Sunday, November 3, 2013

Another Very Warm October in Barrow

Another October has come and gone, and that means that once again Barrow had a very warm October: the average temperature was 24.7ºF, which is 7.5ºF above the 1981-2010 normal. This ties for the fifth warmest October of record and seven of the ten warmest have occurred in the past 15 years. Here's an updated plot of the October mean temperature at Barrow since the second order Weather Bureau station opened in 1920:

I've segregated the data into tercile values for the full 94 years: colder than 14.2F, warmer than 19.6 and then the middle tercile 14.2-19.6F. So this means that by definition, one third of the 94 Octobers  are "warm", one third middle and one third "cold". The green line is a local regression fit (LOESS) that preserves timing of changes multi-year variation (as e.g. a centered running mean would). Obviously, the run of overheated Octobers since 2002 are unprecedented in the 94 years of unbroken instrumental observations.

In spite of the sea ice edge being closer to the Alaska coast at the end of the summer than it has been in some years, the ice was slow to return to the coast. Here was the view from the Barrow sea ice webcam late on the afternoon of October 30th. As you can see, no ice was visible looking north, and reports on the ground confirmed that no sea was visible the on the morning of November 1st.


  1. Rick,

    That chart (and variants of it you've produced before) is one of the most remarkable in all of weather and climate science. The collapse of the variance is just mind-boggling. I wonder though how much of the anomaly this year was caused by the circulation anomaly (as in the rest of AK), and how much by missing sea ice. September in Barrow was the coolest since 1996 and even managed to be below normal.

  2. (My phone doesn't like this site to much.) The shape of the graph reminds me of the general shape found in almost all regional and global temperature reconstructions: high 1930s and present, low 1950s. But the lack of low points for the last few years is WOW.

    What would happen if october temps were plotted against the first day of ocean freezing? What is the profile of Koztebue - since it too gets ice but a different circulation pattern?

  3. We could say warmer than expected surface air temps can be driven by a lack of snow cover for inland locations, or a lack of nearby ocean ice cover for coastal communities.

    After living five years in Sitka I'm convinced the only major source of cold air below nearby ocean surface temps was precipitated by a clear cold air mass from inland Alaska and Canada that moved over that area.