 |
| Titel |
Reconstructing plateau icefields: Evaluating empirical and modelled approaches |
| VerfasserIn |
Danni Pearce, Brice Rea, Iestyn Barr |
| Konferenz |
EGU General Assembly 2013
|
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 15 (2013) |
| Datensatznummer |
250083101
|
|
|
|
|
|
| Zusammenfassung |
| Glacial landforms are widely utilised to reconstruct former glacier geometries with a
common aim to estimate the Equilibrium Line Altitudes (ELAs) and from these, infer
palaeoclimatic conditions. Such inferences may be studied on a regional scale and used to
correlate climatic gradients across large distances (e.g., Europe). In Britain, the traditional
approach uses geomorphological mapping with hand contouring to derive the palaeo-ice
surface. Recently, ice surface modelling enables an equilibrium profile reconstruction tuned
using the geomorphology. Both methods permit derivation of palaeo-climate but no study has
compared the two methods for the same ice-mass. This is important because either approach
may result in differences in glacier limits, ELAs and palaeo-climate. This research uses both
methods to reconstruct a plateau icefield and quantifies the results from a cartographic and
geometrical aspect.
Detailed geomorphological mapping of the Tweedsmuir Hills in the Southern Uplands,
Scotland (c. 320 km2) was conducted to examine the extent of Younger Dryas (YD;
12.9 -11.7 cal. ka BP) glaciation. Landform evidence indicates a plateau icefield
configuration of two separate ice-masses during the YD covering an area c. 45
km2 and 25 km2. The interpreted age is supported by new radiocarbon dating of
basal stratigraphies and Terrestrial Cosmogenic Nuclide Analysis (TCNA) of in situ
boulders.
Both techniques produce similar configurations however; the model results in a coarser
resolution requiring further processing if a cartographic map is required. When
landforms are absent or fragmentary (e.g., trimlines and lateral moraines), like in
many accumulation zones on plateau icefields, the geomorphological approach
increasingly relies on extrapolation between lines of evidence and on the individual’s
perception of how the ice-mass ought to look. In some locations this results in an
underestimation of the ice surface compared to the modelled surface most likely
due to reworking and paraglacial modification. It is suggested the model produces
an overall more holistic reconstruction, providing glaciological insights into an
otherwise static reconstruction. The model should not replace the traditional technique
but should be used in conjunction since it provides important insights into likely
boundary conditions, including shear stress, the presence of plateau ice and thickness. |
|
|
|
|
|
|