Two main reasons. 1. Hot is relative. 2. Upwelling can be a function of Topography (see the upwelliong off the pacific coast of South America for an example of this).
upwelling is a function of current, not climate. In the southern hemisphere, the mean direction of current is to the left of the mean wind direction (in the northen hemi it is to the right) - this is as a result of a process called Eckman transport (AKA Eckman spiral), which in istelf is a function of the coriolis effect. Around the around the antarctic continent the winds circulate in a clockwise direction - this creates a current that moves northwards - away from the continent - as the surface waters move away from the continent, they are replaced by deep water - hence upwelling - in this case it is described as coastal upwelling The real picture of upwelling around antarctica is much more complex though as there is also significant downwelling around the continent.
