glade vs polynya

glade

noun
  • An open space in the ice on a river or lake. 

  • An everglade. 

  • An open passage through a wood; a grassy open or cleared space in a forest. 

  • A bright surface of ice or snow. 

polynya

noun
  • A naturally formed transient area of open water surrounded by sea ice, especially in polar or subpolar seas. 

How often have the words glade and polynya occurred in a corpus of books? (source: Google Ngram Viewer )