according to Gail Norton, they would only drill for a certain portion of time during the winter when ice roads would be viable that would prevent damage to the tundra. This is an article about her lobbying for drilling talking about these "fact".
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http://www.cnsnews.com/ViewPolitics.asp?Page=\\Politics\\archive\\200204\\POL20020402b.html>
Norton's letter went on to explain the steps the administration has proposed to even further limit the potential environmental impact of exploration and production, including only allowing work between November and May, outside the normal breeding months for all species that might enter the area. The plan also requires companies to use "ice roads" that melt each spring, protecting the underlying tundra.
"Moreover, the administration will require directional drilling and smaller production pads, so that energy exploration can be accomplished utilizing just 2,000 of the 1002 Area's 1.5 million acres," Norton concluded.
So I would say that rising temperatures in Alaska could impact this plan considerably. However, I doubt that would matter to them. ANWR is a sacred cow that has nothing to do with the oil there and everything to do with flexing Republican muscle, hand outs to the oil industry and the citizens of Alaska and setting a precedence for circumventing the will of the majority of the people (I believe I read somewhere that much of the oil they get from there may actually be shipped to places like China and Japan though I don't have that link).
As a matter of fact I'd be surprised if Ms. Norton stayed at the Dept. of Interior much longer then it takes to finally get the deal done. This seems to be her particular payoff to the oil industry. She will probably then end up with a cushy and well paid job working for Exxon.