The plot requires the gang to travel to Antarctica. This revelation is automatically the first Clue; no roll is necessary.
If Mystery Inc. travels to the Antarctic by boat, they might begin their investigation during the journey (if the GM can think of a logical reason for there to be Clues on the Boat. The Mystery Machine is in the Cargo Hold and can be offloaded and used once they arrive.
If the Gang travels to the Antarctic by plane, it is a cargo plane, and the Mystery Machine is in the Cargo Hold and can be offloaded and used once they arrive.
If they travel to the Antarctic by helicopter, they cannot bring the Mystery Machine at all. Reduce the number of Clues required to solve the Mystery by 1.