Biogeosciences www.biogeosciences.net 1726-4170 1726-4189 7 6 2010 10.5194/bg-7-1973-2010 http://www.biogeosciences.net/7/1973/2010/ http://www.biogeosciences.net/7/1973/2010/bg-7-1973-2010.html http://www.biogeosciences.net/7/1973/2010/bg-7-1973-2010.pdf 1973 1982 2010-06-22 Shelf erosion and submarine river canyons: implications for deep-sea oxygenation and ocean productivity during glaciation I. Tsandev tsandev@geo.uu.nl C. Rabouille C. P. Slomp P. Van Cappellen Department of Earth Sciences – Geochemistry, Faculty of Geosciences, Utrecht University, P.O. Box 80.021, 3508 TA Utrecht, The Netherlands Laboratoire des Sciences du Climat et de l'Environnement, UMR CEA-CNRS-UVSQ et IPSL, domaine du CNRS, av. de la Terrasse, 91198 Gif sur Yvette, France School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, Georgia, 30332-0340, USA The areal exposure of continental shelves during glacial sea level lowering enhanced the transfer of erodible reactive organic matter to the open ocean. Sea level fall also activated submarine canyons thereby allowing large rivers to deposit their particulate load, via gravity flows, directly in the deep-sea. Here, we analyze the effects of shelf erosion and particulate matter re-routing to the open ocean during interglacial to glacial transitions, using a coupled model of the marine phosphorus, organic carbon and oxygen cycles. The results indicate that shelf erosion and submarine canyon formation may significantly lower deep-sea oxygen levels, by up to 25%, during sea level low stands, mainly due to the supply of new material from the shelves, and to a lesser extent due to particulate organic matter bypassing the coastal zone. Our simulations imply that deep-sea oxygen levels can drop significantly if eroded shelf material is deposited to the seafloor. Thus the glacial ocean's oxygen content could have been significantly lower than during interglacial stages. Primary production, organic carbon burial and dissolved phosphorus inventories are all affected by the erosion and rerouting mechanisms. However, re-routing of the continental and eroded shelf material to the deep-sea has the effect of decoupling deep-sea oxygen demand from primary productivity in the open ocean. P burial is also not affected showing a disconnection between the biogeochemical cycles in the water column and the P burial record. 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