What Would Obama Do?

From Fox News:
Moscow’s annexation of Crimea was condemned worldwide, but some people in Alaska apparently are yearning for the days when they, too, were part of Mother Russia. 
A petition on the White House website created by “S.V.” of Anchorage is calling on Alaskans and others to "vote" for Alaska to secede from the U.S. and become a part of Russia.

In less than a week, the petition, titled “Alaska Back to Russia,” has garnered nearly 30,000 signatures, though it's unclear where they are from. 

“Vote for secession of Alaska from the United States and joining Russia,” the petition says. 
The petition, though strangely worded and difficult to understand, describes how Alaska was originally settled and populated by native Russians. 
Secretary of State William Seward purchased Alaska from Russia in 1867 for $7.2 million, in a decision decried at the time as “Seward’s Folly.” The territory officially became the 49^th state on Jan. 3, 1959. 
Even if the White House responds to the Alaska petition, it is almost certainly going nowhere. The Alaska petition offers no specifics for how the proposed secession would even be executed, whether by referendum or some other process. Further, the Supreme Court ruled, in the wake of the Civil War, that unilateral secession is unconstitutional.   http://www.foxnews.com/politics/2014/03/27/thousands-sign-official-white-house-petition-to-return-alaska-to-russia/
Even though it is unlikely, what would happen if Russia did take over an Alaskan/American island in the Bering Sea?
What would Obama do in response?  Would he use force or would he let Russia take over the land with barely a whimper?
My guess would be the latter.