Meteoric and marine ice crystal orientation fabric observations from the Amery Ice Shelf, East Antarctica

• Main Authors: Treverrow, A, Warner, RC, Budd, WF, Craven, M
• Format: Conference Object
• Language: English
• Published: . 2009
• Subjects: Earth Sciences; Physical Geography and Environmental Geoscience; Glaciology; Amery; Amery Ice Shelf; Austral; East Antarctica; Lambert Glacier; Antarc*; Antarctica; Ice Shelf
• Online Access: http://ecite.utas.edu.au/110661

As a component of the AMISOR (Amery Ice Shelf Ocean Research) project,meteoric and accreted marine ice cores were retrieved from the Amery Ice Shelf,East Antarctica. During the 2001/02 and 2003/04 austral summers ice cores were obtained fromthe AM01 and AM01b sites; approximately 100 km from the shelf front. Furthercores were obtained 70 km upstream, along the same flow line, at the AM04 siteduring 2005/2006. At these sites, the Amery Ice Shelf has a layered structure.The upper layer consists of meteoric ice, from local accumulation and iceentering the shelf through the Lambert Glacier drainage system. The bottomlayer is accreted marine ice, over 200 m thick. Crystal orientation fabric and grain size measurements are presented formeteoric and marine ice cores. Meteoric ice samples are characterized by grainareas >50 mm 2 and multiple- maxima crystal orientation fabrics. It is suggestedthat stress relaxation in ice flowing into the shelf from the Lambert Glacierdrainage basin strongly influences the observed meteoric ice fabrics. Vertical, large circle girdle orientation fabrics observed within the marine ice areinfluenced by the presence of brine and insoluble microparticle inclusions. Grainsizes in the marine ice are <10 mm 2 due to microparticles restricting graingrowth. A strong single maximum fabric and layered, rectangular texture w asobserved in the marine ice sample obtained closest to the ice shelf base. Thefabric and texture of this sample are considered to be evidence for marine icelayer accumulation by frazil ice platelet accretion.