This is the the full years data to 21 November for the anomalies of the sea ice extent in 2016. See my blog post Antarctic sea ice 2016: Historic lows for full context.
The plot shows the difference between the daily ice extent, in each grid cell, for the year to 21 November 2016, and the mean, for each day, based on historical data for the 5 year period 1989-93.
Blue shades imply more sea ice and reds imply decreased sea ice compared with the mean.
To make the plot for each day of the year and each grid cell I worked out the mean sea ice extent for 5-year period 1989-1993. I then used this calculated mean taken away from the 2016 data for the same day to derive the anomaly maps.
For example if the plot shows very dark blue that means that there is 100% sea ice cover in that grid cell in 2016 and none in the 1989-93 mean. A dark red means there is no sea ice in 2016 where we would expect 100% sea ice cover.
The original data come from the DMSP SMMI data set at the NSIDC.
A post describing this data is Antarctic sea ice 2016: Historic lows