 |
| Titel |
Mechanisms of flute formation at a polythermal valley glacier: Midre Lovénbreen, Svalbard. |
| VerfasserIn |
Samuel Roberson, Bryn Hubbard, Hayley Coulson, Ian Fairchild |
| Konferenz |
EGU General Assembly 2010
|
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 12 (2010) |
| Datensatznummer |
250031786
|
|
|
|
|
|
| Zusammenfassung |
| Flutes in front of the margin of a small, polythermal valley glacier, Midre Lovénbreen,
Svalbard, were described in terms of their morphometry. Flutes, subglacial and proglacial
till, debris-rich basal ice and glacier ice were sampled for their sedimentary and
isotopic composition in order to investigate mechanisms of subglacial flute formation.
Flutes are widespread across the glacier forefield and consistently form in the lee of
cobble to boulder-sized clasts ploughed into proglacial till. Physical properties,
including mean particle-size-distributions and oxygen isotope compositions show
that flutes are enriched in 18O and depleted in gravel-sized particles relative to
adjacent subglacial till and overlying debris-rich basal ice. These properties indicate
that flutes are formed by the squeezing of partially fluidized subglacial till into
incipient basal cavities beneath warm-based ice within interior of the glacier. The
formation of flutes beneath relatively thick (>120 m) warm-based ice suggests that
partially fluidized sediment adfreezes onto the bed of the glacier. Melting on the
upglacier side of subglacial boulders is thought to create a heat-pump effect between
a zone of relatively high-pressure of the upglacier face and a zone of relatively
low-pressure on the downglacier face within incipient basal cavities. The presence of this
pressure-temperature gradient across the surface of subglacial boulders is invoked
to account the adfreezing of sediment squeezed into incipient basal cavities. The
distribution of flutes in front of Midre Lovénbreen may therefore be indicative
of the former extent of warm-based ice during periods of active flute formation. |
|
|
|
|
|
|