3 results for Armstrong, Martina, Thesis

  • Antarctica Subglacial Lakes The Race to the Bottom

    Emnet, Philipp; Given, Andrew; Armstrong, Martina; Bouckoms, Sarah (2009)

    Postgraduate Certificate thesis
    University of Canterbury Library

    Ever since subglacial lakes have been known about they have grabbed the attention and imagination of the scientific and general community alike. These lakes may potentially hold the answers to questions on the climate history Of the earth within their sediments, as well as contain unique life forms within their waters that can help us understand the diversity and adaptability of life and its evolution within extreme environments of low temperature, high pressures, and total darkness. The limited knowledge that exists today on subglacial lakes only comes from indirect methods such as sonar and radar, but there are currently two projects underway that propose to drill into a subglacial lake and sample its waters directly. A Russian-led research group and a second group from the UK plan to lead the way in subglacial lake exploration at Lake Vostok and Lake Ellsworth respectively. However because the area of subglacial lakes is still a relatively new to science there is still much debate happening on the proper steps a scientific research group should follow during their research activities to reduce environmental impacts. This report will provide a background on subglacial lakes, and their significance to science. It will also explore the history and future plans of the two research groups interested in Lake Vostok and Lake Ellsworth, while addressing several questions that many believe still need to be fully answered before direct subglacial lake exploration should take place. Ever since subglacial lakes have been known about they have grabbed the attention and imagination of the scientific and general community alike. These lakes may potentially hold the answers to questions on the climate history Of the earth within their sediments, as well as contain unique life forms within their waters that can help us understand the diversity and adaptability of life and its evolution within extreme environments of low temperature, high pressures, and total darkness. The limited knowledge that exists today on subglacial lakes only comes from indirect methods such as sonar and radar, but there are currently two projects underway that propose to drill into a subglacial lake and sample its waters directly. A Russian-led research group and a second group from the UK plan to lead the way in subglacial lake exploration at Lake Vostok and Lake Ellsworth respectively. However because the area of subglacial lakes is still a relatively new to science there is still much debate happening on the proper steps a scientific research group should follow during their research activities to reduce environmental impacts. This report will provide a background on subglacial lakes, and their significance to science. It will also explore the history and future plans of the two research groups interested in Lake Vostok and Lake Ellsworth, while addressing several questions that many believe still need to be fully answered before direct subglacial lake exploration should take place.

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  • West Antarctica Ice Streams – A Review of the Proposed Mechanisms of Ice Streaming.

    Armstrong, Martina (2009)

    Postgraduate Certificate thesis
    University of Canterbury Library

    The Antarctic Ice Sheet, which covers most of the continent’s land surface, is divided into two separate entities by the Transantarctic Mountains. These are regarded as the West and East Antarctic Ice Sheets (Figure 1). The West Antarctic Ice Sheet (WAIS) contains 3.8 million km3 of ice and, unlike the East Antarctic Ice Sheet (EAIS), is a marine ice sheet which implies that the groundingline is below sea-level (Figure 2). Weertman (1974) originally proposed that a marine ice sheet, such as the WAIS, is inherently unstable. However, this analysis was based on a simple model of a marine ice sheet that did not include fast-flowing, wet-based ice streams, which are now known to dominate the grounded ice sheet (Bentley, 1998). It has been estimated that the ice streams on the WAIS move ~10-100 times faster than the adjacent non-streaming ice sheet (Bindschaler and Scambos, 1991; Whillans and van der Veen, 1993). Swithinbank (1954) defines an ice stream as part of an inland ice sheet in which the ice flows more rapidly than, and not necessarily in the same direction as, the surrounding ice. This definition indicates two main points: (1) ice streams are surrounded by ice as, if it were surrounded by rock, it would be considered an outlet glacier, and (2) it is part of the inland ice sheet, therefore it is not floating.

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  • Multichannel Analysis of Surface Waves (MASW) determined surface-wave velocity profile and its relation to observation of the near-surface polar firn layers.

    Armstrong, Martina (2009)

    Postgraduate Certificate thesis
    University of Canterbury Library

    A Multichannel Analysis of Surface-Waves (MASW) determined shear-wave (Vs) profile was related to observations of the near-surface polar firn layers on the Erebus Ice Shelf, Ross Island, Antarctica. The surface-wave method (MASW) provides a useful non-invasive tool where information about elastic properties of near-surface polar firn can be effectively obtained. It is not clear at this point if the method can directly determine density variations of the firn without further correlative P-wave or poisons ratio information. The Vs profile obtained shows a general increase in velocity with increasing depth, from 600 m/s at the surface to 1400 m/s at a depth of 12 m. The results indicate that further experiments are likely to yield useful data on the elastic properties of whole firn zone. Recommendations are made regarding equipment set up for further surveys carried out on the Erebus Ice Shelf.

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