The sentence "others refer to them as giant rivers of ice" is in the present tense.
The past tense would have used referred, the future tense would have used, will refer.
Verbs tell you if a sentence is past present or future.
There is no future tense verb in this sentence. The sentence is present simple (is).
present, current, after, future, following, subsequent
Present tense.
The shift in tense in this sentence is from future tense (will do) to present tense (watches).
The present is a moment in time discernible as intermediate between past and future
It is the present tense, but not true.
the will in your sentence is present tense, so it is present tense
present, current, after, future, following, subsequent
This is a present simple sentence. The verb is pushes.Pushes is the third person singular form of push. The subject - the ice - is singular so the third person form of the verb is used.
Cierran (Present - close) Cerraron (Past - closed) Cerrarán (future - will close)
Many people have no hope for the future. To make the future strong we need work hard on the present.