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
and here’s the clock
Here’s the context of the date in comparison with all of the others since 1917. (I calculated this to be day 124.683 in 2011, please check)
…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.