I can't imagine there's any hemispheric difference in top-of-atmosphere solar irradiation, but there can be a difference in surface insolation due to cloud albedo. Also, I don't really see how clathrate dissociation could significantly warm the regional surface waters.

I'm not sure what's going on here. However, this [blog post](http://bobtisdale.wordpress.com/2009/03/10/the-barents-sea-hotspot-isn%E2%80%99t-so-hot/) suggests it could be an artifact of the NOAA/NESDID SST anomaly data product (see also [here](http://bobtisdale.blogspot.com/2009/09/note-about-sst-anomaly-maps.html)).