Ice cap and Ice mass

Ice cap noun - A mass of ice and snow that permanently covers a large area of land (e.g., the polar regions or a mountain peak).

Ice mass and ice cap are semantically related. In some cases you can use "Ice mass" instead a noun phrase "Ice cap".

Ice mass noun - A large mass of ice.

Ice cap and ice mass are semantically related. Sometimes you can replace phrase "Ice cap" with "Ice mass", this phrases are similar.