A comparison of the Lower Underworlds on the northern and southern hemisphere

Abstract

Every winter a big bubble of potentially cold air arises on the North Pole. This bubble of air is called the Underworld. The coldest part of this Underworld is what we will call the Lower Underworld in this thesis. The total mass of the Lower Underworld on the northern hemisphere has decreased over the past 37 years. This is in line with the widely known phenomenon of global warming. However on the southern hemisphere the trend of the mass of the Lower Underworld is opposite. The mass of the Lower Underworld on the southern hemisphere is showing increase over the past 37 years. In this thesis we investigate the differences between the two Lower Underworlds. Several differences are found; the Lower Underworlds on the northern and southern hemisphere differ greatly in size, meridional profile, seasonal cycle, sea ice cover, snow cover and the topographic distribution of the poleward mass flux. The decrease in sea ice cover and snow cover on the northern hemisphere is a probable reason for the difference in trend in the mass of the Lower Underworld.