For the_nthian: You can bet that neutrinos are crashing into atoms in the North Polar ice, too… Most of these neutrinos will come from "cascades" in Earth's atmosphere caused by cosmic rays, but some unknown fraction may come from astronomical sources. To distinguish these two sources statistically, the direction and angle of the incoming neutrino is estimated from its collision by-products. One can generally say, that a neutrino coming from above "down" into the detector is most likely stemming from an atmospheric shower, and a neutrino traveling "up" from below is more likely from a different source.

Why the South Pole instead of the North? "In order to build the IceCube telescope, we had to find the clearest and purest ice we could find in as large a quantity as possible. In most ice, air bubbles and air pockets form which would distort our measurements. The south pole is basically an enormous glacier and consists almost entirely of ice. This ice is under extreme amounts of pressure as more and more snow falls and the water and ice are compressed tightly until it has been rendered into its purest form. IceCube detects the blue light made by the nuclear reaction initiated by a direct hit of a neutrino on an atom of ice. These hits are rare and it therefore requires a lot of atoms, actually a kilometer cube of ultra transparent ice to do the science. The instrumented ice has to be shielded from the natural radiation at the surface, in our case by a layer of 1.5 kilometer of ice covering IceCube. To build a detector of this complexity requires a scientific infrastructure. The South Pole station constructed on three kilometers of clear natural ice presents us with the opportunity to satisfy all requirements and make neutrino astronomy a reality."

How long before global warming makes IceCube ineffective? Probably right up until the time our atmosphere is gone and cosmic rays eat away our brains…