http://hdl.handle.net/1957/8382 Search the Channel search http://ir.library.oregonstate.edu/dspace/simple-search http://hdl.handle.net/1957/9257 Title: Oceanography in 2028 <br/> <br/>Abstract: This article considers the evolutionary pressures that have brought us to our present state and how these forces will likely change, with a focus on U.S. institutional structures. Fri, 29 Aug 2008 22:58:59 GMT http://hdl.handle.net/1957/8744 Title: Impact of the Ocean’s Overturning Circulation on Atmospheric CO2 <br/> <br/>Abstract: A coupled climate-carbon cycle model and ice core CO2 data from the last glacial period are used to explore the impact of changes in ocean circulation on atmospheric CO2 concentrations on millennial time scales. In the model, stronger wind driven circulation increases atmospheric CO2. Changes in the buoyancy driven deep overturning in the Atlantic affect atmospheric CO2 only indirectly through their effect on Southern Ocean stratification. In simulations with an abrupt and complete shutdown of the Atlantic overturning, stratification in the Southern Ocean decreases due to salinification of surface waters and freshening of the deep sea. Deeper mixed layers and steeper isopycnals lead to outgassing of CO2 in the Southern Ocean and hence gradually increasing atmospheric CO2 concentrations on a multi-millennial time scale. The rise in CO2 terminates at the time of rapid resumption of deep water formation and warming in the North Atlantic, and CO2 levels subsequently gradually decrease. These model responses and a strong correlation between simulated atmospheric CO2 and Antarctic surface air temperatures with little or no time lag are consistent with newly synchronized ice core data from the last ice age. Sensitivity experiments reveal that the amplitude of the response of atmospheric CO2 is sensitive to the model background climatic state and decreases in a colder climate owing to smaller changes in the overturning. Sun, 29 Oct 2006 22:58:59 GMT http://hdl.handle.net/1957/8743 Title: Large fluctuations of dissolved oxygen in the Indian and Pacific oceans during Dansgaard-Oeschger oscillations caused by variations of North Atlantic Deep Water Subduction: Paleoceanography <br/> <br/>Abstract: Paleoclimate records from glacial Indian and Pacific oceans sediments document millennial-scale fluctuations of subsurface dissolved oxygen levels and denitrification coherent with North Atlantic temperature oscillations. Yet the mechanism of this teleconnection between the remote ocean basins remains elusive. Here we present model simulations of the oxygen and nitrogen cycles that explain how changes in deepwater subduction in the North Atlantic can cause large and synchronous variations of oxygen minimum zones throughout the Northern Hemisphere of the Indian and Pacific oceans, consistent with the paleoclimate records. Cold periods in the North Atlantic are associated with reduced nutrient delivery to the upper Indo-Pacific oceans, thereby decreasing productivity. Reduced export production diminishes subsurface respiration of organic matter leading to higher oxygen concentrations and less denitrification. This effect of reduced oxygen consumption dominates at low latitudes. At high latitudes in the Southern Ocean and North Pacific, increased mixed layer depths and steepening of isopycnals improve ocean ventilation and oxygen supply to the subsurface. Atmospheric teleconnections through changes in wind-driven ocean circulation modify this basin-scale pattern regionally. These results suggest that changes in the Atlantic Ocean circulation, similar to those projected by climate models to possibly occur in the centuries to come because of anthropogenic climate warming, can have large effects on marine ecosystems and biogeochemical cycles even in remote areas. Sun, 29 Oct 2006 22:58:59 GMT