Under a variety of conditions and tests there is a consistent and reproducible distinction between “northern” and “southern” European population groups:

most Italian, Spanish, Portuguese, Greek, Ashkenazi and Sephardic Europeans have >85% membership in the “southern” population;

most Northern, Western, Eastern, and Central Europeans have >90% membership in the “northern” population group.

via PLOS Genetics: European Population Substructure: Clustering of Northern and Southern Populations.