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With 2017 ice extent estimates complete we can look at the year in perspective. Above is a graph showing the annual average extents since 2007, comparing MASIE and SII (v3.0). Obviously, the trend in MASIE could not be flatter, while SII shows a decline. The first five years the two indices were nearly the same, and since then SII shows less ice, about 260k km2 each year. Note also how small is the variance year over year: Standard deviation is +/- 260k km2, or about 2.5% of the average annual extent. This holds for both indices. Note also a pattern of three higher years followed by two lower years.
A previous post Sea Ice Index Updates to v.3.0 reported on the newest SII version, and we can see how it compares with MASIE over this last year.
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The first four…
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