Growler

Smallest navigationally hazardous fragment of glacier ice, defined by the World Meteorological Organization (WMO Sea-Ice Nomenclature, WMO-No.259) as less than one metre above water and roughly five metres across. Because growlers ride almost flush with the sea surface and are often translucent, they return little radar signature and are difficult to detect by eye against a confused sea state — the operational reason POLAR Code voyage planning requires dedicated ice lookouts. Growlers calve from larger bergy bits and icebergs and are common downstream of West Greenland and Antarctic Peninsula iceberg sources.