1.   The pack ice and fast ice that spread over polar seas form vast sheets many hundreds of square kilometres in area.

2.   Because polar sea ice is already afloat, it has little direct effect on global sea levels.

3.   General acceptance of the Ice Age began only when Elisha Kent Kane returned from his ill-fated search for an open polar sea.

4.   In this Arctic village, beachfront real estate means a summer view of polar sea ice glinting a few miles offshore.

5.   Shackleton led a terrifying sail across polar seas.

6.   The view reminded scientists of pack ice on a polar sea.