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Dave C
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I wouldn't read too much into the arctic oscillation value. There have been two years this decade with exceptionally low winter ice gains- 2007 and 2010. In winter of 2007 the AO was unusually positive. There have been two years with unusually large winter ice gains- 2008 and this year. In winter 2008 there was a positive AO, but not as big as 2007. It seems unlikely that there is an obvious relationship between AO and ice gain/melt.
Toggle Commented Apr 1, 2013 on Looking for winter weirdness 6 at Arctic Sea Ice
Chris- I understand your points, but remain suspicious of non-quantifiable factors. I guess we will find out a lot more by the end of this melting season. That is a pretty impressive picture. Does anyone here know if there are images from previous years available?
Toggle Commented Mar 13, 2013 on PIOMAS March 2013 at Arctic Sea Ice
Chris Reynolds- It looks to be increasing to me. I guess we could disagree about the meaning of the word "significantly". My main point was that the gap between 2012 and 2013 significantly decreased, which seems clear. My general hypothesis is that 2007 permanently changed ice patterns in the arctic. Because of this I believe that you should overweight melt and gain data from 07 onwards. If you do this, 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 look at the big picture using the easily measurable 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" predictors. You are correct that 2007 was much further below the trend line than 2012 and that ice gains are somewhat countercyclical. Winter gain is countercyclical to the previous summer's loss. However, summer loss does not seem to be countercyclical to the previous winter's gain. Summer loss seems to follow long term trends more closely than winter gain. Those trends predict about 18.5 to 19.0 of summer loss this year. In any case, I am not predicting a 2008 level of gain. 2008 gained 600k km3. I am predicting about a 0 gain or loss for 2013. I could be wrong, but if I am right then a lot of people here might be surprised at how high the volume minimum is this year.
Toggle Commented Mar 12, 2013 on PIOMAS March 2013 at Arctic Sea Ice
Looking at an arctic insolation diagram seems to indicate that the sun is not a large factor until April. http://2.bp.blogspot.com/-k_S7N0VlMRg/UH4RNvJ3cjI/AAAAAAAAFjk/lqjQhGqLWOk/s1600/insolation_latitude.gif 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. I could be wrong on all three of these, but they seem like reasonable guesses. Using another quick metric- Volume peaks on April 15th. Ice is approximately distributed from the 60th to 90th parallel. It's likely that volume is shrinking on April 15th below the 75th parallel but still growing above that. So it would seem that ice in the Beaufort area would have another 30-45 days for ice growth. I guess we'll have a better idea in a few months.
Toggle Commented Mar 12, 2013 on PIOMAS March 2013 at Arctic Sea Ice
Chris- Thickness did increase significantly last month. http://psc.apl.washington.edu/wordpress/wp-content/uploads/schweiger/ice_volume/Bpiomas_plot_daily_heff.2sst.png It looks like we are almost exactly in the same place we were last year with respect to volume, thickness and area. For those keeping track, 16.4 in 2008 was the previous largest volume gain through March 1st. This years volume gain has been 16.7 through March 1st. As we all know, 2008 was the only year this decade with a volume recovery, finishing 600k km3 higher than 2007. Winter ice gain has a large effect on summer minimums. When ice cracks during the winter this opens up water and results in even more ice. We clearly saw this in February. We still have another month for ice to gain even further. Volume peaks in April. It seems that the most likely mechanism for cracks resulting in melt would be increased ice transport. But these cracks are a long ways from the fram strait or eastern edge that ice mostly gets transported to. Also, ice transport by volume through the fram has been remarkably steady over the years. It seems like increased ice mobility is being balanced out by decreased ice volume available to flow through the strait. https://sites.google.com/site/arctischepinguin/home/piomas/grf/fram.png We can also look at melt volume for the last 5 years. Admittedly I know very little about physical changes in the ice. But statistical trends do not seem to point to a record breaking volume melt this summer. I would be surprised if melt was much above 19. 18.1, 18.2, 19.0, 17.9, 18.7. It's possible that there will be record melt this summer to counteract the record ice gain, but I don't see any strong theoretical reason to count on this. Partly as a nod to the similarity in conditions, my current prediction for volume minimum this year is 3.26.
Toggle Commented Mar 12, 2013 on PIOMAS March 2013 at Arctic Sea Ice
Kevin- 2012 was lower. For those keeping track, 16.4 in 2008 was the previous largest volume gain through March 1st. This years volume gain has been 16.7 through March 1st. As we all know, 2008 was the only year this decade with a volume recovery, finishing 600k km3 higher than 2007. Winter ice gain has a large effect on summer minimums. As for why I think the cracks won't result in as much loss this year- When ice cracks during the winter this opens up water and results in even more ice. We clearly saw this February. We still have another month for ice to gain even further. Volume peaks in April. It seems that the most likely mechanism for cracks resulting in melt would be increased ice transport. But these cracks are a long ways from the fram strait or eastern edge that ice mostly gets transported to. Also, ice transport by volume through the fram has been remarkably steady over the years. It's possible that there will be record melt this summer to counterract the record ice gain, but I don't see any strong theoretical reason to count on it.
Toggle Commented Mar 12, 2013 on The cracks of dawn at Arctic Sea Ice
I am far from a global warming denier. You can look at my other posts. I believe in following the facts though. Nobody on this forum predicted we would have record volume gain this winter. This is an unexpected fact. While that fact doesn't fit in with the preferred narrative, you can't just ignore it. Ice has memory, and it is likely that the volume minimum for 2013 will be higher than most people on this forum would have predicted.
Toggle Commented Mar 12, 2013 on The cracks of dawn at Arctic Sea Ice
Wow. That is a massive volume gain for February. We are on pace for a record ice volume recovery. It looks like the wind and cracks caused significant ice gain. As of now my prediction is that this is going to be a recovery year. The expected value is probably slightly below, but there is a decent chance that we won't even break last year's volume record.
Toggle Commented Mar 12, 2013 on The cracks of dawn at Arctic Sea Ice
It is somewhat morbid in a way. Still, I think of it as documenting history. There have been plenty of local effects from global warming. Still, each individual event above the long term average could conceivably be dismissed as natural variation. Most areas haven't noticed huge changes from the 1 degree rise in temperatures. The arctic ice disappearing is the first absolutely undeniable large-scale effect of global warming. There is simply no way to spin this one. If the arctic melts, global warming is happening. Period. I don't know if humanity will effectively respond to global warming. But the melting of the arctic officially moves the debate our of the theoretical and into the actual.
Toggle Commented Mar 11, 2013 on The cracks of dawn at Arctic Sea Ice
"What year do you expect arctic ice volume to dip below 500 km3?". Assume that answers could be given anonymously. Is there any sort of scientific consensus on this question, or would the answers be all over the map? Also, for those who guess much more than 5 years, what sort of negative feedbacks do you think they would cite as the most important? My guess is that on this blog the median answer would be somewhere around 2016. I have no idea what the scientific guess would be.
Toggle Commented Mar 3, 2013 on The cracks of dawn at Arctic Sea Ice
re BICOT. I recently posted a volume chart showing that. 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
"The closest approximation we currently have is a simple exponential decline" I wouldn't really agree with this. The data set is too small to say anything definitively, but based mostly on intuition it seems that ice melt before 2007 was under different conditions. You might be more accurate by looking only at more recent trends. If you look at the last 5 years of melt and refreeze, it seems that refreeze is catching up slightly. 2013 should be a good test. Linear predicts about a 2.6 minimum this year, Exponential 2.0. That is a fairly sizable difference. Still, even if we are on a linear trend that isn't much consolation. Ice-free in 2017 is virtually the same as ice-free in 2015. Volume loss prediction based on last 5 years- 2013-.7 (above average refreeze to date) 2014-.75 2015-.7 2016-.64 2017-.58 (ice-free in 2017) "Which ice pack is better armed for the melting season, the 1 million square km ice pack of 2 metres thick or the 2 million square km ice pack of 1 metres thick?" That is a good question. Based on the last 5 years, the thinner ice does not seem to be resulting in accelerated volume melt. Too few numbers to decide, but the relation looks random to me. 2008---1.55---18.1 2009---1.58---18.2 2010---1.51---19.0 2011---1.41---17.9 2012---1.41---18.7
Toggle Commented Feb 10, 2013 on PIOMAS February 2013 at Arctic Sea Ice
I made a simple chart of winter ice gains. There seems to be a step-change after 2007 in winter gain through January. This year's gain has been slightly above average for the last 6 years, but nothing exceptional. We are 3/4s of the way through the gain season. Gains after today don't seem to be affected by earlier gains or melts. If you assume a 4.3 gain to the max we are at 21.3 for max volume this year. If you take the 10 year linear trend for ice melt then this year should have 19.1 melt. The 5 year trend would be 18.7. I think the 5 year trend is more accurate since it seems that 2007 fundamentally altered things in the arctic. So assuming that this year remains average then an early guess for minimum volume is 2.6. ------Feb1--GnF1--%max--Gmax 2003-22.9-- 12.1-- 73.3-- 4.4 2004-21.5-- 11.3-- 72.4-- 4.3 2005-21.6-- 11.7-- 71.8-- 4.6 2006-20.9-- 11.7-- 73.1-- 4.3 2007-19.7-- 10.7-- 71.8-- 4.2 2008-20.3-- 13.8-- 73.8-- 4.9 2009-20.5-- 13.4-- 74.4-- 4.6 2010-19.0-- 12.1-- 73.3-- 4.4 2011-17.7-- 13.3-- 76.0-- 4.2 2012-17.7-- 13.7-- 76.5-- 4.2 2013-17.0-- 13.7 Feb1- Ice volume through February 1st. GnF1- Ice gain through February 1st. Gmax- Volume gain from February 1st to the maximum.
Toggle Commented Feb 8, 2013 on PIOMAS February 2013 at Arctic Sea Ice
Mostly a guess. Here's my reasoning. Everyone knows that 07 and 10 were monster years. What people don't notice as much is that 06 and 09 were very poor years for volume melt. So both 07 and 10 benefited from a counter-cyclical reversion to the mean. 12 had a much higher melt than 06/09 so 2013 will not be benefiting from this effect. Also, 07 had an extremely low winter recovery while 10 had a very low winter recovery. At current levels 13's winter recovery is running close to average. So it is looking unlikely that 13 will have the massive head start that the two recent big years did. It's not conclusive, but just for the last 5 years Melt seems to have hit a slight plateau. Intuitively this makes sense since it seems that ice gets harder to melt the further north you go. I'm sure oceanic/atmospheric effects eventually will overcome the lack of sunlight but I would guess that melting might slow slightly because oceanic mixing needs time to overcome the relative lack of insolation. At this point no one has much authority when it comes to arctic ice, but I am also reluctant to go against the large majority of scientists. I don't think there are very many scientists predicting that arctic ice will be virtually gone in 3 years. The volume trend has to reverse really soon for the scientific community to avoid being overwhelmingly wrong. Still, as of today it has not. Right now that quoted statement does not have numerical evidence to back it up. So far the trends seem to predict an average volume year, which would result in a drop to about 2.5. So if pressed I guess that is my real prediction, although I will be hypersensitive to any signs of slowing.
Toggle Commented Jan 26, 2013 on PIOMAS January 2013 at Arctic Sea Ice
Arctic Sea Ice Volume by PIOMAS Year---Avg----Max----Min---Melt---Gain 2003---19.0---27.3--10.2---17.1 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 I expanded Donald's numbers to include recoveries. A few things stick out to me. -Recovery in winter is counter-cyclical. The years following big volume losses have tended to have larger gains. -Melt does not seem to be counter-cyclical, but fairly steadily increasing. -Recovery has been increasing, not decreasing. Volume losses are occurring because summer melt is increasing even faster. -2007 and 2010 were anomalous years. Much of their volume loss occurred due to lack of recovery during the winter. -It probably means nothing because the sample size is too small, but if we take this chart literally then every third year has a weak winter recovery. So if 2013 is going to follow the chart pattern then we would see an unusually weak winter Gain followed by a much lower Min. My guess is that the pattern will be broken this year and volume Min will just be similar to 2012.
Toggle Commented Jan 25, 2013 on PIOMAS January 2013 at Arctic Sea Ice
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