This is my initial attempt to make a simple ice model that can make near-term ice volume predictions as measured by PIOMAS. My current prediction for minimum ice volume this year is 3.21k km3. Volume loss does not seem to be following an exponential decrease, but a slowing linear decrease.
My general hypothesis is that 2007 permanently changed ice patterns in the arctic. Arctic ice is a moving target. Every preceding year is less likely to reflect current conditions. An accurate assessment is a balancing act between measuring the actual system and having enough data points. Also, the trends in summer and winter are different enough that I think you should look at them separately. The sun seems to have an increasingly large effect on melt, which means that summer/winter trends are diverging. If you do overweight the recent past then the trend lines(relative to 10 or 30 year) for ice melt are decreased since we have been on a slight ice melt plateau over the last 5 years.
I also tend to focus on the quantified metrics. I'm sure some details are important but in general I assume that various less measurable tendencies will be roughly reflected in the primary numbers. This could be falling prey to the availability fallacy but to adequately look at every factor would be a full time job. This could certainly change in the future, but in the last few years the statistical predictors seem to have done better than the "measure all the details" predictions.
In the last 10 years there have been 2 huge years, 7 average years and 1 recovery year.
Winter tends to get ignored, but accounts for almost as much variation as the summer melt season. 2007 and 2010 had very low winter recovery. They were well on their way to a huge loss by this time of year. By contrast, 2008 and 2013 have had easily the highest winter volume gains. 2008 was the only recovery year. 2013 is pretty unlikely to gain 600 km3 like 2008, but is even more unlikely to be a record shattering year like 2007 and 2010. 2013 is currently on pace to tie the volume gain record, gaining about 18.7 with the likely maximum volume being close to 22.
Arctic Sea Ice Volume by PIOMAS
Year---Avg----Max----Min---Melt---Gain
2003---19.0---27.3--10.2---17.1---16.5
2004---18.5---25.8---9.9---15.9---15.6
2005---17.9---26.2---9.2---17.0---16.3
2006---17.2---25.2---9.0---16.2---16.0
2007---15.5---23.9---6.5---17.4---14.9
2008---16.6---25.2---7.1---18.1---18.7
2009---16.1---25.1---6.9---18.2---18.0
2010---14.0---23.4---4.4---19.0---16.5
2011---13.2---22.0---4.0---17.9---17.5
2012---12.7---21.9---3.3---18.7---17.9
-There seems to be a step-change after 2007 in winter gain through January.
-Recovery in winter is counter-cyclical. The years following big volume losses have tended to have larger gains.
-Summer melt does not seem to be affected by volume losses or winter gains.
-Recovery has been increasing. Volume losses are occurring because summer melt is still larger.
This graph is of adjusted winter volume gain and summer melt. Red is melt, blue is gain. Curved lines are 2 and 3 year moving averages. The two steeper lines are the 10 year linear trends. The 3 other lines are 5 or 6 year trends. Each grid line represents a year, with the dots from 2003-2013. The Y axis is in .5 increments.
http://s16.photobucket.com/user/iciclespike/media/ice.jpg.html?sort=3&o=0Summer loss seems to have plateaued, as reflected in the 2 and 3 year moving average. For this reason it fits the data better to use a 5 year linear trend to predict summer melt rather than a 10 year linear or exponential trend. The prediction for this year is 18.65k km3 of melt.
There is a correlation between winter gain and the previous year's volume loss with a -1 slope. So when looking at winter gain trends you need to add the previous volume anomaly to reduce noise. Winter gain is increasing, but is harder to predict since it is more variable than summer loss. None of the linear curves seem to fit well. If I had to guess I'd predict a slope between the 6 and 10 year slope with gain and loss converging around 2015.
If you assume that this winter wasn't a large deviation from current trends then winter gain is increasing faster than recent summer gain. If these trends hold then the arctic ice would stabilize in the next few years. Of course this will be temporary, with the global heat increase eventually overwhelming the primary negative feedbacks of less sun and higher winter freezing.
Why cracking probably won't have a large effect-
-Ice is always flowing, whether there is cracking or not. This video shows ice flow over the years. Notice that ice always flows through the strait, even in winter.
http://www.climatewatch.noaa.gov/video/2011/old-ice-becoming-rare-in-arctic-There has been very little increase in yearly ice volume through the Fram strait as ice has gotten thinner. Faster ice movement seems to have been equally balanced by less available ice(especially less multiyear ice) to exit the strait.
https://sites.google.com/site/arctischepinguin/home/piomas/grf/fram.png-There was extensive cracking in winter of 2008. That year was the only recovery year in the last decade. It's possible that cracking only indicates thin ice, and is not an indicator of a large melt.
-The AMSR2 diagrams show less ice in the Fram strait than in February and only slightly more than a couple weeks ago. The NSIDC shows that ice is currently average in the Fram strait. These two results seem to indicate that there is not much extra ice transport right now.
-Ice cracking in the winter increases volume. February was a record shattering month for ice gain, yet the temperature was not that far below average. So ice loss due to cracking will have to overcome the extra ice gained by cracking in the winter.
My guess is that the ice cracks before it melts every year. But if the sun isn't shining then it seems that it would not make a difference whether the ice cracks in February or April. As a mild concession to cracking, I'll predict .1k km3 additional expected volume melt this year.
I think the volume anomaly graph supports my claims about melt trends-
https://sites.google.com/site/arctischepinguin/home/piomas/grf/piomas-trnd3.png-The ice anomaly pattern in winter vs summer is increasingly diverging. This adds to the reason to consider winter and summer separately since different processes are occurring.
-Less multiyear ice, ice area and thinner ice means that the solar cycle has a stronger effect, as seen by the steeply downsloping trends in the last few years that match the solar cycle. That the remaining ice is closer to the north pole should also increase the solar effect.
-There is less ice to melt later in the summer and the solar decline is larger so the VA slopes up more.
-More ice regrows in the winter, so the VA slopes up more at the end of the year.
-Transport does not seem to be having an effect. Transport should vary with weather, but variation in the VA is going down. This is partly why I am skeptical that the arctic will have a huge melt year this year.
-While weather seems to be having less of an effect, it still can produce variation. February of this year was probably the largest February ice gain on record. You can also see a downward blip caused by the storm last August.
This year the linear trends and an exponential or ice cracking model are making significantly different predictions. I'm currently predicting 18.75k km3 of melt. An exponential trend is predicting 20, which is much higher than the previous record high of 19.0. If melt is higher than 19.5 I'll admit that I was wrong and that this year is different than all previous years. However, if melt is under 19.0 then that would cast doubt on the exponential and ice-cracking theories.
My model is pretty simple. It's likely that there is some complex curve that fits the data better. However, if the inputs really are changing by year then no amount of curve fitting will guarantee accurate predictions unless you find a way to predict the underlying factors. I've looked for measurable, predictable factors that could reduce the standard error in the ice volume trend predictions. I haven't been able to find much. It might be that whatever is causing the ice loss is not currently quantifiable.
