Shelf erosion and submarine river canyons: implications for deep-sea oxygenation and ocean productivity during glaciation

[摘要] The areal exposure of continental shelves during glacial sea level loweringenhanced the transfer of erodible reactive organic matter to the open ocean.Sea level fall also activated submarine canyons thereby allowing large riversto deposit their particulate load, via gravity flows, directly in the deep-sea.Here, we analyze the effects of shelf erosion and particulate matter re-routingto the open ocean during interglacial to glacial transitions, using a coupled modelof the marine phosphorus, organic carbon and oxygen cycles. The results indicate thatshelf erosion and submarine canyon formation may significantly lower deep-sea oxygenlevels, by up to 25%, during sea level low stands, mainly due to the supply of newmaterial from the shelves, and to a lesser extent due to particulate organic matterbypassing the coastal zone. Our simulations imply that deep-sea oxygen levels candrop significantly if eroded shelf material is deposited to the seafloor. Thus theglacial ocean's oxygen content could have been significantly lower than duringinterglacial stages. Primary production, organic carbon burial and dissolved phosphorusinventories are all affected by the erosion and rerouting mechanisms. However,re-routing of the continental and eroded shelf material to the deep-sea hasthe effect of decoupling deep-sea oxygen demand from primary productivity in theopen ocean. P burial is also not affected showing a disconnection between thebiogeochemical cycles in the water column and the P burial record.

[学科分类] 地球化学与岩石