  The effect of gluon shadowing on charm quark production in large impact
parameter ultrarelativistic heavy ion collisions is investigated. Charm
production cross sections are calculated for a range of non-central impact
parameters which can be accurately inferred from the global transverse energy
distribution. We show that charm production is a good probe of the local parton
density which determines the effectiveness of shadowing. The spatial dependence
of shadowing can only be studied in heavy ion collisions.
