The summer solstice marks the midpoint of the melting season for arctic sea ice. This year we are on track for another record low. The minimum extent of arctic sea ice occurs near the autumnal equinox, which is on September 22nd this year (14:21 MT on a Thursday); on that day the sun will dip below the horizon, and a frigid night will fall on parts of the arctic. Until that time the constant sun will melt anything it touches.
About a week ago the National Snow and Ice Data Center (NSDIC) completed transition of sea ice data gathering from the broken DMSP (Defense Meteorological Satellite Program) F-17 satellite to DMSP F-18. The data from DMSP F-18 had been considered provisional, and showed a shockingly low total arctic sea ice trend. The DMSP F-18 data is no longer provisional, and neither is the shocking sea ice trend.
Arctic sea ice coverage data provide some of the most objective information about the heat level of the planet. Melting sea ice will not raise the level of the oceans. One reason the arctic sea ice coverage is such a good data set is that sea ice looks a lot different than ocean water. This makes it ideal for remote sensing.
An area is considered covered if it is at least 15% sea ice. This means that there is a lot of open ocean in areas that are scored as covered by sea ice. This also means that weather phenomena can compress the sea ice into a very small area, and make it look like a lot of sea ice has been lost at once. This sort of adjustment is common this time of year, and we have not seen a big adjustment in this year's data yet. There was a big adjustment just prior to the summer solstice in 2012, and the current sea ice levels are almost exactly what the post solstice 2012 levels were. If there is an adjustment this year we could see a very low record low level of Arctic sea ice. If there is no adjustment we may see a record low similar to that seen in 2012.
Because there are so many active climate change deniers making noises this campaign year I feel somewhat like I should say something about trendings and confidence intervals. Instead I am just going to wave my little flag and tell you, my readers, that it looks like some interesting data are on their way.