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SUMMARY:Densification in the Greenland dry snow zone - implications for al
 timetry - Prof Elizabeth Morris\, Scott Polar Research Insitute
DTSTART:20120222T163000Z
DTEND:20120222T173000Z
UID:TALK33994@talks.cam.ac.uk
CONTACT:Steven Palmer
DESCRIPTION:As part of the cal/val experiments for the CryoSat radar altim
 eter\, density profiles in the upper 10-14 m of snow have been measured al
 ong a 500 km traverse across the Greenland Ice Sheet\, using a neutron sca
 ttering technique. Repeat measurements\, over periods ranging from a few d
 ays to 5 years allow strain rates and densification rates to be determined
  as a function of depth. As expected\, the strain rate decreases as the ra
 tio of pore space to ice content decreases. Very large strain rates are ob
 served in the surface layer of snow over summer periods. However\, for mul
 ti-year snow\, once the effect of porosity has been removed\, the remainin
 g mean response is constant with depth\, that is the effect of increasing 
 overburden pressure is counteracted by increasing strength of the material
 . The mean strain rate for multi-year snow at a given site is related to t
 he mean annual accumulation rate and mean annual temperature by an express
 ion consistent with the Herron and Langway equation for first-stage densif
 ication. However\, there are fluctuations in strainrate associated with th
 e annual layering which indicate that fine and coarse-grained snow have di
 ffering strengths.  Futhermore\,  the temperature-dependent process equati
 ons proposed by previous workers  are not consistent with the data.  An al
 ternative  approach is suggested. 
LOCATION:Scott Polar Research Institute\, main lecture theatre
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