The issue focused on improving detection methods for isotopic compositions in Antarctic rocks from Greenland ice cores (Ashworth et al., 2003). Several reviewers commented that these observations require confirmation through systematic validation studies using laboratory measurements (Ashworth et al., 2003), although others cited uncertainty about sampling intervals (McClean et al., 2002), contamination from Antarctic sedimentary rocks (Howard et al., 2002), or volcanic fallout from continental eruption (Halliday et al., 2002). Several reviewers commented that measurements were inconsistent between Greenland ice cores (