| Title | Layer disturbances and the radio-echo free zone in ice sheets |
| Author | Drews, R.; Eisen, O.; Weikusat, I.; Kipfstuhl, S.; Lambrecht, A.; Steinhage, D.; Wilhelms, F.; Miller, H. |
| Author Affil | Drews, R., Alfred-Wegener- Institut für Polar- und Meeresforschung, Bremerhaven, Federal Republic of Germany |
| Source | The Cryosphere (Online), 3(2), p.195- 203. Publisher: Copernicus on behalf of the European Geosciences Union, Katlenburg- Lindau, International. ISSN: 1994- 0424 |
| Publication Date | 2009 |
| Notes | In English. Published in The Cryosphere Discussion: 28 April 2009, http://www.the-cryosphere- discuss.net/3/307/2009/tcd-3-307-2009.html; doi:10.5194/tc-3-195-2009; accessed in May, 2010. 30 refs. GeoRef Acc. No: 301236. CRREL Acc. No: 64005576 |
| Index Terms | backscattering; bedrock; dielectric properties; glacial geology; ice; glacier flow; ice sheets; radar; rheology; sounding; temperature; Antarctica--Antarctic ice sheet; Greenland--Greenland ice sheet; Antarctica-- Queen Maud Land; Antarctic ice sheet; Antarctica; Arctic region; echo-free zone; EPICA; Greenland; Greenland ice sheet; ice cores; ice movement; Kirwanveggen Mountains; Kohnen Station; Queen Maud Land; radar methods; radio-wave methods; roughness |
| Abstract | Radio-echo sounding of the Antarctic and Greenlandic ice sheets often reveals a layer in the lowest hundreds of meters above bedrock more or less free of radio echoes, known as the echo-free zone (EFZ). The cause of this feature is unclear, so far lacking direct evidence for its origin. We compare echoes around the EPICA drill site in Dronning Maud Land, Antarctica, with the dielectric properties, crystal orientation fabrics and optical stratigraphy of the EPICA- DML ice core. We find that echoes disappear in the depth range where the dielectric contrast is blurred, and where the coherency of the layers in the ice core is lost due to disturbances caused by the ice flow. At the drill site, the EFZ onset at ~2100 m marks a boundary, below which the ice core may have experienced flow induced disturbances on various scales. The onset may indicate changing rheology which needs to be accounted for in the modeling of ice sheet dynamics. |
| URL | http://www.the-cryosphere.net/3/195/2009/tc-3-195-2009.pdf |
| Publication Type | journal article |
| Record ID | 88877 |