tag:blogger.com,1999:blog-5337555368793819627.post5643013496552280769..comments2023-06-07T09:04:36.390-04:00Comments on More Grumbine Science: Another one bites the dustRobert Grumbinehttp://www.blogger.com/profile/10783453972811796911noreply@blogger.comBlogger2125tag:blogger.com,1999:blog-5337555368793819627.post-64381091071665783332009-04-11T09:49:00.000-04:002009-04-11T09:49:00.000-04:00I'm afraid I don't have much to add. You've found...I'm afraid I don't have much to add. You've found some interesting papers, but if you're read them all, you know more than me. From your note over there (folks, do take a look at the pdf Hank links to)<BR/><I><BR/>Ok, interesting stuff out there on structure:<BR/><BR/>http://voxel.tamu.edu/publications/iceshelf_stru.pdf<BR/><BR/>8/8/2005<BR/>Structure of Eastern Antarctic Peninsula Ice Shelves and Ice Tongues from Synthetic Aperture Radar Imagery<BR/><BR/>______excerpt_follows_____<BR/><BR/>Examination of synthetic aperture radar data collected over the southeastern Antarctic Peninsula shows that features sometimes mapped as ice shelves are more likely composed of numerous ice tongues interspersed within a matrix of fast ice and icebergs. The tongues are formed by the seaward extension of numerous small mountain glaciers that drain from the Antarctic Peninsula. Once afloat, the tongues intermingle with a matrix of fast ice and brash. Examination of 1997 Radarsat-1 image mosaics shows that southeastern Antarctic Peninsula composite-ice-shelves covered an area of about 3500 km2. Similar to ice tongues around the rest of Antarctica, these features are highly fragmented and likely to be susceptible to mechanical failure.<BR/>…<BR/></I><BR/><BR/>This is interesting in its own right. I didn't distinguish ice shelf and ice tongue back in doing my 'types of ice' note. For the most part, this is reasonable. They're both ice that is floating on the ocean being fed by ice on land. The only distinction being that the ice tongue is long and narrow.<BR/><BR/>From this paper, there <I>is</I> a distinction to be drawn between different ice shelves -- some ice shelves have as important components ice that froze from the ocean, sea ice, and which then froze on to land (fast ice, as in frozen fast) or ice tongues. Once enough such freezing has happened between a number of tongues, you've got an ice shelf of a novel sort. (Brash ice refers to a stage of development for sea ice. We've got a million of them, it seems.)<BR/><BR/>The mechanical weakness referred to comes about in two different ways. One part is, the sea ice is much thinner than the ice tongue. Second part is that piling up a bunch of rocks and freezing them together is much weaker than having a solid sheet of the material.<BR/><BR/>Consequently, this sort of ice shelf will be much more inclined to collapse. And, when it goes, it's likely to collapse much faster.<BR/><BR/>The major Antarctic ice shelves, on the other hand, are not of this sort. The Filchner-Ronne and Ross Ice Shelf are the very thick ice extruded from land type. They're also farther south, so in colder areas. This is important because the mechanical strength of ice decreases as the temperature rises. It is concerns about these two which occasioned Mercer's drastic title. There's more to the story about why they're a concern, but I'll take that up separately.Robert Grumbinehttps://www.blogger.com/profile/10783453972811796911noreply@blogger.comtag:blogger.com,1999:blog-5337555368793819627.post-68342209960495960132009-04-10T14:00:00.000-04:002009-04-10T14:00:00.000-04:00Can I be lazy and ask if you have comments on some...Can I be lazy and ask if you have comments on some of the papers I noted at RC? Either here or there. <BR/><BR/>Some ice is a mix:<BR/>http://www.realclimate.org/index.php/archives/2009/04/wilkins-ice-shelf-collapse/langswitch_lang/de#comment-119049<BR/><BR/>Gavin suggested at the top that the pattern of fracture is interesting and hoped for comments from the researchers.<BR/><BR/>A few other comments earlier in the same thread, and a pointer to:<BR/>http://www.uni-muenster.de/Physik.GP/Polargeophysik/Wilkins-Schelfeis.html in hope someone reading German will interpret.Hank Robertshttps://www.blogger.com/profile/07521410755553979665noreply@blogger.com