http://hdl.handle.net/1957/1312 Search the Channel search http://ir.library.oregonstate.edu/dspace/simple-search http://hdl.handle.net/1957/3864 Title: Reconstructing salinity conditions in Nares Strait (Canadian Archipelago) from stable isotope profiles in bivalve shells <br/> <br/>Abstract: Nares Strait is one of three main passages of the Canadian Archipelago that channels freshwater from the Arctic Ocean to the North Atlantic. There are very few observations regarding the role of this region on the present day Arctic freshwater budget, and even less regarding the changes in freshwater fluxes through time. Larger scale Arctic Ocean circulation features have recently been observed to shift. Such changes will likely be manifest in Nares Strait before propagating into Baffin Bay and Labrador Sea. The δ18O of the water in Nares Strait strongly co varies with salinity. We analyzed the isotopic composition of bivalve shells collected live from the Greenland and Ellesmere Island sides of the Strait in an effort to reconstruct salinity changes with time along this passage over the 5-30 m depth range where these organisms live. Specimens of Hiatella arctica and Astarte borealis collected at the northernmost station show a strong shift towards lighter δ18O values in the most recently accreted sections of their shells, which corresponds to significant freshening with salinity as low as 23. These specimens at the northern end of Nares Strait began experiencing an increase in freshwater input as far back as 20 years ago. Similar freshwater pulses occur with diminishing frequency and magnitude through the 30 and 40 year timeslices. Lesser signals occur further south, probably reflecting significant along channel mixing. <br/> <br/>Description: Graduation date: 2007 Mon, 29 Jan 2007 18:16:40 GMT http://hdl.handle.net/1957/3773 Title: Development of an autonomous in-situ instrument for long-term monitoring of Cu(II) in the marine environment <br/> <br/>Abstract: An autonomous, in-situ instrument was developed to detect dissolved copper in seawater, suitable for deployment on time scales from weeks to months. A commercially available in-situ nitrate analyzer (YSI 9600) was adapted to measure copper (II) in seawater by chemiluminescence. Modifications included construction of a photomultiplier (PMT) based detector and flow-cell, the use of more chemically resistant plastics for parts in contact with the reagents, addition of an in-line acidification step and optimization of the method and flow parameters. Filtration to 0.45μm and acidification online (pH ~1.7) produces a measurement of total dissolved Cu(II). Calibration is achieved by periodically analyzing ligand-stabilized seawater standard and blank solutions stored at pH 8 and acidified online. Micro solenoid pumps take in sample and dispense reagent, standard, and blank solutions, which are stored in 1L plastic bags. All waste is collected in two 5L bags. In-situ, the instrument has an average detection limit of 0.8(3) nM, a sample precision of 7%, and an accuracy, assessed over all deployments, of 17%. The instrument is capable of functioning autonomously for 25 days sampling every hour and calibrating every six hours, with reagent consumption being the limiting factor. <br/> <br/>Description: Graduation date: 2007 Thu, 07 Dec 2006 22:58:59 GMT http://hdl.handle.net/1957/2372 Title: Contribution of cold seep barite to the barium geochemical budget of a marginal basin <br/> <br/>Abstract: Large barite (BaSO4) structures mark cold seeps in the southern San Clemente Basin. Barium flux to San Clemente sediments is two to three times greater than fluxes measured in surrounding California Borderland basins. Analyses of sediment trap material, water column samples, sediments and pore water indicate that expected bariumbearing mineral phases (e.g. detrital aluminosilicates, biogenic material and Fe/Mn oxyhydroxides) cannot account for excess barium accumulating in the San Clemente Basin. This excess represents 7-70 % by weight of total sedimentary barium. Cold seep barite is accumulating in San Clemente sediments at an average rate of approximately 11 μmol m-2 day-1, a value that is comparable to the combined flux of detrital and biogenic material to the basin floor. Cold seep barite is largely unaccounted for in sedimentary barium inventories. The magnitude of cold seep barite flux to San Clemente Basin sediments and the occurrence of cold seeps throughout the oceans necessitate consideration of this phase in the development of barium geochemical budgets and the variety of paleoproxies involving barium in marine sediments. <br/> <br/>Description: Graduation date: 2007 Thu, 18 May 2006 22:58:59 GMT