Digital Diatribes

A presentation of data on climate and other stuff

Quick hit post on the Arctic Ice

Posted by The Diatribe Guy on June 4, 2009

Very quick post here: Click the link to the right (IJIS) to check out the latest Arctic ice extent. As of today, June 4, it is below the 2003 level, but holding in second position. As an aside, I wouldn’t at all be surprised to see this tail off quite a bit and dip below most of the years again. Looking at 2008 this happened, but not to the extent that it melted in 2007. It can reasonably be expected that the ice just won’t jump by leaps and bounds at maximum melt, while still in an increasing mode. So, 2009 may well dip below normal before it’s said and done, but my own guess is that it will still end up higher than 2008, thus continuing the upward trend.

What I wanted to point out, however, is this little jump that occurs on June 1 of each year. Why does that happen?

I was curious, and looked into it a bit, and what I learned was that there is an adjustment that occurs at that point. During the winter, satellite readings of open water accurately decipher it as open water. During the spring melt, however, pools of water can start to form on the ice, and satellites may start to read these pools as open water. This assumption is made in the satellites prior to June 1. As of June 1, an adjustment is made to recognize this pooling of water on the ice, and so the ice extent increases a bit. This happens every year, so we see a little jump on June 1 each year.

What I couldn’t find was the date for the counter adjustment in the late fall/early winter, which I’m assuming has to occur at some point in order for there to be a consistent spring adjustment made. Nor does the chart seem to indicate what that date may be. My guess is it’s December 1 (6 months offset).

I’m uncertain as to why they don’t just always make that same adjustment. If it’s exceptionally warm for a bit, and there is pooling earlier than normal, a pre-June reading will understate ice extent. It seems to me that if the criteria for determining whether or not some water is open ocean or a swimming pool are good, the season shouldn’t matter.

But what do I know? Anyway, just wanted to share that little tidbit.


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