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- Title
Extreme snow metamorphism in the Allan Hills, Antarctica, as an analogue for glacial conditions with implications for stable isotope composition.
- Authors
DADIC, Ruzica; BERTLER, Nancy A. N.; SCHNEEBELI, Martin; MATZL, Margret; SCHWIKOWSKI, Margit
- Abstract
Understanding physical processes in near-zero accumulation areas can help us to better understand polar ice-core records, particularly during periods when accumulation rates were lower than today. We report measurements from a 5m firn core from the Allan Hills, Antarctica, which include physical properties using computer tomography, stable isotope ratios δD and δ18O, and 210Pb activity. The core shows a highly metamorphosed firn with homogeneous and stable structure, but with discrete layers near the surface. The observed firn structure is caused by a combination of unique depositional and post-depositional processes. The irregular dD and d18O signal does not follow the stratigraphic sequence and implies post-depositional modification caused by microscopic pressure gradients in the firn that can result from either forced ventilation over rough surfaces in the presence of wind or alternating temperature-gradients between the firn and the atmosphere. Our results also indicate impact snow deposition under high winds and with a high initial density and air exchange between the atmosphere and the snowpack. 210Pb activity below 0.3m falls below the detection limit, implying that most of the core is more than 100 years old. We conclude that the Allan Hills record provides a unique opportunity to investigate important processes that would have affected ice-core records from glacial periods.
- Subjects
ANTARCTICA; SNOW analysis; ICE-atmosphere interaction
- Publication
Journal of Glaciology, 2015, Vol 61, Issue 230, p1171
- ISSN
0022-1430
- Publication type
Article
- DOI
10.3189/2015JoG15J027