http://hdl.handle.net/1957/1312 Search the Channel search http://ir.library.oregonstate.edu/jspui/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/>Authors: Zima, Daniela<br/><br/>Abstract: Nares Strait is one of three main passages of the Canadian Archipelago thatchannels freshwater from the Arctic Ocean to the North Atlantic. There are very fewobservations 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 scaleArctic Ocean circulation features have recently been observed to shift. Such changes willlikely 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 theisotopic composition of bivalve shells collected live from the Greenland and EllesmereIsland sides of the Strait in an effort to reconstruct salinity changes with time along thispassage over the 5-30 m depth range where these organisms live.Specimens of Hiatella arctica and Astarte borealis collected at the northernmoststation show a strong shift towards lighter δ18O values in the most recently accretedsections of their shells, which corresponds to significant freshening with salinity as lowas 23. These specimens at the northern end of Nares Strait began experiencing anincrease in freshwater input as far back as 20 years ago. Similar freshwater pulses occurwith diminishing frequency and magnitude through the 30 and 40 year timeslices. Lessersignals 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/>Authors: Holm, Christopher E.<br/><br/>Abstract: An autonomous, in-situ instrument was developed to detect dissolvedcopper in seawater, suitable for deployment on time scales from weeks to months.A commercially available in-situ nitrate analyzer (YSI 9600) was adapted tomeasure copper (II) in seawater by chemiluminescence. Modifications includedconstruction of a photomultiplier (PMT) based detector and flow-cell, the use ofmore chemically resistant plastics for parts in contact with the reagents, additionof an in-line acidification step and optimization of the method and flowparameters. Filtration to 0.45μm and acidification online (pH ~1.7) produces ameasurement of total dissolved Cu(II). Calibration is achieved by periodicallyanalyzing ligand-stabilized seawater standard and blank solutions stored at pH 8and acidified online. Micro solenoid pumps take in sample and dispense reagent,standard, and blank solutions, which are stored in 1L plastic bags. All waste iscollected in two 5L bags. In-situ, the instrument has an average detection limit of0.8(3) nM, a sample precision of 7%, and an accuracy, assessed over alldeployments, of 17%. The instrument is capable of functioning autonomously for25 days sampling every hour and calibrating every six hours, with reagentconsumption 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/>Authors: McQuay, Erica L.<br/><br/>Abstract: Large barite (BaSO4) structures mark cold seeps in the southern San ClementeBasin. Barium flux to San Clemente sediments is two to three times greater than fluxesmeasured in surrounding California Borderland basins. Analyses of sediment trapmaterial, water column samples, sediments and pore water indicate that expected bariumbearingmineral phases (e.g. detrital aluminosilicates, biogenic material and Fe/Mnoxyhydroxides) cannot account for excess barium accumulating in the San ClementeBasin. This excess represents 7-70 % by weight of total sedimentary barium. Cold seepbarite is accumulating in San Clemente sediments at an average rate of approximately 11μmol m-2 day-1, a value that is comparable to the combined flux of detrital and biogenicmaterial to the basin floor. Cold seep barite is largely unaccounted for in sedimentarybarium inventories. The magnitude of cold seep barite flux to San Clemente Basinsediments and the occurrence of cold seeps throughout the oceans necessitateconsideration of this phase in the development of barium geochemical budgets and thevariety of paleoproxies involving barium in marine sediments.<br/><br/>Description: Graduation date: 2007 Thu, 18 May 2006 22:58:59 GMT