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Friday, July 4, 2008

Arctic melting - no problem???

In the popular press I've recently read the opinion that after the Arctic ice melts, it will be business as usual. I think someone is missing the obvious. As has been noted by many scientists, when the Arctic becomes open ocean, instead of reflecting 90% of the light falling on it, as it does now, due to the albedo of the snow which covers the  ice, it will absorb 90%. The Arctic ocean becomes a giant solar collector.  There are a number of obvious possible consequences.

Shifting of the Earth's Circulation Cells
At present in the northern hemisphere there are three atmospheric circulation cells. The polar cell circulates air from the poles to approximately 60 degrees north, the Hadley cell from the equator to about 30 degree north and the Ferrel cell fits between these two like a gear cog. Sometimes all three of these cells are referred to as Hadley cells.  In the (equatorial)  Hadley cell, air rises at the equator powered by the heating of the earth's surface, the release of latent heat from condensing water vapor and the fact that water vapour weighs about 3/5 as much as air*. The air descends at about 30 degrees North and flows back to the equator along the surface of the earth. The Coriolis effect skews the air flow to the right.

*At the same temperature and pressure, there are the same number of molecules of any gas in a given volume.  You can, therefore, use the molecular weight of a gas to work out the relative density of a gas.  Air is a mixture of O2 and N2 with molecular weights of 32 and 28 so roughly speaking, air has a relative density of 30.  Water vapor has a molecular weight of 18 so water vapor is 18/30 = 3/5 = 60% as dense as air.

In the polar cell, air falls at the poles as it radiates heat into space,  cools and contracts. It then flows south over the tundra and taiga and rises at 60 degrees north. The Ferrel cell fits between the Equatorial Hadley cell and the Polar Hadley cell.   Jet streams occur at the locations where these circulation cells meet. The strength of the Jet streams depends on the rotational speed of the two circulation cells where they meet.  The importance of this will become apparent later.

 

These zones shift north and south from summer to winter as solar radiation shifts due to the tilt of the earth. Now consider this.

At present, most of the radiation falling on the Arctic is reflected by the ice and snow cover and therefore the Arctic ocean doesn't warm up much. The air over the north pole radiates heat to space, cools and sinks, flowing  south over the tundra and taiga. This cold air keeps the permafrost frozen. As soon as the Arctic ocean is open water, it will absorb most of the energy falling on it. The sun angle is shallow above the arctic circle, but the sun in the summer shines 24 hours a day. A lot of energy falls on the Arctic ocean. In fact at the Summer Solstice, using a little simple trig, and considering the difference in day length, it would appear that the amount of sun energy falling on a square meter at the North Pole is about 80% of the energy falling on a square meter at the Tropic of Cancer, directly under the sun.

Because of this heat input, there is a reasonable chance that as the Arctic  ocean becomes ice free and  warms up it will become a zone of rising air. The air will be replaced by air flowing along the ground from the south. Evaporation is much stronger than sublimation so the air above the ice free ocean will contain increased water vapor. Three effects then kick in. Water vapor weighs 3/5 as much as air so the mix of air and increased water vapor is lighter than dryer air.  As the air with its load of water vapor from the open, warmer arctic ocean rises, it cools by expansion and reaches a point where the air is saturated (dew point). Above this, the water vapor condenses, releasing latent heat, and accelerating the  air upwards.  In addition, the water vapor shrinks 1600 times as it condenses, pulling more air after it. The water  falls out of the air, leaving much of its heat behind in the air. Heat that remains in the falling precipitation is returned to the sea.  All this encourages the rise of air above the Arctic ocean.

This effect might be most noticeable in the fall* when the land begins to cool off quickly while the Arctic ocean is releasing the heat accumulated over the summer. Because solar radiation is only absorbed in the top few tens of cm of land but is absorbed through meters of water, land heats up and cools down rapidly, water more slowly. In the fall, you could well have a typical off-shore wind such as is experienced in the evening in many parts of the world except this offshore wind would be experienced over an extended period in the fall until the Arctic ocean is coated in ice and evaporation is replaced by sublimation. Incidentally, much latent heat is produced when water freezes and this could extend the period of reversed polar winds.

*Go to the NSIDC web site and look at the report for October 2012 about half way down.  There they report rising air over open water and winds from the south.

The Arctic ocean is surrounded by land and the air flowing off the surrounding land is skewed to the right by Coriolis.  This will result in a typical northern hemisphere counterclockwise circulation over the Arctic ocean.  As this wind warms over the open ocean and picks up water vapour, Arctic storms are likely.  The land around the ocean is radiating heat, cooling the air in contact with it and increasing the density gradient of air over land in comparison with air over water.  This density difference along with the release of latent heat is what determines the strength of storms.  This counter clockwise air flow if strong enough and long enough will likely reverse the Beaufort gyre with some very interesting results.

If the Arctic Hadley cell does reverse it is any one's guess what will happen.  Initially, as the air cools off over the Tundra and sinks, you might have a 4 Hadley cell system developing as falling air over the tundra flows north and south.  Later as the Arctic ocean gains power by more open water occurring ever earlier, the whole Polar Hadley Cell might reverse.  This would  suck masses of heat from mid latitudes towards the Arctic, causing the permafrost to melt even faster than it is doing at present and give off masses of methane.  Essentially we would have a two cell system in the northern hemisphere.

Aug31, 2012
Have a look at the appendix at the end of this blog. After seeing the melt this month I had another think about two and four cells.

Aug28, 2012
Have a look at this site.   Go down on the right and choose Aug or Sept 2012 from the archives.  Note how much ice is showing along the coast of the Arctic ocean.  Now go back to previous years for the same month.  Much less ice is visible along the coast.  This is consistent with the theory that the Arctic Hadley cell will reverse and is already showing signs of doing so (weakening of the Polar Jet Stream).  What is apparently happening is that cold air is being drawn from the rapidly cooling continent and is causing freezing along the shore.  Of course, when ice freezes it gives up 80cal per gram of water frozen which warms the air (toward zero degrees).  The air then flows over open water gaining a little more heat and some water vapor.  All this despite the fact that 2012 is a new record for ice melt over all.  Air which is warmer and more humid than surrounding contental air is likely to rise as described elsewhere in this blog, dragging more air after it.

December 2012
Here is an interesting paragraph from the November NSIDC (National Snow and Ice Data Center) web site:

November air temperatures at the 925 hPa level (approximately 3,000 feet) were above average over most of the Arctic Ocean. Notably, temperatures in the Barents and Kara seas were up to 6 degrees Celsius (11 degrees Fahrenheit) higher than average. This reflects in part the lingering open water in the regions, allowing strong upward transfers of heat from the ocean to the atmosphere. Unusually strong winds from the south contributed to the warmth and also helped keep the region ice free.

Here we have rising air over open water with air being sucked along the ground from the South.  Locally and in miniature a reversal of the Polar Hadley Cell.  Flash forward to a year when the Arctic ocean is ice free in, say, the end of June.  Over July, August and half of September there is no ice to cool surface waters or to reflect solar radiation and no melting fresh water ice to dilute surface waters and maintain the Halocline.  Storms and even normal winds mix the layers and heat is absorbed for these two and a half months into the ocean.

Note that sea water has a peculiar characteristic.  For fresh water, it reaches its maximum density at 4 degrees C and then become lighter as it cools further.  This stops convection and hence the sinking of cold water and it's replacement by deeper warmer water.  In a fresh water lake, in the absence of wind to mix surface layers, this peculiarity of fresh water retards the flow of heat to the atmosphere and hence the rate of freezing.  

In the Sea over salinities of 24.7 ppt this is not so.  Sea water continues to become more dense until it reaches the freezing point at which time, fresh water ice is frozen out of the sea water.  More important for this discussion, as it becomes denser, it sinks and warmer deeper water replaces it at the surface. If sufficient mixing occurs early in the summer, when fall arrives, the whole depth of the Arctic ocean with it's huge reserves of heat will be available to come to the surface and keep the ice from refreezing.  This looks to be another one of these tipping points that will cause a paradigm shift in the whole Arctic ice regime.



Unstable climate
Another effect could be what climatologist have taken to calling 'flickering'. That is, the bouncing back and forth of the climate between two states*. One mechanism for this is fairly well established. If Greenland melts rapidly, it will freshen the surface water in high latitudes. When this water freezes, it won't leave behind water which is dense enough to sink and power the Gulf Stream. England and Northern Europe can expect to have some very cold winters despite world wide global warming. The very cold winters would lead to more freezing and the enhancing of the Gulf Stream.  Hence the climate changing back and forth between a warm and a cold phase.  Flickering would be much more devastating to Northern Hemisphere agriculture than a permanent shift to a new climate regime. If you never know what to expect from year to year it is hard to produce good crops.

*Get a copy of Allen's book "A two kilometre time machine"

I haven't been able to find any information on the delay between the push (freezing of sea water producing cold salty water) and the move (Gulf stream flowing) but if it had a delay of, say, 6 months we would have a fast flowing
Gulf Stream in the summer and a weak one in the winter.  In other words, warm wet summers and nasty cold winters in the UK.

Another odd effect might kick in here.  When the Arctic ocean is completely ice covered, in order to make more ice, heat has to conduct through the ice into the colder air above. New ice is frozen to the bottom of the floating ice.   With really thick ice still covering the ocean at the beginning of the freezing period on Sept 15, not much new ice will be formed.  With an open ocean, there is no insulating cover and a lot of ice should form. Freezing sea water produces brine which flows downward and out of the Arctic ocean.  Water must come into the Arctic to replace this flow.  This may explain why the Gulf Stream seems to have shifted from turning toward Europe at about Newfoundland and seems to be now flowing through Fram Straight into the Arctic.

Melting of Greenland
Looking  at Greenland, such reversal of the polar Hadley cell would be most expected in the fall as the land rapidly cools but the Arctic ocean retains the heat gained over the summer. It would be a large scale off-shore wind such as one gets in the evenings all over the world. Over Greenland there are  Katabatic winds which occur because air in contact with ice cools, becomes more dense and flows down slope. This pulls in more air from its surroundings. You have a relatively warm ocean sending warm air up into high altitudes and this air being sucked towards Greenland to flow down to the ocean again. Such couplings are called Walker Cells.##  Because of the latent heat of condensing water vapour, this air is much warmer than previously at a given altitude. At more or less the same altitude that it cools to zero degrees by adiabatic cooling as it rises above the ocean, it will warm to zero degrees by adiabatic warming as it is katibatically sucked down over Greenland. Note that while sunshine is not a very effective melter of snow due to its albedo and a poor melter of deep ice due to the large amounts of heat needed to heat the ice over the penetration depth of the solar radiation to its melting point, warm winds, by contrast, are very effective. This is due to the concentration of energy on the very surface of the ice and due to the continual import of energy from far afield by the wind*. In addition as the air sinks, it warms by compression and this greater delta T can pass more energy to the ice$.

*Read chapter 42 of Jean Auel's book, Plains of passage. It is only a novel but Jean did her homework and is describing what generations of polar and glacier explorers have experienced when a foehn wind hits the ice.



##Note:  If you look at this picture of the pressure contours over the arctic, you see relatively high pressure (in red) over the area around Greenland.  Greenland itself has a local low pressure indicating that air is being drawn down by the ice.

$ Sept17,2012
The lapse rate for descending air (latent heat plays no part in descending air in contrast to rising air) is 9.8 degrees centigrade per thousand meters.  The Greenland ice sheet at its peak is a little over 3km above sea level.  A body of air flowing from the top to the bottom, if it started at zero degrees would be at 29.4 degrees when it reached the sea.  of course this doesn't happen since the warming air gives up it's heat to the ice as it flows down slope.

Reversal of the Polar Vortex
Putting together the above information, we see what powers the polar vortex.  As the Arctic air radiates heat into space, it sinks, sucking high altitude air toward the poles.  Coriolis effect skews this flow of air to the right so at high latitudes, on the surface of the earth there are North East winds (flowing towards the South West)    With more and more heat being absorbed by an ice free Arctic ocean and transmitted to the air, this circulation pattern should reverse.  This would be expected to bring a huge flux of warm air from the south which would exacerbate the effect and cause sudden extremely warmer conditions in the Arctic for the months in question. These will be South West winds (flowing toward the North East)

Clatrate Beak Down
The melting of clathrates is another likely effect. Clathrates are peculiar substances. They occur when water and certain gases are mixed under pressure. In our case, the clathrate of most interest is the one formed with methane. A peculiar property of methane clathrate is that with enough pressure, in the presence of methane, water can freeze at well above 0 degrees centigrade.    At zero degrees, clathrates will form at around 300 metres and at about 350m at the 2 to 4 degrees found in the deep ocean. A kg of methane clathrate can hold as much as 160l of methane*.  The source of the methane is both from the anaerobic breakdown of organic material which constantly rains down on the ocean bottom and from methane seeps from deep hydrocarbon, shale and coal deposits. Right on the surface of the ocean bottom, Carbon dioxide is  produced by aerobic bacteria using the  oxygen in the water. Oxygen is used up as it diffuses into the sediment and as little as a few centimeters below the ocean floor, in areas of high organic loading, methane is produced by anaerobic bacteria.  The methane combines with pore water forming a sort of clathrate permafrost.  The arctic ocean has been ice covered for at least 125,000 years since the Eemian interglacial and hence its temperature has probably been very stable for this time. It seems likely that on the bottom of the Arctic ocean, clathrates occur right up to their temperature-pressure boundary. A little warming will start to release the stored up methane.

Note.  Apparently at the end of the last ice age, when sea level rose 120m,  permafrost  existed off the coasts of the Arctic ocean and was covered as the ocean rose.  The continental shelf off Russia is the widest in the world and averages about 100m deep.  In late 2011, reports started to appear of massive evolutions of methane, especially above the extensive continental shelf off Siberia.  The suggestion is that this is the release of clathrates, stored up during the 125,000 years between the end of the Eemian interglacial and the start of the present Holocene interglacial. The Arctic ocean
 is said to be warming faster than any other ocean of the world.



* At STP (standard temperature and pressure)

Note: since the writing of this article, approximately 250 methane plumes have been observed rising from the bottom of the ocean in the vicinity of Spitsbergen



Note: December 2011.  This link describes a massive evolution of methane from the ocean floor in the Arctic.  At the same time, acidic water has been observed in the Bearing Strait and in some places off California.  This may be an early sign that we are entering the period of climate shift.  The acidic water is arguably   caused by methane release from the ocean floor.   The methane that remains dissolved in the water (as opposed to escaping to the atmosphere) combines with dissolved oxygen making Carbon dioxide and thus lowering the pH

Clatrates also occur in permafrost at similar depths. It seems most likely that if the Arctic ocean warms up, a great deal of the greenhouse gas, methane, will be released from the ocean bottom.  It seems likely also that if the permafrost of the tundra melts and warms up, a lot more methane will be released from permafrost clathrates. Methane is not the only problem. Over the past 11,000 years or so, since the continental ice sheets melted, layer upon layer of mosses, lichens and dwarf trees have accumulated in areas of permafrost making deep carbon rich peat deposits. In the summer only the top foot or two of the soil thaws and from there down is frozen organic soil. The organic layer, preserved by freezing, is very deep in high latitudes. All this is a huge store of Carbon which may start to be released by oxidation or anaerobic bacterial action if the permafrost melts. If water drains away due to holes melting in the permafrost, such areas which are now soggy boggs could dry out and burn if lit by lightning or  by careless people.

Methane is a very potent green house gas, some 30 times more effective than Carbon Dioxide. The only saving grace is that it fairly rapidly oxidizes into Carbon Dioxide. Some estimates are that the half life of Methane in the atmosphere is about 7 years. A big danger is that the sudden release of clathrates in the Arctic and the Tundra will come in such a sudden pulse that it will cause enough warming in the atmosphere and hence in other oceans to start the break down of their clathrates as well. Remember that clathrates exist on ocean bottoms right up to their pressure/depth contour. It only takes a degree of warming at the upper border of their existence to start the release.

Another disquieting effect then cuts in. At present in the high mountains of Europe and other countries, above a certain height there is permafrost. Above this level, the ice holds the loose rock in place. Recently, with global warming, the permafrost border has been rising. With the melting of the ice, more rock avalanches have been occurring. The same effect is likely on the continental slope. As the clathrate 'permafrost' breaks down, the sediment is loosened and disturbances such as earth tremors will be able to trigger avalanches. Under sea avalanches have the nasty habit of breaking under-sea cables, but of more importance, of causing localized but very severe tsunamis.


Striping of Oxygen from the Oceans
Another disquieting effect of methane release is related to what happens when you bubble a gas through a liquid. The surface of each bubble acts as a semi-permeable membrane. Gases diffuse across the surface of the bubble in proportion to the difference in their concentration on either side of the 'membrane'. In the case of a bubble of methane, the oxygen from the water diffuses into the bubble and is carried to the surface of the ocean. In other words, an extensive evolution of methane gas from the ocean bottom would scrub the oxygen out of the water. Methane which remains dissolved in the water reacts with the oxygen, depleting it and forming Carbon dioxide. Not only do you have a depletion of oxygen but also an acidification of the water from the Carbon dioxide. If this happens, all water breathing life, may die and the Arctic will become an anaerobic cess pool. This adds a further dimension. All the dead sea life, under anaerobic conditions, will also liberate methane as it breaks down not to mention oxides of nitrogen and sulphur. There is also the possibility that under deep ocean pressure, methane will dissolve in large amounts in the water and as currents bring this water closer to the surface, the methane may start to bubble out, causing an upwelling like an air lift, far from the original source of the methane. This will pull more methane rich water upwards to release its burden of methane suddenly into the atmosphere.

Original calculations of how fast glaciers could melt only considered thermodynamics. No account was taken of the effect of water pouring down to the bottom of the glaciers increasing mass transport of ice to the sea. Similarly, an "air lift" effect could increase the release of methane from the ocean above what simple calculations of diffusion would indicate.


Cryoconite Acceleration of Melting
Cryoconite is the accumulation of dust and soot that falls on the northern ice sheets. It absorbs heat from the sun and melts the ice it is in contact with. Deep ice is very poorly melted by solar radiation since a huge block of ice to the depth of the light penetration must be raised to zero degrees before melting starts. Cryoconite concentrates all this energy on the top few centimeters of the ice. As the ice melts, more cryoconite is exposed from lower levels of ice and the process accelerates. If the Hadley cells do shift so that air is being pulled along the earths surface from mid latitudes towards the Arctic, then one would expect that more soot and dust will accumulate on the remaining ice including on Greenland. Air over Asia, North America and Europe is full of soot from internal combustion engines, cooking fires, peat fires and forest fires. Even while suspended in the air, this material will have an effect. By far the largest part of solar radiation travels through clear air without being absorbed. It is absorbed or reflected when it reaches the surface of the earth. With a burden of dust, heat is absorbed within the air column. This will result in warmer air than would otherwise be the case, moving northward with its greater capacity to melt and sublimate ice.  As this dust and soot accumulates on the ice it will further accelerate its melting.

The melting of the arctic sea-ice is proceeding at least 2 decades ahead of the predictions of the most extreme models. Predictions are that we will see a virtually ice free Arctic ocean within a few decades. Some say by September 2013 or 2015. The process is exponential. As more and more water becomes ice free, more heat is absorbed and more ice is melted. To an extent it will be like a drink with an ice cube in it. As long as there is some ice to absorb heat as it melts, the temperature of the drink doesn't rise. Once all the ice is used up the temperature starts to rise rather quickly and clathrate breakdown can really start in earnest. We will all be able to see how this natural experiment proceeds in the very near future.


There are two theories which may be applicable here. There are some good indications that the solar cycle effects the amount of heat reaching the earth. The most commonly quoted indication of this is the little ice age, when the Thames froze over. It was an extended period of low sun spot numbers. At present we in the low part of the sun spot cycle and it is extremely low. Some observers predict that this will continue, some that it will lead to  a particularly strong sun spot cycle. If the Arctic ocean has become ice free for the first time in living memory during a period of low sun spot activity, what might happen over the next few years as we approach the peak of the next cycle of sun spots.

At the same time, there is a suggestion that an El Nino causes greater melting in the Arctic. If the sun spots do rise, the peak will likely be around 2014-2016. It is likely that in one of these years there will be an El Nino. This may be when we can expect ice melting even greater than in 2007.

Some argue that the warming of the permafrost areas will provide large new areas for agriculture. This may well be a valid argument. Northern Canada and Siberia could become huge bread baskets. However, farmers own land. They live in certain areas. When the climate changes, farmers first have to be convinced that this is a permanent situation and then take the necessary measures to change their farming practices to suit the new conditions. An even bigger decision for them to take is to move to new areas. Even in technically advanced, science based countries like Canada, this takes time. Farmers may well start to move to more northern areas to farm. Again they must mount the learning curve and infrastructure must be established in what now is barren areas.  New varieties of wheat must be developed that can grow in longer days but shorter seasons. All this takes, at an optimistic evaluation, a few years to a decade. Once we had mountains of food and had at least a year's supply of wheat, butter and so forth stored up. This is no longer so **and the world population is ever increasing. If we do have a climate shift as outlined above, the starvation in the interim learning years will be huge.

**Note: this article was written in 2006!!!

A greater worry than a sudden change to a new climate is if the climate flick flacks (flickers) back and forth for a couple of decades between the different states before it settles down. This will make adaptation much harder and will cause much more devastation than a sharp shift to a new climate regime.

If the above scenario does occur, we may see its first effects in the fall. After a summer of warming, the sun once more leaves the Arctic and the adjacent land rapidly cools. This will trigger rising air over the relatively warm ocean (like offshore night winds) with the release of latent heat as the water vapor from the now warmer Arctic ocean condenses. One would expect longer warmer autumns in the north. The fall may be when we observe the first indications that the new circulation system is establishing itself. We would expect prevailing winds in these northern areas to reverse. With Coriolis, a North East wind would become a South West wind. Climate change has happened suddenly in the past and could well happen suddenly relatively soon.http://www.wunderground.com/education/abruptclimate.asp

Note that in Northern BC, Canada, Lodge Pole pines are being replaced at a rapid rate by Poplars due to milder winters which no longer knock back the fungus carrying Pine Beetle each winter. This could be an early indicator that the process has already begun.

An indication that this is happening will likely also come from the jet stream. The jet streams occur at the border between Hadley cells. If the Hadley cells shift and with them the climate zones of the Northern hemisphere, one would expect the jet stream and especially the polar jet stream to weaken, to shift north and  to disappear. This may be one of the first indications that the change mentioned is occurring. Commercial airlines use the jet streams when flying East and any change in the location of the jet stream will be swiftly noticed.

Iceland Blowing Up
A hugely disastrous scenario may involve Iceland.  Iceland not only lies over the Mid Atlantic Ridge and is continually splitting apart but apparently it also lies over a deep magma plume or hot spot as does Hawaii.  At present she has a large ice sheet which adds considerable weight above this hot spot.  Iceland's main shield glacier is 800m deep.  If the Iceland ice sheet melts, the pressure on the magma will decrease and with the released pressure, gases will start to come out of solution, powering the magma upwards (sort of a molten rock airlift!!).  This is self perpetuating as the volcanism melts more ice and as the rising magma releases pressure on deeper magma.  Apparently this has happened in the past when large melts have occurred and could happen again.  The result could be a year or two without crops in the Northern Hemisphere.  This would spell disaster with our present  lack of stored food.  In 1816 a similar situation occurred with the eruption of a number of volcanoes.  These volcanoes were much further away from Europe.  A summer was missed in the northern hemisphere with much starvation.  A mega eruption in Iceland would focus her effects on Europe and would also effect the wheat fields of North America.  Note that the eruption of that unpronounceable Icelandic volcano that shut down air traffic in Europe is often followed by the eruption of its sister volcano a few years later.

If the above scenarios are correct, we no longer have the luxury of choosing this location or that one for wind farms because of visual pollution as perceived by a few. We no longer have the luxury of not allowing the construction of a hydro dam because it would flood a pristine river of great beauty. We need wind turbines in both this location and that one and lots more hydro power. We also need to get solar electric to such a price that people want to install it for economic reasons and governments have to take serious steps to encourage people to install all the renewable power possible and to stop trying to milk the situation for revenue. Only with all these measures do we have a chance to avoid the coming climate shift.

Being selfish and just looking at the good of New Zealand, in the face of coming disasters New Zealand needs to become as  independent as is possible.  Having in-house energy supplies and having them distributed over the country is a very significant step in this direction.

Note: In New Scientist, 29 Aug, 2009, p10, it was reported that for every degree day above 29 degrees centigrade crops such as soy bean, cotton and maize loose 0.6% of their productivity. If the Hadley cells do shift, even if production of these crops is not completely wiped our, production will fall precipitously.

Sept. 2012
An Arctic Storm
We have just had an Arctic storm.  I wrote to a very prominent scientist and suggested that this would cause upwhelling along the Arctic coasts.  She pointed out to me that I had got my wires crossed (she was much more diplomatic than this) and had got the Coriolis effect reversed.  I did and boy did I feel like a dummy.  Lets look at a storm such as we had on Aug6 this year.  It is a counter clockwise flow of air with winds predominantly from the West flowing around the low pressure area.  Coriolis in the northern hemisphere shifts moving air and water to the right.  This would tend to pile water up along the shore.  More important though, it would tend to push surface water (cold, low salinity) out the various outlets of the Arctic basin.  The upwhelling should actually occur in the middle of the storm pulling slightly warmer salty water up to the surface.  Perhaps this is the source of the sharp melting observed this year following the storm.  We need a recording/transmitting buoy in the eye of next fall's storm.  What would such an upwhelling do to the strength and duration of an Arctic storm.

The Horror Scenario
So far, what has been described would be very serious but we would probably still be here, albeit in a new dark age.  Lets look at the full doomsday scenario.  As mentioned earlier, the Ocean circulation system which is typified by the Gulf Stream is powered by two engines. One is the freezing of Ocean water in the Arctic (and Antarctic).  This freezes out fresh water leaving the salt in the water.  This water is not only cold but saltier and is hence dense.  It sinks.  As it sinks, water is drawn northward on the surface to replace it.  This surface water  has been evaporating down around Florida but is too warm to sink through the thermocline.  Surface water is around, say, 20 degrees while water below the thermocline is only a few degrees above freezing.  As this water flows north into more temperate climates, it cools.  Eventually, it is dense enough to sink into the depths.  This sinking of cooling surface tropical water further adds power to the Gulf Stream.

We see that with the amount of climate change we have had so far, the polar regions are warming more than the tropics. When it is warm enough, freezing in the polar regions decreases.  This weakens the ocean overturn.  It also reduces the effect of sucking warm, salty surface water from the tropics; the second engine for circulating water in the oceans.  

Initially, this reduction of the flow of the Gulf stream should allow cooling of the Arctic and an increase in the production of ice, starting up the flow again.  We should have the flickering previously mentioned.  In other words, a shift back and forth between very harsh and very mild weather in Europe.*  However, as we pour Carbon dioxide into the air, we move the whole system up notch by notch in the temperature scale.  At some point we will no longer have cool enough conditions to initiated significant freezing of ocean water in the Arctic and the circulation system will stop.  The flow of oxygen rich water to the ocean depths ceases and the deep ocean turns anaerobic.  In the mean time, upwelling and hence nutrient flow to the photic zone from the depths also ceases.  Algae production becomes what one associates with an El Nino (very poor) rather than a La Nina.  The production of diMethyl Sulphide by algae, which is responsible for seeding clouds, dies down and with it cloud formation.  The albedo of the earth drops sharply with the decrease in cloud cover and lots more radiation reaches the surface of the earth.  Now we really start to warm up and the ocean stratification becomes even stronger.  Deep corals die due to a lack of oxygen, shallow corals due to the warming of the sea (heat is no longer being taken away from the tropics due to the failure of the ocean circulation system).  

*An interesting possibility is that with the inertia of the water of the Gulf Sream the push and the movement could get out of phase by 6 months.  This would result in warm wet summers and cold miserable winters in Britain during the transition until the whole system warms up enough so that significant freezing no longer occurs in winter.

The surface of the ocean is much warmer and remember, about 25 degrees or greater is necessary to breed hurricanes.  In effect, instead of moderate cloud and rain from the sea, it warms up until a hurricane is inevitable.  The climate is like a car with a new driver, starting and stopping in jerks.  Since the warm water is much further toward the poles than previously, hurricanes spread poleward.  The hurricanes mix deep and shallow water and so we get some phytoplankton blooms but not the steady ones that power good fish production.  The oceans are pretty much dead*.  Our climate becomes one of long periods of clear, extremely warm weather punctuated by hurricanes.

 Note that in New Scientist it was reported that a large proportion of the fish in the sea have ancestors in lakes and rivers.  One possible explanation for this is that in the past the oceans have become sterile with great die offs and have been repopulated by river fish.  The periodic die off of the oceans may be a regular occurrence with climate change.

Postscript
In May, 2011, I have been talking with a climatologist.  I haven't got his permission to mention his name so please excuse the omission.  He gave me some  interesting information.  He said  
"The polar cell is very weak -- it is not like the Hadley cell -- it is not an engine, rather a residual and very seasonally dependent"

I interpret this to mean that the Hadley cell (the one on both sides of the equator) is driven by the heating of the tropical areas.  Air rises up due to its heat content both sensible and latent, flows away from the equator, cools and falls at about 30 degrees north.  This falling air pulls air down to the north and powers the Ferrel cell which circulates air from about 30 degrees north to 60 degrees north.  The Ferrel cell is weaker than the Hadley cell.  The Ferrel cell makes the polar cell circulate and it circulates air from 60 degrees north to the pole.  Each successive cell is weaker than the previous one.  Now what happens when the Arctic ocean becomes a heat collector due to the disappearance of the ice cover.  Will it become a driven cell.  I would think that there is a good chance that this will occur.

August 2012
In correspondence with a climatologist, Jennifer Francis, she pointed out that the elephant in the room is the warm salty Atlantic water that underlies the colder, fresher Arctic water.  I had a look at the temperature contours on this site and wondered what all the fuss was about. The temperature of the deep water under the ice is only at most 2.5 degrees warmer than the freezing point of sea water and much of the depth as little as 1 degree warmer.   Then I had another look at the graph and got out my old physics book and the back of an envelope (apparently necessary for the very best type of calculations).    Try this for a mental exercise.  I'm going to use calories rather than SI units because it is a little easier to see what is happening.

Assume you have a perfectly insulated tank a meter by a meter and about 1.2 meters deep.  You put a slab of ice on top and under it you have water which is 1 degree above the melting temperature of the ice.  The water is 1 meter deep.  It doesn't matter how deep the ice is.  Our question is, what if the water gives up it's heat to the ice as it cools by 1 degree.  Clearly when it reaches the melting temperature of the ice, it can't give up any more heat to the ice.  What depth of ice will be melted.  First we need three facts.

1.  If you put one calorie into one gram of water, it will heat it up by 1 degree centigrade.

2.  To melt one gram of ice takes 80 calories.

3.  One gram of water occupies one cubic centimeter. 

So let's do some calculations.  A cubic meter of water is 100 by 100 by 100 cm.  Its volume is 10^6 or one million cm^3 (cubic centimeters).  As it cools by one degree to the melting point of ice, it will release one million calories.  Divide this one million calories by 80 and we see that it will be enough to melt 12,500 cubic centimeters of ice.  Now the area of the bottom of our ice cover is 100 x 100 cm or 10000 square centimeters.  Divide our 12,500 by 100000 and we see that it can melt 1.25cm of ice.  ie.  every cubic meter of water which is one degree above the temperature of melting ice, if it gave up it's heat to the ice, could melt 12.5mm of ice.

The Arctic ocean is one third continental shelf with a depth averaging around 100m.  The rest averages about 1000m.  Just the water from one hundred meters contains enough heat to melt 1.2m of ice.  (actually more but we are being very conservative and pretending that the water is only one degree above the freezing point of ice).  The Arctic ice at present is around 3m deep in the middle of winter.  Just the heat from the top three hundred meters is more than enough to melt all the existing ice.  So how could this heat reach the ice.

Just a couple of weeks ago, (Aug6, 2012) we had a fairly severe storm in the Arctic.  The pressure in the centre of the storm reached about 960mb.  A storm over ice has very little effect on the underlying water.  Open water is something else again and tends to mix layers of water as the wind pushes the top layers off shore and brings up deep water.  Storms are also much more likely when there is open water because of the latent heat of water vapor from the open water.  As we have more and more open water, there should be more storms and more mixing and even more ice melting as a result.  Have a look at this site and go to August 2012.  You will note that the blue line showing the extent of ice is diving down.  Could this be due to the recent storm.  As of today (Aug 15, 2012) there is no telling if this dive will continue but if it does, we are in for a new record in September for less ice than ever measured before.

Appendix Aug31, 2012
Two vs 4 Hadley cell system.
This month we have seen the Ice Extent graph nose dive in a most atypical fashion.  We also see atypical freezing around the shores of the Arctic ocean.  At the same time, as of today, the graph continues to plummet and has even steepened slightly over the past few days.  It seems most likely that we now have an off-shore wind in the Arctic.  As the land cools off in Siberia and Northern Canada, the air will be cooling and falling and spreading North and South.  In other words, we are seeing the beginning of a 4 cell system.  This will be due to the increasing power of open water to cause rising air and suck air toward the North Pole.  For the first time we are seeing the power of open Arctic water express itself.  As we have more open water earlier and earlier and less ice to keep surface waters cool, we will likely have earlier, more severe storms than the one that occurred on Aug6 this year.  This will cause upwelling of the deep warmer Arctic water that fills the Arctic basin.  The Arctic Ocean will gain power.  When it is strong enough, presumably we will shift into a two cell system with all the consequences mentioned above.

Sept9, 2012
The Sea Ice Extent graph seems to be leveling out finally at about 3.5 million square miles of ice.  I wonder if we might see a wee storm fairly soon.  Sea water gives up 80cal of heat per gram as it freezes and there is a lot of open water this year.  In the mean time, the land and the air above it is going to start to cool off pretty fast in the next few weeks.   This cold dense air will likely move offshore  under the warmer air above the ocean and could well trigger the release of latent heat from the condensation of water vapour.  If this doesn't happen this year, could it happen in the years to come at about this time.   We might also see accelerated freezing starting from the coast while the main ice sheet floating on the ocean stays as is or even continues to melt slightly.  We need an animation of the Ice Extent maps with a day per frame, played at somewhere between 5 and 10 frames per second.

Just a word here about the Arctic Oscillation.  This is a measure of the pressure difference between the Arctic ocean and land areas around 45 degrees North.  A negative value means that there is high pressure over the Arctic and low pressure (relative to each other) over  mid latitudes.  Sinking air and clear skies are high pressure areas.  This is your typical "good weather".  This is the typical scenario when the Arctic is covered with ice and is reflecting most of the incoming radiation back into space.  A positive AO indicates low pressure over the Arctic.  In other words, rising air, storms, precipitation.  Typical "bad weather".  Look for periods of positive AO.  This is when we should see a reversal of the Polar Hadley cell (surface winds being sucked from the south toward the Arctic) and should typically occur initially, in  the fall.  A graph of the ocurance of positive and negative AO's over the years would be most instructive.

5 comments:

Ray said...

I get your point about the reflected light causng a problem, however, I'm a tad confused about the water level as a result of the melting.

If you put water in the freezer in a bottle, the wtare (ice?) expands as it freezes. so If you don't leave enough room and you have the lid on the bottle suffers, as does your freezer.

So my point is, surely the opposite is true, when the artic ice caps melt then surely the water levels will lower. Or have I got it all wrong.

Anyway, the melting isn't a good thing.

zefiriel said...

@Ray
A simple experiment. Put a big chunk (or many small chunks) of ice in a container filled to a certain level with water. Mark the level of water.

When all the ice melts, not the level of water. I think you'll be surprised.

gzuckier said...

Floating ice, like floating anything, displaces only its weight in water. If you think about it some, you can see that means when it melts the water level doesn't change.

The problem is, as alluded to in the article, ice which is on land, i.e. Greenland. Obviously, when that melts and runs into the ocean, sea level rises. And there is an awful lot of ice on Greenland, second only to Antarctica.

Anonymous said...

Hello William
Interesting post!
I really don't like the sound of that potential methane scenario.
I've wondered if when the ice melts out there could be enough evaporation to actually increase the speed of the currents flowing into the arctic, another uneasy thought is that the kinetic energy, from the earths rotation, contained in the ocean will drive whatever 'cell' gets established at the pole. It just seems that slowing from 290kph [at 80degN] to zero has to generate significant amounts of heat not neccasarily a huge increase in temperature given the specific heat of salt water but certainly enough to stop a refreeze. The turbulence is only going to mix the layers and make things worse. I'm only an amateur so this is just speculation, what do you think?
It seems to me that north america is going to bear the brunt of the consequences having no lattitudinal mountains to prevent storms blowing all the way to texas.
When i looked into the last great climate change i got the sense that the 'flicker' effect went on for a millenia and a half, and behaved more like someone in agony jerking between postures to try to find ease.
johnm33

Anonymous said...

I copied a part of the post and added a link here
http://neven1.typepad.com/blog/2012/08/record-dominoes-8-nsidc-daily-sea-ice-extent.html?cid=6a0133f03a1e37970b017c317a428b970b#comment-6a0133f03a1e37970b017c317a428b970b
johnm33