ice field

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. A large, level expanse of floating ice that is more than eight kilometers (five miles) in its greatest dimension.

Century Dictionary and Cyclopedia

1. n. A great sheet or floe of ice, at times so extensive in arctic seas that its limits cannot be seen from the masthead.

Wiktionary

1. n. a network of interconnected glaciers or ice streams having a common source
2. n. a large expanse of floating ice (several miles long)

GNU Webster's 1913

1. n. an extensive sheet of ice.

WordNet 3.0

1. n. a large flat mass of ice (larger than an ice floe) floating at sea