Snow Stratigraphic Investigations at Dome C, East Antarctica

Current i n t e r e s t i n stu d i e s of past c l i m a t i c changes as revealed in long i c e cores has stressed a need f o r understanding the development of the record preserved i n these cores. This study i n v e s t i g a t e s whether the record preserved a t depth i s more a fu n c t i o n of deposit i o n a l processes or of processes a c t i n g during or soon a f t e r b u r i a l . The temporal and a r e a l v a r i a b i l i t y of accumulation are i n v e s t i g a t e d w i t h a view to understanding how representative a s i n g l e core i s f o r a c e r t a i n r e gion, both i n time and space. The v a l i d i t y of c e r t a i n s t r a t i g r a p h i c i n t e r p r e t a t i o n s f o r dating i s a l s o assessed. Evidence from snow p i t studies made at Dome C, East A n t a r c t i c a , (74 34'S, 123 10'E) suggests that a major part of the d e p o s i t i o n a l features are preserved with depth. V i s i b l e annual s t r a t a are composed of t h i n hard c r u s t s o v e r l y i n g t h i c k e r l a y e r s of s o f t to medium hard snow. Depth h o a r l i k e low den s i t y l a y e r s , when they occur, are most often found below the t h i n hard c r u s t s . Cycles i n the concent r a t i o n of gross Beta r a d i o a c t i v i t y and m i c r o p a r t i c l e s occur and can be a c c u r a t e l y dated when studied i n conjunction with a d e t a i l e d record of the v i s i b l e s t r a t i g r a p h y . Accumulation stake measurements are used to study the formation of annual l a y e r s at Dome C. These measurements support the b e l i e f that d e p o s i t i o n a l processes can account f o r a major part of the s t r a t i g r a p h i c record. Strong near surface temperature gradients and the associated e f f e c t s of thermal conduction, vapor d i f f u s i o n and a i r convection c o n t r i b u t e to the development of depth hoar and with time may lead to s i g n i f i c a n t changes i n the v a r i a t i o n s i n hardness, d e n s i t y , grain s i z e and p o s s i b l y i m purity concentration and t o t a l mass preserved i n i n d i v i d u a l l a y e r s .