macdoc
Philosopher
The seasonal variation is due to the difference in sea area between the hemispheres. You see similar variation in the CO2 concentration because of spring / summer vegitation growth in the Northern Hemisphere.
Maybe needs to be refined as the focus seems on the equinoxes where the changes over time period are most notable....sea ice forming / sea ice melting both of which are phase change with the accompanying thermal implications with heat of fusion.
Lots of good stuff here
http://nsidc.org/cryosphere/seaice/characteristics/polynyas.html
But I could not begin to guess the level of influence on the global energy picture

Ice melting in spring is going to cool the ocean surface and drop the sealevel...again - I do not have any idea of the broad scale numbers that entails nor what the implications are of the resulting fresh water layer on ocean levels.


