The Eye (2) - S1-E11
Visible crew/equipment: In the beginning of the show (before the intro starts), when you look out the window you can actually see two people shaking the small trees in the storm... Come to think of it, why would there be trees in the first place? How could they survive out there if Atlantis submerged in the ocean? (00:02:21)
Chosen answer: Because the ZPM allowing them to dial Atlantis was being used at the Antarctic defense outpost. They couldn't risk making Earth vulnerable to attack from Anubis by depleting it with repeated dialing to the Pegasus galaxy. Once they knew Atlantis was in serious danger, they had no choice.
Grumpy Scot
ZPM from Antarctic was depleted in first dial, dial in Siege was done via ZPM from Egypt (SG-1: Moebius Part-1/2).