[Folda] Fwd Reminder Today's Seminar 12:30 - Eyjólfur?==?utf-8?q? Magnússon: Monitoring ice cauldrons with radio echo sounding

[Siqi Li]

-------- Original Message -------- 
Subject: [Jhi] Reminder Today's Seminar 12:30 - Eyjólfur Magnússon: Monitoring ice cauldrons with radio echo sounding 
Date: Friday, September 22, 2017 07:06 GMT 
From: "Maxwell Christopher Brown" <maxwell at hi.is> 
To: jhi at hi.is 
 
 
Dear all,

Today's seminar will be given by:

 Eyjólfur Magnússon (Institute of Earth Sciences, University of Iceland)

Title: Monitoring ice cauldrons with radio echo sounding. Examples from the cauldrons of Mýrdalsjökull and the Skaftá cauldrons. 

Date: Friday, 22nd September
Time: 12:30
Place: 3rd Floor meeting room, Askja

Abstract: A jökulhlaup, draining from the ice cauldrons of Mýrdalsjökull and destroying the bridge over the river Múlakvísl in July, 2011, raised two important questions. Firstly, what happened? This is still debated and will not be discussed specifically in this talk. Secondly, what kind of monitoring might help us foreseeing jökulhlaup of this magnitude? For more than a decade prior to this jökulhlaup the depth of the cauldrons had been surveyed approximately biannually using airborne surface profiling (radar). Often a decrease in cauldron depth has been considered as a sign of water accumulation beneath a cauldron. Decreased cauldron depth can however also be a consequence of reduced melting at the glacier bed allowing ice flow and snow drift to even out the topographic depression in the glacier surface. Water accumulation can also result in minor increase in cauldron depth if caused by subglacial melting directly beneath the cauldron; the volume of the melt is less than that of the melted ice. Changes in the surface shape of ice cauldrons do therefore not tell a full story on what happens beneath them. This provokes the idea of monitoring water accumulation beneath ice cauldrons with Radio Echo Sounding (RES). Since May 2012 most of the cauldrons of Mýrdalsjökull have been monitored with RES along the same profiles 1-2 times a year. In the talk, the added value of this type of cauldron monitoring is described.  Limitation RES survey will be discussed and also attempts to expand the survey from single repeated profiles to dense set of repeated profiles to extract high resolution elevation models of the glacier bed (5x20 m cell size). Results from RES surveys on Mýrdalsjökull in 2012-2017 and in the Eastern Skaftá cauldron (Western Vatnajökull) in 2014-2017 will be presented as case studies. In both cases the repeated RES survey provides new insights into the nature of the water bodies forming beneath the cauldrons.       

All are welcome.

Best wishes
Maxwell

-- 
Maxwell Brown
Research specialist
Institute of Earth Sciences
University of Iceland
Askja, Room 333 
Sturlugata 7
101 Reykjavík
Iceland
 
email: maxwell at hi.is
tel (office): +354-525-4730
tel (lab): +354-525-4794
tel (mobile): +354-832-0015  
  
 
 
 

 


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