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The Melting of Arctic Ice - Dont Miss the Latest News from the Arctic

There seems to be a lot of confusion about the melting of the arctic.  Experts have been heard to say that without better models we will not understand it.  In fact the climate models that are used at present are hopeless:

Graph 1: Arctic sea ice area, observed versus predicted from climate models. Based on Climate Denial Crock of the Week (Originally from Stroeve et al 2007)
This failure of climate models is a bit unforgivable because science is supposed to fit the data.  It is even more unforgivable because the Arctic is acting like a simple system even though it might be complicated.  The net effect is simple.  The amount of ice that is melted every year is surprisingly constant at around 17000 cubic kilometres:

Graph 2: Volume of Arctic Ice Lost Annually. Data from the Polar Science Center
Somewhat surprisingly the amount of ice melted each winter-summer cycle is almost the same every year:

Maximum and Minimum Ice Volumes in the Arctic. Graphic courtesy: Seke Rob
This suggests that there has been a fairly constant net loss of ice going on for a long time although the loss rate has been accelerating in the last 6 years.

The heat used every year to melt the ice can easily be calculated from the amount of ice lost (It is approximately equal to 334 joules times the volume in cc).  The graph below shows that this heat has been fairly constant between 1979 and 2001:


Graph3: Heat used to melt the arctic ice. (1 petajoule = 10^15 joules)
The amount of heat used to melt the ice varies from year to year by a maximum of plus or minus 10% and usually by much less.  This steady, lumbering behaviour of the arctic ice should not surprise anyone, the ice on the Arctic Ocean is a truly huge lump of frozen water. (1 peta joule is 1015 joules 5.5x1021 joules are used annually to melt the ice). The US Naval Research Laboratory has some images that show how the ice is stirred over the year April 2012-April 2013:

Arrows show direction, colours show speed

It is a feature of polar ice that if the amount of melting slightly exceeds the amount of freezing then the ice will eventually all disappear one summer.  You can see from the graph above that about 5,400,000 petajoules of heat are used to melt the ice every summer and, if the ice is to stay constant, about the same amount of heat must be lost to refreeze the ice in the winter .  It turns out that slightly more heat is supplied in the summer than is lost in the winter.   This only amounted to about 99,000 petajoules excess heat every year between 1979 and 2000 but this was enough to cause an excess loss of about 300 cubic kilometres extra ice every year.  The loss of the ice is cumulative so that in 3 years the annual excess of 99,000 petajoules causes the total loss of almost 1000 cubic kilometres of ice.  So no more than about 2% excess heat between summer and winter will melt the arctic ice:

Graph 4: Change in minimum, summer volume of Arctic ice.
Eventually all the ice will disappear if there is a constant excess loss each year.  If there is 3500 cubic kilometres of ice and this is lost at 300 cubic kilometres per year it will all disappear one summer in about 12 years time (2024).  However, the linear loss of ice during the period from 1985 to 2001 has taken a turn for the worse.  We will lose all the ice well before 2024 if the fall in 2012 persists.


It is clear from graph 4 that twenty years ago the arctic was getting a constant excess of heat every year but over the past 10 years this has been increasing year on year.  This would be expected because as large areas of sea become exposed the albedo of the arctic will fall.  It might also be expected if methane is being released because of the higher water temperatures in the arctic continental shelf, this methane will cause local greenhouse warming at first.

Minimum Arctic Sea Ice Volume.  Graphic from Arctic News Blog: http://arctic-news.blogspot.co.uk/2012/07/albedo-change-in-arctic.html
When the ice has finally gone in the summer the decreased albedo will  increase the temperature of the water. We also know that 6,000,000 petajoules are supplied to melt the ice during the 100 day melt period - 60,000 petajoules a day.  This heat will raise the temperature of the water once the ice has gone.  4.18 * 10^12 joules are needed to raise the temperature of a square kilometer of surface to a depth of 1 metre by 1 degree centigrade, the surface of the arctic ocean is 14 x 10^6 square kilometres so 6 x 10^19 joules will raise the whole surface by one degree.  If the ocean were ice free for 10 days the arctic ocean temperature would rise by 1 degree to a depth of 10 metres even if the amount of heat were the same as currently received (but see below).

So when is Armageddon?  Well, we are losing about 1000 cu km of ice per annum at the moment and there are about 3,500 cu km of summer ice left.  An optimistic estimate for the disappearance of all the ice is 2015-16.  Start of armageddon in 2016-17 .  If the Arctic Ocean is really behaving like a well stirred tumbler of ice then even the thick, multi-year ice will be melted away at the same rate as the thin stuff.  Will the ice really will be gone by 2015-16?  We should always be sceptical of exponential trends, the linear trend suggests the ice will be lost by 2024-2027 ish.

Although all the arctic summer ice might be gone by 2015-27 whether or not armageddon happens depends on whether this results in the massive release of methane.  We will need to wait and see.  See Arctic News Blog

The Arctic Emergency people are right about the problem but not the solution. They really cannot be certain that geo-engineering will not make matters worse.  Matters really can get worse, a few people will survive in the arctic and antarctic but if they geo-engineer the globe and we carry on with business as usual then any major dislocation would lead to no-one and no creature surviving.  Don't be fooled by people who say they can fix nature.  Remember, the Japanese were assured that building nuclear power stations on the coast on a fault line was safe.

I would also rather die than never see a blue sky again.

A note on albedo

It is puzzling how little effect the change of albedo has had on the amount of heat reaching the ice.  The albedo of sea ice is about 0.7 and the albedo of the sea is about 0.08. 

Graph from Arctic News Blog
About 500,000 petajoules of extra energy were being used to melt the ice in 2011 compared with 2001 (See graph 3) but this is only equivalent to about 2-3% of the extra solar energy hitting the freshly exposed sea all day for 100 days  (see note below).  So where does all the extra heat go? Cloud could be reducing the irradiance or sea currents or some other factors must be removing this heat from the vicinity of the ice.  If we take a low figure for heat input from the sun of twice the 60,000 petajoules a day that is currently melting the ice then in 10 days the ocean temperature would rise by 2 degrees to a depth of 10 metres as a result of the 120,000 petajoules per day input.  There would also be serious disruption to currents in the arctic ocean

Note: 4 million extra square kilometres of sea are exposed in 2011 compared with 2001,  1.6 x 10^13 square metres of sea would absorb about 100 watts of extra polar solar irradiation per square metre, this is about 2.4^20 joules per day - 160,000 petajoules per day.  The 500,000 petajoules of extra energy would be supplied in only 3 days if this calculation is correct.


See

Even More Disturbing Events in the Arctic

NSIDC Data on Albedo and Irradiance at the Poles



Why is the Arctic so predictable?  The arctic seems to be acting like a well stirred tumbler of water with ice cubes in it.  The arctic is well stirred because of the circular currents:






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