Thesis (doctoral)--Universität Rostock. / Also issued without thesis statement and issued in the series Mitteilungen der Geographischen Gesellschaft in München vii. Bd. (1912), 4. Heft. Vita. Includes bibliographical references and index.

Thesis (doctoral)--Universität Rostock. / Also issued without thesis statement and issued in the series Mitteilungen der Geographischen Gesellschaft in München vii. Bd. (1912), 4. Heft. Vita. Includes bibliographies and index.

Measurements by the TOMS instrument aboard the Nimbus 7 satellite, of total column ozone over polar regions have been studied to determine the effects of solar induced natural ozone modulation. Two different analysis methods were employed to ascertain short term (days to months) and long term (months to years) solar influences on polar ozone. Bursts of intense solar activity can result in solar proton events (SPE's). The high energy protons, originating in solar flares, produce secondary electrons which can generate large concentrations of odd nitrogen in the middle atmosphere. These reactive species can catalytically destroy ozone. Three case studies are presented in an attempt to quantify the effect of SPE's on ozone mass over a latitude region 90 to 70°. In order to monitor the ozone response following a SPE over both hemispheres simultaneously, the SPE must occur during the equinox period when both poles are irradiated. Fortuitously, a SPE was recorded in March 1989, the analysis of which forms a case study in this thesis. Ozone depletions of 7.4 x 10 to the power of 9 kg for the south polar cap and 8.0 x 10 to the power of 9 kg for the north polar cap indicate the degree of symmetry for this event. Longer term effects of solar variability are investigated by Fourier techniques. A Fourier transform of eleven years of total ozone mass values, over the region 90 to 70° S, was performed. Inspection of the Fourier spectrum reveals peaks associated with solar cycle, annual and semi-annual oscillations, that may be attributed directly to solar variation. Other peaks, corresponding to QBO and ENSO periodicities, may be ascribed to indirect solar influences i.e. thermally driven dynamics. Finally, a comparison between the phase of the solar cycle peak in this spectrum with that in a spectrum of daily values of solar radio flux, reveals that the austral polar ozone solar cycle periodicity lags solar forcing by 2.8 years. Portions of chapters have been reported at the 1990 South African Institute of Physics Annual Conference, University of Port Elizabeth, South Africa and as a poster at the 1992 Quadrennial Ozone Symposium, Charlottesville, United States of America, 4-13 June 1992. In addition, various parts of this work has been submitted for publication, viz: Stephenson, J. A. E. and M. W. J. Scourfield, Importance of energetic solar protons in ozone depletion, Nature, 352, 137: 1991. / Thesis (Ph.D.)-University of Natal, Durban, 1994.

The primary objective of the NASA sponsored ICESat mission is to study the short and long term changes in the ice mass in the Greenland and Antarctica regions. The satellite was therefore placed into a frozen near-polar near-circular repeat groundtrack to ensure an adequate coverage of the polar regions while keeping the groundtrack periodic and reducing the variations in the orbital elements, and more specifically the semi-major axis of the ICESat orbit. After launch, a contingency plan had to be devised to compensate for a laser that dangerously compromised the lifetime of the ICESat mission. This new plan makes an intensive use of the ICESat subcycles, a characteristic of the repeat groundtrack orbits often over-looked. The subcycle of a repeat groundtrack orbit provide global coverage within a time shorter than the groundtrack repetition period. For a satellite with an off-nadir pointing capacity, the subcycles provide near-repeat tracks which represents added opportunity for altimetry measurement over a specific track. The ICESat subcycles were also used in a very innovative fashion to reposition the satellite within its repeat cycle via orbital maneuvers called phasing maneuver. The necessary theoretical framework is provided for the subcycle analysis and the implementation of phasing maneuvers for any future repeat orbit mission. In the perspective of performing cross-validation of missions like CryoSat using the ICESat off-nadir capacity, a study was conducted to determine the geolocations of crossovers between two different repeat groundtrack Keplerian orbits. The general analytical solution was applied to ICESat vs. several other repeat groundtrack orbit mission, including the future ICESat-II mission. ICESat’s repeat groundtrack orbit was designed using a disturbing force model that includes only the Earth geopotential. Though the third body effect from the Sun and the Moon was neglected in the orbit design, it does in fact disrupt the repeatability condition of the groundtrack and consequently implies orbit correction maneuvers. The perturbations on ICESat orbit due to the third body effect are studied as a preliminary work towards including these forces in the design of the future ICESat-II repeat groundtrack orbit. / text

Coincident with human activity in recent decades, human-associated microorganisms have arrived to the Antarctic region, possibly linked to increasing presence of scientific bases and ship-borne tourists. In the Arctic, humans have been present for a very long time, and the few parts of the Arctic without human activities is decreasing with time. The studies in this thesis investigate the occurrence of different pathogens in Antarctic and Arctic wildlife, especially in birds. The first study shows the existence of Enteropatogenic Escherichia coli (EPEC) in Antarctic fur seals. The EPEC isolates were so called atypical EPECs, carrying the eae gene but lacking the bfp gene. This is the first record of a diarrheogenic E. coli in wild animals in the Antarctic. The second study displays that spreading of antibiotic resistance mechanisms appears to be much more efficient than previously was known. Enterococcus faecium isolated from Alaskan birds showed high resistance to vancomycin and teicoplanin, but also to ampicillin and ciprofloxacin. These isolates also carried vanA genes and the virulent esp gene, which places the isolates in the clinical clone CC17 and indicates the isolates had a human origin. Bacteria from birds that reside in the Bering Strait region in the third study, demonstrates that only six of 145 E. coli from 532 birds had reduced antibiotic susceptibility. Despite this, selective screen on E. coli showed only four ESBL-producing isolates. The four E. coli isolates carried CTX-M genes. One isolate belonged to the E. coli O25b - ST131 genotype, which is a successful clone with a global spread. In the fourth study, 123 seawater samples and 400 fresh penguin feces were analyzed. From these, 71 E. coli strains were isolated and only one E. coli from penguins was resistant to one antibiotic (cloramfenicol), whereas in E. coli from seawater, resistance against ampicillin, tetracycline, streptomycin and trim-sulfa were detected. E. coli carrying ESBL type CTX -M genes were also detected and Multilocus Sequencing Typing (MLST) showed six different sequence types (ST) previously reported in humans: ST131, ST227, ST401, ST410, ST685 and ST937. In the short time interval between the second study (2005) and the third study (2010) in relation to the fifth study (2012) we found a dramatic increase in antibiotic-resistant genes in the Arctic region. Enterococci, E. coli, and Kl. pneumoniae carried antibiotic resistance genes to an extent and variety not previously reported. E. coli from Arctic birds showed resistant to 1, 2, 3, 4, and 5 different antibiotics. Resistant gene type vanA was confirmed in enterococci and ESBL genes type TEM, SHV and CTX-M in E. coli and Kl. pneumoniae was detected. Multilocus Sequencing typing (MLST), indicating that both E. coli and Kl. pneumoniae carrying ESBL markers that connects them to the humans. In summary, the combined studies strengthen that bacteria that cause infections in humans could spread to relatively pristine environments. We concluded that human and associated antibiotic-resistant bacteria has reached a global level, then we showed that ESBL- carrying bacteria circulating nowadays also in the last ESBL-free continent, Antarctica.

Thesis (Ph.D.) -- University of Adelaide, School of Chemistry and Physics, Discipline of Physics, 2005. / Includes author's previously published papers. Includes bibliographical references. Also available in a print form.

This paper discusses the development of the Polar UDC. It examines some elements of the UDC specific to the Polar context, in particular the geographical auxiliary schedule. Some future plans for the implementation of UDC in a library and also in a museum context are outlined.

The dynamics of the polar mesosphere and lower thermosphere ( MLT ) is investigated using MF radars at Davis ( 69 ° S, 78 ° E ), Syowa ( 69 ° S, 40 ° E ) and Rothera ( 68 ° S, 68 ° W ) in the Antarctic, and Poker Flat ( 65 ° N, 147 ° W ) and Andenes ( 69 ° N, 16 ° E ) in the Arctic. Mean winds and gravity waves are investigated on a climatological scale and also during sudden stratospheric warmings. Mean wind climatologies in the MLT show differences that are often hemispheric in nature. For example, summer peaks in westward and equatorward winds occur earlier ( closer to the solstice ) in the Antarctic than in the Arctic. The greater symmetry around the solstice of phenomena such as these indicates that radiative effects may play a greater role in controlling the state of the Antarctic MLT than in the Arctic, where dynamical effects might be more important. Gravity wave observations are consistent with this theory, suggesting more wave drag may occur in the Arctic MLT. The equatorward jet persists for about 2 weeks later in summer in the Arctic than in the Antarctic, as do satellite observations of polar mesospheric clouds ( PMCs ) ( a temperature dependent phenomenon ). It is proposed that the meridional winds can be used as a proxy for gravity wave driving and consequent adiabatic cooling in the MLT. VHF radar observations of polar mesospheric summer echoes ( PMSEs ) at Davis, and the satellite PMC observations, both occur at a similar time to the equatorward jet. Seasonal variations in gravity wave activity are generally a combination of annual ( with winter maxima and summer minima ) and semi - annual ( with maxima near the solstices and minima near the equinoxes ) components. The winter maxima and spring / summer minima both occur about 3 weeks later in the Antarctic than in the Arctic, with the difference in magnitude between these extrema being about 90 % larger in the Antarctic. The available MF radar data include six major sudden stratospheric warmings in the northern hemisphere, and the unprecedented southern event which occurred during 2002 splitting the Antarctic ozone hole apart. Three of the six northern events are relatively weak and could almost be classed as minor warmings, while the larger three are similar in strength and duration to the southern event. Gravity wave activity reduces dramatically at Davis during the southern event, but not at Syowa ( possibly due to differences in critical level filtering ). The influence of major warmings on mesospheric gravity wave strength and polarisation varies significantly between locations, and individual events. Zonal wind reversals associated with the large major warmings are all weaker and occur earlier in the mesosphere than in the stratosphere. Another hemispherically common response is zonal wave - 1 planetary wave signatures in the mesospheric meridional winds ( i.e., a flow over the pole ). The planetary wave signatures have 14 - day periodicity and are westward propagating leading up to the southern event. The zonal winds are weaker than average during the 2002 southern winter, and also during the transition to the summer circulation. This is not seen for the large northern major warmings. There appears to be both hemispheric similarities and differences in polar middle atmosphere dynamics during stratospheric warmings, and also on a climatological scale. / Thesis (Ph.D.)--School of Chemistry and Physics, 2005.

The dynamics of the polar mesosphere and lower thermosphere ( MLT ) is investigated using MF radars at Davis ( 69 ° S, 78 ° E ), Syowa ( 69 ° S, 40 ° E ) and Rothera ( 68 ° S, 68 ° W ) in the Antarctic, and Poker Flat ( 65 ° N, 147 ° W ) and Andenes ( 69 ° N, 16 ° E ) in the Arctic. Mean winds and gravity waves are investigated on a climatological scale and also during sudden stratospheric warmings. Mean wind climatologies in the MLT show differences that are often hemispheric in nature. For example, summer peaks in westward and equatorward winds occur earlier ( closer to the solstice ) in the Antarctic than in the Arctic. The greater symmetry around the solstice of phenomena such as these indicates that radiative effects may play a greater role in controlling the state of the Antarctic MLT than in the Arctic, where dynamical effects might be more important. Gravity wave observations are consistent with this theory, suggesting more wave drag may occur in the Arctic MLT. The equatorward jet persists for about 2 weeks later in summer in the Arctic than in the Antarctic, as do satellite observations of polar mesospheric clouds ( PMCs ) ( a temperature dependent phenomenon ). It is proposed that the meridional winds can be used as a proxy for gravity wave driving and consequent adiabatic cooling in the MLT. VHF radar observations of polar mesospheric summer echoes ( PMSEs ) at Davis, and the satellite PMC observations, both occur at a similar time to the equatorward jet. Seasonal variations in gravity wave activity are generally a combination of annual ( with winter maxima and summer minima ) and semi - annual ( with maxima near the solstices and minima near the equinoxes ) components. The winter maxima and spring / summer minima both occur about 3 weeks later in the Antarctic than in the Arctic, with the difference in magnitude between these extrema being about 90 % larger in the Antarctic. The available MF radar data include six major sudden stratospheric warmings in the northern hemisphere, and the unprecedented southern event which occurred during 2002 splitting the Antarctic ozone hole apart. Three of the six northern events are relatively weak and could almost be classed as minor warmings, while the larger three are similar in strength and duration to the southern event. Gravity wave activity reduces dramatically at Davis during the southern event, but not at Syowa ( possibly due to differences in critical level filtering ). The influence of major warmings on mesospheric gravity wave strength and polarisation varies significantly between locations, and individual events. Zonal wind reversals associated with the large major warmings are all weaker and occur earlier in the mesosphere than in the stratosphere. Another hemispherically common response is zonal wave - 1 planetary wave signatures in the mesospheric meridional winds ( i.e., a flow over the pole ). The planetary wave signatures have 14 - day periodicity and are westward propagating leading up to the southern event. The zonal winds are weaker than average during the 2002 southern winter, and also during the transition to the summer circulation. This is not seen for the large northern major warmings. There appears to be both hemispheric similarities and differences in polar middle atmosphere dynamics during stratospheric warmings, and also on a climatological scale. / Thesis (Ph.D.)--School of Chemistry and Physics, 2005.

Thesis (M. S.)--Earth and Atmospheric Sciences, Georgia Institute of Technology, 2008. / Committee Chair: David Tan; Committee Member: Greg Huey; Committee Member: Marc Stieglitz; Committee Member: Paul Wine; Committee Member: Robert Black.