2014/05/07 Updated with correct date !
The Tanana River officially broke up and the Tripod moved down river stopping the clock at 3:48 PM Alaska Standard Time April 25th, 2014
This makes last years very late breakup seem anomalous. But of course its only weather!
Adding this years figures to the data and you get plots which seems to follow the various global temperature profiles of: warming since 1970s until 1998 then static to present.
People have said the earlier times of the breakup is due to industrialisation upstream of Nenana - However the static/reversed slope seems to show that either industrialisation has reversed or perhaps, maybe, the temperature is having an effect!:
Top 2 traces show timings from beginning of the year
Final trace is timing from vernal Equinox
All plots use AK time:
The first splits the data into 3 segments
The second assumes that there is no upturn and hence only 2 lines
Smoothing is done with Hodrick Prescott filter from http://www.web-reg.de/hp_addin.html
Breakup data from