tag:blogger.com,1999:blog-7729093380675162051.post7678063616279699579..comments2024-03-28T13:56:47.604+11:00Comments on moyhu: Daily Arctic TemperaturesNick Stokeshttp://www.blogger.com/profile/06377413236983002873noreply@blogger.comBlogger14125tag:blogger.com,1999:blog-7729093380675162051.post-10334597142743346222017-07-01T19:57:05.468+10:002017-07-01T19:57:05.468+10:00Thanks, Steven, I'll fix the 2016. I said earl...Thanks, Steven, I'll fix the 2016. I said earlier that the main issue with allowing past year comparisons is the amount of data entailed, to allow for arbitrary choice of cell. But I'll see if I can do it for some popular choices.Nick Stokeshttps://www.blogger.com/profile/06377413236983002873noreply@blogger.comtag:blogger.com,1999:blog-7729093380675162051.post-73667418298148775822017-07-01T19:05:00.329+10:002017-07-01T19:05:00.329+10:00Nick, your Arctic temperature graphs at this link ...Nick, your Arctic temperature graphs at <a href="https://moyhu.blogspot.be/p/latest-ice-and-temperature-data.html#arctic" rel="nofollow">this link</a> are still labeled "2016" although the graphs currently show data for 2017. Also, as some other commenters have suggested, I think it would be very interesting to be able to make comparisons with other years, for example years like 2016, 2015, 2012 and 2007.Steven Dnoreply@blogger.comtag:blogger.com,1999:blog-7729093380675162051.post-21758783080237178252015-06-06T21:49:42.641+10:002015-06-06T21:49:42.641+10:00Peter,
Yes, I certainly use trig area averaging bo...Peter,<br />Yes, I certainly use trig area averaging both for Arctic and globe. It's essential near the poles - I'm pretty amazed DMI doesn't.Nick Stokeshttps://www.blogger.com/profile/06377413236983002873noreply@blogger.comtag:blogger.com,1999:blog-7729093380675162051.post-91770037113643637442015-06-06T21:00:20.569+10:002015-06-06T21:00:20.569+10:00How are you doing the averaging? Are you adjustin...How are you doing the averaging? Are you adjusting for grid box area? DMI doesn't, it simply uses a 0.5 degree grid and averages together all the points with equal weighting. That means it's not a true measurement of the average temperature for the area above 80N, but is very heavily weighted towards the Pole. Maybe also helps explain the shape difference?Peterhttps://www.blogger.com/profile/12559721137290332762noreply@blogger.comtag:blogger.com,1999:blog-7729093380675162051.post-60076898890324199612015-06-01T17:27:58.680+10:002015-06-01T17:27:58.680+10:00Nick: What gives the average temperature series su...Nick: <i>What gives the average temperature series such a marked flat top in summer at about 0°C?</i><br /><br />I think you're trying to get the tail to wag the dog here. This is just due to the much larger transfer of heat energy from the open ocean and the air above it than there is between the ice and the air. <br /><br />In wintertime conditions, the surface boundary layer looks pretty much the same over the (frozen) Arctic Ocean, but in summer, once the big melt gets under way, the open water moderates the temperature of the air.<br /><br />Put another way, the reason why the surface air temperature is relatively flat in summer is unrelated to why the sea ice melts. <br /><br />The main thing that having the surface air temperature above 0°C does is the snow on the top melts, forming melt pools. And there's some pretty interesting things that happen because of that. But it's my understanding this is a pretty minor source of sea ice loss. <br /><br />The heat conduction between the ocean and the ice is much, much larger than that of the air and the snow layer on top of the (still briny) sea ice. As far as I can see, adding more heat energy into the surface layers of the ocean is still going to be the primary way you're going to accelerate the rate of ice loss. Carrickhttps://www.blogger.com/profile/03476050886656768837noreply@blogger.comtag:blogger.com,1999:blog-7729093380675162051.post-9175895494441201782015-06-01T04:41:58.625+10:002015-06-01T04:41:58.625+10:00Carrick,
Yes, but the question is, what influences...Carrick,<br />Yes, but the question is, what influences air temperature? What gives the average temperature series such a marked flat top in summer at about 0°C?<br /><br />I think it is the temperature of melting ice on the upper surface which is in contact with air, not with sea water. Not so much salt there.<br />Nick Stokeshttps://www.blogger.com/profile/06377413236983002873noreply@blogger.comtag:blogger.com,1999:blog-7729093380675162051.post-22053491513782133462015-06-01T01:30:55.453+10:002015-06-01T01:30:55.453+10:00As I understand it, bottom melting is the primary ...As I understand it, <a href="http://onlinelibrary.wiley.com/store/10.1029/2008GL034007/asset/grl24626.pdf?v=1&t=iaclqm3t&s=fc0daaca873fbf2c785dc8ba0d3da693377cbcac" rel="nofollow">bottom melting is the primary thermodynamic mechanism for sea ice loss. </a> (The primary mechanical one is transport of ice from colder regions to warmer regions.)<br /><br />When sea air temperatures go above -1.8°C, it's no longer possible for sea ice to form on the surface of the ocean. Open ocean surface implies an increased rate of solar radiation absorption by the ocean, and in turn an increase in the rate of bottom melting.Carrickhttps://www.blogger.com/profile/03476050886656768837noreply@blogger.comtag:blogger.com,1999:blog-7729093380675162051.post-82884893565673003162015-05-31T09:28:22.266+10:002015-05-31T09:28:22.266+10:00Carrick,
More important I think is the melting poi...Carrick,<br />More important I think is the melting point of the upper surface, which is likely much closer to 0°C.Nick Stokeshttps://www.blogger.com/profile/06377413236983002873noreply@blogger.comtag:blogger.com,1999:blog-7729093380675162051.post-69800616616484745852015-05-31T09:12:38.998+10:002015-05-31T09:12:38.998+10:00Nick Stokes: I have however used Celsius - I can&#...Nick Stokes: <i>I have however used Celsius - I can't see the point of Kelvin here, especially with freezing being prominent.</i><br /><br />0°C isn't really the right threshold either. A better value is -1.8°C, which is the freezing point of sea water.<br /><br />Kevin---I think the apparent "shoulder" is a visual illusion. <br /><br />Here's an animation of the Arctic temperature for the year, averaged in 5° bands (annular rings), using Nick's widget:<br /><br /><a href="https://dl.dropboxusercontent.com/u/4520911/ArcticIce/Arctic_movie-desktop.m4v" rel="nofollow">animation</a><br /><br />As the radius of the annular ring decreases, you get more or less the same warming trend, just with progressively larger amplitude shorter period fluctuations.<br /><br />Our brains try and combine the phenomena of the warming trend and e.g. the peak around 70 days, so we see what looks like a shoulder.<br /><br />(This is easier to see if you download the m4v file and view it in a player that allows you to use the left & right arrows to rock the image back and forth.)Carrickhttps://www.blogger.com/profile/03476050886656768837noreply@blogger.comtag:blogger.com,1999:blog-7729093380675162051.post-87648115071391930562015-05-31T02:29:21.026+10:002015-05-31T02:29:21.026+10:00Nick, the timing isn't consistent - so they av...Nick, the timing isn't consistent - so they average out over any period of years - but if you view the individual years you will find that more often than not there is a spring shoulder between 260 and 265K. The fall shoulder is less pronounced or gets lost in noise more often, but it's still there in many years. Kevin O'Neillhttps://www.blogger.com/profile/06692943768484857724noreply@blogger.comtag:blogger.com,1999:blog-7729093380675162051.post-45354460909268379482015-05-30T15:50:24.571+10:002015-05-30T15:50:24.571+10:00Kevin,
I can't think of a reason. Actually, th...Kevin,<br />I can't think of a reason. Actually, there aren't pronounced shoulders in the 80N averages, either mine or DMI. A small one in fall in mine. <br /><br /><br />This gadget let's you try to localise effects. This year there was a big peak in to 0-90E quarter at about 100 days, which then fell away. That would be a big part of the apparent shoulder in >80N.Nick Stokeshttps://www.blogger.com/profile/06377413236983002873noreply@blogger.comtag:blogger.com,1999:blog-7729093380675162051.post-80110508328956620642015-05-30T14:31:26.114+10:002015-05-30T14:31:26.114+10:00Nick, in many years there is a 'shoulder' ...Nick, in many years there is a 'shoulder' at approximately -14C; both in spring and fall. Any idea what this might represent?Kevin O'Neillhttps://www.blogger.com/profile/06692943768484857724noreply@blogger.comtag:blogger.com,1999:blog-7729093380675162051.post-38217055880065265142015-05-30T01:07:51.443+10:002015-05-30T01:07:51.443+10:00Mainly a matter of data download. There are 24*6*3...Mainly a matter of data download. There are 24*6*365 datapoints for a full year. That's about 300 KB. I could set up a request data download for specific years.Nick Stokeshttps://www.blogger.com/profile/06377413236983002873noreply@blogger.comtag:blogger.com,1999:blog-7729093380675162051.post-80120244122806322282015-05-30T01:02:03.887+10:002015-05-30T01:02:03.887+10:00Why can't previous years be plotted (e.g. 2012...Why can't previous years be plotted (e.g. 2012)?Nightvidhttps://www.blogger.com/profile/03320916322586904305noreply@blogger.com