In case you missed it, the official result for 2011 is in:
The Tanana River officially broke up on May 4, 2011 at 4:24 PM
Here’s the context of the date in comparison with all of the others since 1917:
and since Willis mentioned it, there is a correlation between the Nenana break-up date and the Pacific Decadal Oscillation, although I think the warming recorded since the 1960s (with the trending of the breakup earlier in the year) might correlate with the growth of Fairbanks upstream.
I inverted the Nenana breakup date so that up is earlier in the year (ie warmer). The PDO data was filtered to remove the high frequency noise.