Originally posted 7-11-2011
This is a time series graph (see below) that shows the area of ice cover in the Arctic Ocean from the beginning of April through July 11, 2011. As the legend in the graph indicates, the solid gray line represents the average ice cover (in millions of square Km) for all years between 1979 when satellite images of the summer Arctic first became available through 2000. This constitutes a baseline average for comparison to the current extent of ice cover. The lighter gray area bounding the dark gray line shows the amount of variability around the average. This area is two standard deviations. For those of you who have not studied statistics, a + 2 standard deviation range includes 95% of all observations in the data set (of observations between 1979-2000). This also means that any observation that falls outside of that lighter gray area is considered to be significantly different than the baseline average.
OK, with that in mind, look at the graph below. This graph shows the historical 1979-2000 average as well as the sea ice extent for 2007, the year that we had the maximum recent observed sea ice melt (the dashed green line), and the 2011 sea ice extent through July 11, 2011 (the blue line). The 2011 line dipped below the 2007 line a few days ago, which, for this date, had the largest ice melt extent on record. If this trend continues we will see another sea ice melt maximum.
In 2007 the maximum ice melt extent resulted in ice cover that was over 3 million square Km less than the historical average. Some climatologists suggest that if the trend in sea ice melt continues we may see an ice-free Arctic Ocean in the next 50 years. Of course, only time will tell on that prediction.
This link (see below), also from the NSIDC, will take you to the NSIDC website where you can view an animation that shows the maximum extent of ice melt from 1979 - 2009. The white area in the animation represents ocean area that has at least 15% ice cover, and the pink line around the edge represents the 1979-2000 average extent of maximum summer melt.
http://nsidc.org/images/arcticseaicenews/20091005_Figure6.mov
For me, the conditions in the Arctic are one of the indicators, like a canary in a coal mine, of the status of climate shift on the planet.
The bottom line? It's getting warmer out there. Of course there is variability around the average, but that's the case for any natural system. What you have to look at are trends. And here's the trend in sea ice cover for the Month of June since 1979. There are some observations above the trend line, and some below, but the overall trend shows decreasing ice cover over the past 30+ years.
If you look at the graph above, you will see that for the month of June, 2011 had the 2nd largest ice melt on record, exceeded only by 2010, and 2007 is a close 3rd. Whether we will see a new maximum ice melt by the end of the summer depends entirely on local weather conditions in the Arctic.
This graph, also from the NSIDC, shows the temperature anomalies, i.e., deviations from long-term averages for June, over the Arctic Ocean and nearby land masses. Take a few minutes to familiarize yourself with this north polar view - it's not the way most of us are used to looking at the world.
You will see warmer than average temperatures over most of the Arctic Ocean, as well as Siberia and northern Greenland (2-5 oC warmer than the historical average for this time of year!). Cooler than average conditions existed over Iceland and northern Canada east of Alaska and west of Hudson Bay (-1 to -2 oC cooler than the historical average for this time of year). If these conditions persist, we could see another record ice-melt year.
(Graph courtesy of the National Snow and Ice Data Center, U. Colorado, Boulder.)
Well, this is something to think about! I like to keep an eye on the Arctic
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