The white part is ice (or snow) on the land. The multi-colored key on the upper left shows the different thicknesses of sea ice 100 being the thickest. I don't see a lot of difference myself. Yes, there is somewhat less sea ice this year on the same date as in 1979 but not a lot. I expect that not every year is the same or every decade on a given date.
Houston, we have a problem. And the problem is lying propagandists who want our money.