Nenana Ice Classic 2013 - the ice has moved 2013/05/20 14:41

Second latest time from beginning of the year
The record was set in 1964 which was a leap year. The movement happened 140.4868 days from January 1st

This year the movement occurred 139.6118 days from January 1st

Hmmm! Perhaps this all need rejigging to relate the breakup time to the vernal equinox and z-time

Anyway, here are 2 plots using 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
http://www.nenanaakiceclassic.com/

Heres the modified plot with days since vernal equinox instead of start of year:

So this year now becomes the latest date for breakup! Otherwise the shape remains.