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SUMMARY:Jökulhlaup impact on sub- and englacial environments: examples fr
 om southern Iceland - Andy Russell\, Newcastle University
DTSTART:20100316T140000Z
DTEND:20100316T150000Z
UID:TALK23677@talks.cam.ac.uk
CONTACT:Christian Franzke
DESCRIPTION:Hydrodynamic processes responsible for governing steady-state 
 water flow through glaciers are relatively well understood. However less i
 s known about the erosional and depositional impacts of glacier outburst f
 loods or jökulhlaups characterised by transient hydraulic processes and r
 outeways.  Despite the ubiquity of tunnel channels and tunnel valleys with
 in formerly glaciated areas\, their origin remains enigmatic. Few tightly 
 constrained modern analogues exist for event-related subglacial fluvial er
 osion and deposition. At Skeiðarárjökull\, Iceland\, sudden-onset\, hig
 h-magnitude jökulhlaups exiting overdeepened subglacial basins have gener
 ated a variety of hydro-mechanical erosional forms at and beneath the glac
 ier bed. We present geomorphological and stratigraphic evidence for subgla
 cial jökulhlaup erosion in form of tunnel channels and also sub- glacier-
 bed erosion associated with the development of hydrofracture and channel n
 etworks.  The spatial distribution of subglacial erosional forms is influe
 nced by sub- and proglacial topography and the distribution of buried glac
 ier ice. Zones of glacier bed erosion are also associated in many cases wi
 th hydrofracture-fill and esker ridges demonstrating interconnection of su
 bglacial and sub-glacier bed (subterranean) jökulhlaup flow pathways. The
 se findings may help explain complexity with the sediment and landform rec
 ord of formerly glaciated areas where tunnel channels are often found in a
 ssociation with subglacial deposits such as eskers. Subglacial meltwater s
 torage and movement beneath modern ice sheets may be associated with simil
 ar landforms and deposits. 
LOCATION:British Antarctic Survey\, Room 307
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