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John Christiansen wrote: Since the Arctic Ocean is highly stratified with cold water layers at the top, as long as the water is covered by ice, the cold top-water should remain somewhat intact in that state, but as soon as the ice is gone, the radiation will reach the darker water and heat it to expand melting of nearby ice. One thought that's been going through my mind recently that I may have seen mentioned in a minor way but seems fairly significant to me is the increased mixing of temperature and salinity layers due to storms, which I think would have greater impact and likely be more frequent as the ice recedes. Last November when there was a big storm near Alaska I read the following paper, which seemed applicable then, but as I said I think could have broader significance: "Storm-driven mixing and potential impact on the Arctic Ocean" http://www.whoi.edu/fileserver.do?id=48251&pt=10&p=33752 Especially interesting is Figure 22 which shows an increasing number of anomalous stormy days over the 5 year periods from 1980 - 1999. I think this effect could even be contributing to the increasingly early drop in the PIOMAS volume to CT area ratio graph Neven created in a separate thread, because if ice area or quality is decreasing and storms are increasing then greater mixing could bring a significant amount of nearby heat to bear on the ice volume, and do so fairly early in the season before the sun has had much time to take effect. This is all hand waving of course, and it would be interesting to quantify it somehow, but I thought I'd throw the idea into the mix. Thanks again to all for their contributions.
Toggle Commented Apr 26, 2012 on ASI 2012 update 1: a new beginning at Arctic Sea Ice
Hello gentlemen, These are very good points and suggestions, and since I'm on the trail I think I'll keep digging a little deeper, so to speak. Here's an interesting paper that seems relevant to the circumstances: "Storm-driven mixing and potential impact on the Arctic Ocean" http://www.whoi.edu/fileserver.do?id=48251&pt=10&p=33752 I just started looking at some of the other buoy data, and check out ITP54: http://www.whoi.edu/page.do?pid=75638 Not sure what's happening there but something seems to be. I've read only the first two pages of the paper, but hit some interesting sentences already, for example "In this study we will show that intense storms could actually force mixing through the Arctic halocline to the thermocline." (p. 2). Also "...a storm in October 1988 intensified vertical mixing, enhanced the entrainment of warm and salty Atlantic water into the mixed layer, and resulted in considerable melting of sea ice [Steele and Morison, 1993]." (p. 2-3) As I said, I'll keep digging but thought I'd share what I've found so far in case others are interested in joining in. All the best, David
Toggle Commented Nov 22, 2011 on Storm impacts at Arctic Sea Ice
Hi everyone, I've really enjoyed following the blog since the summer but haven't had anything to contribute so far. Here's one observation for others to critique, but looking at the ITP55 salinity data for November 11th, I interpret the black colors before then to mean the salinity was below the scale, i.e. below 25. After the storm passed the salinity was raised to 25. The temperature for that day in that region seems to be about -1.2 - -1.3. Google leads us to a water freezing temperature by salinity calculator: http://www.csgnetwork.com/h2ofreezecalc.html At 23 PSU salinity the freezing temperature is -1.255 deg C; at 25 PSU salinity the freezing temperature is -1.366 deg C, so even if the temperature remained constant the changed salinity due to storm mixing might have melted the ice, as it seems to be right on the phase transition. The next question this raises is energy (enthalpy/entropy?) changes in a unit of water due to dissolved salt versus energy changes due to raised temperature, but I'm afraid my thermodynamics skills were never adequate to answer that question and certainly aren't now. Anyways, just thought I'd contribute to the conversation. Thanks again to everyone for their erudition, civility and hard work.
Toggle Commented Nov 19, 2011 on Storm impacts at Arctic Sea Ice
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Nov 19, 2011