Answer:
Nominative absolute.
Step-by-step explanation:
Nominative absolute in grammar is a sentence construction where a noun, noun phrase, or pronoun is in the nominative and is used to start or end a sentence. It is normally used as a loose modifier of the whole sentence, with the noun, noun phrase, or pronoun followed by the modifiers.
In the given sentence, the nominative absolute is "the weather remaining turbulent", which also acts as a modifier for the independent clause "we will postpone our canoe trip."
Thus, the correct answer is nominative absolute.