S.O.S. iceberg

The story involves an expedition of four men who set off to Greenland to rescue an explorer previously presumed dead, but whose survival is attested to by a note written on a piece of jetsam. The expedition itself gets into fatal trouble when, trying to cross a half-frozen fjord, it is swept out to sea. This will be no leisurely drift into the ocean; they constantly see similar icebergs rolling over due to uneven melting. A similar roll would surely be their sudden end.