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Oops! Should have signed the above. Chris R.
Toggle Commented Aug 19, 2011 on Polar ice caps can recover at Arctic Sea Ice
Reasonablemadness, But there are strong cooling forces. The loss of heat to the atmosphere due to prolonged open water into the freeze season is shown by Tietsche's model study to cool the region, by both radiation to space and reduction of inward atmospheric heat transport. This happens to such a degree that even with a total removal of sea-ice the ice recovers to it's equilibrium state prior to the removal of the ice. Regards tipping points, one would expect one to exhibit hysteresis e.g. http://en.wikipedia.org/wiki/File:Ehysteresis.PNG So to get back to where you started you have to back-track to well before the point the state flipped. The research is telling us that the Arctic is not like that (and there's a growing body of such research using models of various complexity). For me the most surprising result is the extraordinary high CO2 needed to hold a perennial ice free state. I'd thought it was around 1000ppm and above - based on paleo studies. The increased atmospheric heat transport implied by the Arctic Dipole could account for a lower level of CO2 maintaining year-round sea ice free. Watanabe et al 2006 used MIROC3.2 and found the AD was reproduced well. I don't know if the model used in this study, CCSM3, reproduces the AD. But as MIROC does, perhaps the high CO2 finding takes into account atmospheric heat transport. In which case we may only cause a seasonally sea ice free state, not a perennial one. Interestingly both CCSM3 and MIROC were two of the models chosen by Wang & Overland in their 2009 study "A sea-ice free summer Arctic within 30 years?" In that paper the ensembles of CCSM3 used seem to be indistinguishable from observations. Yet the ensemble members closely agree on a seasonally sea-ice free state around 2050. With a virtually (<1M km^2) state around 2040. So perhaps I'm being too pessimistic in expecting a virtually sea ice free state by next decade.
Toggle Commented Aug 19, 2011 on Polar ice caps can recover at Arctic Sea Ice
Hello Russell, Sorry but I don't get this paragraph: "Another thought - If at the start of the melt the difference between actual edge and the Ti2 edge is... ....at some time the final minimum edge will be passed through. " With regards the T2 as a predictor. As I've said upon seeing it I was initially persuaded. My main line of reasoning was that T2 was somehow showing us the thicker, probably multi-year (MY} ice, that which is harder to melt. As I mentioned, I used to follow Quikscat when it covered Arctic sea-ice, and found that the ice retreated back to the MY ice. Quikscat used to be obscured by June, so it was basically an effort to track where the MY ice had moved and get a guesstimate of where the minimum area would be. I have to say not always an accurate one, weather always plays a major role. I've looked at my reply and still stand by what I said about the dangers of spotting correlations where there aren't any because of a restricted dataset (restricted in the frequency domain, or in terms of general shape). That's not intended as any kind of personal criticism, the Wunsch study I referred to was criticising a large range of papers by professional scientists. Chris R
Toggle Commented Aug 1, 2011 on An observer's prediction at Arctic Sea Ice
Hi Neven, I've replied to the comment at my blog, but to save you going there - yes feel free to comment on / link to / reproduce as you need to. You directed me to a new Maslanik paper "Distribution and trends in Arctic sea ice age through spring 2011." No I'd not seen it. Before I consider buying a copy - can't get hold of one for free - do you have a copy you could send me? If so, my email is chris886222 at btinternet.com I won't steal your thunder but will await your posting with interest. Chris R.
Neven, I read the science as a hobby and have finally booted myself into doing a blog. I've just dumped on a series of articles I was going to do as overlong posts at the science forums where I normally post. The most recent one is about why my scepticism about an imminent sea-ice free summer minimum is wavering. There are 2 other posts about thickness of Arctic sea ice. http://dosbat.blogspot.com/2011/07/in-flux.html Regards, and thanks for your efforts (I now know how much time it takes). Chris
Toggle Commented Jul 17, 2011 on SIE 2011 update 11: the heat is on at Arctic Sea Ice
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Apr 28, 2011