To start with, this is the Charctic graph from NSIDC for July 4:
As you can see, the current extent is competing with the lowest extents ever recorded for this date.The actual extent NSIDC reports for July 15 this year is 7.857 million square kilometers, which is more than 1.7 million square kilometers below the 1981-2010 average extent of 9.564 million square kilometers for that date.
This is the sea extent as shown by the Climate Change Institute (click on the image to view a larger version):
Here is the map of the sea ice extent from the Danish Polar Portal:
|Source: Polar Portal|
But, extent isn't the only factor we need to consider. We also need to look at the ice thickness. This is the sea ice thickness as provided by the Polar Institute with the scale shown on the bottom of the image:
|Source: Polar Portal|
The cooler the color, the thinner the ice. This shows the ice is not only breaking up, but is also very thin.
Comparing these graphs makes me believe we will see all of the dark blue, purple and violet areas in the above graph melt by the end of the melt season in September. The red and white areas will survive. At this time of year, I think the green areas will, too, but in a much thinner state. Which leaves the light blue areas and I think about half of those areas will melt. On the map above, I estimate the minimum extent will still cover about half of the circular area around the pole and fill approximately two of the 10-degree blocks south of that circle. Using the same math I used in my March 22 posting, this comes out to be about 2 million square kilometers for the northernmost circle and about 325,000 square kilometers for each of the squares. This comes out to a total of approximately 2.7 million square kilometers.
A major factor is the weather. The Arctic weather started the year much warmer than average, but it has been mild-to-cold this summer and not as conducive to melting sea ice as in previous years. Here is a graph from NSIDC showing the cumulative freezing days starting on July 1 of the previous year and continuing to July 1 of the current year. The shaded areas show the percentile ranges (as listed) over the period 1981 through 2010:
The weather factor is discussed at length in this PIOMASS posting. In particular, take a look at the graph of the Daily Average Arctic Sea Ice Thickness From PIOMASS located at the bottom of the posting, right before the comments section. This graph shows the thickness is not only historically low, but it has been all year. But, one of the things documented in this post is that the difference between 2017 and 2012 (the year of record low extent) is closing, where 2017 was much lower than 2012 to begin with. Using this input, let's postulate that the ice melt will not occur quite as severely as I speculated above. Based on that input from PIOMAS and NSIDC, let's bump the minimum extent estimate up to an even 3.0 million square kilometers.
This estimate is consistent with my March estimate and would be dangerously lower than the previous lowest minimum extent of 3.4 million square kilometers that occurred in 2012.