ablation  
noun uk/əˈbleɪ.ʃən/ us/ˌæbˈleɪ.ʃən/
  (OF ICE OR ROCK)      
 [ U ] environment, geology specialized(冰川、冰山)消融;(岩石等物质)融蚀、水蚀 
the loss of ice or snow from a glacier or iceberg, or the loss of rock or similar material, caused by a process such as melting or erosion (= gradual damage and removing by waves, rain, or wind)
  Annual measurements have revealed that ice motion and ablation are not uniform from place to place or from year to year.