That's what I asked Dr. Webb, and here, paraphrased, is what Dave said,

Tyhee hasn't yet made that decision. Soon, with warmer temperatures, the ice will be too thin to drive on, but the lake water will become "less thick" so that a plane can land on it. This period is known as the "break-up" period and often lasts for two to three weeks. So, if it's decided to move the drill, it'll probably be after that time.

Cheers,

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