subterranean ice

例句：

1. 1. The subterranean ice is melting due to global warming.
   由于全球变暖，地下冰正在融化。
2. 2.The glaciers are slowly advancing towards the coastline.
   冰川正缓慢地向海岸线推进。
3. 3. The permafrost is a fascinating phenomenon that scientists study.
   永久冻土是一种令人着迷的现象，科学家们正在研究它。