Shepard, 1963, Shepard, 1981 recognised that submarine canyons may have several origins and restricted his definition to “steep-walled, sinuous valleys with V-shaped cross sections, axes sloping outward as continuously as river-cut land canyons and relief comparable to even the largest of land canyons”. Submarine canyons are incised into the continental shelf and slope of all continental margins and they act as conduits for the transfer of sediment from the continents to the deep sea (Nittrouer and Wright, 1994). On this basis, the importance of conservation for submarine canyon ecosystems is greater for Australia, islands and northeast Asia than for other regions. The present study provides the means to assess the relative significance of canyons located in different geographic regions. Other workers have shown that benthic ecosystems in shelf-incising canyons contain greater diversity and biomass than non-incising canyons, and that ecosystems located above 1500 m water depth are more vulnerable to destructive fishing practices (bottom trawling) and ocean acidification caused by anthropogenic climate change. This observation is consistent with the origins of some canyons being related to erosive turbidity flows derived from fluvial and shelf sediment sources. Geographic areas having relatively high rates of sediment export to continental margins, from either glacial or fluvial sources operating over geologic timescales, have greater numbers of shelf-incising canyons than geographic areas having relatively low rates of sediment export to continental margins. They are most common on the western margins of South and North America where they comprise 11.7% and 8.6% of canyons respectively, but are absent from the margins of Australia and Antarctica. River-associated, shelf-incising canyons are more numerous on active continental margins (n = 119) than on passive margins (n = 34). The greatest canyon spacing occurs in the Arctic and the Antarctic whereas canyons are more closely spaced in the Mediterranean than in other areas. This study confirms observations of earlier workers that a relationship exists between canyon slope and canyon spacing (increased canyon slope correlates with closer canyon spacing). Active continental margins contain 15% more canyons (2586, equal to 44.2% of all canyons) than passive margins (2244, equal to 38.4%) and the canyons are steeper, shorter, more dendritic and more closely spaced on active than on passive continental margins. Based on an analysis of the ETOPO1 data set, this study has compiled the first inventory of 5849 separate large submarine canyons in the world ocean. The technical and tactical developments implemented by the opposing sides are documented in detail, including US improvements to submarine design and weaponry and more aggressive tactics, and the Japanese development of destroyer escorts, changes to depth charge design, and improved submarine detection capacity.The aim of this study is to assess the global occurrence of large submarine canyons to provide context and guidance for discussions regarding canyon occurrence, distribution, geological and oceanographic significance and conservation. This book explores all these factors, and the role that US submarines played in supporting the major fleet operations in the Pacific Theater, notching up almost 500 patrols by war's end for the loss of 52 submarines to the Japanese. Antisubmarine warfare was initially accorded a low priority by the Imperial Japanese Navy the lack of ASW escorts and modern weaponry, and an inability to develop tactics, resulted in devastation to vital convoys, and hampered its ability to deter and destroy enemy submarines. Eventually, though, a new generation of wartime submarine commanders, combined with reliable torpedoes, new generation boats, improved intelligence, and advanced radar, inflicted devastating losses on Japanese shipping. In 19, US Navy submarine operations in the Pacific were largely ineffective, hampered by faulty torpedo design, conservative tactics, and insufficiently aggressive submarine captains. This fully illustrated study examines and compares the roles of the US Navy submarines and the Imperial Japanese Navy's anti-submarine warfare capabilities during World War II.
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