That's because there are different factors affecting Arctic and Antarctic sea ice.
The thing is... the Arctic has, or at least had, "permanent" sea ice. Sea ice that would be there for multiple decades, even during the summer. But that ice is going away. You still get new ice every winter, but that ice melts every summer.
As I understand it, Antarctica has little or no "permanent" sea ice, all the permanent ice is on land. So, any change in Antarctic sea ice is pretty much only during winter. And, actually, more Antarctic sea ice is an expected result of global warming. As some of the land ice melts (or, at least, calves icebergs), the water around Antarctica becomes less saline--which means it now freezes at a higher temperature, which in turn means that more of it freezes. Also, there's some serious weirdness about Antarctic air and water currents, that kind of make Antarctica a "bubble" mostly isolated from the rest of the biosphere.
And, of course, there's the fact that ice mass/volume is a *much* better and more meaningful measure than ice extent. Since ice extent is measured essentially as a grid system (that is, "does this "pixel" have ice or not"), it can change drastically without *any* change in ice mass or volume, simply by moving some of the ice around so it's more or less bunched up.
Hmm! It must be summer in the Northern hemisphere.
This by itself is meaningless, since you are comparing apples to oranges. The Arctic is water mass while the Antarctic is land mass. The heat sinks are of different coefficients. Plus, as one answerer put it, that you also have to consider the depth of the ice. Another factor would be precipitation in each area. Yet another factor would be the water density in each area. There are just too many variables involved to make a blanket judgment.
I find that I have the same problem. Every summer I lose about 0.000000005 million kilometers. Then winter arrives and it seems I gain about 0.000000006 back. Every year I seem to have a net gain and I have to buy new pants.
2012 Part 2.
Sure, due to global warming ice sheets are melting rapidly. this may lead to the great damage.
very good... now go check the total VOLUME of ice.
A check today reveals that Arctic ice has a deficit 1.006 million kilometers compared to average, but Antarctic ice extent is growing and has a positive 1.187 million kilometers.
http://arctic.atmos.uiuc.edu/cryosphere/IMAGES/seaice.recent.arctic.png
http://arctic.atmos.uiuc.edu/cryosphere/IMAGES/seaice.recent.antarctic.png
