I may be miss-remembering it, actually.
What you need to do is as follows:
* Find the pump lever in the temple, there should be a scientist guy in a room with it.
* Bring the pump back to the caves to clear the water.
* Go to the part of the caves where there was a door you couldn't get to. The water will have been drained, and you can access this room, where you will fight a boss.
* After the boss is defeated, the blocks of ice will be cleared from the temple.
* Back in the temple, there will be a pickaxe that was sitting on one of the blocks of ice before. Pick it up.
* Head back outside and give the pickaxe to the guy on the far left, and the rocks will clear away.
* Head into the temple through an alternate entrance on the other side of the rocks.