tag:blogger.com,1999:blog-4100428215696856631.post7507011172680704407..comments2023-06-21T10:16:57.377-04:00Comments on Shaking Earth: Seismic time - change your watchesRob Sternberghttp://www.blogger.com/profile/01612449964830289194noreply@blogger.comBlogger2125tag:blogger.com,1999:blog-4100428215696856631.post-3228330568841863212008-12-10T06:50:00.000-05:002008-12-10T06:50:00.000-05:00An online article, Earth rotation and global chang...An online article, Earth rotation and global change, by Clark R. Wilson at the University of Texas, Austin (U.S. National Report to IUGG, 1991-1994 Rev. Geophys. Vol. 33 Suppl., 1995 American Geophysical Union) discusses this at http://www.agu.org/revgeophys/wilson01/wilson01.html. In the section "LOD [length of day] and PM [polar motion] at Longer Periods", he says "it has become common to invoke the core as the major cause of decadal LOD changes. Although some climatic forcing of long period LOD has been recognized, (Salstein and Rosen, 1986; Eubanks, 1993), it is uncertain at what time scale air and water become less important than the core. Unfortunately, the role of the core remains largely unquantified because it is too remote to be easily observed."<BR/><BR/>And, the web page for the Royal Observatory of Belgium says "On decadal time scales, the variations in the LOD have been shown to be correlated with the secular variation of the magnetic field. This suggests that the core plays an important role in these LOD changes. These LOD variations are thus believed to be associated with the changes in the core angular momentum" (http://www.astro.oma.be/SBC/earthrot.html).Rob Sternberghttps://www.blogger.com/profile/01612449964830289194noreply@blogger.comtag:blogger.com,1999:blog-4100428215696856631.post-31406261415831036712008-12-09T15:03:00.000-05:002008-12-09T15:03:00.000-05:00The long-term trend is explained by tidal friction...The long-term trend is explained by tidal friction, and the very short-term fluctuations I assume are due to seasonal shifts of air masses. But what is the cause of the intermediate cycle (looks like a period of about 15 years)?Anonymousnoreply@blogger.com