Ma c'è un mare che si "circumnaviga" su strade rialzate "dentro" il mare?
L'unico che conosco è il mare d'Azov, le lunghezze coincidono e torna anche la traduzione letterale del nome ("Nord del mare", il mar d'Azov si può vedere come il nord del mar Nero).

21. Haibei 海北 [Hai-pei], literally: ‘North of the Sea,’ must refer to the lands between Babylonia and what is now Jordan and/or Syria. See note 10.12 above and also Graf (1996) – especially the section on ‘The Western Regions’ on p. 204 and the map at the end of his article.

[omiss]

In my view the Chinese division of these regions makes excellent sense. Thus we have: ‘West of the Sea’ (= Egypt); ‘East of the Sea’ (the lands on the east coast of the Persian Gulf) and, finally, ‘North of the Sea,’ the region in between and joining them: (probably northern Saudi Arabia, Jordan and southern Israel).