and under ice, the Canadian drainage was an ice dam, and the Arctic Ocean was that deep puddle under the middle, with, at most, a very narrow channel in the depths connecting it to a cold north Atlantic, and not much circulation.

But once those ice dams get lifted and start to melt, perhaps under exceptional tides and with extra insolation / longer summers (as per Milankovitch), then the cycle of melt can proceed to a new stability point at the next blocked depth.

In Conclusion

This needs a lot more to tie it all together. At this stage, it is just a speculation. Actual basin depths, volumes, etc. would need to be modeled. Actual (expected) ice volumes, depths, floatation ocean depths, etc. too. Then the lunar cycles matched to onset times (if available to that 1800 year precision) and the whole model set in motion to see if it had better explanatory power or predictive skill.

With that said: I do think that too little attention has been paid to the ocean bottom profile interaction with ocean depths and ice volumes. Adding in a lunar ‘kicker’ to get thing started would explain some exact timings, should they match, and at a minimum the bottom profile effects need to be added to any lunar flushing / interglacial thesis. Just I don’t have the time to do it right now. But at least I can point at it ;-)

Maybe Clive can do it. (hint hint ;-)

Subscribe to feed

About E.M.Smith

A technical managerial sort interested in things from Stonehenge to computer science. My present "hot buttons' are the mythology of Climate Change and ancient metrology; but things change...
This entry was posted in Earth Sciences and tagged , , , , , . Bookmark the permalink.

24 Responses to Arctic Flushing and Interglacial Melt Pulses

  1. p.g.sharrow says:

    Your post is about something that I have considered for some time. I lived for a time in coastal Alaska and observed that Glacial Ice is not created by cold, rather, HEAVY SNOWS, often, maybe even some cold rain. As long as the surface temperature is near freezing the stuff accumulates and turns to cement like ICE. Your Bathymetric Arctic view above points to the fact that “Warm” wet flows up from the Atlantic create heavy snow deposits where they encounter the Cold from the west and east land masses. Ice representations of the Arctic Ocean, demonstrate warm currents from the Atlantic into the Arctic and cold water and ice out the Bering Straits. With the Bering straits blocked the warming from the Atlantic would be reduced. I would posit that the Canadian Shield and the Canadian Rockies build snow cover due to atmospheric moisture and cold intrusions, such as this winter, to increase Albedo and slow melt to begin persistent northern continental coverage with a “warm” semi open Arctic Ocean. The Continental Ice did not flow down from the north, rather it built in place. The buildup caused the sea level to lower as well as lower the snow level. The snow level would lower as well as the persistent Northern ice fields summit rise to make them permanent glacials. This warmed evaporating Arctic contributes to the snow falls and sucks Warm Atlantic water until circulation is stopped by lowered sea levels and freeze over happens. This long term Moon tides changes would have a great deal to do with the strength of circulations due to the slosh of the oceans in their basins pumping water past the continents. pg

  2. E.M.Smith says:

    @PG: Interesting idea. I ran into a paper that found the Artic Ocean was warmer during the glacial than now, but didn’t link it as I didn’t see a connection… I’ll see if I can find it again.

  3. Good post; I enjoyed it. Thanks!

    There is another confounding effect: The weight of that ice changes the shape and contours of ocean bottom, continental shelves, and the continents themselves. This effect tends to take thousands of years to be established, and to rebound after the weight is gone. It will also tend to reshape the flows, the depths, and thus the surfaces and points in time wherein ice lifts off the bottom or is otherwise tidally affected.

    Iceland’s expansion is an issue, but for a long time in the future — just as the volcanic expansion of the occasional island in Central America took millions of years to close off the north-south gap and form an isthmus, which was evidently the major reshaper of flows a few million years ago and the reason we now are in an ice age.

    Of course, Iceland could surprise us with major volcanic activity.

    ===|==============/ Keith DeHavelle

  4. philjourdan says:

    If PG is correct, that kind of blows the Great Lakes creation theory. Or more work has to be done on it. I have read about the Glacial Moraines that fit nicely with the theory of moving glaciers. But that could be because they were looking for them.

    One thing about your narrative that is the key seems to be the Antarctic. Once that one gets cranked up, it is the catalyst for the NH glaciation and ice age.

    The warmer Arctic sea would also play into the glaciers in the north. Regardless of whether they moved or were created in place, they would need precipitation.

  5. p.g.sharrow says:

    @Philjourdan; the glacial flows that gouged and built the features of the northeast were caused by ice movements after the Ice Mountains were formed and then flowed under gravity to the melting edges. Ice is not ridged but flows like cold tar or taffy. Much as the Greenland ice sheet behaves. Snow piles up on the mound and extrudes at the margins. Some of the Great Lakes features are Ice gouged and some are just valleys that land movements have drowned. In Prince William Sound, Alaska the ice gouged fiords over 600 feet deep in the continental shelf that was the above sea level of that time. So the Sound is now much shallower then the fiords that enter it. pg

  6. Terry Jay says:

    pg sharrow is on to something. Moderately warm and wet winters and moderately cool summers, with high snowfall and less-than-complete melting.. You could see that on Alaska’s Kenai Peninsula a few years ago, where heavy winter snow patches were still visible in patches in the Kenai mountains past the end of August.. by then, those mountain patches would be having overnight freezing, and still be there going into the coming winter.

    True High Arctic snowfall is really fairly low. If memory serves, total precip on Alaska’s North Slope is under 6 inches. The wind can blow it into deep drifts, or nearly blow another area clean of snow. Deep cold does not produce a lot of snow.

    Put another way, I am a bit sceptical that only cold is needed for glaciation.

  7. p.g.sharrow says:

    @EMSmith; This intermediate warm layer could expand and be exposed to the surface if less salty surface waters recede due to evaporation and are not replaced by surface runoff from the land. Ice forms from the surface then down as the cold above sucks energy from the water. Thaw takes place from the bottom up as the warmth from below eats at the cold ice above. Warm air does little to melt ice, a warm rain does speed the melt, cold rains not so much. just not enough free BTUs.
    Keith DeHavelle brings up the point of Iceland somewhat blocking the Fram. Interesting observation. I wonder if Iceland’s age is similar to the age of this series of IceAges? The concept that the sealing of the Central American connection of the oceans is the cause seems weak to me. pg

  8. @p.g.sharrow: Weak it may seem, but it is well-supported. When I first proposed it a decade or so ago, based upon learning the age of that closure and noting the tremendous trenches carved by the previous flow of the Gulf Stream from the Atlantic to the Gulf to the Pacific, I’d thought I had come up with something knew. I eventually found that mine was not the first such observation, and now it is becoming pretty well-accepted. The same thing happened with my realization more than a decade ago that the K-T impact was fairly closely aligned with the magma plume under India (at the time), and thus the vulcanism and meteor damage were related by virtue of transmitted shock waves through the globe.

    I was not the first, I learned, to surmise this.

    The paper below actually attacks the Central-America/ice age notion — but does so in such a weak way that they actually inadvertently support it. They’re basically saying “It’s all coincidence!” But they reluctantly list evidence that they struggle to interpret in some other way each time:
    http://onlinelibrary.wiley.com/doi/10.1029/2007PA001574/abstract
    (Click the tab for the full article.)

    Imagine if they took the same skeptical approach to a global warming paper!

    ===|==============/ Keith DeHavelle

  9. p.g.sharrow says:

    @Keith DeHavelle
    Further consideration of the Isthmus closure would lead me to believe that, in fact, the opening would reduce the gulf stream and thereby reduce Arctic heating. Tidal drag would pull gulf heated waters into the Pacific, reduce Hurricane strength in the Caribbean and Gulf, as well as the strength of storms in the northwest Atlantic. Meanwhile greatly increase storms in the eastern Pacific off of Mexico and California.
    The dispersal of grazers would most likely take place during Ice Ages when the continental shelves were exposed as open plains. pg

  10. J Martin says:

    KDH mentioned glacial rebound. In some places in Scandinavia, glacial rebound is up to 4mm per year, a stggering amount. Over the 10,000+ years of the Holocene that could amount to nearly 40m. Perhaps glacial rebound of what is currently seabed may play a role in reducing current flows and making seabed more accessible to ice build up, and in addition, the effect of increaing depth caused by glacial build up could be a factor in bringing about the end of glaciation.

  11. @p.g.sharrow, who wrote:

    @Keith DeHavelle
    Further consideration of the Isthmus closure would lead me to believe that, in fact, the opening would reduce the gulf stream and thereby reduce Arctic heating. Tidal drag would pull gulf heated waters into the Pacific, reduce Hurricane strength in the Caribbean and Gulf, as well as the strength of storms in the northwest Atlantic. Meanwhile greatly increase storms in the eastern Pacific off of Mexico and California.
    The dispersal of grazers would most likely take place during Ice Ages when the continental shelves were exposed as open plains. pg

    I think you’ve got it right, here. A whole lot of heat transport was happening through the Gulf, laterally into the Pacific. Perhaps it was not as much “heat transport” then, as the temperature gradient at virtually the same latitude would not have been as large. I don’t know how much effect this flow into the southbound side of the Alaskan Polar Current and the Humbolt would have had.

    You’d think that the Arctic being colder then, without the Gulf Stream feeding heat into it, should have caused rather than prevented an ice age. But clearly, as the Isthmus gradually closed off over a few million years, the global temperature (as recorded by currently reported proxies) dropped steadily and began an oscillation that resulted in the 40,000-year and then the 100,000 year ice age cycling we’re in now. Perhaps warming the Arctic, since it also means necessarily cooling the lower latitudes in return, redistributed energy enough to push things the wrong way.

    The Milankovitch orbital cycles have always been there, but they had been of little consequence prior to this point. Something else changed, and the major closure of the circulation around South America (look at the trenches in Google Maps at the north and south!) seems likely to have played a major role. The timing, at least, is perfect.

    But I am always looking for more and better evidence, one way or the other.

    ===|==============/ Keith DeHavelle

  12. tom0mason says:

    Paul Homewood has some comment on the back of Joe Bastardi piece over at Patriot Post, regarding NOAA forecasts for Arctic ice this summer.
    http://notalotofpeopleknowthat.wordpress.com/2014/05/05/major-arctic-sea-ice-story-lurking-but-is-anyone-watching/

  13. p.g.sharrow says:

    It w3ould appear that oldest part of “Iceland” is about 20 million years old on the Greenland side and has been slowly moving east and closing off the Fram:
    http://en.wikipedia.org/wiki/Iceland_plume
    Good article on Iceland geology. the hot spot originated about 65 million years ago under Greenland during the opening of the Atlantic and has been moving east as the North American plate slides west. Em.. the head waters of the Atlantic river may have been in central Greenland.? ;-)
    Hmmm I seem to remember that 65 million years ago has some other significance! pg

  14. David A says:

    Re J Martin says: 5 May 2014 at 8:47 pm
    ================================================
    Your post on vertical surface movements stirred a speculative thought. There appears to be a bit of a teeter-totter between the land and oceans; with the land sinking as the ocean surface rises. How much of this happens along plate boundaries? We tend to think of plate tectonics as being the result of lateral forces. Yet is seams that this teeter-totter movement would likely create or relieve vertical forces as well, and at the same time increase or decrease the tension required to release lateral stress.

  15. clivebest says:

    This is a great article Chiefio and thanks also for the plugs! You highlight how the bathymetry of the Arctic Ocean causes it to get isolated from circulation. This is new to me and what is better is that this could also be a possible cause of the polar oscillation effect, since expanding ice sheets over Antarctica (with precession) will reduce global sea levels and close the Bering Straights in the Arctic. This then leads to delayed cooling in the Arctic. The metronome governing the north south cooling cycle is the 23000 year change in precession.

    What breaks the cycle ?

    We propose that this is due to a strong increase in regular Tidal flushing of the Arctic coincident with the Milankovitch 100,000y eccentricity cycle. The reason for this increase in lunar tidal forces is because the moon is subject to exactly the same solar system planetary re-alignments that perturb the earth’s orbit. This must also change the eccentricity of the moon’s orbit around the earth because the bodies have different mass and angular momentum must be conserved. The net result of an increased lunar ellipticity is that the distance of closest approach of the moon to the earth reduces and tidal forces increase rapidly as 1/R^3. This triggers massive spring tides, which combined with higher insolation trigger interglacials.

    I have been able to use the French INPOP10 ephemeris to calculate lunar positions and tides back 1000 years, but so far I can’t find a general ephemeris going back a million years. Instead there are just solutions for the earth’s orbital parameters but not the moon. I have an idea how to derive this though – so thanks for reminder !

  16. tomwys says:

    Check out Ewing & Donn for their theory of the Ice Ages and perhaps Google search “Alex Pope Climate” for another version that contrasts accumulating Glaciers with an Open Arctic!

  17. p.g.sharrow says:

    @clivebest; That concept that the Antarctic acts as the depository for the ice that reduces the oceans level, to reduce circulation in the Arctic is not one examined much. Everyone focuses on the north in their thinking.The North South dance of ice accumulation is well known and the water depth of of much of the northern oceans connection the rest of the seas is quite shallow. Tidal pumping of water into the Atlantic has to go somewhere. Reduced circulation through the Arctic would reduce the warm Gulf stream flow through the Fram and the North Atlantic. Reduced or stopped flow out the north connections might slow or even reverse the flow around the tip of South America. Vastly changing the weather around Antarctica. This North South dance is known to exist on Mars so this is a solar system caused thing and not oceanic circulation caused phenomena. The oceans would have a great deal to do with the outcome, maybe even the duration. Lots of moving parts here. pg

  18. rob r says:

    A couple of things.

    Isostatic impacts are not just restricted to post-glacial rebound. Some of the areas scoured by ice at the depth you mention may have been uplifted on pro-glacial bulges when the scouring occurred. So these features may have been created in water that is shallower than a mere 100 to 120 m of glacial sea level depression would indicate.

    Quite a bit is known about surface conditions in the Arctic Ocean from sediment cores. The fact that there were ice sheets nearby on land does not of itself indicate that the Arctic Ocean was permanently choked with ice. Sediment cores indicate long periods of seasonally ice-free conditions at high latitude. You can tell from the 14C dated planktonic foraminiferal fauna in the finely layered sediment (fauna that requires extensive open water).

    I am generally not a great fan of computer modelling exercises but the growth of ice sheets over NW Europe and Nth America has been modelled frequently. To grow the vast ice sheets you need sources of moisture for precipitation. It is not possible to source all the moisture from the Pacific. The modellers have difficulty growing ice sheets if as a condition the Arctic ocean and adjacent seas are under permanent sea ice. They need open (but rather cold) water to generate evaporation that is sufficient to supply the water precipitated as snow over the ice sheets. They then need open water to maintain the ice sheets.

    Closure of the Bering Strait during glacial periods is well known. This area is usually depicted as open tundra rather than under glacial ice. Like most of Siberia it seems that this area, along with large parts of Alaska, were too dry to allow for the development of thick continental ice sheets. Thick ice either required sufficient precipitation, or considerable altitude, so around the Siberian and Alaskan arctic margins the ranges were glaciated and the lowlands were generally not glaciated.

  19. p.g.sharrow says:

    @rob R ; you are so correct! The creation of the Ice Mountains requires large amounts of snow, not colder temperatures. The areas of the Ice Mountains is plenty cold in winter already. In summer those areas would stay cooler due to the ice. As the mountains grew in height they would approach the permanent snow level for that latitude. Warn open oceans is the requirement for heavy snows as well as the right air currents, such as last winter, for heavy accumulations of snow. I agree, an open Arctic would be an enhancing effect on the creation of the Ice Mountains of the north hemisphere. Once created they would be a permanent feature such as the Greenland Ice Cap is. Only an extraordinary warm spell could begin their demise. Such as the posited 20F increase that ended the last Ice Age. Mr Smith has posited that we may already be in the beginning of the next ice cycle due to solar output. pg

  20. clivebest says:

    There’s a new paper in Journal of Geophysical Research: Oceans !
    The evolution of tides and tidal dissipation over the past 21,000 years, S.-B. Wilmes* andJ. A. M. Green

    The 120m sea-level drop during the Last Glacial Maximum (LGM; 18–22 kyr BP) had a profound impact on the global tides and lead to an increased tidal dissipation rate, especially in the North Atlantic. Here, we present new simulations of the evolution of the global tides from the LGM to present for the dominating diurnal and semidiurnal constituents. The simulations are undertaken in time slices spanning 500 to 1000 years. Due to uncertainties in the location of the grounding line of the Antarctic ice sheets during the last glacial, simulations are carried out for two different grounding line scenarios. Our results replicate previously reported enhancements in dissipation and amplitudes of the semidiurnal tide during LGM and subsequent deglaciation, and they provide a detailed picture of the large global changes in M2 tidal dynamics occurring over the deglaciation period. We show that Antarctic ice dynamics and the associated grounding line location have a large influence on global semidiurnal tides, whereas the diurnal tides mainly experience regional changes and are not impacted by grounding line shifts in Antarctica.

  21. Pingback: Lunar Months, Tides; for Vukcevic | Musings from the Chiefio

  22. Very interesting. But I don’t think the numbers add up to the Arctic becoming a big puddle. As you stated, the Bearing Sea and Barents Sea became land masses when the sea level drops 120 meters, but a significant portion of the Arctic is deeper than the 1000 meters where the effects of ice has been noted. The Fram Straits are 2.6km deep and currently 500 km wide. Even with the drop in sea level of 120 meters and 1000 meters of ice, there would still be a large opening where water would flow. The Canada Basin is approx 3000 meters and the Markarov Basin is approx 4000 meters and parts of the Amundsen Basin are 4500 meters deep. I would expect the polar ice would float like a cork up and down over the deeper portions of the Arctic because of the tidal forces.

    But that doesn’t mean I disagree with you; what you’re describing is what seems to be happening in the Antarctic, where the glaciers are retreating from the ocean. The glacial meltwater is eating away at the undersides of the glaciers so when the tides come in, the formerly completely grounded ice sheets are floating at high tides, allowing the ocean water further inland, further eroding the undersides of the glaciers, allowing them to float more, etc. Same idea, opposite polarity.

    Reply: The idea is just that there is less flushing and less floating ice, more grounded ice, during glacials; and that as the interglacial happens, it swaps the other way (more floating, less grounded). That, then, differential tidal flushing for different lunar tidal extremes would have different levels of impact. Oh, and as of the last decade or so the ANTARCTIC is expanding, not ‘retreating from the ocean’. Highest extent on record right now IIRC… Yes, there is a polar-sea-saw but right now it has Arctic low and ANTArctic high ice levels.They do often move in opposition, though, so watch for it. It is the notion that CO2 has effect at either pole that is rather broken. (What effect it has is on Stratospheric temps, where it cools, so the downwelling Polar Vortex can get colder, not warmer… but the UV Solar changes swamp that anyway. -E.M.Smith)

  23. Pingback: Arctic Sea Ice Factors | Science Matters

Comments are closed.