It sounds like the call of a mythological (Scottish?) mermaid, whose been trapped in human form by having her seal skin cap taken from her (kinda like Ceres), and longs for the sea so much that her heart will eventually break and stop. Specifically, it sounds like an orphan of said mermaid, who feels the call, but doesn't know what it is, because its human father never told him/her what its mother was. Winter freezes the ice so the merpeople can't travel back and forth, and they were only known to change under the light of the moon. There's my only explanation that fits. Oh, hi issachan! Write to me!!!

yeah...my call is suicide, always...so i really doubt my interpretation is quite what you're looking for...