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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
41

Investigation of meteorological events preserved in high resolution snow pit and fin core records

McMorrow, AJ Unknown Date (has links) (PDF)
A key problem in ice core palaeclimate studies is the interpretation of the various measurable parameters in ice in terms of climate and environmental conditions. This study is aimed at developing a closer understanding of the connection between high resolution snow/firn measurements and meteorological conditions. Ultra high resolution snow pit and shallow firn core records of oxygen isotope ratios (del18O) and a suite of trace chemical species including marine biogenic sulphur compounds (methane sulphonate (MSA), non-sea salt sulphate), nitrate and major sea salt ions (sodium, chloride, magnesium), were generated at a high accumulation site on Law Dome, East Antarctica. Concordance between accumulation events identified in the records up to 7.7 km apart confirms that the observed chemical and isotopic variations are the result of regional rather than local surface effects. This allows calibration of the snow pit and firn core records with measured meteorological parameters. Event scale dating of the records was established using hourly snow accumulation measurements from a co-located automatic weather station (AWS). The ultra high resolution nature of this study and independent dating scale provide an opportunity to examine exact timings in the seasonality of each chemical species. The traditional summermaximum species of del18O and MSA show consistent relative phasing during mid-summer over four annual cycles. Nitrate shows an erratic seasonal cycle with a general trend characterised by narrow peaks during spring and early summer, preceding the mid-summer peaks in del18O and MSA. Non-sea salt sulphate cycles indicate similar characteristics to MSA signals during summer, but are more comparable to nitrate signals during spring, autumn and winter. This suggests the summer non-sea salt sulphate signal is driven by biological activity, yet appears to be linked with nitrate signals outside the summer season. Finally, the sea salt species indicate a seasonal cycle characterised by maximum concentrations during autumn, winter and spring. Event scale dating of the snow pit and firn core records allows direct comparisons between the chemical and isotopic signals and observed meteorological conditions. Local meteorological conditions recorded by the AWS are combined with synoptic scale meteorology derived from Advanced Very High Resolution Radiometer satellite imagery and back trajectory analysis to identify potential source regions and transport mechanisms influencing the chemical and isotopic signals. Potential source regions and transport mechanisms are examined for the marine biogenic indicators (MSA, non-sea salt sulphate). Results indicate that the seasonal variation in marine biogenic activity is reflected in the Law Dome records, and the sea ice zone provides an important source region. However, results also indicate that lower latitudes, and the Heard Island region (50 degrees S, 70 degrees E) in particular, may provide an important additional source region for MSA and non-sea salt sulphate outside the summer season. High sea salt signals are generally associated with intense cyclonic systems, yet variations in atmospheric circulation and transport mechanisms also impact on the sea salt record. Comparisons between del18O signals and local air temperatures reveal the del18O record is an excellent proxy for temperature at Law Dome, although high (warm) del18O events are found to be influenced by atmospheric circulation and associated with rapid advection of air from low latitudes. Finally, results suggest that spring nitrate signals at Law Dome may be linked to the intrusion of stratospheric air through the breakdown in the polar vortex during spring.
42

Geochemically tracing the intermediate and surface waters in the Tasman Sea, southwest Pacific /

Bostock, Helen C. January 2004 (has links)
Thesis (Ph.D.)--Australian National University, 2004. / CD contains thesis in pdf and data files. Text organised differently in printed version.
43

Stable isotopic variation in particulate organic matter and dissolved inorganic compounds in a northern fjord : implications for present and past environments /

Ostrom, Nathaniel Emil. January 1992 (has links)
Thesis (Ph.D.)--Memorial University of Newfoundland. / Typescript. Bibliography: leaves 321-342. Also available online.
44

The marine geochemistry of the hydrolysis elements, aluminum and gallium

Orians, Kristin Jean. January 1900 (has links)
Thesis (Ph. D.)--University of California, Santa Cruz, 1988. / Typescript. Includes bibliographical references.
45

Nd and Sr isotopic evolution of the oceans of the past 800 million years

Keto, Lisette Scott. January 1987 (has links)
Thesis (Ph. D.)--Harvard University, 1987. / Includes bibliographical references.
46

Simulations of the phosphorus and oxygen cycles in the world ocean using a general circulation model

Najjar, Raymond Gabriel. January 1990 (has links)
Thesis (Ph. D.)--Princeton University, 1990. / Includes bibliographical references.
47

The chemical composition of Antarctic pack ice communities in early austral winter

Close, Ann Rubin. January 1989 (has links)
Thesis (M.S.)--University of California, Santa Cruz, 1989. / Typescript. Includes bibliographical references.
48

An investigation of the distribution of carbon dioxide between the atmosphere and the sea

Ibert, Edward R. January 1963 (has links)
Thesis (Ph. D. in Oceanography)--Texas A & M University.
49

1. Trace metal distributions and stable lead isotopic composition in surface waters along the United States-Mexican boundary in the northeast Pacific ; 2. Trace metal distributions in surface waters along the United States-Mexican boundary multivariate statistical analysis /

Sañudo Wilhelmy, Sergio Adolfo. January 1989 (has links)
Thesis (M.S.)--University of California, Santa Cruz, 1989. / Typescript. Includes bibliographical references.
50

Cycling of reduced trace gases and hydroxylamine in coastal waters

Butler, James Hall. January 1986 (has links)
Thesis (Ph. D.)--Oregon State University, 1986. / Includes bibliographical references (leaves 169-181).

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