After writing my earlier piece showing changes in the Arctic maximum since 2007, Willis requested the same image for the minimum. NSIDC does not archive extent images, but fortunately UIUC does archive sea ice concentration images. Below is the equivalent image for September 15, 2007/2009. Yellow represents areas of 30% concentration ice common to both images. Green represents 2009 ice that was not present in 2007. Red represents 2007 ice that was not present in 2009.
Note the disappearance of the Northwest Passage.
DMI measures extent as areas of greater than 30% concentration, so the graph below is a good representation of the ~33% gain in summer ice seen between 2007 and 2009.