There may be a correlation between ice extent loss in the Arctic and ice extent gain in the Antarctic.
Over the past decade, Antarctic ice reached record highs for the satellite period. The Arctic reached record lows for that same period. In order to show a possible correlation, I put the graphs through four steps. First is the overlay above.
Next comes a vertical flip across the x-axis.
Next step is to shift Antarctica left by six months, so that we are comparing NH winter to SH winter and NH summer to SH summer.
Final step is to shift Antarctica downward by 0.5 Mkm². This is done because the magnitude of ice loss in the Arctic has generally been greater than the magnitude of ice gain in the Antarctic.
Is it a perfect correlation? No. But there is something there worth investigating. Note that the record (low/high) peaks in both hemispheres between 2007 and 2008. The video below shows the whole process.
h/t to rbateman for the idea of merging the two graphs.