Of sentimental interest only, the last remnants of Big Block disappeared today!
People first starting saying this back in late July. BB is not gone at the better resolution of UHH 3.1k. Above, Hycom even sees it growing out in coming days. The animation below analyzes the concentration distribution pixel by pixel on five days ending Sept 12th (pretending, as a practice drill, that the data really has this precision).
Open water here (the darkest blue RGB = 0,7,135 in AMSR2) has been replaced throughout by yellow. The palette stripes show utilization of concentration classes that make up BB's image on successive days. They can be seen to shift in the direction of zero (dark blue). This type of analysis is not feasible on dithered maps in which the correspondence between key and map colors has been lost.
It is fair to say that the area of the remnant dropped precipitously overnight, from 5738 to 1296 (77% drop) and a secondary floe of 4504 disappeared altogether. The current location is 73.089º N by 142.670º W.
The Arctic Ocean in the UHH large format AMSR2 comprises 1 792 243 pixels; wikipedia gives the area as 14 056 000 km
2 so (ignoring variation due to map projection) 7.8 km
2 per pixel. On Sept 12th, Big Block consisted of 1296 pixels at 3x resolution (scale of first animation) with one-ninth of that being 144 pixels or 1129 sq km which corresponds to a circle of 38 km in diameter. That's a lot of soccer fields. However not all of this is ice as AMSR2 is showing concentration percentiles; the average BB pixel on the 12th represents only 15% ice.
The Beaufort has been so cloudy that higher resolution visible imagery is scarcely available. A possible image from 09 Sept 16 is shown below,
http://go.nasa.gov/2cUybVP; there has not been coverage by Sentinel active radar for a long while. If BB had been visible at Modis resolution of 250 m, it would be 4 x 38 = 152 pixels across, providing 23104 pixels on WorldView.
The persistence is probably attributable to Big Block's initial size (and 4 m thickness) which meant very little perimeter area relative to volume. This suggests that side melt is more significant than bottom melt on smaller floes. BB thus serves as an excellent local proxy for melting conditions this season in the Beaufort, as well as serving as a buoy that monitors current- and wind-driven drift and rotation.