Glacial troughs – Shelf valleys at high latitudes incised by glacial erosion during the Pleistocene ice ages form elongate troughs, typically trending across the continental shelf and extending inland as fjord complexes (Hambrey, 1994). The largest of these features are glacial troughs, characterised by depths of over 100 m (often exceeding 1,000 m depth) and are distinguished from shelf valleys by an over-deepened longitudinal profile that reaches a maximum depth inboard of the shelf break, thus creating a perched basin on the shelf with an associated sill (Hambrey, 1994; Anderson, 1999).
Glaciation of the continents during the last ice age extended across what are now the continental shelves of Antarctica, western and northeastern North America (eg. Barrie et al., 2012), western Europe, Greenland, Iceland, South America, and New Zealand. U-shaped glacial valleys that exist as fjords along the coast extend in places across the full width of the continental shelf. The Arctic Ocean has the largest absolute area of glacial troughs although they are more common in the Antarctic as a percentage of shelf area, covering more than 40% of the Antarctic shelf (see Table).